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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• How to write a literature review faster with Paperpal? 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

Whether you’re exploring a new research field or finding new angles to develop an existing topic, sifting through hundreds of papers can take more time than you have to spare. But what if you could find science-backed insights with verified citations in seconds? That’s the power of Paperpal’s new Research feature!  

How to write a literature review faster with Paperpal?

Paperpal, an AI writing assistant, integrates powerful academic search capabilities within its writing platform. With the Research feature, you get 100% factual insights, with citations backed by 250M+ verified research articles, directly within your writing interface with the option to save relevant references in your Citation Library. By eliminating the need to switch tabs to find answers to all your research questions, Paperpal saves time and helps you stay focused on your writing.   

Here’s how to use the Research feature:  

• Ask a question: Get started with a new document on paperpal.com. Click on the “Research” feature and type your question in plain English. Paperpal will scour over 250 million research articles, including conference papers and preprints, to provide you with accurate insights and citations. 
• Review and Save: Paperpal summarizes the information, while citing sources and listing relevant reads. You can quickly scan the results to identify relevant references and save these directly to your built-in citations library for later access. 
• Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

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• 04 December 2020
• Correction 09 December 2020

How to write a superb literature review

Andy Tay is a freelance writer based in Singapore.

You can also search for this author in PubMed   Google Scholar

Literature reviews are important resources for scientists. They provide historical context for a field while offering opinions on its future trajectory. Creating them can provide inspiration for one’s own research, as well as some practice in writing. But few scientists are trained in how to write a review — or in what constitutes an excellent one. Even picking the appropriate software to use can be an involved decision (see ‘Tools and techniques’). So Nature asked editors and working scientists with well-cited reviews for their tips.

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doi: https://doi.org/10.1038/d41586-020-03422-x

Interviews have been edited for length and clarity.

Updates & Corrections

Correction 09 December 2020 : An earlier version of the tables in this article included some incorrect details about the programs Zotero, Endnote and Manubot. These have now been corrected.

Hsing, I.-M., Xu, Y. & Zhao, W. Electroanalysis 19 , 755–768 (2007).

Article   Google Scholar  

Ledesma, H. A. et al. Nature Nanotechnol. 14 , 645–657 (2019).

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Brahlek, M., Koirala, N., Bansal, N. & Oh, S. Solid State Commun. 215–216 , 54–62 (2015).

Choi, Y. & Lee, S. Y. Nature Rev. Chem . https://doi.org/10.1038/s41570-020-00221-w (2020).

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How To Write An A-Grade Literature Review

3 straightforward steps (with examples) + free template.

By: Derek Jansen (MBA) | Expert Reviewed By: Dr. Eunice Rautenbach | October 2019

Quality research is about building onto the existing work of others , “standing on the shoulders of giants”, as Newton put it. The literature review chapter of your dissertation, thesis or research project is where you synthesise this prior work and lay the theoretical foundation for your own research.

Long story short, this chapter is a pretty big deal, which is why you want to make sure you get it right . In this post, I’ll show you exactly how to write a literature review in three straightforward steps, so you can conquer this vital chapter (the smart way).

Overview: The Literature Review Process

• Understanding the “ why “
• Finding the relevant literature
• Cataloguing and synthesising the information
• Outlining & writing up your literature review
• Example of a literature review

But first, the “why”…

Before we unpack how to write the literature review chapter, we’ve got to look at the why . To put it bluntly, if you don’t understand the function and purpose of the literature review process, there’s no way you can pull it off well. So, what exactly is the purpose of the literature review?

Well, there are (at least) four core functions:

• For you to gain an understanding (and demonstrate this understanding) of where the research is at currently, what the key arguments and disagreements are.
• For you to identify the gap(s) in the literature and then use this as justification for your own research topic.
• To help you build a conceptual framework for empirical testing (if applicable to your research topic).
• To inform your methodological choices and help you source tried and tested questionnaires (for interviews ) and measurement instruments (for surveys ).

Most students understand the first point but don’t give any thought to the rest. To get the most from the literature review process, you must keep all four points front of mind as you review the literature (more on this shortly), or you’ll land up with a wonky foundation.

Okay – with the why out the way, let’s move on to the how . As mentioned above, writing your literature review is a process, which I’ll break down into three steps:

• Finding the most suitable literature
• Understanding , distilling and organising the literature
• Planning and writing up your literature review chapter

Importantly, you must complete steps one and two before you start writing up your chapter. I know it’s very tempting, but don’t try to kill two birds with one stone and write as you read. You’ll invariably end up wasting huge amounts of time re-writing and re-shaping, or you’ll just land up with a disjointed, hard-to-digest mess . Instead, you need to read first and distil the information, then plan and execute the writing.

Step 1: Find the relevant literature

Naturally, the first step in the literature review journey is to hunt down the existing research that’s relevant to your topic. While you probably already have a decent base of this from your research proposal , you need to expand on this substantially in the dissertation or thesis itself.

Essentially, you need to be looking for any existing literature that potentially helps you answer your research question (or develop it, if that’s not yet pinned down). There are numerous ways to find relevant literature, but I’ll cover my top four tactics here. I’d suggest combining all four methods to ensure that nothing slips past you:

Method 1 – Google Scholar Scrubbing

Google’s academic search engine, Google Scholar , is a great starting point as it provides a good high-level view of the relevant journal articles for whatever keyword you throw at it. Most valuably, it tells you how many times each article has been cited, which gives you an idea of how credible (or at least, popular) it is. Some articles will be free to access, while others will require an account, which brings us to the next method.

Method 2 – University Database Scrounging

Generally, universities provide students with access to an online library, which provides access to many (but not all) of the major journals.

So, if you find an article using Google Scholar that requires paid access (which is quite likely), search for that article in your university’s database – if it’s listed there, you’ll have access. Note that, generally, the search engine capabilities of these databases are poor, so make sure you search for the exact article name, or you might not find it.

Method 3 – Journal Article Snowballing

At the end of every academic journal article, you’ll find a list of references. As with any academic writing, these references are the building blocks of the article, so if the article is relevant to your topic, there’s a good chance a portion of the referenced works will be too. Do a quick scan of the titles and see what seems relevant, then search for the relevant ones in your university’s database.

Method 4 – Dissertation Scavenging

Similar to Method 3 above, you can leverage other students’ dissertations. All you have to do is skim through literature review chapters of existing dissertations related to your topic and you’ll find a gold mine of potential literature. Usually, your university will provide you with access to previous students’ dissertations, but you can also find a much larger selection in the following databases:

• Open Access Theses & Dissertations
• Stanford SearchWorks

Keep in mind that dissertations and theses are not as academically sound as published, peer-reviewed journal articles (because they’re written by students, not professionals), so be sure to check the credibility of any sources you find using this method. You can do this by assessing the citation count of any given article in Google Scholar. If you need help with assessing the credibility of any article, or with finding relevant research in general, you can chat with one of our Research Specialists .

Alright – with a good base of literature firmly under your belt, it’s time to move onto the next step.

Need a helping hand?

Step 2: Log, catalogue and synthesise

Once you’ve built a little treasure trove of articles, it’s time to get reading and start digesting the information – what does it all mean?

While I present steps one and two (hunting and digesting) as sequential, in reality, it’s more of a back-and-forth tango – you’ll read a little , then have an idea, spot a new citation, or a new potential variable, and then go back to searching for articles. This is perfectly natural – through the reading process, your thoughts will develop , new avenues might crop up, and directional adjustments might arise. This is, after all, one of the main purposes of the literature review process (i.e. to familiarise yourself with the current state of research in your field).

As you’re working through your treasure chest, it’s essential that you simultaneously start organising the information. There are three aspects to this:

• Logging reference information
• Building an organised catalogue
• Distilling and synthesising the information

I’ll discuss each of these below:

2.1 – Log the reference information

As you read each article, you should add it to your reference management software. I usually recommend Mendeley for this purpose (see the Mendeley 101 video below), but you can use whichever software you’re comfortable with. Most importantly, make sure you load EVERY article you read into your reference manager, even if it doesn’t seem very relevant at the time.

2.2 – Build an organised catalogue

In the beginning, you might feel confident that you can remember who said what, where, and what their main arguments were. Trust me, you won’t. If you do a thorough review of the relevant literature (as you must!), you’re going to read many, many articles, and it’s simply impossible to remember who said what, when, and in what context . Also, without the bird’s eye view that a catalogue provides, you’ll miss connections between various articles, and have no view of how the research developed over time. Simply put, it’s essential to build your own catalogue of the literature.

I would suggest using Excel to build your catalogue, as it allows you to run filters, colour code and sort – all very useful when your list grows large (which it will). How you lay your spreadsheet out is up to you, but I’d suggest you have the following columns (at minimum):

• Author, date, title – Start with three columns containing this core information. This will make it easy for you to search for titles with certain words, order research by date, or group by author.
• Categories or keywords – You can either create multiple columns, one for each category/theme and then tick the relevant categories, or you can have one column with keywords.
• Key arguments/points – Use this column to succinctly convey the essence of the article, the key arguments and implications thereof for your research.
• Context – Note the socioeconomic context in which the research was undertaken. For example, US-based, respondents aged 25-35, lower- income, etc. This will be useful for making an argument about gaps in the research.
• Methodology – Note which methodology was used and why. Also, note any issues you feel arise due to the methodology. Again, you can use this to make an argument about gaps in the research.
• Quotations – Note down any quoteworthy lines you feel might be useful later.
• Notes – Make notes about anything not already covered. For example, linkages to or disagreements with other theories, questions raised but unanswered, shortcomings or limitations, and so forth.

If you’d like, you can try out our free catalog template here (see screenshot below).

2.3 – Digest and synthesise

Most importantly, as you work through the literature and build your catalogue, you need to synthesise all the information in your own mind – how does it all fit together? Look for links between the various articles and try to develop a bigger picture view of the state of the research. Some important questions to ask yourself are:

• What answers does the existing research provide to my own research questions ?
• Which points do the researchers agree (and disagree) on?
• How has the research developed over time?
• Where do the gaps in the current research lie?

To help you develop a big-picture view and synthesise all the information, you might find mind mapping software such as Freemind useful. Alternatively, if you’re a fan of physical note-taking, investing in a large whiteboard might work for you.

Step 3: Outline and write it up!

Once you’re satisfied that you have digested and distilled all the relevant literature in your mind, it’s time to put pen to paper (or rather, fingers to keyboard). There are two steps here – outlining and writing:

3.1 – Draw up your outline

Having spent so much time reading, it might be tempting to just start writing up without a clear structure in mind. However, it’s critically important to decide on your structure and develop a detailed outline before you write anything. Your literature review chapter needs to present a clear, logical and an easy to follow narrative – and that requires some planning. Don’t try to wing it!

Naturally, you won’t always follow the plan to the letter, but without a detailed outline, you’re more than likely going to end up with a disjointed pile of waffle , and then you’re going to spend a far greater amount of time re-writing, hacking and patching. The adage, “measure twice, cut once” is very suitable here.

In terms of structure, the first decision you’ll have to make is whether you’ll lay out your review thematically (into themes) or chronologically (by date/period). The right choice depends on your topic, research objectives and research questions, which we discuss in this article .

Once that’s decided, you need to draw up an outline of your entire chapter in bullet point format. Try to get as detailed as possible, so that you know exactly what you’ll cover where, how each section will connect to the next, and how your entire argument will develop throughout the chapter. Also, at this stage, it’s a good idea to allocate rough word count limits for each section, so that you can identify word count problems before you’ve spent weeks or months writing!

PS – check out our free literature review chapter template…

3.2 – Get writing

With a detailed outline at your side, it’s time to start writing up (finally!). At this stage, it’s common to feel a bit of writer’s block and find yourself procrastinating under the pressure of finally having to put something on paper. To help with this, remember that the objective of the first draft is not perfection – it’s simply to get your thoughts out of your head and onto paper, after which you can refine them. The structure might change a little, the word count allocations might shift and shuffle, and you might add or remove a section – that’s all okay. Don’t worry about all this on your first draft – just get your thoughts down on paper.

Once you’ve got a full first draft (however rough it may be), step away from it for a day or two (longer if you can) and then come back at it with fresh eyes. Pay particular attention to the flow and narrative – does it fall fit together and flow from one section to another smoothly? Now’s the time to try to improve the linkage from each section to the next, tighten up the writing to be more concise, trim down word count and sand it down into a more digestible read.

Once you’ve done that, give your writing to a friend or colleague who is not a subject matter expert and ask them if they understand the overall discussion. The best way to assess this is to ask them to explain the chapter back to you. This technique will give you a strong indication of which points were clearly communicated and which weren’t. If you’re working with Grad Coach, this is a good time to have your Research Specialist review your chapter.

Finally, tighten it up and send it off to your supervisor for comment. Some might argue that you should be sending your work to your supervisor sooner than this (indeed your university might formally require this), but in my experience, supervisors are extremely short on time (and often patience), so, the more refined your chapter is, the less time they’ll waste on addressing basic issues (which you know about already) and the more time they’ll spend on valuable feedback that will increase your mark-earning potential.

Literature Review Example

In the video below, we unpack an actual literature review so that you can see how all the core components come together in reality.

Let’s Recap

In this post, we’ve covered how to research and write up a high-quality literature review chapter. Let’s do a quick recap of the key takeaways:

• It is essential to understand the WHY of the literature review before you read or write anything. Make sure you understand the 4 core functions of the process.
• The first step is to hunt down the relevant literature . You can do this using Google Scholar, your university database, the snowballing technique and by reviewing other dissertations and theses.
• Next, you need to log all the articles in your reference manager , build your own catalogue of literature and synthesise all the research.
• Following that, you need to develop a detailed outline of your entire chapter – the more detail the better. Don’t start writing without a clear outline (on paper, not in your head!)
• Write up your first draft in rough form – don’t aim for perfection. Remember, done beats perfect.
• Refine your second draft and get a layman’s perspective on it . Then tighten it up and submit it to your supervisor.

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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38 Comments

Thank you very much. This page is an eye opener and easy to comprehend.

This is awesome!

I wish I come across GradCoach earlier enough.

But all the same I’ll make use of this opportunity to the fullest.

Thank you for this good job.

Keep it up!

You’re welcome, Yinka. Thank you for the kind words. All the best writing your literature review.

Thank you for a very useful literature review session. Although I am doing most of the steps…it being my first masters an Mphil is a self study and one not sure you are on the right track. I have an amazing supervisor but one also knows they are super busy. So not wanting to bother on the minutae. Thank you.

You’re most welcome, Renee. Good luck with your literature review 🙂

This has been really helpful. Will make full use of it. 🙂

Thank you Gradcoach.

Really agreed. Admirable effort

thank you for this beautiful well explained recap.

Thank you so much for your guide of video and other instructions for the dissertation writing.

It is instrumental. It encouraged me to write a dissertation now.

Thank you the video was great – from someone that knows nothing thankyou

an amazing and very constructive way of presetting a topic, very useful, thanks for the effort,

It is timely

It is very good video of guidance for writing a research proposal and a dissertation. Since I have been watching and reading instructions, I have started my research proposal to write. I appreciate to Mr Jansen hugely.

I learn a lot from your videos. Very comprehensive and detailed.

Thank you for sharing your knowledge. As a research student, you learn better with your learning tips in research

I was really stuck in reading and gathering information but after watching these things are cleared thanks, it is so helpful.

Really helpful, Thank you for the effort in showing such information

This is super helpful thank you very much.

Thank you for this whole literature writing review.You have simplified the process.

I’m so glad I found GradCoach. Excellent information, Clear explanation, and Easy to follow, Many thanks Derek!

You’re welcome, Maithe. Good luck writing your literature review 🙂

Thank you Coach, you have greatly enriched and improved my knowledge

Great piece, so enriching and it is going to help me a great lot in my project and thesis, thanks so much

This is THE BEST site for ANYONE doing a masters or doctorate! Thank you for the sound advice and templates. You rock!

Thanks, Stephanie 🙂

This is mind blowing, the detailed explanation and simplicity is perfect.

I am doing two papers on my final year thesis, and I must stay I feel very confident to face both headlong after reading this article.

thank you so much.

if anyone is to get a paper done on time and in the best way possible, GRADCOACH is certainly the go to area!

This is very good video which is well explained with detailed explanation

Thank you excellent piece of work and great mentoring

Thanks, it was useful

Thank you very much. the video and the information were very helpful.

Good morning scholar. I’m delighted coming to know you even before the commencement of my dissertation which hopefully is expected in not more than six months from now. I would love to engage my study under your guidance from the beginning to the end. I love to know how to do good job

Thank you so much Derek for such useful information on writing up a good literature review. I am at a stage where I need to start writing my one. My proposal was accepted late last year but I honestly did not know where to start

Like the name of your YouTube implies you are GRAD (great,resource person, about dissertation). In short you are smart enough in coaching research work.

This is a very well thought out webpage. Very informative and a great read.

Very timely.

I appreciate.

Very comprehensive and eye opener for me as beginner in postgraduate study. Well explained and easy to understand. Appreciate and good reference in guiding me in my research journey. Thank you

Thank you. I requested to download the free literature review template, however, your website wouldn’t allow me to complete the request or complete a download. May I request that you email me the free template? Thank you.

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Reference management. Clean and simple.

Literature review

How to write a literature review in 6 steps

How do you write a good literature review? This step-by-step guide on how to write an excellent literature review covers all aspects of planning and writing literature reviews for academic papers and theses.

How to write a systematic literature review [9 steps]

How do you write a systematic literature review? What types of systematic literature reviews exist and where do you use them? Learn everything you need to know about a systematic literature review in this guide

What is a literature review? [with examples]

Not sure what a literature review is? This guide covers the definition, purpose, and format of a literature review.

Doing a literature review: an 8-step process

Overview of my presentation in the Middlesex University PhD coursework - with embedded videos of the 8 steps

Anne-Wil Harzing - Mon 1 Jan 2024 09:31 (updated Tue 2 Jan 2024 08:14)

Copyright 2024 Anne-Wil Harzing. All rights reserved. First version, 2 January 2024

Step 1: Information management strategies

Step 2: situating the literature review, step 3: sources of literature, step 4: keeping current, step 5: how much is enough, step 6: different types of papers.

• Step 7a: Seven criteria to evaluate coverage
• Step 7b: Twelve guidelines to evaluate references

Step 8: The literature review in your thesis

Your challenge is very different from what mine was during my PhD. I completed my PhD before the internet was available. So my challenge was to get access to information and find the time and money to do so. Oftentimes, this involved traveling to various libraries across the country.

Your challenge is to manage the wealth of information you have easy access to, but not to waste too much time on completely irrelevant information. This step provides you with some tips on how to approach this.

In this step, you learn why a literature review is important in no less than six of the nine stages of the research process. Before watching it, try and list the stages where you think it might be important.

In this step, we review the various sources you can use for literature reviews: books, journal articles, government and industry resources, working papers, and conference papers. I show you the relative merits of each of these.

Here I share my top tips on how to keep up to date with new publications. You can find more information about this here: How to keep up-to-date with the literature, but avoid information overload? .

Note that my tips focus on the "old-fashioned" tried-and-tested approaches. This process has now been facilitated by many dedicated tools, often using artificial intelligence. I can't say I like working with these as they do not facilitate the deep engagement that I think is needed for academic research, but they might well work for you.

The next step is deciding when to stop. How do you know you have "enough"? When can you stop? Well obviously, you never completely stop reviewing the literature, as it is important in so many stages of the review process (see step 2).

But in deciding when you can start writing up, I do suggest the use of a relevance tree in this video. I also show how you can use tables to effectively summarise literature. Further tips on how many references to use in writing up can be found here: How many references is enough?

In this step, I review three types of papers to look out for to maximise the effectiveness of your literature review: review papers, star papers, model papers.

Step 7a: 7 criteria to evaluate coverage

How do you evaluate whether all the literature you have collected is actually useful for your thesis or article?

In this step I go through seven criteria you can use to evaluate coverage of the collected literature: relevance, currency, reliability, audience, accuracy, scope, and objectivity.

Step 7b: 12 guidelines to evaluate references

If you are going to use the literature to reference arguments in your thesis, this step covers twelve guidelines you can use to evaluate other academics' referencing practices as well as to make sure you do this right. They are also described in detail in this blogpost: Are referencing errors undermining our scholarship and credibility?

My twelve guidelines are based on research in my own PhD, written up as a paper that turned out to be very hard to publish. If you are interested, you can read the full story here: How to publish an unusual paper? Referencing errors, scholarship & credibility .

This last step reveals what criteria are used to evaluate the literature review in your own thesis: synthesis, critical appraisal, and application to the research question. I also explain what your literature should not look like and why a good literature review helps you to get papers published.

Related blogposts

• Want to publish a literature review? Think of it as an empirical paper
• Do you really want to publish your literature review? Advice for PhD students
• How to keep up-to-date with the literature, but avoid information overload?
• Is a literature review publication a low-cost project?
• Using Publish or Perish to do a literature review
• How to conduct a longitudinal literature review?
• New: Publish or Perish now also exports abstracts
• A framework for your literature review article: where to find one?

Find the resources on my website useful?

I cover all the expenses of operating my website privately. If you enjoyed this post and want to support me in maintaining my website, consider buying a copy of one of my books (see below) or supporting the Publish or Perish software .

Copyright © 2024 Anne-Wil Harzing . All rights reserved. Page last modified on Tue 2 Jan 2024 08:14

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ENGL 417 - Written Communication for the Workplace

• Grey Literature & White Papers

Library Research Guide

Overview of grey literature and white papers, evaluating white papers and grey literature, searching for grey literature and white papers, white paper clearinghouses, examples of organizations that publish white papers and grey literature, example government websites for grey literature, websites containing academic and other professional research.

• Business Databases
• Topic Exploration

Grey literature (also spelled gray literature) is created and distributed outside of formal commercial and academic publishing processes. A valuable source of information for people working in diverse professions, it is produced by government agencies, universities, corporations, research centers, associations, and professional organizations.

"White paper" is the term commonly applied to publications in business and industry, usually featuring research or detailed product reports.

Characteristics of grey literature:

• Not  formally published; therefore, not usually available in library databases, which typically include published sources like journals and books.
• Often free and posted on the organization's website. Older reports may be taken down and difficult to locate.
• May be described in a press release as "a recent report from..."
• Represents the views and objectives of the organization that produced it.
• May provide valuable schematics, in-depth product details, consumer information, or industry data.
• OWL White Papers More information on white papers from the Purdue Online Writing Lab (OWL).

White papers are a valuable source of industry and public policy information. However, you must approach the information in the reports as critically as you would other sources of information. When reading a white paper, try to identify the following pieces of information and ask yourself how that could impact the relevance and accuracy of the report.

• Who paid for the report's research?
• Who donates to the organization that produces the research?
• Are they trying to sell something (industry)?
• Do they have a social or political agenda (public policy)?
• Do they have a defined mission/objective (non-governmental organization)?
• Are they required to perform and publish research by law (government agency)?
• How old is the report?
• While newer reports are more likely to account for changes in industry practices or laws, older reports may provide pertinent background information or technical specs for older products and practices.
• What makes the report researchers and/or writers experts on the topic?
• Evaluating Think Tanks The Harvard Kennedy School library provides resources for evaluating whether to use a think tank's research.

Search for a Known Report

1. If the title of the report is known (you've seen it in a bibliography or a press release), Google the title. Often, placing the title in quotation marks increases the likelihood that the report you want will rise to the top of your search results.

2. If you know what organization issued the white report, but don't know the exact title, Google the topic of the report and the organization's name. OR do a site search in Google. Use this syntax to perform a site search using Google:

Search for Reports on a Topic

1. Many reports are published as PDFs, adding PDF to your Google search can narrow your results to these reports. 

2. Professional organizations may produce white papers on trending issues for their members.

These websites collect or link to white papers on specific topics.

Business and Industry

• BizReport Marketing Research Library Focused on online marketing, this site includes "white papers, reports, case studies, magazines, and eBooks."

Technical Reports

• TechRepublic White Papers "TechRepublic's Resource Library is the web's largest directory of free vendor-supplied technical content."

Public Policy Reports

• Congressional Research Services Reports Official site, as of 2018, for reports researched for members of Congress on wide-ranging issues of relevance to public laws and policies.Inclusion of prior reports not ensured.
• Congressional Research Services Reports - Federation of American Scientists Hosts CRS reports dating back to the 1990s. The site is not comprehensive, but is one of the most complete sources for CRS reports.
• Congressional Research Services Reports - University of North Texas Created to download, digitize, and archive CRS reports prior to the 2018 law permitting the CRS to publicly distribute the reports. This site now acts as an archive for pre-2018 reports, to include digitizing donated reports. Not comprehensive. Coverage extends back to 1970.

NGO's Non-governmental Organizations

• The Word Bank: Research & Publications The World Bank publishes research reports and data on sustainability, development, and finance.
• OECD iLibrary The Organisation for Economic Cooperation and Development (OECD) publishes free and fee-based reports and data on topics such as development, education, finance, and industry.

Corporations

• PwC (PricewaterhouseCoopers) PwC is a professional services company that publsihes free and fee-based research reports on topics such as cybersecurity and privacy, human resources, and more.
• Deloitte Deloitte is a professional services company that publishes free and fee-based research reports on wide-ranging topics, including accounting standards, consumer trends, and human capital.
• Nielsen Reports Nielsen is global measurement and data analytics company that provides some free reports in their website.
• DOE Office of Scientific and Technical Information Provides the science, technology, and engineering research information from the US Department of Energy
• Jet Propulsion Laboratory Provides access to JPL authored, externally published papers and reprints
• DTIC Defense Technical Information Center
• NASA Technical Reports Server Technical reports from NASA and NACA
• TRAIL Technical Reports Archive and Image Library provides historic technical reports from a number of federal agencies
• OAIster Catalog of millions of records to open access digital resources including data sets
• arxiv.org/ Maintained by Cornell University, contains open access to 1,118,279 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics
• Networked Computer Science Technical Reference Library  [NCSTRL] Contains full-text computer science technical reports mainly from universities and research centers
• The National Agricultural Library (Agricola) Contains agricultural information
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Writing a Literature Review: General Guidelines

Table of contents

• 1 What Is a Literature Review?
• 2 What Is the Purpose of a Literature Review?
• 3 Steps in the Literature Review Process
• 4.1 Chronological
• 4.2 Thematic
• 4.3 Methodological
• 4.4 Theoretical
• 5 Literature Review Outline
• 6 Literature Review: Writing Tips

Writing a literature review for a research paper is an important stage in the academic research process. It entails doing a critical review of existing literature to provide a comprehensive overview of current knowledge on a certain issue. In this article, we will walk you through the important processes for writing an excellent literature review. We’ll discuss how to discover relevant literature, combine findings, and arrange your review to provide clear insights. Whether you’re a seasoned researcher or a first-time writer, this guide will give you essential advice and tactics for improving the quality and impact of your literature reviews.

What Is a Literature Review?

A literature review is a survey of key scholarly sources to do with a particular topic. It lists a number of important and relevant pieces of writing and, in doing so, gives the reader a summary of the topic’s current knowledge and debates. When writing a literature review, a student should do more than just summarise each individual source. They should analyze them closely and compare them with one another.

A key part of academic writing involves understanding what has been said and debated about the chosen topic. Once a student has done their research, they’re in a better place to write their research paper and put their point across. A good literature review should let the reader know what the salient points from the student’s research are.

What Is the Purpose of a Literature Review?

The purpose of a literature review is to show the reader what research has been carried out on the chosen topic in the past. When writing one, you’re aiming to bring the reader up to speed with other people’s research before sharing your own findings. You should summarise where the topic’s at right now before building on it with your research.

Another important purpose is to give more weight to a student’s key arguments. By listing and comparing some of the key sources, a student can give context to the main points in their research paper; they can even fill any gaps in certain areas that others haven’t yet managed to fill.

If you want to know how to write a literature review in a research paper, carry on reading. We’ll run you through the process of putting one together, and we’ll talk about some of the different approaches you can take in writing one.

Steps in the Literature Review Process

A literature review can make a Ph.D. dissertation, or any other kind of  research paper more convincing. For a review to be effective, it should be detailed and have substance but without overdoing it; in other words, it should be concise.

If you’re not sure how to write a literature review for a research paper, we’ll show you how in this section. Here are the main steps to take:

• Decide on your topic Your topic is the base on which you build your research. It also determines what research you carry out.
• Search for sources to include The sources you look at for your research paper should be authoritative and relevant. They should be scholarly in nature, though not all of them will be.
• Determine which ones are the most useful Look through your sources and think about how much each one adds to both the topic you’re exploring and the research you’re carrying out. Including all sources isn’t practical, so only choose the most appropriate and fitting ones.
• Identify where the research is currently at By reading other people’s research, you can get an idea of what the current thoughts and debates relating to your chosen topic area.
• Come up with a structure Literature reviews have quite simple structures. More information on these is given below. Think about how you want to present yours and how you’re going to arrange your findings.
• Write your literature review A well-written literature review gives the reader all the necessary information about each of the sources. It clearly explains how the sources are connected and what they contribute to the chosen topic.

It’s a good idea to come up with headings and subheadings and go from there. These are both important, and we’ll talk about them in more detail later on. During the planning process, they can help you come up with a definitive structure for your literature review and consolidate your thoughts.

You may want to pay someone to write a literature review for you. Many people who are struggling with literature reviews do this. They don’t hand in the work that someone else has done for them. Instead, they read through the other person’s work to get ideas and inspiration. Doing this can help people write their own literature review much more effectively.

• Free unlimited checks
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How to Structure a Literature Review

For this section, we’ll look at how to write a literature review. We’ll focus on the different approaches you can take according to the type of research you’re doing and how you wish to present it.

Chronological

Listing your sources in chronological order is perhaps the simplest approach to take. However, make sure you don’t just list the sources and summarise them. You should still try to establish some sort of connection between them. Highlight movements, patterns, and new ideas. Show the reader how scholarship on the topic has changed over time. You could even organize your sources into broad historical periods and have these as subheadings in the literature review, for example.

When writing a thematic literature review , you should organize your sources by theme. You should consider this approach if you’ve found multiple themes during your research. Create literature review subheadings for each theme that stands out to you. If you go for a thematic style, think about what your RRL subtopics are and what themes you would use to organize them.

Methodological

A methodological literature review is one whose sources involve the use of different research methods . You could have one source that’s numerical and involves graphs and statistics, for example, and another that’s entirely made up of written text. The subheadings in a literature review that’s methodological could focus on different types of research, focusing not so much on what has been researched but how it’s been researched. As a literature review subheadings example, you could therefore have one subheading for literary sources, another for numerical/graph-based data, and so on.

Theoretical

With a theoretical approach, the focus is on the body of theories relating to the topic that’s being discussed. The aim is to determine what theories there currently are, how they relate to one another, and how much they’ve been looked into.

These are just some of the different ways you can go about writing a literature review. The approach you take will depend on the nature of your review and the topic you’re looking at.

Writing a literature review can be an intimidating task to tackle, especially if you are not familiar with the literature in the field. Fortunately, there is a  paper writing service online that can help you create an outstanding literature review in no time. Our service is helpful for students, researchers, and others who need to compile a comprehensive and informative literature review.

Literature Review Outline

Writing a good outline for a literature review is important for your research paper. It helps you organize your thoughts and ideas and gives you a clear direction for the writing process.

An outline is not a formal document but rather an informal guide to assist you in organizing the information you want to include in your paper. The outline should be written in paragraph form, with each paragraph representing one major idea that will be expanded upon in subsequent paragraphs of the paper.

The main purpose of writing an outline is so that you can organize all of your sources in a way that will help you write a clear, concise essay. You just want to throw together quotes and facts without any order or reason. This will make it hard for the reader to follow along with what you are saying and make it appear that you have no idea what you’re talking about. This can result in a low grade for your paper and make it difficult for them to understand what is happening within the text.

• Introduction The introduction should include a brief summary of the literature that is being reviewed, including the general topic and your specific focus. You should also provide some background information on the topic to help the reader understand why it is important. You should not include any citations in this section, because you will do that later in the paper.
• Body The body is where you provide an overview of all the sources or literature, you have used for your paper. You should include an introduction to each source and a brief summary of what was found in each source. In addition to providing summaries, you should also describe how each source relates to your research question or hypothesis and then relate them back to each other if they are similar enough to be compared. Finally, you should explain how each source relates to one another in addition to explaining how they relate to your research question or hypothesis.
• Conclusion The conclusion should summarize your arguments throughout the paper and then tie all of these things together into one coherent argument that proves or disproves your hypothesis or research question in relation to other sources discussed throughout this paper (and/or).

Writing a literature review is an integral part of a successful research article or dissertation, as it helps to synthesize and connect the existing body of knowledge. To write your lit review relevantly, it is important to ensure that you include new information when constructing your review and connect existing ideas and themes. A useful literature review outline can provide a structure for expressing your views, allowing you to connect and organize your ideas consistently and effectively.

Literature Review: Writing Tips

When writing a literature review, it’s important to include all of the information your assignment requires. Sometimes, instructors will give you specific guidelines for how long your literature review should be and how many sources it needs to include. If they don’t, however, you’ll need to decide what works best for your situation.

A literature review outline will be the foundation of your paper. It will tell you what information is important and how to write it cohesively and logically. When writing, it’s important to only include facts backed up by evidence. This means that if you are writing about any research topic, there must be at least one piece of published work that backs up each claim or opinion you present.

If there isn’t a source supporting your writing, don’t put it in because it makes your paper seem like speculation or opinion rather than fact-based knowledge about the issue at hand. Another tip for writers is to write clearly and concisely so that readers can understand what they are reading quickly without having any difficulty following along from one point to another throughout the entire essay (or book).

Readers may get bored very quickly if they feel like they have to struggle through something too much before getting into where things go next. Therefore, proper grammar usage should also be kept while doing this type as well, so there are no mistakes left behind after editing later down the line during the publishing stage itself.

The following are the most important tips for writing a literature review:

• Make sure that each paragraph covers a single subject or idea.
• Start with a thesis statement, which should sum up the paper’s main idea in one sentence.
• Write each paragraph in a way that flows from one point to another logically and coherently.
• Include quotes and paraphrases from sources you have read in order to support your arguments and conclusions.
• Make sure that you use credible sources as evidence for your claims and arguments in your paper.

As well as learning how to write a literature review for a research paper, you’ll learn to be more productive and use your time more wisely. Writing services help you put together literature reviews more efficiently. They give you the opportunity to work with an experienced writer who can offer tips in writing RRL, help you with literature review formatting, and more. For example, you can even get things like literature review headings and subheadings so you can see how best to write your headings.

Remember that while the literature review isn’t the main part of a research assignment, it’s still significant. It’s important that you write it as best you can so that your research has more backing and will be taken more seriously.

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Writing Your White Paper

A white paper  is an authoritative report or guide that discusses related issues and makes recommendations for addressing them or making decisions about them. Your white paper will draw on academic research, but it should be written for a lay audience.

Part 1. Introduction/Executive Summary

Summarizes what you will write and puts it into context. Should consist of 3 parts:

• "What You're Studying": start with background contextualizing your topic/issue
• "So What?": demonstrate why your topic/issue and its impacts are important and why your reader should care about them
• "Game Plan": outline the main points of your paper and the order in which you will address them

Part 2. Background/Literature Review

You will synthesize your sources to provide a comprehensive review of your topic, its background and context. Your literature review should provide a compelling narrative about the importance of your topic/issue to stakeholders and build your evidence-based arguments that you will then use to build your policy recommendations in Part 3. Your literature review will bring together a variety of sources: 

• theories and study results from peer-reviewed journals
• health data, statistics, and demographics
• policy reports

Each paragraph of  this section represents one aspect of the paper's main focus. Each paragraph should include a topic sentence, evidence, analysis, and a transition sentence:

• The topic sentence summarizes the paragraph's main idea
• Use evidence from your research sources to support or make the argument for your assertions about your main idea
• Analyze your evidence to show how it links to your broader white paper topic/issue
• Include a transition sentence at the end of each paragraph to connect what you discussed in that paragraph with the main idea of the next paragraph

Part 3. Policy Argument/Solution and Conclusion

Build on your evidence-based arguments from your Literature Review to make a strong argument for a policy recommendation(s). Explain why your recommendations are preferable to other options in terms of feasibility, cost, efficacy, etc.

For more writing help, contact  the Writing Center   and  make an online appointment  to meet with one of their consultants.

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Grey Literature Vs White Papers for Systematic Reviews

You’ve probably heard about grey/gray literature in systematic reviews. If you’re looking for the difference between grey literature and white papers, then you’re in the right place. In this article, we will define grey literature vs white papers and discuss their suitability in systematic reviews and meta-analyses.

Table of Contents

What is grey literature?

According to Jean Adams , Programme Leader and Professor (MRC Epidemiology Unit) at the University of Cambridge, and his colleagues, grey literature can be defined as documents not controlled by publishing companies. Since you’re probably going to use data from primary research in your systematic review, the expanded definition of grey literature could be a set of primary research articles not controlled by publishing companies.

Arsenio Paez , a clinical specialty lead of the IDEAL Collaboration at the University of Oxford, provided the following examples of grey literature: academic papers (including theses and dissertations), research and committee reports, government reports, conference papers, and ongoing research, among others. The Table below provides a comprehensive list of grey literature types, according to Richard Adams :

What is the purpose of grey literature in a systematic review?

The primary purpose of including grey literature in your systematic review is to address publication bias. This kind of bias arises when authors are propelled to publish only significant and positive findings. Grey literature, such as doctoral theses do not undergo the same process as published literature, therefore can publish both negative and positive findings, as well as significant and non-significant findings. This provides a balanced view of the evidence.

Publication bias can be detected when there is inconsistent findings between published and unpublished (grey) studies.

In another post , I emphasized the importance of searching Google Scholar as a source of grey literature. This is because grey literature, not being controlled by publishing companies, cannot be found in commercial databases such as EMBASE, Web of Science, and Scopus. Apart from Google Scholar, you can find grey literature using the following sources, as recommended by Mahood and colleagues : “online databases (e.g., ProQuest), Web search engines and websites, university and institutional repositories, library catalogues, as well as contacting subject specialists, handsearching and consulting reference lists of relevant documents.”

What is a white paper?

Before defining a white paper, let’s acknowledge the fact that many experts consider white papers as grey literature. Consider for example Kansas State University and UC Davis Library positions, whereby they explicitly indicate that white papers are one of the types of grey literature in academia. We take a similar position that white papers are categorized under grey literature. Let’s define them!

According to Arianna Psichas and colleagues from Costello Medical in Cambridge, UK, white papers are frequently published in medical literature. The researchers discovered that, unlike the conventional definition of white papers as policy documents presenting the government’s stance on complex issues, the white papers published in medical literature serve various purposes, including raising awareness, promoting alignment, providing education, and fostering collaboration.

How frequently are white papers used in systematic reviews?

So far, I have not come across an expert advising on the use of white papers in systematic reviews. Instead, what I have seen is a systematic review within a white paper. Consider the example of a white paper published by Barbara Pieper , who at the time was a Professor/Nurse Practitioner at the College of Nursing, Wayne State University, Detroit, and colleagues. What they did was publish a white paper to communicate their position on pressure ulcer pain management, and within this white paper, they conducted a rigorous systematic review to support their position.

To address the lack of knowledge about the use of white papers in systematic reviews, we conducted a search for systematic reviews that utilized white papers. I searched for the following terms on PubMed: (“systematic review” OR meta-analysis) AND “white paper.” A total of 31 results were found. After reviewing all of them, we did not come across any systematic reviews that explicitly mentioned the use of white papers. However, we did find over ten articles that were identified as white papers and utilized systematic review and meta-analysis methodologies to support their perspectives.

Grey Literature Vs White Papers: Recommendations for Systematic Reviews

Whenever possible, use grey literature in your systematic review or meta-analysis. On the other hand, you may need to be a bit cautious if you decide to include white papers in your systematic review. This is because so far, we couldn’t locate a single systematic review that has ever used a white paper. Our finding is consistent with Richard Adams , who after reviewing ten scientific manuscripts found that none listed white papers as an example of grey literature.

Also, white papers are generally used in communicating positions on complex issues. That means they mostly do not contain primary research data that may be eligible for inclusion in a systematic review. However, if you find a white paper publishing primary data and meeting quality guidelines and published in a reputable journal or source (search databases like EMBASE, Web of Science, and Scopus), you can definitely include it in your systematic review without hesitation.

Challenges of Using Grey Literature in a Systematic Review

Remember our position is that white papers are a type of grey literature. Therefore, challenges of using grey literature will encompass the challenges of using white papers. The challenges of using grey literature, as outlined by Arsenio Paez, are as follows:

i. Time-consuming to search in multiple sources. There are also few resources on grey literature search methodologies.

ii. Apart from theses and dissertation and conference abstracts, other types of grey literature may lack the methodological quality required to be included in a rigorous systematic review.

The challenges above may be tempting to abandon the idea of including grey literature in your review. But it may not be a wise decision. Paying the price is worth it because your review would have efficiently mitigated publication bias.

In conclusion, grey literature refers to documents that have not undergone the traditional journal publication process and are not controlled by publishing companies. It includes white papers, although they are less commonly used in systematic reviews due to the challenges associated with searching for them. Even when easily found, white papers are less likely to contain primary data.

Searching and synthesising ‘grey literature’ and ‘grey information’ in public health: critical reflections on three case studies. Link: https://systematicreviewsjournal.biomedcentral.com/articles/10.1186/s13643-016-0337-y

Gray literature: An important resource in systematic reviews. Link: https://onlinelibrary.wiley.com/doi/10.1111/jebm.12266

Shades of Grey: Guidelines for Working with the Grey Literature in Systematic Reviews for Management and Organizational Studies. Link: https://onlinelibrary.wiley.com/doi/full/10.1111/ijmr.12102

Publication bias: what is it? How do we measure it? How do we avoid it? Link: https://www.tandfonline.com/doi/abs/10.2147/OAJCT.S34419

Searching for grey literature for systematic reviews: challenges and benefits. Link: https://onlinelibrary.wiley.com/doi/abs/10.1002/jrsm.1106

Pressure Ulcer Pain: A Systematic Literature Review and National Pressure Ulcer Advisory Panel White Paper. Link: https://www.medline.com/media/mkt/pdf/research/Wound-Skin-Care/pressure-ulcer-pain.pdf

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Answered By: James Adams Last Updated: Mar 14, 2024     Views: 3471

Articles in a peer-reviewed or "refereed" journal are reviewed prior to publication by experts (usually faculty members) with credentials in the article's field of study. Many Harvard article databases allow you to limit your search results to only include peer-reviewed journals.

Other material like white papers and policy briefs that are not peer-reviewed can still be valuable for your research. Relevant preprints that will eventually be peer-reviewed or gray literature unlikely to be published in a journal could be included as long as they pass the C.R.A.A.P. test, evaluating Currency , Relevancy , Authority , Accuracy , and Purpose . 

A good strategy for finding gray literature is to conduct a search in the HKS Library Customized Google Think Tank search , which includes over 700 think tank sites from across the world. If you are uncertain about whether to include grey literature in your research project, check with your class instructor.

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A conceptual framework proposed through literature review to determine the dimensions of social transparency in global supply chains

• Published: 16 May 2024

Cite this article

• Preethi Raja 1 &
• Usha Mohan   ORCID: orcid.org/0000-0003-2161-7600 1  

The current focus in supply chain management (SCM) research revolves around the relationship between sustainability and supply chain transparency (SCT). Despite the three pillars of sustainability – environmental, social, and economic- the limited and scattered analysis is on the social part, and the least is on socially responsible supply chain management (SR-SCM). SCT plays a significant role in elevating the sustainability of the supply chain. This review paper emphasizes the integration of SCT and sustainable supply chain, especially the social aspect as SR-SCM, and coining the new term social transparency (ST). ST is openness to communicating details about the impact of business on people, their well-being, and compliance with social sustainability standards and policies. This paper establishes a conceptual framework using three research methods. systematic literature review, content analysis-based literature review, and framework development. By locating studies in databases like EBSCO, Scopus, and Web of Science, 273 peer-reviewed articles were identified in the intersection of social sustainability, supply chains, and transparency. Finally, the framework proposes five dimensions: tracking and tracing suppliers till provenance, product and process specifications, financial transaction information, social sustainability policies and compliance, and performance assessment to determine ST in global supply chains.

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Supply chain disruptions and resilience: a major review and future research agenda

A Stakeholder Theory Perspective on Business Models: Value Creation for Sustainability

Global value chains: A review of the multi-disciplinary literature

Data availability.

The data that supports the findings of this systematic literature review and content analysis are either included in this manuscript or are publicly available in the referenced sources. All included studies and their respective citations are provided in the reference section. Any additional data or materials used for this review can be obtained upon request from the corresponding author.

Abbreviations

Supply chain management

Socially responsible supply chain management

Supply Chain Transparency

Social Transparency

Multinational Corporations

Code of Conduct

Corporate Social Responsibility

Preferred Reporting Items for Systematic Reviews and Meta-analyses

Radio frequency Identification

Internet of Things

Sustainable Supply Chain Management

Supply Chain

Textile Standard Certification

Worldwide Responsible Accredited Production

Global Organic Textile Standard

Global Recycled Standard

Registration, Evaluation, Authorization and Restriction on the use of Chemicals

Social Accountability International Certification

Indian Standards Institution Mark

Bureau of Indian Standards

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Raja, P., Mohan, U. A conceptual framework proposed through literature review to determine the dimensions of social transparency in global supply chains. Manag Rev Q (2024). https://doi.org/10.1007/s11301-024-00440-1

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DOI : https://doi.org/10.1007/s11301-024-00440-1

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National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Division on Earth and Life Studies; Board on Population Health and Public Health Practice; Board on Environmental Studies and Toxicology; Committee on the Guidance on PFAS Testing and Health Outcomes. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. Washington (DC): National Academies Press (US); 2022 Jul 28.

Guidance on PFAS Exposure, Testing, and Clinical Follow-Up.

• Hardcopy Version at National Academies Press

Appendix E White Paper: Review of the PFAS Personal Intervention Literature

Prepared for: Elizabeth B. Boyle Senior Program Officer Board on Environmental Studies and Toxicology Board on Population Health and Public Health Practice National Academies of Sciences, Engineering, and Medicine and Committee on the Guidance on PFAS Testing and Health Outcomes Washington, DC, USA Prepared by: Judy S. LaKind, Ph.D. LaKind Associates, LLC Catonsville, MD, USA Josh Naiman, B.A. LaKind Associates, LLC Philadelphia, PA, USA

ACRONYMS AND ABBREVIATIONS

E-1 INTRODUCTION

E-2 METHODS

Literature Identification

Literature Review and Data Extraction

Assessment of Evidence

E-3 RESULTS

Food Preparation: Fish, Shellfish, and Mollusks

Food Preparation: Other

Local Food Consumption Advisories

Drinking Water

Breast Milk and Infant Formula

Indoor Dust

Other Potential Interventions

Modeled Intakes as the Basis for Recommendations for Reducing Exposure to PFAS

E-4 DISCUSSION

• Acronyms and Abbreviations

activated carbon

Agency for Toxic Substances and Disease Registry

Centers for Disease Control and Prevention

confidence interval

U.S. Environmental Protection Agency

2-(n-ethyl-perfluorooctane sulfonamido) acetic acid

U.S. Food and Drug Administration

granular activated carbon

2H,2H-perfluorodecanoic acid

1H,1H,2H,2H-perfluorooctane sulfonic acid

2H,2H,3H,3H-perfluoroundecanoic acid

sodium perfluoro-1 heptanesulfonate

limit of detection

limit of quantitation

Minnesota Department of Health

2-(n-methyl-perfluorooctane sulfonamido) acetic acid

Minimum Reporting Level

n-ethyl-perfluoro-1 octanesulfonamido acetic acid.

n-methylperfluoro-1 octanesulfonamido acetic acid

n-perfluorooctanoic acid

n-perfluorooctane sulfonic acid

N-ethyl perfluorooctane sulfonamidoethanol

National Health and Nutrition Examination Survey

National Institute of Environmental Health Sciences

polybrominated diphenyl ether

polychlorinated biphenyl

perfluoroalkyl acid

per- and polyfluoroalkyl substances

perfluorobutanoate

perfluorobutane sulfonic acid

perfluorinated compound

perfluoroalkyl carboxylic acid

perfluorodecanoic acid

perfluorodecanoate

perfluorododecanoic acid

perfluorodecane sulfonate

perfluoroheptanoic acid

perfluoroheptane sulfonate

perfluorohexanoate

perfluorohexane sulfonic acid

perfluorononanoic acid

perfluorooctanoic acid

perfluorooctane sulfonic acid

perfluorooctane sulfonamide

perfluoropentanoate

perfluorotetradecanoate

perfluorotetradecanoic acid

perfluorotridecanoate

perfluorotridecanoic acid

perfluoroundecanoate

perfluoroundecanoic acid

point of entry

publicly owned treatment work

point of use

reverse osmosis

branched perfluorooctanoic acid

standard deviation

perfluoromethylheptane sulfonic acid

Unregulated Contaminant Monitoring Rule

This white paper provides an overview of the published literature on whether personal behavior modifications can demonstrably reduce exposure to per- and polyfluoroalkyl substances (PFAS) (e.g., by showing decreases in serum levels). The reviewed studies are presented by exposure source. The preponderance of the identified literature relates to diet and drinking water. Literature on interventions for other exposure sources, such as dust and consumer products, is more limited. Breastfeeding is an important potential source of exposure for infants; the effect of lactation on mothers’ PFAS levels is unclear. For communities with high levels of PFAS in drinking water, interventions related to tap water filtration showed some efficacy in reducing PFAS levels in the water. It is possible that an intervention may reduce PFAS levels in a particular medium, but if this medium is not a major source of overall exposure, then that intervention may not contribute significantly to reduction in human exposures. Overall, the intervention literature is sparse and has many limitations. Thus, the committee may have to rely on assumptions and other bodies of evidence to make recommendations to individuals and communities about exposure reduction.

E-1. Introduction

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have been produced and utilized globally since the 1940s. 1 PFAS have garnered attention for several reasons, including their ubiquitous presence in the environment ( Ahrens and Bundschuh, 2014 ; von der Trenck et al., 2018 ) and in humans ( Calafat et al., 2019 ; Göckener et al., 2020 ; Health Canada, 2019 ; Kannan et al., 2004 ), and because—as their epithet “forever chemicals” suggests—many of these chemicals are persistent both in the environment and in humans, with half-lives estimated to be several years ( Li et al., 2018 ; Myers et al., 2012 ). Exposure to PFAS has been linked with such health endpoints as reduced immune response, lipid metabolism, and kidney function; thyroid disease; liver disease; glycemic parameters and diabetes; cancer; and impaired fetal and child development ( ATSDR, 2020 ).

Activities to limit the production and use of exposure to PFAS compounds include regulatory limits, voluntary reductions in manufacture ( Butenhoff et al., 2006 ) and use in products, cleanup of contaminated sites, and modifications to publicly owned treatment works (POTWs) to reduce PFAS in drinking water. However, as evidenced by studies of measurements of PFAS in serum from nationally representative populations in the United States ( Calafat et al., 2019 ), as well as serum measurements in communities near sites with known contamination ( Herrick et al., 2017 ), exposure to PFAS is ongoing. It has been well documented that PFAS are present in numerous media and products, including drinking water; breast milk; other foods and food packaging material; cosmetics; and household products, including carpets, stain- and water-repellent fabrics, nonstick products, polishes, waxes, paints, and cleaning products ( D’Hollander et al., 2010 ; EFSA, 2020 ; Eichler and Little, 2020 ; Fromme et al., 2009 ; Sajid and Ilyas, 2017 ; Sunderland et al., 2019 ). 2

Communities impacted by PFAS exposure would like advice on how they can prevent its potential health effects. To help clinicians respond to patient concerns about PFAS exposure, the Agency for Toxic Substances and Disease Registry (ATSDR) has published PFAS: An Overview of the Science and Guidance for Clinicians on Per- and Polyfluoroalkyl Substances (referred to hereafter as the ATSDR PFAS Clinical Guidance) ( ATSDR, 2019 ). This guidance summarizes general information about PFAS and PFAS health studies and suggests answers to example patient questions. Some people living in PFAS-impacted communities have voiced frustration that the clinical guidance lacks clear recommendations to their physicians about what people can do to protect their health, which prompted the ATSDR and the National Institute of Environmental Health Sciences (NIEHS) to request that the National Academies of Sciences, Engineering, and Medicine convene a committee to provide advice for clinicians about PFAS testing, such as when to test, whom to test, how to test, what to test for, and the risks of testing. The committee is also charged with developing principles clinicians can use to advise patients on exposure reduction. 3 The committee commissioned this white paper to determine whether evidence exists that supports the effectiveness of these types of behavior changes. The literature review in this white paper is intended to help the National Academies committee evaluate possible evidence-based recommendations for improving the ATSDR’s PFAS Clinical Guidance. This white paper is not intended to be a comprehensive review of human exposure to PFAS; the National Academies have other sources for that information.

Various organizations have provided suggestions for personal actions to lower individual PFAS exposure. These include avoiding contaminated water or fish and selecting personal care products that do not contain PFAS and related compounds ( ATSDR, 2020 ; EWG, 2016 ; Loria, 2019 ; ODH, 2020 ). Reducing intake of PFAS should reduce exposure, but people may not necessarily know whether their foods, beverages, or products contain PFAS. This review addresses the following question: Based on current research, are there interventions or personal changes that individuals can make to effectively reduce their PFAS exposure? This question includes two key concepts. First, “personal” indicates that the focus is on research related to media and products that people may be able to control partly or wholly (see Figure E-1 ) as opposed to activities that occur on a larger scale, such as contaminated site cleanup, changes in occupational exposures, or modifications to publicly owned water treatment plants. Second, “effectively” refers to changes in personal behavior that can result in measurable or substantial reductions in exposures.

Human PFAS exposure pathways. The area inside the dashed red line denotes pathways for which individual actions may lower PFAS exposures. NOTE: PFC = per-/polyfluorinated chemical; WWTP = wastewater treatment plant. SOURCE: Adapted from Oliaei et al., (more...)

To answer the above question, it is important to consider several factors related to reducing human PFAS exposure. First, PFAS must be present in the media or products of interest. While this seems like a straightforward notion, information on PFAS concentrations in local media (e.g., local drinking water) and specific products (e.g., cookware) may in fact be sparse or unavailable. Second, there must be a complete exposure pathway between the medium or product and humans. In other words, if PFAS are present in a medium or product but there is no human contact, then exposure will not occur. Third, an exposure pathway may be complete but not contribute substantially to overall human exposure. In this case, a reduction in the PFAS source may not result in a meaningful reduction in human PFAS exposure. Fourth, actions to reduce PFAS exposure from one pathway may result in exposure to PFAS or other chemicals from a new pathway (e.g., an action to remove exposure to one food item with known PFAS levels may result in exposure to another food item that has not yet been analyzed for PFAS or other chemicals). Finally, PFAS tend to have long physiological half-lives; thus, interventions or changes in behavior may not produce near-term changes in internal PFAS levels (i.e., serum levels).

Taking these issues into consideration, this white paper explores the following three questions:

Is there research that links specific interventions or changes to reductions in human exposures? This paper focuses on studies seeking to establish that an intervention or behavioral change produces a quantifiable reduction in human exposure as evidenced by measurements of PFAS in the media of interest or directly in humans. As noted above, studies relying on biomonitoring to assess the efficacy of an intervention must consider the long half-lives of many PFAS and must be of appropriate duration to enable observation of postintervention decreases in serum levels.

Can information from exposure assessments that estimate human intakes from multiple pathways of exposure and exposure routes be used as the basis for individual or community recommendations? In this type of study, measurements of PFAS in various media are used to model human PFAS intake (i.e., nanograms [ng] per day or ng/kilogram [kg] per day). If sufficient measurement data are available, it may be possible to estimate the relative importance of various pathways of exposure.

Is the available research sufficiently robust such that recommendations for modifications to behavior can be made? Studies differ in terms of their quality and generalizability (i.e., how well the results translate from the studied population and conditions to other populations and conditions). They therefore also differ in terms of the confidence one can place in the results. Factors impacting confidence in studies can include sample size, quality assurance, inter- and intrastudy consistency in results, and completeness of reporting. In addition, for recommendations applicable to the United States, it is important to consider whether the studies reflect conditions that apply to behaviors and exposures in this country.

The remainder of this paper first describes our approach to identifying and reviewing the literature. We then provide results by medium. Next, we discuss efforts to model relative contributions of media and products to overall PFAS intakes in the United States.

We note that there are more than 9,000 PFAS compounds ( NASEM, 2021 ), and any given study generally examines only a very small subset of these. We focus here on the 16 PFAS 4 chemicals included in the Centers for Disease Control and Prevention’s (CDC’s) National Report on Human Exposure to Environmental Chemicals ( CDC, 2009 ).

E-2. Methods

This review is a scoping review that aims to (1) “identify the types of available evidence in a given field,” (2) “report on the types of evidence that address and inform practice in the field and the way the research has been conducted,” (3) “examine how research is conducted on a certain topic,” and (4) “identify and analyze gaps in the knowledge base” ( Munn et al., 2018 ).

LITERATURE IDENTIFICATION

Online data sources, including PubMed, EMBASE, and Google Scholar, were used to conduct the initial literature searches. We used such keywords as “(PFBS OR PFDA OR PFDoA OR PFHpA OR PFHxS OR PFNA OR PFOA OR n-PFOA OR sb-PFOA OR PFOS OR n-PFOS OR Sm-PFOS OR PFOSA OR FOSA OR EtFOSAA OR MeFOSAA OR PFUnDA OR PFAS),” “PFAS,” “perfluoroalkyl,” “human,” “exposure,” “cooking,” “dust,” “fish,” “shellfish,” “water,” “nail polish,” “cleaning,” “consumer products,” “filter,” “water filter,” “filtration,” “intervention,” “determinant,” “reduction,” “diet,” “vacuum,” “popcorn,” “biomonitor,” “breast milk,” “breastfeeding,” “infant formula,” “milk powder,” “carpeting,” “packaging,” “indoor,” “bottled water,” “air conditioning,” “fabrics,” “well water,” “water treatment,” “apparel,” “inhalation,” “ventilation,” “cosmetics,” “dental floss,” and “personal care products,” as well as various combinations of these and related keywords. We selected articles describing interventions designed to reduce human exposure to PFAS, specifically interventions that could be carried out by individuals (e.g., excluding site cleanups, modifications of publicly owned treatments works [POTWs]). Secondary references of retrieved articles were reviewed to identify publications not identified by the electronic search. Additional literature searches were conducted to identify reviews that contained estimates of human PFAS intakes using the following keywords in different combinations: “(PFBS OR PFDA OR PFDoA OR PFHpA OR PFHxS OR PFNA OR PFOA OR n-PFOA OR sb-PFOA OR PFOS OR n-PFOS OR Sm-PFOS OR PFOSA OR FOSA OR EtFOSAA OR MeFOSAA OR PFUnDA),” “PFAS,” “exposure,” “review,” “biomonitor,” “PFOA,” and “human.” The final search date was March 5, 2021.

The criteria for inclusion in the review were as follows: studies of interventions related to personal modifiable behavior and English-language publications. Exclusion criteria included the following: occupational studies and those interventions requiring professional activities, such as modifications to POTWs. For publications on modeled intake estimates, we were interested primarily in PFAS intakes in the United States. Research focused on clinical interventions is outside the scope of this review (e.g., Ducatman et al., 2021 ; Genuis et al., 2014 ).

LITERATURE REVIEW AND DATA EXTRACTION

Each study that met the above inclusion criteria was examined by both authors. The data from each intervention study were tabulated. Information extracted from each study included (where available 5 ) the following:

• description of the study population: size, composition, source, and location;
• study design: laboratory and population;
• type of specimen and number of samples;
• PFAS and concentrations or changes in concentrations; and
• results: percent decrease/increase, concentration decrease/increase, and a measure of precision (e.g., 95% confidence interval [CI], standard deviation [SD]). (For publications with results reported qualitatively, the text was extracted and reproduced verbatim.)

ASSESSMENT OF EVIDENCE

We evaluated the overall strength of evidence for each medium, considering such elements as overall study design, participant selection, sample size, and exposure assessment ( LaKind et al., 2014 ; Vandenbroucke et al., 2007 ). For studies using biomonitoring data to assess the efficacy of an intervention, we considered whether sampling intervals were designed to capture potential effects of the intervention. To assess the utility of the available evidence for providing recommendations for behavior modifications to reduce PFAS exposures, we examined such factors as (1) the number of available studies for each medium/PFAS chemical/intervention type combination, (2) the quality of the individual studies, (3) the intra- and interstudy consistency in results, and (4) the generalizability of the information to U.S. populations.

E-3. Results

Studies with the potential to provide information on methods that could be used by individuals for reducing exposure to PFAS were identified. The intervention areas include preparation of fish and other foods, reduction of exposure to PFAS in drinking water either via water filtration at point of entry (POE) or point of use (POU) or via consumption of bottled water, selection of cookware, minimization of indoor dust exposure through modification of indoor products, and use of personal care products or dietary fiber. Literature on breast milk/infant formula and both mother and infant PFAS exposure reduction is discussed. Finally, studies on source contributions to overall PFAS intake in the United States were identified. Each of these bodies of literature is described in the following sections.

FOOD PREPARATION: FISH, SHELLFISH, AND MOLLUSKS

Fish, shellfish, and mollusks have been studied for their potential as a source of PFAS exposure in humans. Nine studies examining the effect of various fish and seafood preparation methods on PFAS levels were identified. The studies included different species, cooking practices, and PFAS. We briefly summarize these studies here.

Alves and colleagues (2017) measured PFOS and PFUnA levels in mackerel and flounder purchased in markets in Spain, Italy, and the Netherlands (25 samples per species/location). PFAS were measured in raw samples and from samples steamed at 105°C for 15 minutes. No significant differences in concentrations were found between the steamed and raw samples. Mean concentrations of PFOS in flounder for raw and steamed samples were 24±1.5 nanograms per gram (ng/g) wet weight (ww) and 22±1.5 ng/g ww, respectively. Mean concentrations of PFUnA in mackerel for raw and steamed samples were 3.1±0.2 ng/g ww and 2.9±0.1 ng/g ww, respectively.

The 16 PFAS compounds identified previously (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDcA, PFUnA, PFDoA, PFTrA, PFTeA, PFBS, PFHxS, PFHpS, PFOS, and PFDS) were measured in raw and steamed tuna, hake, plaice (n = 25 each; fillets), and mussels (n = 50) purchased in European markets ( Barbosa et al., 2018 ). Steaming was performed at 105°C for 15 minutes (fish) or 5 minutes (mussels). The effects of steaming varied considerably by both species and compound. Selected results shown in Figure E-2 illustrate these differences.

Examples of PFAS content (micrograms per kilogram [μg/kg] wet weight [ww]) in raw and steamed seafood samples and percentages of PFAS content increase (+) and decrease (−) after steaming (mean ± standard deviation [SD]). NOTE: (more...)

Bhavsar and colleagues (2014) measured various PFAS (including perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters) in fresh-caught Chinook salmon, lake trout, common carp, and walleye obtained in Ontario, Canada (fillets from four or five fish per species). PFAS levels in the cooking oil were below the limit of detection (LOD). Fillet samples were placed on a layer of canola oil and fried, baked, or broiled for 10–15 minutes. PFOS was by far the dominant PFAS in each species; thus, the results were focused on the effects of cooking methods on PFOS fish concentrations. All cooking methods resulted in mostly statistically significant increases in concentrations of PFOS in salmon, trout, and walleye (the increase in walleye after frying did not appear to be statistically significant). For example, PFOS concentrations in raw, baked, broiled, and fried chinook salmon (mean ± standard deviation [SD]) were, respectively, 12.70±12.61 ng/g ww, 16.56±18.00 ng/g ww, 16.45±15.63 ng/g ww, and 16.03±15.19 ng/g ww. For carp, broiling and frying resulted in no significant changes. The authors also assessed the change in amount of PFOS (in contrast with the concentration change) to account for loss in mass due to cooking. With this approach, results were mixed in directionality and mostly nonsignificant.

Del Gobbo and colleagues (2008) analyzed fish and shellfish species purchased in Canadian markets for PFOA, PFNA, PFDA, PFUA, PFDoDA, PFTeDA, and PFOS. Species included catfish, cuttlefish, grey mullet, grouper, monkfish, octopus, red snapper, sea squirt, skate, whiting, and yellow croaker. Composites from each species were comprised of at least three individuals from three different sources or markets (total of nine). The fillets (sometimes with skin) were baked, boiled, or fried in water, sesame oil, rice wine, or vegetable oil. PFAS levels in the cooking oil were below the LOD. Baking and frying times were 15 minutes at 163°C or 325°C. All cooking interventions were found to decrease PFAS concentrations, with boiling and frying reducing total PFAS concentrations by an average of 79 percent and 54 percent, respectively. Baking reduced all measured PFAS to below the LOD (0.03–10 ng/g ww). Boiling appeared to increase concentrations of PFOS in octopus (from nondetect to 0.23 ng/g ww) but not in red snapper, skate, or yellow croaker. The authors hypothesize that large loss of mass in the boiled octopus (87 percent) may have resulted in an increase in levels above the LOD.

Hu and colleagues (2020) measured 13 PFAS compounds (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFBS, PFHxS, PFOS, and FOSA) in grass carp taken from Tangxun Lake, China (n = 5). The fillets were either steamed, boiled, fried, or grilled, with cooking temperatures for the various processes ranging from 100°C to 210°C. The authors note that in the “cooking blank juice samples all PFAS were below the MLQs [Method Quantitation Limit] except PFBS and PFOS. The concentrations of PFBS and PFOS in cooking blank samples were 1.31–2.43 ng/g and 0.131–0.169 ng/g, respectively” ( Hu et al., 2020 , p. 4). The effects of the cooking methods on concentrations of various PFAS compounds were found to be inconsistent. For example, median PFOS concentrations increased from 71.3 ng/g ww in uncooked fish to 146 ng/g ww in fried fillets. In contrast, median PFBS concentrations decreased from 20.3 ng/g ww in raw fish to 8.08 ng/g ww after grilling. These results exemplify the difficulty in characterizing the directionality and magnitude of the effectiveness of cooking fish as a proposed type of intervention.

Kim and colleagues (2020) measured 19 PFAS (PFOS, PFDS, PFHxS, PFTeDA, PFTrDA, PFDoA, PFUnDA, PFBS, PFDA, PFNA, PFOA, PFHpA, PFHxA, PFPeA, PFOSA, N-EtPFOSAA, N-MePFOSAA, L-PFHpS, and PFBA) in mackerel bought from a market in Korea (n = 10). Composited fillets from three mackerels each were prepared with various washing, soaking, and cooking (grill, braise, steam, or fry) methods (two composites each). The fish were cooked between 6 and 25 minutes with various ingredients including oil, water, potato, soy sauce, pepper paste, sugar, garlic, and ginger. Preparation methods included such traditional Korean practices as soaking the fillets in sake or rice-washed solutions. These soaking practices reduced PFAS levels by 51 to 80 percent. Washing the mackerel with water resulted in a reduction in PFAS of 74 percent. Similarly, all cooking methods reduced total PFAS content compared with the raw samples: grilling—91 percent, steaming—75 percent, frying—58 percent, and braising—47 percent. While cooking with potatoes further reduced PFAS levels in the mackerel, it also increased the levels in the potatoes.

Luo and colleagues (2019) assessed the effect of pretreatments and cooking on levels of 19 PFAS (PFOA, PFOS, PFBA, PFPeA, PFHxA, PFHpA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA, PFBS, PFHxS, L-PFHpS, PFDS, PFOSA, N-MePFOSAA, and N-EtPFOSAA) in fish cakes (n = 4 brands) and swimming crabs (n = 100) purchased in markets in Korea. The effects of a wide range of cooking methods were evaluated. Additional foods used in the cooking processes included soybean oil, two types of soy sauce, and Korean radish. Blanching, commonly used as a pretreatment before cooking fish cakes, did not yield significant changes in PFAS levels. Significant reductions in total PFAS were observed after boiling, frying, and stir-frying fish cakes (total PFAS in control, boiled, fried, and stir-fried fish cakes, respectively, were as follows: 2.96 ± 0.6 ng/g, 1.60 ± 0.16 ng/g, 1.93 ± 0.19 ng/g, and 1.94 ± 0.07 ng/g). For the crabs, presoaking reduced PFAS levels. PFAS in the crabs were significantly decreased after steaming and stewing.

Taylor and colleagues (2019) collected school prawn, blue swimmer crab, and dusky flathead from contaminated or reference estuaries in New South Wales and analyzed them for 20 PFAS compounds (PFAS above the limit of quantitation [LOQ] were PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFBS, PFHxS, PFOS, PFDS, FOSA, and NEtFOSE) before and after cooking. Dusky flathead fillets were baked or pan-fried in olive oil, while the crab and prawn were boiled in salted water. PFAS were below LODs in the cooking water and oil. Five or six replicates were used for each species and each cooking treatment (for prawns, each replicate was comprised of a composite of 10 individuals). The effect on PFAS concentrations varied with species, cooking method, and chemical. For instance, PFOS concentrations showed no change in crab following boiling, whereas PFHxS and PFOA concentrations were reduced. However, PFOS, PFHxS, and PFOA concentrations increased in prawns after cooking. For the dusky flathead, PFOS levels did not change significantly after frying, but baking resulted in a small but significant increase. The authors conclude that “cooking does not consistently reduce PFAS concentrations, and cannot mitigate dietary exposure” ( Taylor et al., 2019 , p. 280).

Vassiliadou and colleagues (2015) obtained several species of fish (anchovy, bogue, hake, picarel, sardine, sand smelt, and striped mullet) and shellfish (Mediterranean mussel, shrimp, and squid) from local markets in Greece and mussels from a mariculture farm. Twelve PFAS compounds (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoA, PFBS, PFHxS, and PFOS) were measured in raw or washed samples that were then fried (in virgin olive oil at 170°C) or grilled (at 180°C). Total PFAS concentrations were found to be mostly higher after grilling and after frying, but changes in individual PFAS were inconsistent.

In general, there appear to be numerous factors related to preparation of fish, shellfish, and mollusks that can impact changes (increases or decreases) in concentrations of PFAS. Taylor and colleagues (2019) observe that whether cooking reduces PFAS concentrations in fish depends on the physicochemical properties of the chemical, the cooking method used, and the species. They note several processes that could impact changes in PFAS levels in fish from food preparation: losses to the cooking medium (e.g., cooking oil), moisture loss during cooking, PFAS precursors in fish tissues transforming during cooking to PFAAs, protein loss, or protein increase. Additional factors possibly affecting changes in concentration are the size, shape, and thickness of fish fillets ( Hu et al., 2020 ).

Overall, robust recommendations for fish preparation interventions would ideally be based on consistent intra- and interstudy results; use of fish species and preparation methods common to the United States; and well-powered, replicated studies. The results from the studies reviewed here indicate that the effects of preparation of fish and shellfish on PFAS levels are inconsistent (examples are shown in Figure E-3 ). It is therefore difficult to use this information to inform recommendations regarding the efficacy of fish and shellfish preparation for reducing PFAS intake.

Examples of inconsistent changes in selected PFAS concentrations after fish and shellfish preparation (arrows indicate direction of concentration change). SOURCES: Blue swimmer crab information is from Taylor et al., 2019. Carp information is from Hu (more...)

Furthermore, some of the fish species and preparation methods included in this body of research are not common to the United States, limiting the generalizability of results for U.S. communities. Additionally, because very few of these studies used the same cooking methods and species, it is difficult to corroborate even the instances in which a particular intervention appears to have been effective (within this small group of studies, various cooking preparation approaches included soaking followed by stewing, steaming, boiling, frying, or stir-frying; grilling, steaming, baking, boiling, or frying without presoaking; and baking in rice wine or vegetable oil). Furthermore, several of the studies included very small sample sizes. Finally, while some studies considered the effect of moisture or mass variations on PFAS concentration changes, others reported only concentration data. A more relevant metric in terms of human exposure would be the mass of PFAS remaining in the samples after preparation.

FOOD PREPARATION: OTHER

Two studies were identified that examined the effect of preparation on PFAS levels in foods other than fish ( Binnington et al., 2017 ; Jogsten et al., 2009 ). Jogsten and colleagues (2009) measured several PFAS in various uncooked and cooked foods (see Table E-1 ). 6 Specifically, composite samples (n = 2) of beef, pork, or chicken were cooked in an oil mixture using nonstick cookware. Only PFHxS, PFOS, PFHxA, and PFOA were detected in at least one of two composite samples. PFOS levels increased in grilled pork, grilled chicken, and fried chicken compared with the raw samples. In contrast, levels did not increase in cooked veal or fried pork. The results from this study are not directly relevant for intervention recommendations. First, foods were purchased outside of the United States, and it is not known whether PFAS in these foods are similar to those in foods found in the United States. Second, only two samples per food type were included; there was no information on brands and limited information on cooking procedures; and results were inconsistent regarding the efficacy of cooking in reducing PFAS concentrations. Finally, it is not clear whether the effects of cooking can be disentangled from those of the Teflon-coated cookware used in this study.

Summary of Results of Studies Examining the Effect of Food Preparation on PFAS Levels.

Binnington and colleagues (2017) studied the effects of preparation of beluga whale blubber on nutrients and environmental chemicals, including PFAS. They collected samples from two male whales (aged 24 and 37 years) from the Northwest Territories and prepared them using traditional approaches. Measured PFAS (detected in ≥50 percent of the samples) were PFNA, PFDA, PFUnDA, PFDoDA, and PFOS. PFAS were measured in raw and prepared (boiled, roasted, and aged) samples. Roasting increased concentrations of some of the PFAS compared with certain other treatments (e.g., air-drying, hang-drying, and boil pot), but were reduced in oil ( Table E-1 includes concentration results for PFOS). According to the authors, issues with sample preparation may prevent these results from being considered representative of the overall mixture.

In summary, only two studies of changes in PFAS levels associated with cooking foods were identified. These studies included small sample sizes and yielded inconsistent results.

LOCAL FOOD CONSUMPTION ADVISORIES

State advisories for guidance on consumption of locally grown foods could be a source of information to inform exposure reduction decisions. Eleven states have advisory guidelines for consumption of fish, wildlife, and other foods (California [seafood], Connecticut, Hawaii [in process], Maine [fish, beef, and milk], Michigan [fish and deer], Minnesota, New Hampshire, New Jersey, New York, Washington [in process], Wisconsin [fish and deer]) to protect human health from exposure to PFAS. 7 These advisories offer guidance on limiting the quantity of these foods consumed. Depending on the state-specific PFAS and concentrations, different consumption levels are indicated, ranging from do not eat (e.g., fish or deer in Michigan with PFOS concentrations of more than 300 parts per billion [ppb]) to unlimited consumption (e.g., fish in New Jersey with 0.56 ng/g PFOS). While fish consumption has a role in a healthy diet ( Mozaffarian and Rimm, 2006 ), weighing the risks of PFAS exposure from fish consumption against the benefits of fish consumption is a complex process, and no intervention studies were identified that evaluated the impact of reduced consumption of fish on PFAS levels in blood and urine.

DRINKING WATER

Ingestion of drinking water is thought to be a major pathway for PFAS exposure ( Domingo and Nadal, 2019 ). Research on two types of drinking water interventions is described in this section. The first addresses whether—and the extent to which—the use of water filters at POE into the home, under the sink (POU), or in water pitchers reduces PFAS exposure. The second addresses whether the use of purchased bottled water results in lower PFAS exposure compared with the use of tap water. Because PFAS levels in water can vary widely, we focus on studies that measured PFAS in tap and bottled water obtained from the same geographic area.

Six publications and one agency report evaluating possible drinking water interventions were identified. Four ( Ao et al., 2019 ; Iwabuchi and Sato, 2021 ; MDH, 2008 ; Patterson et al., 2019 ) evaluated use of POE, POU, and water pitcher filtration devices; and three ( Ao et al., 2019 ; Gellrich et al., 2013 ; Heo et al., 2014 ) evaluated differences in PFAS concentrations between tap water and bottled water. These studies are summarized here. Also discussed is one association paper assessing the relationship between drinking water source and serum levels in a highly contaminated area ( Emmett et al., 2006 ).

POE, POU, and Water Pitcher Filtration

Ao and colleagues (2019) (also discussed in the next section) measured six PFAS compounds (PFOA, PFOS, PFNA, PFBS, PFHpA, and PFHxS) in tap (n = 9), filtered (n = 9), and bottled (n = 9) water in Shanghai, China. Paired tap and filtered water samples were collected from each of nine homes served by three different water sources. The filtered water samples were collected from the effluent of the home’s water purification device. No further information on sampling or quality control in the field was given, nor was information on the type or brand of filter provided. ΣPFAS median concentrations in tap water and filtered water were 4.44 nanograms per Liter (ng/L) and 3.13 ng/L, respectively, but the differences were not statistically significant.

Herkert and colleagues (2020) tested municipal, well, and filtered (n = 89) and unfiltered (n = 87) tap water in residences (n = 73) in North Carolina for 11 PFAS compounds (GenX, PFBS, PFBA, PFHxS, PFOS, PFPA, PFHxA, PFHpA, PFOA, PFNA, and PFDA). The 89 POE and POU filters tested varied in both type (e.g., pitcher, under sink, faucet, whole house) and filtration method (reverse osmosis [RO], granular activated carbon [GAC], single-stage, two-stage). Notably, RO filters and dual-stage filters were found to consistently remove most measured compounds (except PFNA and GenX) at an average of ≥90 percent efficiency. On the other hand, GAC filters had more variable performance and were far less effective in removing short-chain PFAS compounds, with an average removal efficiency of just 41 percent for those chemicals. Whole-house activated carbon POE systems resulted in increased levels of PFAS in half of the tests (n = 4). The authors did not observe any correlations between removal efficiency and brand, source water, loading, or filter age.

Iwabuchi and Sato (2021) tested pitcher-type water filters for their ability to reduce concentrations of six PFAS compounds (PFOA, PFOS, PFHxA, PFDA, PFDoA, and PFHxS). Four different models from four manufacturers were evaluated—two with a carbon, ceramic, and hollow fiber membrane design; and two with an activated carbon (AC) and ion exchange design (brand names not given). One liter of the test water was applied to the water filters 200 times, with filtrate analyzed after 10 L, 100 L, and 200 L had been passed through the filters. For each model, filtration effectiveness decreased with prolonged use, but three of the four models were effective in removing the majority of all PFAS compounds. Removal efficiency did not appear to be related to filter material type. Removal efficiency varied by carbon-chain length (i.e., more efficient removal was observed for longer-carbon-chain PFAS) and the PFAS functional group (PFOS >PFOA, and PFHxS >PFHxA). All tests were performed with initial PFAS concentrations of 50 ng/L. It is possible that filter effectiveness may vary with initial concentration levels. Iwabuchi and Sato (2021) conclude that household water purifiers are effective at reducing PFAS levels in drinking water.

Patterson and colleagues (2019) tested five commercially available POU/POE water treatment systems for six PFAS (PFOS, PFOA, PFHpA, PFHxS, PFBS, and PFNA). These included three RO systems (iSpring RCS5T, HydroLogic Evolution RO1000, and Flexeon LP-700) and two GAC systems (Calgon Filtrasorb 600 AR+ and Evoqua 1230CX). The filters were tested at various flow rates. The authors found that both RO and GAC systems had the potential to remove PFAS to below the LOD under their experimental water quality and operational conditions. They note, though, that performance was variable and that the long-term performance of the systems was not tested.

In addition to the publications described above, the Minnesota Department of Health ( MDH, 2008 ) conducted a survey of POU water filtration devices for PFAS. Fourteen filters were lab-tested, and 11 of these that passed initial testing were field-tested using water from municipal wells. The brands were AC (n = 8)—Aquion Rainsoft Hydrefiner P-12 9878, Kinetico MACguard 7500, and Sears Kenmore Elite 625.385010; and RO (n = 6)—GE Smartwater GXRM10GBL and Watts Premier WP-4V. The four AC devices removed PFAS compounds to below the analytical reporting level (0.2 micrograms [μg]/L). The RO devices also removed PFAS to below the reporting limit. In terms of use by consumers, MDH notes, AC filters, RO membranes, and other filter elements have a limited service life and must be periodically replaced. Manufacturer recommendations vary, but many suggest replacing filters after 500 gallons of treatment or every 6 months ( MDH, 2008 ).

MDH also tested a small, inexpensive, faucet-mounted carbon filter (PUR models FM-2000B, FM-3333B) using chlorinated and unchlorinated water with levels of PFAS that exceeded the U.S. Environmental Protection Agency (EPA) Lifetime Health Advisory Levels. The filter removed all PFAS from the unchlorinated water to below the LODs (which ranged from 5 to 10 ng/L). Some breakthrough of PFBA occurred for the chlorinated water test, but even at the filter capacity recommended by the manufacturer (100 gal), the filter was still removing 73 percent of the PFBA. 8

In the course of their work sampling private well water in Washington County, Minnesota, MDH staff collected incidental samples of water treated by homeowner-installed carbon and RO systems. While many of these systems performed quite well, others achieved only partial removal of PFAS or none at all. MDH did not have the capacity to investigate further regarding the reasons for poor performance, but suspected that inadequate system maintenance may have been the main cause. When conveying the results of such tests, whether the system was performing well or not, MDH cautions homeowners that no guarantee can be made regarding long-term effectiveness of the system and recommends that they work with a qualified water treatment company to ensure proper maintenance of their system (Virginia Yingling, personal communication, July 14, 2021).

For those homes that exceed the state’s drinking water guidance values, the Minnesota Pollution Control Agency installs and maintains whole-house GAC filter systems consisting of two 90 lb carbon canisters in series. As there are currently more than 1,000 of these systems in place, the state does not manage them individually, but changes the carbon out annually (which is more frequent than needed for the levels of PFAS present in the groundwater). Testing shows that the state’s GAC systems remove all PFAS below reporting limits (4.4 ng/L). However, some trace levels, especially of PFBA, have been detected above the method detection limits (which range from 0.5 to 1.0 ng/L). In a few instances, the filter systems were found not to be working, but these cases were related to the homeowners having accidentally switched the bypass valve or altered the plumbing in a way that bypassed the filter. As a result, the state’s contractor now inspects every system and plumbing at the annual filter changeout (Virginia Yingling, personal communication, July 14, 2021).

A study of residents living in an area served by the Little Hocking water system in Ohio—with water PFOA levels in the low ppb range at the time of the study—examined whether a community relying on highly contaminated public water could significantly reduce exposure through the use of a carbon water filter ( Emmett et al., 2006 ). Serum PFOA was measured in a random sample of study participants (n = 324), who also provided information on their drinking water habits. Those who used only water from the Little Hocking water system in their homes were categorized as using a home carbon water filtration system (n = 64) versus no home water filtration system, a system not known to remove PFOA, or a system of unknown type (n = 209). Participants with home carbon water filters were shown to have statistically significantly (p = 0.008) lower median serum PFOA levels compared with those who did not (318 nanograms per milliliter [ng/ml] versus 421 ng/ml, respectively). The difference in serum PFOA levels in these two groups of participants was not as large as that seen for individuals using bottled, spring, or cistern water (see the next section for more information). The authors ascribe this finding to the limited effectiveness of water filters, as well as reliability issues associated with filter maintenance. They do not recommend use of home filtration systems that were available at the time.

All but one of the studies reviewed here found that various filtration methods showed evidence of their potential effectiveness. These studies suggest that pitcher-type, POE, and POU filtration systems can reduce PFAS levels in drinking water under the conditions tested. It is worth noting that optimal filtration depends on the user’s actively maintaining these devices, and no study has yet looked at the effectiveness of these interventions in real-world circumstances. 9

Bottled Water (Versus Tap Water)

Here we summarize three studies that included measurements of PFAS in bottled, tap, or filtered water from the same area in order to compare levels across drinking water sources. This research was conducted in China, Germany, and Korea.

Ao and colleagues (2019) measured six PFAS compounds (PFOA, PFOS, PFNA, PFBS, PFHpA, and PFHxS) in tap (n = 9), filtered (n = 9), and bottled (n = 9) water in Shanghai, China. Tap and filtered water samples were collected from each of nine families served by three different water sources. Paired tap and filtered water samples were taken from each home. The filtered water samples were collected from the effluent of the home’s water purification device. Bottled water was purchased from local markets and represented nine best-selling brands. No further information on sampling or quality control in the field was given. ΣPFAS median concentrations in tap water, filtered water, and bottled water were 4.44 ng/L, 3.13 ng/L, and 2.36 ng/L, respectively; the differences were not statistically significant.

Mineral water (n = 119), tap water (n = 26), and spring water (n = 18) samples were measured for 10 or 19 (tap water only) PFAS compounds (PFBA, PFBS, PFPeA, PFHxA, PFHxS, HPFHpA, PFHpA, PFOA, H4PFOS, PFOS, FOSA, PFNA, H2PFDA, PFDA, PFDS, H4PFUnDA, PFUnDA, PFDoDA, and PFTeDA) ( Gellrich et al., 2013 ). The mineral water samples were from Germany; spring water samples from Switzerland, the Czech Republic, and Germany; and tap water samples from homes in unidentified locations. No further information on water sampling was given. The highest ΣPFAS concentration was in tap water (42.7 ng/L). The proportions of individual PFAS differed across water type. For example, PFOS was below the LOD in all of the spring water samples but was detected in 9 percent of all of the mineral water samples. The authors note that the PFAS concentrations in the three water types were similar and described the concentrations as “low.” For example, the median PFOA levels in mineral, spring, and tap water samples were 1.6 ng/L, 1.4 ng/L, and 2.6 ng/L, respectively.

Heo and colleagues (2014) measured 16 PFAS compounds (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA, PFBS, PFHxS, PFHpS, PFOS, and PFDS) in tap (n = 34) and bottled (n = 8) water from Busan, Korea. The bottled water samples were purchased in markets, and the tap water samples were collected from 16 districts in Busan (no further information on types of bottled water or sampling methods for tap water was provided). PFAS concentrations and detection frequencies were higher in the tap water than in the bottled water samples. For example, mean ΣPFAS levels in bottled and tap water were 0.48 ng/L and 41.3 ng/L, respectively. The authors do not provide information on whether the observed differences were statistically significant.

A study of residents living in an area served by the Little Hocking water system in Ohio suggests that a community relying on highly contaminated public water could significantly reduce exposure through the use of bottled water ( Emmett et al., 2006 ). Serum PFOA was measured in a random sample of study participants (n = 324), who also provided information on their drinking water habits. Residents who reported drinking primarily bottled/spring/cistern water had a median serum PFOA level of 71 ng/mL, compared with a statistically significantly higher level of 374 ng/mL for those who drank only Little Hocking system water. Overall, the authors observed a strong relationship between serum PFOA levels and PFOA concentrations in the drinking water source.

For communities with highly contaminated water supplies, the use of alternative drinking water sources has been shown to be associated with significantly reduced exposures. However, none of the intervention studies reviewed here provide robust evidence for the effectiveness of replacing tap water with bottled water for U.S. locations with background levels of PFAS. The studies reviewed here were conducted in Europe and Asia, and the water PFAS concentrations there may not be generalizable to the United States. Lack of brand information and small sample sizes present additional challenges for evaluating this intervention.

Use of bottled water as a replacement for tap water can be expensive and inconvenient. To be confident that the use of bottled water will result in a reduction in PFAS exposure, an understanding of local water conditions in comparison with PFAS levels in specific types of bottled water is needed. As described above, while PFAS levels in bottled water tend to be approximately between <LOD to <100 ng/L, it cannot be assumed that levels in bottled water are always lower than those in tap water. Outside of highly contaminated areas, the degree of spatial granularity for concentration data required to ensure that replacing tap water with bottled water will reduce PFAS exposure is not well understood. However, based on public data POTWs ( EPA, 2017 ), PFAS levels in treated water can vary widely within regions or states (e.g., PFOS water concentrations in Delaware ranged from <MRL [Minimum Reporting Level] of 0.04 to 1.8 µg/L, while PFOA water concentrations in Pennsylvania ranged from <MRL of 0.02 to 0.349 µg/L).

The EPA’s Third Unregulated Contaminant Monitoring Rule (UCMR) ( EPA, 2017 ) includes monitoring data for PFOS, PFOA, PFNA, PFHxS, PFHpA, and PFBS (data from 2013 to 2015 from a representative sample of public water systems serving ≤10,000 people). Figure E-4 shows varying concentrations of these six PFAS across the United States for PFAS levels above the method reporting limits. Levels in drinking water can vary across the United States by at least an order of magnitude. The concentrations are in the low ng/L range, similar to reported levels in bottled water. Also note that for much of the United States, PFAS levels in drinking water are below the method reporting limit (see Figure E-5 , green symbols) and so would possibly be similar to those in bottled water.

Variation in PFAS levels above the method reporting limit in drinking water in the United States. NOTES: The relative sizes of the symbols correspond to the actual measured water concentrations. The legends show exemplar concentrations. Plotted: log 10 (more...)

PFAS levels above (red) and below (green) the method reporting limit in drinking water in the United States. NOTES: The symbols represent a total of 215,963 measurements from the U.S. Environmental Protection Agency’s (EPA’s) Third Unregulated (more...)

BREAST MILK AND INFANT FORMULA

In considering the idea of “intervention” as it pertains to breast milk, there are two underlying concepts. The first is whether there are interventions that could reduce exposure to the breastfeeding infant, and the second is whether lactating can be an effective method for reducing the mother’s levels of PFAS compounds. We discuss each of these concepts in this section.

The Infant’s Exposure: Does Formula Feeding in Place of Breastfeeding Reduce Exposure?

Many mothers choose to breastfeed rather than use infant formula. Breastfeeding confers various health advantages to the infant and mother ( AAP, 2012 ; WHO, 2020 ). At the same time, breast milk includes environmental chemicals ( LaKind et al., 2001 , 2018 ; Lehmann et al., 2018 ) that derive from the mother’s body and are transferred to the infant via breastfeeding. Thus, concern has been expressed about the possible health effects on the infant from those environmental chemical exposures. This concern raises the question of whether formula feeding would serve as a method for “intervening,” or reducing infant exposure to PFAS.

At least two factors need to be taken into consideration. The first is that infants’ exposures begin in utero. Some studies suggest that despite environmental chemical exposures associated with breastfeeding, infants who are breastfed may do better in a number of health-related aspects compared with formula-fed infants ( LaKind et al., 2008 ). The World Health Organization has stated, “in studies of infants, breastfeeding was associated with beneficial effects, in spite of the contaminants present. The subtle effects noted in the studies were found to be associated with transplacental, rather than lactational, exposure” ( WHO, 2000 , p. 237). These conclusions are drawn from research on persistent chemicals, such as dioxins; to our knowledge, there is no PFAS-specific literature on health effects of breastfed versus formula-fed infants. At present, there does not appear to be sufficient PFAS-related research that would allow for a definitive conclusion regarding infant health and the choice between breastfeeding and use of infant formula. Thus, it is not clear that formula feeding is a scientifically supported “intervention” that would prevent adverse health outcomes.

The second factor is that in choosing formula feeding to reduce infant exposure to PFAS, the assumption is being made that infant formulas do not themselves contain PFAS compounds. While studies have reported on detectable levels of PFAS in infant formula in other countries (e.g., Llorca et al., 2010 ; Macheka et al., 2021 ), it is instructive to review available data on levels of PFAS in breast milk versus infant formula in the United States to assess whether levels in formula are lower than those found in breast milk. As an additional complication, it is not uncommon to purchase powdered formula and reconstitute it with drinking water. Therefore, we provide here a synopsis of U.S. levels of PFAS in breast milk, formula, and drinking water.

PFAS in Breast Milk in the United States

Reviews of PFAS in breast milk ( Lehmann et al., 2018 ; Liu et al., 2020 ) identify three studies reporting measurements of PFAS levels in breast milk in the United States. One of these studies ( Kuklenyik et al., 2004 ) is an analytical methods study. No information on either the milk donors or the sampling procedures is reported; the information from this study is not relevant to this discussion. In a second study, von Ehrenstein and colleagues (2009) collected milk samples from 34 breastfeeding women in North Carolina at 2–7 weeks and 3–4 months postpartum. Nine PFAS were measured (PFOS, PFOA, PFNA, PFHxS, PFOSA, MeFOSAA, EtFOSAA, PFBS, and PFDA). Measurements below the LOD were assigned a value of LOD/sqrt2. PFAS levels were below the LOQ in most of the 34 milk samples collected at both sample times (note that the LOQs for PFAS in milk ranged from 0.15 to 0.60 ng/ml, or ppb). Specifically, PFAS were detected in samples from only 4 of the 34 women, and of these only three PFAS were above the LOQ: Et-PFOSA-AcOH (1.0 ng/ml) and Me-PFOSA-AcOH (0.7 ng/ml) in one woman, and PFOSA in three women (0.3 ng/ml, 0.5 ng/ml, and 0.6 ng/ml). The remainder of the milk samples from both collections were found to have concentrations <LOQ.

In contrast, Tao and colleagues (2008a) measured PFAS (PFOS, PFOA, PFHxS, PFNA, PFHpA, PFDA, PFUnDA, and PFDoDA) in milk samples collected from 45 primiparous and multiparous women in Massachusetts. Levels that were below the detection limit were assigned a value of zero, while those detected but below the LOQ were assigned a value of one-half the LOQ. Mean levels of PFOS and PFOA were 131±103 parts per trillion (ppt) (mean±SD) and 43.8±33.1 ppt, respectively. Mean PFHxS and PFNA levels were 14.5±13.7 ppt and 7.26±4.70 ppt, respectively. The remainder of the PFAS were detected in only ≤4 samples (<24 ppt).

PFAS in Infant Formula in the United States

In a 2018 review of environmental chemicals in breast milk and infant formulas ( Lehmann et al., 2018 ), only one publication is identified with measurements of PFAS in infant formula in the United States ( Tao et al., 2008b ). Tao and colleagues (2008b) measured PFAS in 21 formula samples purchased in Washington, DC, and Boston, Massachusetts. The brands represented >99 percent of the U.S. market. Most of the samples were organic or nonorganic milk- or soy-based powders and ready-to-use or concentrated liquids. PFOS was detected in one sample (11.3 ppt; LOQ = 11.0 ppt). PFHxS was detected in two samples (1.36 ppt and 3.59 ppt; LOQ = 1.35 ppt). No other PFAS (PFOA, PFNA, PFBS, PFHpA, PFDA, PFUnDA, and PFDoDA) were detected in any samples.

PFAS in Drinking Water in the United States

An assessment of infant exposure to environmental chemicals would not be complete without considering exposures via drinking water used to reconstitute infant formula ( LaKind et al., 2005 ). ATSDR (2019) has noted that a source of PFAS exposure to infants and toddlers is “formula mixed with PFAS contaminated water.” It is important to be able to provide information on what is meant by “contaminated,” as PFAS levels in tap water vary widely. For example, Andrews and Naidenko (2020) , using national and state databases, estimated that 18−80 million people in the United States use tap water containing at least 10 ng/L (ppt) PFOA and PFOS combined, and more than 200 million people may have water with a combined PFOA and PFOS level of at least 1 ng/L.

Formula may also be reconstituted with bottled water. There is a paucity of data on PFAS levels in bottled water in the United States. Akhbarizadeh and colleagues (2020) reviewed the international literature on PFAS levels in bottled water (with none from the United States) and report levels of various PFAS in the low ng/L range, with some levels as high as the low 100s ng/L depending on the type and number of PFAS included in the reporting. They note that researchers have attributed the PFAS in bottled water to several possible sources, including PFAS from the plastic bottles themselves; introduction of PFAS to the water before bottling or during bottle closure; or contamination of contact materials during bottling, handling, and storage of the bottles. In a study of tap, spring, and mineral water from Germany, Gellrich and colleagues (2013) found PFAS levels to be generally in the low ng/L range.

Looking beyond the peer-reviewed literature, Consumer Reports ( Felton, 2020 ) conducted a study on PFAS levels in bottled water purchased in stores in the United States and from online retailers. The noncarbonated water levels in 31 brands were less than 1 ppt, and two other brands had levels of 1.21 ppt and 4.64 ppt. These results derive from the averages of two to four samples of each product, but it is not clear whether these were replicates from the same bottle or different bottles. The report does not include information on detection limits or specific PFAS compounds detected, but merely describes “total PFAS as the sum of average concentrations of all PFAS detected in the samples tested of a product.”

The U.S. Food and Drug Administration (FDA) measured PFOA and PFOS in carbonated and noncarbonated bottled water (n = 30; brands not identified) and found that levels were below the lower LOQ in all samples (0.004 µg/L). 10

Studies have also detected PFAS in bottled water from other countries (see, e.g., Le Coadou et al., 2017 ). As brand names are not provided by these authors, it is not clear how this information could be used for intervention recommendations for the United States.

Based on these very limited data, it is possible that ready-to-use formulas may have lower PFAS levels than formulas reconstituted with tap or bottled water (see Figure E-6 ). However, the following caveats must be noted: data comparisons across studies are complicated by differences in total PFAS included; measurements may include more legacy PFAS compounds and not include PFAS compounds used to replace the older chemistries; studies use varying detection limits and approaches for assigning values to measurements below the LOD; and sampling in these studies is not representative of regions within the United States.

Limited data on PFAS levels in breast milk and infant formula in the United States show general overlapping concentrations, which also overlap with PFAS concentrations in drinking water that could be used to reconstitute formula. NOTES: Double-headed (more...)

The Mother’s Exposure: Does Lactation Reduce Internal Exposure?

There are two likely sources of persistent chemicals in breast milk: legacy stores in the mother from her lifetime exposure, and current sources of exposure, such as diet ( LaKind, 2007 ). So the question arises: If a mother lactates, can she lower the stores of chemicals in her body, thus reducing her internal exposures? (If she disposes of her milk rather than breastfeeding, a process referred to as pumping-and-dumping, can she similarly reduce her exposure?) The reduction in chemical levels in the body via lactation, referred to as depuration, has been studied for such persistent chemicals as dioxins, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and chlorinated organic compounds ( LaKind, 2007 ). Those studies have yielded mixed results (reviewed by LaKind et al., 2001 ), with some showing substantial declines in breast milk levels over time ( Klein et al., 1986 ; Yakushiji et al., 1978 ) and others showing either minimal declines, no changes, or increasing levels over the course of lactation ( Hooper et al., 2007 ; LaKind et al., 2009 ).

If lactation is an effective process for reducing the legacy stores of PFAS in the mother, one would expect to see levels of PFAS in serum and breast milk decline as lactation progressed and the mother’s stores were depleted. We review here the literature on this topic.

In a review of the literature on breastfeeding and serum levels in mothers, VanNoy and colleagues (2018) conclude that the published studies support an association between breastfeeding and serum PFAS concentrations among women. However, they also observe that key aspects of breastfeeding, including duration, exclusivity, and timing of sample collection, should influence the breastfeeding–serum relationship, yet only one study in their review included all three exposure variables. They further describe the importance of parity for predicting maternal serum PFAS levels and note that most of the studies reviewed were unable to disentangle the effects of breastfeeding versus those of parity on PFAS exposure. The ability to fully assess the impact of breastfeeding on maternal PFAS levels is therefore limited.

Another approach to assessing the impact of breastfeeding on maternal PFAS exposure is to examine changes in PFAS levels in breast milk over the course of lactation. If stores of PFAS predominate over current exposures via diet and other sources, and if lactation resulted in mobilization and excretion of those stores, then lactation (with either breastfeeding or “pump-and-dump”) could result in lower internal exposures for the mother. Three studies were identified that followed individual women over the course of lactation and collected multiple breast milk samples, which were analyzed for PFAS.

Lee and colleagues (2018) collected breast milk samples (n = 293) from 127 mothers at four different times postpartum (<7, 15, 30, and 90 days) as part of the Children’s Health and Environmental Chemicals in Korea Cohort study. Samples were measured for 16 PFAS. Of the 127 women, only 15 provided samples across the lactation period, and samples from these women were pooled by sampling time. The concentrations of PFOS, PFOA, PFNA, and ΣPFAS 30 days postpartum were statistically significantly higher than in milk from sampling at <7 days postpartum.

In a study in Norway with nine women ( Thomsen et al., 2010 ), milk samples were collected monthly from approximately 2 weeks postpartum up to 1 year postpartum (n = 3–10 per woman). The authors found a consistent decrease in concentrations of PFOS and PFOA, except for PFOS in one woman (these were the only PFAS >LOQ). The modeled depuration rates were reported as 7.7 percent and 3.1 percent reduction per month for PFOA and PFOS, respectively. Regarding generalizing these results, the authors note that because they did not have information on changes in the mothers’ body weight or diet during the sampling timeframe, they could not evaluate the influence of these factors on depuration rates.

Fromme and colleagues (2010) also measured PFAS in breast milk samples collected monthly over 5 months from seven women. No significant differences in PFOS levels over the 5 months were observed.

In summary, our understanding of PFAS depuration based on breast milk measurements rests on three studies with between 7 and 15 women that yielded conflicting results. This is not necessarily surprising as depuration rates likely depend on numerous factors, such as current exposures, volume of breast milk excreted, and initial levels of PFAS in the body. Thus, the value of lactation as an intervention is unknown and requires additional study.

Would “Real-Time” Testing of Milk Help Guide Decision Making Regarding Infant Feeding?

It is unclear whether “real-time” testing of breast milk is an advantageous approach to guiding new mothers in decision making regarding infant feeding. First, testing requires sampling, shipping to laboratories, and conducting the analyses, which comes with a monetary cost. But even with unlimited resources, the time component is a critical consideration, as results may not be available until well into the infant’s first few weeks or months. Second, a single measurement may not capture the infant’s actual exposure as PFAS levels in milk may change over the duration of lactation, and the direction and rate of change are not well understood.

INDOOR DUST

Dust is a potential exposure pathway for PFAS compounds ( Trudel et al., 2008 ). One dust-related PFAS intervention study was identified ( Young et al., 2021 ). Dust samples were collected from floors by vacuum in “PFAS-free” refurbished rooms (7 with a full intervention and 28 with a partial intervention) and 12 control rooms at a university in the northeastern United States. Fifteen PFAS compounds were measured (PFOS, PFOA, PFHxA, PFHxS, FOSA, PFHpA, PFPeA, PFNA, PFBS, PFDS, PFBA, PFDA, PFUnDA, PFDoDA, and N-MeFOSAA), with detection limits ranging from 0.06 to 1.5 ng/g. PFAS levels in field blanks were either below the LOD or substantially lower than levels in the samples.

The geometric mean ΣPFAS levels were 481 ng/g (225–1,140 ng/g) in rooms with no intervention, 252 ng/g (18.1–8,310 ng/g) in rooms with partial interventions, and 108 ng/g (43.6–243 ng/g) in rooms with full interventions. Use of PFAS-free furnishing resulted in a statistically significant (78%, 95% CI: 38–92) ΣPFAS reduction in dust compared with control rooms. The results from this study suggest a possible intervention for reducing exposure to PFAS in dust.

While not an intervention study, research conducted by Scher and colleagues (2019) examined associations between PFAS-contaminated soil outside of homes and dust concentrations inside of the homes. The authors collected dust samples from the interior of the house and entryways to determine whether entryway dust levels indicate that “track-in” is an important contributor to house dust PFAS levels. They observed higher PFAS levels in the interior of the homes compared with soil levels, and suggest that soil track-in was not an important source of PFAS in interior dust.

Interpretation of PFAS dust studies is complicated by the lack of standardized sampling techniques for dust collection; the impact of use of different sampling methods on PFAS concentrations is unknown ( Scher et al., 2019 ). Furthermore, for interventions that reduce PFAS in dust, the extent to which overall human intakes of PFAS would be reduced is not known. Estimates of the PFAS intake via dust have varied considerably ( Nadal and Domingo, 2014 ).

OTHER POTENTIAL INTERVENTIONS

Other possible actions that could be considered interventions include limiting the use of PFAS-containing household goods and personal care products and introducing substances to the diet specifically intended to remove PFAS from the body. No intervention studies for these behavioral changes were identified, but here we describe one study on nonstick cookware, one study related to use of dental floss, and one dietary modification approach in the context of future exploration.

Nonstick Cookware

Nonstick cookware has been studied as a source of PFAS exposure. In terms of interventions, at issue is whether replacing nonstick cookware with items that do not contain PFAS would result in a measurable decrease in human PFAS exposures. While no intervention studies were identified, we briefly describe one study conducted in the United States that compared the release of PFAS into air and water from nonstick versus stainless steel frying pans. Sinclair and colleagues (2007) purchased four brands of domestic and imported nonstick frying pans and one brand of stainless steel frying pan (three to five of each brand) in New York. The pan brand names are not identified. All pans were precleaned with hot, soapy water; rinsed with Milli-Q water; and dried with a towel. The stainless steel pans were used as controls. The authors report that under normal cooking conditions (179°C to 233°C surface temperature), PFOA in the gas phase was measured at 11–503 picograms per square centimeter (pg/cm 2 ) from the nonstick frying pans. (Fluorotelemer alcohols were also detected, but these are not chemicals of focus in this paper and are not discussed further.) Gas-phase PFOA decreased after repeated use of one brand of pan but not the others (n = 1 for each brand). The authors also measured PFOA in Milli-Q water boiled for 10 minutes in selected pans and found inconsistent results (certain pans resulted in measurable levels of PFOA in the water, while others did not).

Since brand names are not included in the publication, this information cannot be used as the basis for specific intervention recommendations. Even if brand names were included, given the small sample size and the lack of study replication, it would be difficult to use this information as the basis for general recommendations. Finally, as neither air nor water concentrations are provided, the extent to which this exposure source contributes to overall intake is unclear.

Dental Floss

One study examined the association between use of dental floss and serum PFAS (PFOA, PFNA, PFDeA, PFHxS, PFOS, and Me-PFOSA-AcOH) levels ( Boronow et al., 2019 ). Serum PFAS levels were measured in 178 middle-aged women. An administered questionnaire included one question on use of dental floss: “In the last month, how often did you use Oral-B Glide dental floss?” Response choices were as follows: “Never or almost never, Several times a month, 2 or more times a week, Every day.” Only “ever” and “never” were used in the regression analysis. While five of the PFAS compounds did not show significant associations, a 24.9 percent (95% CI: 0.2–55.7) higher level of PFHxS was found in subjects who used Oral-B Glide floss. It is worth noting that the questionnaires were administered several years after blood sample collection.

The authors also analyzed 18 dental floss products (only one or two samples per brand were analyzed, except the Oral-B Glide brand [five samples]) for total fluorine (as an indicator for polytetrafluoroethylene or PTFE), 6 of which yielded detectable levels. Given the lag in time between blood collection and questionnaire administration, the small number of floss samples analyzed, and the mostly nonsignificant results, it is not clear whether dental floss is an important route of human exposure to PFAS.

Fiber Intake

Studies have observed relationships between higher fiber intake and lower serum PFAS levels (e.g., PFOA, PFOS, and PFNA [ Dzierlenga et al., 2021 ]; PFOS and PFOA [ Halldorsson et al., 2008 ]; PFOS, PFOA, PFHxS, EtFOSAA, MeFOSAA, and PFNA [ Lin et al., 2020 ]). This finding is based on studies examining associations between dietary recall information and serum levels in cross-sectional study designs. Thus, it is unknown whether other factors (e.g., whether diets with high fiber generally have lower levels of PFAS) influence this relationship.

MODELED INTAKES AS THE BASIS FOR RECOMMENDATIONS FOR REDUCING EXPOSURE TO PFAS

Well-conducted and generalizable intervention studies can be considered the gold standard for recommending approaches to reductions in personal exposure to PFAS. In the absence of such studies, it may be informative to use results from studies designed to model the relative contributions of exposure pathways to overall PFAS exposure. This approach would focus attention and intervention strategies on the most important exposure pathways. In this section, we discuss results from studies using concentration data from several media and products (e.g., soil, water, and food concentration data) in combination with generic intake factors (e.g., g intake/kg body weight per day) to model human intakes of PFAS. We explore whether any common, generalizable themes emerge from such modeling studies regarding dominant intake pathways.

Because of geographic differences in both environmental media and product concentrations, the emphasis here is on studies conducted for the U.S. population. First, however, we provide a brief synopsis of reviews on studies conducted for populations outside of the United States. Although some of the modeling efforts included less well-studied PFAS (e.g., PFHxS), the most commonly assessed PFAS were PFOA and PFOS. Sunderland and colleagues (2019) recently compiled data from the literature on percent source contribution in adults. The results are summarized in Figures E-7 and E-8 . The modeling approaches represented by the underlying papers included different concentration data and intake assumptions. Regardless of the approach used, diet appears to be the major pathway of exposure to PFOS, with the percent contribution ranging from 65 to 96 percent. For PFOA, the range of percentages for dietary contributions is wider (6–86 percent). While these results point to the importance of diet, the location of a study and the presence or absence of point sources will influence the relative contributions of various pathways to overall PFAS intake. Behavioral differences across countries can also impact the results and their generalizability to communities in the United States. We therefore focus on two studies that modeled source contributions for PFOA ( Lorber and Egeghy, 2011 ) and PFOS ( Egeghy and Lorber, 2011 ) in the United States.

Relative contribution percentiles for various pathways of exposure to PFOA. NOTE: Values less than 1 percent were assigned a value of zero. SOURCE: Data from Sunderland et al., 2019.

Relative contribution percentiles for various pathways of exposure to PFOS. NOTE: Values less than 1 percent were assigned a value of zero. SOURCE: Data from Sunderland et al., 2019.

For PFOA intake modeling, Lorber and Egeghy (2011) used the following data, assumptions, and approach. Their intakes were developed for adults and 2-year-old children. PFOA concentrations in various media from the published literature were used in combination with EPA exposure contact rates. The authors generated intake distributions by inputting different exposure media concentrations into the model. They assumed that PFOA concentrations in indoor air were 20 times higher than those in outdoor air, with outdoor air data being derived from a study in Albany, New York. Whether these air concentrations represent more general U.S. exposures is not discussed. The authors also used dietary data from the Canadian Total Dietary Survey ( Tittlemier et al., 2007 ); thus, it is not known whether this aspect of the model is representative of exposures to PFOA in the United States. PFOA levels in drinking water were estimated from surface water concentrations in various parts of the United States (New York, North Carolina, New Jersey [drinking water], Great Lakes, Tennessee, and Florida). Dust concentration data were obtained from dust samples from homes and day care centers in Ohio and North Carolina.

Lorber and Egeghy (2011) 11 discuss numerous limitations around their estimates of intakes, including the following: no estimates of intake via direct contact with consumer products (e.g., treated carpets or cosmetics), no inclusion of PFOA precursors, and a lack of PFOA data for food in the United States. However, Lorber and Egeghy (2011) also used a simple one-compartment, first-order pharmacokinetic model in combination with National Health and Nutrition Examination Survey (NHANES) 2003–2004 data and back-calculated intakes. Their central tendency intake estimates for adults and children (70 ng/day and 26 ng/day, respectively) are not dissimilar to the intakes back-calculated from the NHANES data (56 ng/day and 37 ng/day for males and females, respectively). These models would benefit from the use of improved measurement data in food and other media specific to—and representative of—the United States (or at least areas or regions of interest within the United States) and the use of more recent NHANES data.

Egeghy and Lorber (2011) used a similar approach to model intakes of PFOS and its precursors. In addition to modeling of precursors, this effort differs from the PFOA models described above in that the models were developed for both “typical” and “contaminated” scenarios. (The contaminated scenario was similar to the background scenario except that much higher water concentrations were used.) In terms of available data on environmental concentrations of PFOS and precursors, the authors note that “measurement of PFCs in exposure media in North America was relatively sparse for all media compared with European data with the possible exception of dust. Food data are sparse for both continents. No measurements of PFOS in uncontaminated soil could be found” ( Egeghy and Lorber, 2011 , p. 158). The authors found that diet was the main route of exposure in the general population, while for children, dust ingestion was almost as important a contributor to intake as diet. Perhaps most important in the context of using modeled uptakes as the basis for recommendations for modifying behaviors to reduce exposure, Egeghy and Lorber (2011) found that the pathway-specific contributions spanned several orders of magnitude and overlapped substantially. 12

Use of model estimates of dominant pathways of PFAS exposure for making recommendations to individuals regarding exposure reduction faces a number of challenges. First, while diet appears to be a major pathway of exposure, there is little information on PFAS in commercial foods commonly consumed in the United States. The FDA has released PFAS data for certain foods, which could be used in future studies involving modeling of source contributions to PFAS intake. 13 However, the FDA observed that its data for produce, meat, dairy, and grain products are based on a small sample size, and the results “cannot be used to draw definitive conclusions about the levels of PFAS in the general food supply” (para. 3). It is not currently well understood whether the data on commercial foods from other countries used in the intake models are representative of levels in the United States. Wu and colleagues (2015) state, “Information on dietary predictors in U.S. is still limited” and “more data are needed to determine the relative contributions of food and dust to serum PFCs for both adult and child populations” (p. 265). A review of PFAS in foods by Domingo and Nadal (2017) identifies only two recent studies for the United States: one focused on PFAS uptake by lettuce and strawberries irrigated with reclaimed water ( Blaine et al., 2014 ) and the other on concentrations of PFAS in freshwater fish samples from urban rivers and the Great Lakes ( Stahl et al., 2014 ).

Furthermore, the relative importance of different sources varies by study (see Figures E-7 and E-8 ) and by demographic group and population ( Sunderland et al., 2019 ). In describing the findings of their recent review on nonoccupational intakes via background exposures, De Silva and colleagues (2021) observe that the inconsistency in the relative importance of different exposure sources from one study to the next may be due to differing concentrations of PFAS in media, as well as the assignment of different values for exposure intake factors (e.g., exposure frequency and duration). They conclude, “Without rigorously conducted exposure studies it is challenging to rank order the most important human exposure pathways and without these data, our ability to design evidence-based exposure intervention strategies will be limited” ( De Silva, 2021 , p. 644).

Within even a small geographic area, one could envision varying exposure characteristics that could, in turn, affect sources of PFAS intakes. Vestergren and Cousins (2009) explored this possibility by estimating relative intakes for those with exposure to background PFAS levels, exposure to higher levels in drinking water or drinking water impacted by a PFAS point source, or occupational exposures; they found substantial differences in the relative contributions to overall intakes (see Figure E-9 ).

Estimated daily intakes for male adults (D) and relative source contributions. NOTES: Data for sources are derived from different studies and different countries. Bracketed numbers refer to citations in Vestergren and Cousins, 2009. (a) = background concentrations (more...)

Another factor related to modeling principal sources of exposure is the changes in production and use of individual PFAS over time. Sunderland and colleagues (2019) describe the changes in serum PFAS levels following the phase-out of production of PFOS and its precursors, with PFOS declining, but other PFAS, such as PFHxS, increasing. They observe that while exposures to PFOS and PFOA “have been successfully reduced by product phase-outs for many populations, exposures to C-9-C-11 PFCAs have not followed the same trends” ( Sunderland et al., 2019 , p. 138). Thus, it is important to use recent environmental and consumer product and dietary data to develop robust estimates of current dominant pathways of exposure.

E-4. Discussion

In this review, we have sought to address the following question: Based on current research, are there interventions or personal modifiable behavioral changes that individuals can make to effectively reduce their PFAS exposure? We have described research on potential ways in which an individual could reduce exposure to PFAS. It is important to acknowledge that communities across the United States have received guidance from state and federal agencies regarding PFAS exposure reduction, including advisories around consumption of drinking water and fish. While it may seem obvious that avoiding exposure to sources of PFAS would result in reduced intake of PFAS and, in turn, lower internal PFAS levels, some caution in assuming that exposure and risk reduction would ensue is warranted. For example, if one is advised to avoid locally caught fish because of known PFAS contamination in that fish, such avoidance could result in reduced exposure. However, if dietary fish is replaced by another food that is also high in PFAS, avoiding the fish may not result in lower PFAS exposure. Another issue to consider is that avoiding one group of chemicals by changing diet or other behaviors can result in increased exposures to other chemicals. Finally, if a certain PFAS source is related to a small portion of overall exposure, then avoidance of that source may not result in appreciable reductions in internal levels of PFAS. Thus, while avoiding known sources of PFAS exposure may be a useful approach to lowering overall exposure, these other considerations should be taken into account; research on the efficacy of various interventions could help shed light on these complexities.

The number of intervention studies available to address the question of whether there are interventions or personal modifiable behavioral changes that individuals can make to effectively reduce their PFAS exposure ranged from 1 to 11, depending on the source of exposure; for some pathways, no studies were found (see Figure E-10 ). Overall, only the water filtration studies provided relatively consistent evidence of an effective reduction in PFAS levels. No studies were identified that confirmed reduction in human exposure via biomonitoring. To fully demonstrate the efficacy of an intervention, a study would need to be conducted over a timeframe sufficient to account for the long half-lives of PFAS.

Figure E-10

Summary of numbers of studies identified for each PFAS exposure source. NOTE: “Other” includes nonstick cookware, dental floss, and fiber intake, which these sources are described in the text but for which no intervention studies were (more...)

Demonstration that PFAS exposures are reduced in a meaningful way through biomonitoring confirmation is an important step. It is possible that an intervention may reduce PFAS levels in a particular medium, but if this medium is not a major source of overall exposure, then that intervention may not contribute significantly to reduction in human exposures. Overall, the intervention literature is sparse and has many limitations. Thus, the committee may have to rely on assumptions and other bodies of evidence to make recommendations to individuals and communities about exposure reduction.

We also considered whether intake models could assess with some degree of confidence the relative source contributions to overall intake and whether this approach could be used to inform decisions regarding community recommendations. While diet appears to be a major contributor to overall intake, dietary data from the United States were not used in these models. It is not known whether the Canadian data used are representative of levels in the United States. As observed by Macheka-Tendenguwo and colleagues (2018) , “numerous investigations have attempted to establish the main exposure pathway of PFAS in humans, but differing viewpoints make the results inconclusive” (p. 36066).

In conclusion, other than using certified POE or POU water filters, the available intervention studies generally do not appear to be sufficiently robust to support recommendations for personal behavioral modifications for communities in the United States. The studies reviewed here were limited by small sample sizes, generally inconsistent study designs and results, and a possible lack of generalizability to the United States. It is also important to consider additional factors when developing recommendations for changes in personal behavior, such as the ease and cost of an intervention, associated trade-offs (i.e., If an intervention lowers concentrations of PFAS, does it increase exposures to other chemicals, including other PFAS?), and whether enough is known about varying PFAS levels in the environment and consumer products to understand the necessary scale of an intervention recommendation (e.g., individual, local, or regional). Information will be needed on local levels of PFAS in drinking water, as well as levels in breast milk, for any recommendations regarding infant nutrition to be well supported.

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See https://www ​.epa.gov/pfas ​/basic-information-pfas (accessed May 12, 2021).

See also https://www ​.epa.gov/pfas ​/basic-information-pfas (accessed May 12, 2021).

See the committee’s full Statement of Task at https://www ​.nationalacademies ​.org/our-work ​/guidance-on-pfas-testing-and-health-outcomes (accessed May 19, 2021).

PFBS: perfluorobutane sulfonic acid; PFDA: perfluorodecanoic acid; PFDoA: perfluorododecanoic acid; PFHpA: perfluoroheptanoic acid; PFHxS: perfluorohexane sulfonic acid; PFNA: perfluorononanoic acid; PFOA: perfluorooctanoic acid; n-PFOA: n-perfluorooctanoic acid; Sb-PFOA: branched perfluorooctanoic acid; PFOS: perfluorooctane sulfonic acid; n-PFOS: n-perfluorooctane sulfonic acid; Sm-PFOS: perfluoromethylheptane sulfonic acid; PFOSA or FOSA: perfluorooctane sulfonamide; EtFOSAA: 2-(n-ethyl-perfluorooctane sulfonamido) acetic acid; MeFOSAA: 2-(n-methyl-perfluorooctane sulfonamido) acetic acid; PFUnDA: perfluoroundecanoic acid. The various PFAS abbreviations used in this paper are defined in the listing at the beginning of the paper. For brevity, these abbreviations are not spelled out further in the text of this paper.

Because of the disparate nature of the identified studies, it was often possible to include only a portion of the elements.

Jogsten and colleagues (2009) also measured PFAS in foods wrapped in different types of packaging. The foods were purchased in Spain, and the brands were not identified, so the relevance to the U.S. population is unclear. Egeghy and Lorber (2011) note that while fluorochemical-treated food packaging can be a source of PFAS in food, it appears that PFAS levels in packaging such as fast-food wrappers have decreased over time.

See https://www ​.ecos.org ​/wp-content/uploads/2021 ​/04/Updated-Standards-White-Paper-April-2021.pdf (accessed June 30, 2022).

The information in this and the subsequent two paragraphs was provided by Virginia Yingling, Environmental Health Division, Minnesota Department of Health, Saint Paul, Minnesota.

Information on certified water filters can be found at the following website: https://www ​.nsf.org/knowledgelibrary ​/perfluorooctanoic-acid-and-perfluorooctanesulfonic-acid-in-drinking-water (accessed May 12, 2021). Note that the certification applies only to PFOA and PFOS, and the water filter must be able to reduce these chemicals to under 70 parts per trillion (ppt).

See https://www ​.fda.gov/media ​/130564/download (accessed May 12, 2021).

This text has been changed since the release of the pre-publication version of the report to remove reference to a figure that cannot be reproduced due to lack of copyright permissions.

See https://www ​.fda.gov/food ​/cfsan-constituent-updates ​/update-fdas-continuing-efforts-understand-andreduce-exposure-pfas-foods (accessed May 12, 2021).

• Cite this Page National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Division on Earth and Life Studies; Board on Population Health and Public Health Practice; Board on Environmental Studies and Toxicology; Committee on the Guidance on PFAS Testing and Health Outcomes. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. Washington (DC): National Academies Press (US); 2022 Jul 28. Appendix E, White Paper: Review of the PFAS Personal Intervention Literature.
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Title: large language models for cyber security: a systematic literature review.

Abstract: The rapid advancement of Large Language Models (LLMs) has opened up new opportunities for leveraging artificial intelligence in various domains, including cybersecurity. As the volume and sophistication of cyber threats continue to grow, there is an increasing need for intelligent systems that can automatically detect vulnerabilities, analyze malware, and respond to attacks. In this survey, we conduct a comprehensive review of the literature on the application of LLMs in cybersecurity (LLM4Security). By comprehensively collecting over 30K relevant papers and systematically analyzing 127 papers from top security and software engineering venues, we aim to provide a holistic view of how LLMs are being used to solve diverse problems across the cybersecurity domain. Through our analysis, we identify several key findings. First, we observe that LLMs are being applied to a wide range of cybersecurity tasks, including vulnerability detection, malware analysis, network intrusion detection, and phishing detection. Second, we find that the datasets used for training and evaluating LLMs in these tasks are often limited in size and diversity, highlighting the need for more comprehensive and representative datasets. Third, we identify several promising techniques for adapting LLMs to specific cybersecurity domains, such as fine-tuning, transfer learning, and domain-specific pre-training. Finally, we discuss the main challenges and opportunities for future research in LLM4Security, including the need for more interpretable and explainable models, the importance of addressing data privacy and security concerns, and the potential for leveraging LLMs for proactive defense and threat hunting. Overall, our survey provides a comprehensive overview of the current state-of-the-art in LLM4Security and identifies several promising directions for future research.

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Sexual and reproductive health implementation research in humanitarian contexts: a scoping review

• Alexandra Norton 1 &
• Hannah Tappis 2  

Reproductive Health volume  21 , Article number:  64 ( 2024 ) Cite this article

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Meeting the health needs of crisis-affected populations is a growing challenge, with 339 million people globally in need of humanitarian assistance in 2023. Given one in four people living in humanitarian contexts are women and girls of reproductive age, sexual and reproductive health care is considered as essential health service and minimum standard for humanitarian response. Despite growing calls for increased investment in implementation research in humanitarian settings, guidance on appropriate methods and analytical frameworks is limited.

A scoping review was conducted to examine the extent to which implementation research frameworks have been used to evaluate sexual and reproductive health interventions in humanitarian settings. Peer-reviewed papers published from 2013 to 2022 were identified through relevant systematic reviews and a literature search of Pubmed, Embase, PsycInfo, CINAHL and Global Health databases. Papers that presented primary quantitative or qualitative data pertaining to a sexual and reproductive health intervention in a humanitarian setting were included.

Seven thousand thirty-six unique records were screened for inclusion, and 69 papers met inclusion criteria. Of these, six papers explicitly described the use of an implementation research framework, three citing use of the Consolidated Framework for Implementation Research. Three additional papers referenced other types of frameworks used in their evaluation. Factors cited across all included studies as helping the intervention in their presence or hindering in their absence were synthesized into the following Consolidated Framework for Implementation Research domains: Characteristics of Systems, Outer Setting, Inner Setting, Characteristics of Individuals, Intervention Characteristics, and Process.

This review found a wide range of methodologies and only six of 69 studies using an implementation research framework, highlighting an opportunity for standardization to better inform the evidence for and delivery of sexual and reproductive health interventions in humanitarian settings. Increased use of implementation research frameworks such as a modified Consolidated Framework for Implementation Research could work toward both expanding the evidence base and increasing standardization.

Plain English summary

Three hundred thirty-nine million people globally were in need of humanitarian assistance in 2023, and meeting the health needs of crisis-affected populations is a growing challenge. One in four people living in humanitarian contexts are women and girls of reproductive age, and provision of sexual and reproductive health care is considered to be essential within a humanitarian response. Implementation research can help to better understand how real-world contexts affect health improvement efforts. Despite growing calls for increased investment in implementation research in humanitarian settings, guidance on how best to do so is limited. This scoping review was conducted to examine the extent to which implementation research frameworks have been used to evaluate sexual and reproductive health interventions in humanitarian settings. Of 69 papers that met inclusion criteria for the review, six of them explicitly described the use of an implementation research framework. Three used the Consolidated Framework for Implementation Research, a theory-based framework that can guide implementation research. Three additional papers referenced other types of frameworks used in their evaluation. This review summarizes how factors relevant to different aspects of implementation within the included papers could have been organized using the Consolidated Framework for Implementation Research. The findings from this review highlight an opportunity for standardization to better inform the evidence for and delivery of sexual and reproductive health interventions in humanitarian settings. Increased use of implementation research frameworks such as a modified Consolidated Framework for Implementation Research could work toward both expanding the evidence base and increasing standardization.

Peer Review reports

Over the past few decades, the field of public health implementation research (IR) has grown as a means by which the real-world conditions affecting health improvement efforts can be better understood. Peters et al. put forward the following broad definition of IR for health: “IR is the scientific inquiry into questions concerning implementation – the act of carrying an intention into effect, which in health research can be policies, programmes, or individual practices (collectively called interventions)” [ 1 ].

As IR emphasizes real-world circumstances, the context within which a health intervention is delivered is a core consideration. However, much IR implemented to date has focused on higher-resource settings, with many proposed frameworks developed with particular utility for a higher-income setting [ 2 ]. In recognition of IR’s potential to increase evidence across a range of settings, there have been numerous reviews of the use of IR in lower-resource settings as well as calls for broader use [ 3 , 4 ]. There have also been more focused efforts to modify various approaches and frameworks to strengthen the relevance of IR to low- and middle-income country settings (LMICs), such as the work by Means et al. to adapt a specific IR framework for increased utility in LMICs [ 2 ].

Within LMIC settings, the centrality of context to a health intervention’s impact is of particular relevance in humanitarian settings, which present a set of distinct implementation challenges [ 5 ]. Humanitarian responses to crisis situations operate with limited resources, under potential security concerns, and often under pressure to relieve acute suffering and need [ 6 ]. Given these factors, successful implementation of a particular health intervention may require different qualities than those that optimize intervention impact under more stable circumstances [ 7 ]. Despite increasing recognition of the need for expanded evidence of health interventions in humanitarian settings, the evidence base remains limited [ 8 ]. Furthermore, despite its potential utility, there is not standardized guidance on IR in humanitarian settings, nor are there widely endorsed recommendations for the frameworks best suited to analyze implementation in these settings.

Sexual and reproductive health (SRH) is a core aspect of the health sector response in humanitarian settings [ 9 ]. Yet, progress in addressing SRH needs has lagged far behind other services because of challenges related to culture and ideology, financing constraints, lack of data and competing priorities [ 10 ]. The Minimum Initial Service Package (MISP) for SRH in Crisis Situations is the international standard for the minimum set of SRH services that should be implemented in all crisis situations [ 11 ]. However, as in other areas of health, there is need for expanded evidence for planning and implementation of SRH interventions in humanitarian settings. Recent systematic reviews of SRH in humanitarian settings have focused on the effectiveness of interventions and service delivery strategies, as well as factors affecting utilization, but have not detailed whether IR frameworks were used [ 12 , 13 , 14 , 15 ]. There have also been recent reviews examining IR frameworks used in various settings and research areas, but none have explicitly focused on humanitarian settings [ 2 , 16 ].

Given the need for an expanded evidence base for SRH interventions in humanitarian settings and the potential for IR to be used to expand the available evidence, a scoping review was undertaken. This scoping review sought to identify IR approaches that have been used in the last ten years to evaluate SRH interventions in humanitarian settings.

This review also sought to shed light on whether there is a need for a common framework to guide research design, analysis, and reporting for SRH interventions in humanitarian settings and if so, if there are any established frameworks already in use that would be fit-for-purpose or could be tailored to meet this need.

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews was utilized to guide the elements of this review [ 17 ]. The review protocol was retrospectively registered with the Open Science Framework ( https://osf.io/b5qtz ).

Search strategy

A two-fold search strategy was undertaken for this review, which covered the last 10 years (2013–2022). First, recent systematic reviews pertaining to research or evaluation of SRH interventions in humanitarian settings were identified through keyword searches on PubMed and Google Scholar. Four relevant systematic reviews were identified [ 12 , 13 , 14 , 15 ] Table 1 .

Second, a literature search mirroring these reviews was conducted to identify relevant papers published since the completion of searches for the most recent review (April 2017). Additional file 1 includes the search terms that were used in the literature search [see Additional file 1 ].

The literature search was conducted for papers published from April 2017 to December 2022 in the databases that were searched in one or more of the systematic reviews: PubMed, Embase, PsycInfo, CINAHL and Global Health. Searches were completed in January 2023 Table 2 .

Two reviewers screened each identified study for alignment with inclusion criteria. Studies in the four systematic reviews identified were considered potentially eligible if published during the last 10 years. These papers then underwent full-text review to confirm satisfaction of all inclusion criteria, as inclusion criteria were similar but not fully aligned across the four reviews.

Literature search results were exported into a citation manager (Covidence), duplicates were removed, and a step-wise screening process for inclusion was applied. First, all papers underwent title and abstract screening. The remaining papers after abstract screening then underwent full-text review to confirm satisfaction of all inclusion criteria. Title and abstract screening as well as full-text review was conducted independently by both authors; disagreements after full-text review were resolved by consensus.

Data extraction and synthesis

The following content areas were summarized in Microsoft Excel for each paper that met inclusion criteria: publication details including author, year, country, setting [rural, urban, camp, settlement], population [refugees, internally displaced persons, general crisis-affected], crisis type [armed conflict, natural disaster], crisis stage [acute, chronic], study design, research methods, SRH intervention, and intervention target population [specific beneficiaries of the intervention within the broader population]; the use of an IR framework; details regarding the IR framework, how it was used, and any rationale given for the framework used; factors cited as impacting SRH interventions, either positively or negatively; and other key findings deemed relevant to this review.

As the focus of this review was on the approach taken for SRH intervention research and evaluation, the quality of the studies themselves was not assessed.

Twenty papers underwent full-text review due to their inclusion in one or more of the four systematic reviews and meeting publication date inclusion criteria. The literature search identified 7,016 unique papers. After full-text screening, 69 met all inclusion criteria and were included in the review. Figure  1 illustrates the search strategy and screening process.

Flow chart of paper identification

Papers published in each of the 10 years of the review timeframe (2013–2022) were included. 29% of the papers originated from the first five years of the time frame considered for this review, with the remaining 71% papers coming from the second half. Characteristics of included publications, including geographic location, type of humanitarian crisis, and type of SRH intervention, are presented in Table  3 .

A wide range of study designs and methods were used across the papers, with both qualitative and quantitative studies well represented. Twenty-six papers were quantitative evaluations [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ], 17 were qualitative [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ], and 26 used mixed methods [ 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 ]. Within the quantitative evaluations, 15 were observational, while five were quasi-experimental, five were randomized controlled trials, and one was an economic evaluation. Study designs as classified by the authors of this review are summarized in Table  4 .

Six papers (9%) explicitly cited use of an IR framework. Three of these papers utilized the Consolidated Framework for Implementation Research (CFIR) [ 51 , 65 , 70 ]. The CFIR is a commonly used determinant framework that—in its originally proposed form in 2009—is comprised of five domains, each of which has constructs to further categorize factors that impact implementation. The CFIR domains were identified as core content areas influencing the effectiveness of implementation, and the constructs within each domain are intended to provide a range of options for researchers to select from to “guide diagnostic assessments of implementation context, evaluate implementation progress, and help explain findings.” [ 87 ] To allow for consistent terminology throughout this review, the original 2009 CFIR domains and constructs are used.

Guan et al. conducted a mixed methods study to assess the feasibility and effectiveness of a neonatal hepatitis B immunization program in a conflict-affected rural region of Myanmar. Guan et al. report mapping data onto the CFIR as a secondary analysis step. They describe that “CFIR was used as a comprehensive meta-theoretical framework to examine the implementation of the Hepatitis B Virus vaccination program,” and implementation themes from multiple study data sources (interviews, observations, examination of monitoring materials) were mapped onto CFIR constructs. They report their results in two phases – Pre-implementation training and community education, and Implementation – with both anchored in themes that they had mapped onto CFIR domains and constructs. All but six constructs were included in their analysis, with a majority summarized in a table and key themes explored further in the narrative text. They specify that most concerns were identified within the Outer Setting and Process domains, while elements identified within the Inner Setting domain provided strength to the intervention and helped mitigate against barriers [ 70 ].

Sarker et al. conducted a qualitative study to assess provision of maternal, newborn and child health services to Rohingya refugees residing in camps in Cox’s Bazar, Bangladesh. They cite using CFIR as a guide for thematic analysis, applying it after a process of inductive and deductive coding to index these codes into the CFIR domains. They utilized three of the five CFIR domains (Outer Setting, Inner Setting, and Process), stating that the remaining two domains (Intervention Characteristics and Characteristics of Individuals) were not relevant to their analysis. They then proposed two additional CFIR domains, Context and Security, for use in humanitarian contexts. In contrast to Guan et al., CFIR constructs are not used nor mentioned by Sarker et al., with content under each domain instead synthesized as challenges and potential solutions. Regarding the CFIR, Sarker et al. write, “The CFIR guided us for interpretative coding and creating the challenges and possible solutions into groups for further clarification of the issues related to program delivery in a humanitarian crisis setting.” [ 51 ]

Sami et al. conducted a mixed methods case study to assess the implementation of a package of neonatal interventions at health facilities within refugee and internally displaced persons camps in South Sudan. They reference use of the CFIR earlier in the study than Sarker et al., basing their guides for semi-structured focus group discussions on the CFIR framework. They similarly reference a general use of the CFIR framework as they conducted thematic analysis. Constructs are referenced once, but they do not specify whether their application of the CFIR framework included use of domains, constructs, or both. This may be in part because they then applied an additional framework, the World Health Organization (WHO) Health System Framework, to present their findings. They describe a nested approach to their use of these frameworks: “Exploring these [CFIR] constructs within the WHO Health Systems Framework can identify specific entry points to improve the implementation of newborn interventions at critical health system building blocks.” [ 65 ]

Three papers cite use of different IR frameworks. Bolan et al. utilized the Theoretical Domains Framework in their mixed methods feasibility study and pilot cluster randomized trial evaluating pilot use of the Safe Delivery App by maternal and newborn health workers providing basic emergency obstetric and newborn care in facilities in the conflict-affected Maniema province of the Democratic Republic of the Congo (DRC). They used the Theroetical Domains Framework in designing interview questions, and further used it as the coding framework for their analysis. Similar to the CFIR, the Theoretical Domains Framework is a determinant framework that consists of domains, each of which then includes constructs. Bolan et al. utilized the Theoretical Domains Framework at the construct level in interview question development and at the domain level in their analysis, mapping interview responses to eight of the 14 domains [ 83 ]. Berg et al. report using an “exploratory design guided by the principles of an evaluation framework” developed by the Medical Research Council to analyze the implementation process, mechanisms of impact, and outcomes of a three-pillar training intervention to improve maternal and neonatal healthcare in the conflict-affected South Kivu province of the DRC [ 67 , 88 ]. Select components of this evaluation framework were used to guide deductive analysis of focus group discussions and in-depth interviews [ 67 ]. In their study of health workers’ knowledge and attitudes toward newborn health interventions in South Sudan, before and after training and supply provision, Sami et al. report use of the Conceptual Framework of the Role of Attitudes in Evidence-Based Practice Implementation in their analysis process. The framework was used to group codes following initial inductive coding analysis of in-depth interviews [ 72 ].

Three other papers cite use of specific frameworks in their intervention evaluation [ 19 , 44 , 76 ]. As a characteristic of IR is the use of an explicit framework to guide the research, the use of the frameworks in these three papers meets the intention of IR and serves the purpose that an IR framework would have in strengthening the analytical rigor. Castle et al. cite use of their program’s theory of change as a framework for a mixed methods evaluation of the provision of family planning services and more specifically uptake of long-acting reversible contraception use in the DRC. They describe use of the theory of change to “enhance effectiveness of [long-acting reversible contraception] access and uptake.” [ 76 ] Thommesen et al. cite use of the AAAQ (Availability, Accessibility, Acceptability and Quality) framework in their qualitative study assessing midwifery services provided to pregnant women in Afghanistan. This framework is focused on the “underlying elements needed for attainment of optimum standard of health care,” but the authors used it in this paper to evaluate facilitators and barriers to women accessing midwifery services [ 44 ]. Jarrett et al. cite use of the Centers for Disease Control and Prevention’s (CDC) Guidelines for Evaluating Public Health Surveillance Systems to explore the characteristics of a population mobility, mortality and birth surveillance system in South Kivu, DRC. Use of these CDC guidelines is cited as one of four study objectives, and commentary is included in the Results section pertaining to each criteria within these guidelines, although more detail regarding use of these guidelines or the authors’ experience with their use in the study is not provided [ 19 ].

Overall, 22 of the 69 papers either explicitly or implicitly identified IR as relevant to their work. Nineteen papers include a focus on feasibility (seven of which did not otherwise identify the importance of exploring questions concerning implementation), touching on a common outcome of interest in implementation research [ 89 ].

While a majority of papers did not explicitly or implicitly use an IR framework to evaluate their SRH intervention of focus, most identified factors that facilitated implementation when they were present or served as a barrier when absent. Sixty cite factors that served as facilitators and 49 cite factors that served as barriers, with just three not citing either. Fifty-nine distinct factors were identified across the papers.

Three of the six studies that explicitly used an IR framework used the CFIR, and the CFIR is the only IR framework that was used by multiple studies. As previously mentioned, Means et al. put forth an adaptation of the CFIR to increase its relevance in LMIC settings, proposing a sixth domain (Characteristics of Systems) and 11 additional constructs [ 2 ]. Using the expanded domains and constructs as proposed by Means et al., the 59 factors cited by papers in this review were thematically grouped into the six domains: Characteristics of Systems, Outer Setting, Inner Setting, Characteristics of Individuals, Intervention Characteristics, and Process. Within each domain, alignment with CFIR constructs was assessed for, and alignment was found with 29 constructs: eight of Means et al.’s 11 constructs, and 21 of the 39 standard CFIR constructs. Three factors did not align with any construct (all fitting within the Outer Setting domain), and 14 aligned with a construct label but not the associated definition. Table 5 synthesizes the mapping of factors affecting SRH intervention implementation to CFIR domains and constructs, with the construct appearing in italics if it is considered to align with that factor by label but not by definition.

Table 6 lists the CFIR constructs that were not found to have alignment with any factor cited by the papers in this review.

This scoping review sought to assess how IR frameworks have been used to bolster the evidence base for SRH interventions in humanitarian settings, and it revealed that IR frameworks, or an explicit IR approach, are rarely used. All four of the systematic reviews identified with a focus on SRH in humanitarian settings articulate the need for more research examining the effectiveness of SRH interventions in humanitarian settings, with two specifically citing a need for implementation research/science [ 12 , 13 ]. The distribution of papers across the timeframe included in this review does suggest that more research on SRH interventions for crisis-affected populations is taking place, as a majority of relevant papers were published in the second half of the review period. The papers included a wide range of methodologies, which reflect the differing research questions and contexts being evaluated. However, it also invites the question of whether there should be more standardization of outcomes measured or frameworks used to guide analysis and to facilitate increased comparison, synthesis and application across settings.

Three of the six papers that used an IR framework utilized the CFIR. Guan et al. used the CFIR at both a domain and construct level, Sarker et al. used the CFIR at the domain level, and Sami et al. did not specify which CFIR elements were used in informing the focus group discussion guide [ 51 , 65 , 70 ]. It is challenging to draw strong conclusions about the applicability of CFIR in humanitarian settings based on the minimal use of CFIR and IR frameworks within the papers reviewed, although Guan et al. provides a helpful model for how analysis can be structured around CFIR domains and constructs. It is worth considering that the minimal use of IR frameworks, and more specifically CFIR constructs, could be in part because that level of prescriptive categorization does not allow for enough fluidity in humanitarian settings. It also raises questions about the appropriate degree of standardization to pursue for research done in these settings.

The mapping of factors affecting SRH intervention implementation provides an example of how a modified CFIR framework could be used for IR in humanitarian contexts. This mapping exercise found factors that mapped to all five of the original CFIR domains as well as the sixth domain proposed by Means et al. All factors fit well within the definition for the selected domain, indicating an appropriate degree of fit between these existing domains and the factors identified as impacting SRH interventions in humanitarian settings. On a construct level, however, the findings were more variable, with one-quarter of factors not fully aligning with any construct. Furthermore, over 40% of the CFIR constructs (including the additional constructs from Means et al.) were not found to align with any factors cited by the papers in this review, also demonstrating some disconnect between the parameters posed by the CFIR constructs and the factors cited as relevant in a humanitarian context.

It is worth noting that while the CFIR as proposed in 2009 was used in this assessment, as well as in the included papers which used the CFIR, an update was published in 2022. Following a review of CFIR use since its publication, the authors provide updates to construct names and definitions to “make the framework more applicable across a range of innovations and settings.” New constructs and subconstructs were also added, for a total of 48 constructs and 19 subconstructs across the five domains [ 90 ]. A CFIR Outcomes Addendum was also published in 2022, based on recommendations for the CFIR to add outcomes and intended to be used as a complement to the CFIR determinants framework [ 91 ]. These expansions to the CFIR framework may improve applicability of the CFIR in humanitarian settings. Several constructs added to the Outer Setting domain could be of particular utility – critical incidents, local attitudes, and local conditions, each of which could help account for unique challenges faced in contexts of crisis. Sub-constructs added within the Inner Setting domain that seek to clarify structural characteristics and available resources would also be of high utility based on mapping of the factors identified in this review to the original CFIR constructs. As outcomes were not formally included in the CFIR until the 2022 addendum, a separate assessment of implementation outcomes was not undertaken in this review. However, analysis of the factors cited by papers in this review as affecting implementation was derived from the full text of the papers and thus captures content relevant to implementation determinants that is contained within the outcomes.

Given the demonstrated need for additional flexibility within an IR framework for humanitarian contexts, while not a focus of this review, it is worth considering whether a different framework could provide a better fit than the CFIR. Other frameworks have differing points of emphasis that would create different opportunities for flexibility but that do not seem to resolve the challenges experienced in applying the CFIR to a humanitarian context. As one example, the EPIS (Exploration, Preparation, Implementation, Sustainment) Framework considers the impact of inner and outer context on each of four implementation phases; while the constructs within this framework are broader than the CFIR, an emphasis on the intervention characteristics is missing, a domain where stronger alignment within the CFIR is also needed [ 92 ]. Alternatively, the PRISM (Practical, Robust Implementation and Sustainability Model) framework is a determinant and evaluation framework that adds consideration of context factors to the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) outcomes framework. It has a stronger emphasis on intervention aspects, with sub-domains to account for both organization and patient perspectives within the intervention. While PRISM does include aspects of context, external environment considerations are less robust and intentionally less comprehensive in scope, which would not provide the degree of alignment possible between the Characteristics of Systems and Outer Setting CFIR domains for the considerations unique to humanitarian environments [ 93 ].

Reflecting on their experience with the CFIR, Sarker et al. indicate that it can be a “great asset” in both evaluating current work and developing future interventions. They also encourage future research of humanitarian health interventions to utilize the CFIR [ 51 ]. The other papers that used the CFIR do not specifically reflect on their experience utilizing it, referring more generally to having felt that it was a useful tool [ 65 , 70 ]. On their use of an evaluation framework, Berg et al. reflected that it lent useful structure and helped to identify aspects affecting implementation that otherwise would have gone un-noticed [ 67 ]. The remaining studies that utilized an IR framework did not specifically comment on their experience with its use [ 72 , 83 ]. While a formal IR framework was not engaged by other studies, a number cite a desire for IR to contribute further detail to their findings [ 21 , 37 ].

In their recommendations for strengthening the evidence base for humanitarian health interventions, Ager et al. speak to the need for “methodologic innovation” to develop methodologies with particular applicability in humanitarian settings [ 7 ]. As IR is not yet routinized for SRH interventions, this could be opportune timing for the use of a standardized IR framework to gauge its utility. Using an IR framework to assess factors influencing implementation of the MISP in initial stages of a humanitarian response, and interventions to support more comprehensive SRH service delivery in protracted crises, could lend further rigor and standardization to SRH evaluations, as well as inform strategies to improve MISP implementation over time. Based on categorizing factors identified by these papers as relevant for intervention evaluation, there does seem to be utility to a modified CFIR approach. Given the paucity of formal IR framework use within SRH literature, it would be worth conducting similar scoping exercises to assess for explicit use of IR frameworks within the evidence base for other health service delivery areas in humanitarian settings. In the interim, the recommended approach from this review for future IR on humanitarian health interventions would be a modified CFIR approach with domain-level standardization and flexibility for constructs that may standardize over time with more use. This would enable use of a common analytical framework and vocabulary at the domain level for stakeholders to describe interventions and the factors influencing the effectiveness of implementation, with constructs available to use and customize as most appropriate for specific contexts and interventions.

This review had a number of limitations. As this was a scoping review and a two-part search strategy was used, the papers summarized here may not be comprehensive of those written pertaining to SRH interventions over the past 10 years. Papers from 2013 to 2017 that would have met this scoping review’s inclusion criteria may have been omitted due to being excluded from the systematic reviews. The review was limited to papers available in English. Furthermore, this review did not assess the quality of the papers included or seek to assess the methodology used beyond examination of the use of an IR framework. It does, however, serve as a first step in assessing the extent to which calls for implementation research have been addressed, and identify entry points for strengthening the science and practice of SRH research in humanitarian settings.

With one in 23 people worldwide in need of humanitarian assistance, and financing required for response plans at an all-time high, the need for evidence to guide resource allocation and programming for SRH in humanitarian settings is as important as ever [ 94 ]. Recent research agenda setting initiatives and strategies to advance health in humanitarian settings call for increased investment in implementation research—with priorities ranging from research on effective strategies for expanding access to a full range of contraceptive options to integrating mental health and psychosocial support into SRH programming to capturing accurate and actionable data on maternal and perinatal mortality in a wide range of acute and protracted emergency contexts [ 95 , 96 ]. To truly advance guidance in these areas, implementation research will need to be conducted across diverse humanitarian settings, with clear and consistent documentation of both intervention characteristics and outcomes, as well as contextual and programmatic factors affecting implementation.

Conclusions

Implementation research has potential to increase impact of health interventions particularly in crisis-affected settings where flexibility, adaptability and context-responsive approaches are highlighted as cornerstones of effective programming. There remains significant opportunity for standardization of research in the humanitarian space, with one such opportunity occurring through increased utilization of IR frameworks such as a modified CFIR approach. Investing in more robust sexual and reproductive health research in humanitarian contexts can enrich insights available to guide programming and increase transferability of learning across settings.

Availability of data and materials

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Availability, Accessibility, Acceptability and Quality

Centers for Disease Control and Prevention

Consolidated Framework for Implementation Research

Democratic Republic of the Congo

Exploration, Preparation, Implementation, Sustainment

• Implementation research

Low and middle income country

Minimum Initial Service Package

Practical, Robust Implementation and Sustainability Model

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Reach, Effectiveness, Adoption, Implementation, Maintenance

• Sexual and reproductive health

World Health Organization

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White Paper Argues for Changes to Parole Review for Those Committing Crimes As Youths

• Children and the Law
• Civil Rights
• Criminal Law

The parole process for people who committed crimes under age 18 should be reformed to account for an evolving understanding of human development, according to a new white paper from the Civil Rights Litigation Clearinghouse. 

In the 1980s and ’90s, the notion of dangerous young “superpredators” took hold in the public consciousness, leading to the imposition of harsher sentences—often in the adult justice system—for many young people. At the same time, sentencing practices were trending toward longer terms and mandatory penalties.

A better understanding about the cognitive development of young people and falling crime rates, however, discredited the superpredator theory. 

“What we now know about young people who commit crimes is that they’re much more likely to reform and change, that the crimes are actually often related to features of their youth rather than some inherent intractable criminality,” said Clearinghouse Managing Attorney Tessa Bialek, who authored the white paper. “There actually are meaningful differences between most people who commit crimes under the age of 18 and people who commit crimes as adults, and that should be reflected in sentencing.”

Starting in 2005, the US Supreme Court responded to the evolving understanding of youth crime in several cases that prohibited some of the harshest sentences, including the death penalty and life without the possibility of parole for nonhomicide crimes. And many states have reformed the way that they sentence young people for crimes, Bialek said. Even so, thousands of people across the country continue to serve lifelong sentences for crimes committed when they were under age 18.

Those with parole-eligible sentences often face parole systems designed mainly for adults. Such systems are poorly suited to considering youth at the time of the crime or post-crime maturity and rehabilitation, and they fail to provide a realistic path to release.

“These young people should have a chance for a productive life outside of prison,” Bialek said.

The Civil Rights Litigation Clearinghouse, which is housed at Michigan Law, collects and presents documents and information from large-scale civil rights cases across the United States. The new white paper draws on the collection to recommend that the parole process for people sentenced as youth should include the following reforms:

• A meaningful opportunity for release based on demonstrated maturity and rehabilitation
• Evaluation of maturity, rehabilitation, and the mitigating factors of youth
• Access to rehabilitative programming and services
• An in-person parole hearing with counsel
• Access to the court record; ability to contribute to and correct the record
• Board decisions supported by written explanations 
• Judicial review of parole denial
• Data collection, annual monitoring, and review of processes by the parole board
• Qualifications and training for parole board members and staff

Read the Full White Paper

Bialek sees the recommendations as falling into two buckets. 

First is the basis for deciding whether to grant release. 

“The release decision should be grounded in how someone has grown and changed since the crime,” Bialek said. “The release decision should look at how someone has changed and grown, how they now reflect on the crime, and the ways that they might be able to make amends for that crime outside of prison, to make positive contributions to their community—both in spite of and in light of the crime that they’ve committed.”

Second is procedural support, which includes policies intended to support in-depth and accurate parole review, like an opportunity to correct the record or permitting live back-and-forth with the parole board. 

“For example, counsel can be especially important for this cohort of people,” Bialek said. “Parole boards aren’t necessarily used to seeing parole candidates who committed these kinds of crimes and have been incarcerated for decades. Counsel can help offer context for the crime and grounding in the relevant constitutional and other requirements. Counsel can also be useful in marshaling the evidence that might be required or helping someone with a reentry plan.” 

The new white paper is the third in a series called Learning from Civil Rights Lawsuits . The series looks to the tens of thousands of litigation documents in the clearinghouse collection to explore promising practices and develop model policies for criminal justice reform. The first paper in the series, released in 2022, was “ Effective Communication with Deaf, Hard of Hearing, Blind, and Low Vision Incarcerated People .” The second, released last year, was “Policies for Expanding Hepatitis C Testing and Treatment in United States Prisons and Jails.”

Banner Image Photo credit: © Richard Ross (2012), used with his permission.

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