Cited by 219Per- and polyfluoroalkyl substances researchFluorine in Organic ChemistryToxic Organic Pollutants Impact

The DOI matches its Crossref record; 140 of the 141 references it cites were found in a registry or an index; none of the 99 sources its claims cite is checked for support yet.

What is the effect of phasing out long-chain per- and polyfluoroalkyl substances on the concentrations of perfluoroalkyl acids and their precursors in the environment? A systematic review

Open access

Abstract

Background: There is a concern that continued emissions of man-made per- and polyfluoroalkyl substances (PFASs) may cause environmental and human health effects. Now widespread in human populations and in the environment, several PFASs are also present in remote regions of the world, but the environmental transport and fate of PFASs are not well understood. Phasing out the manufacture of some types of PFASs started in 2000 and further regulatory and voluntary actions have followed. The objective of this review is to understand the effects of these actions on global scale PFAS concentrations. Methods: Searches for primary research studies reporting on temporal variations of PFAS concentrations were performed in bibliographic databases, on the internet, through stakeholder contacts and in review bibliographies. No time, document type, language or geographical constraints were applied in the searches. Relevant subjects included human and environmental samples. Two authors screened all retrieved articles. Dual screening of 10% of the articles was performed at title/abstract and full-text levels by all authors. Kappa tests were used to test consistency. Relevant articles were critically appraised by four reviewers, with double checking of 20% of the articles by a second reviewer. Meta-analysis of included temporal trends was considered but judged to not be appropriate. The trends were therefore discussed in a narrative synthesis. Results: Available evidence suggests that human concentrations of perfluorooctane sulfonate (PFOS), perfluorodecane sulfonate (PFDS), and perfluorooctanoic acid (PFOA) generally are declining, while previously increasing concentrations of perfluorohexane sulfonate (PFHxS) have begun to level off. Rapid declines for PFOS-precursors (e.g. perfluorooctane sulfonamide, FOSA) have also been consistently observed in human studies. In contrast, limited data indicate that human concentrations of PFOS and PFOA are increasing in China where the production of these substances has increased. Human concentrations of longer-chained perfluoroalkyl carboxylic acids (PFCAs) with 9–14 carbon atoms are generally increasing or show insignificant trends with too low power to detect a trend. For abiotic and biological environmental samples there are no clear patterns of declining trends. Most substances show mixed results, and a majority of the trends are insignificant with low power to detect a trend. Conclusions: For electrochemically derived PFASs, including PFOS and PFOA, most human studies in North America and Europe show consistent statistically significant declines. This contrasts with findings in wildlife and in abiotic environmental samples, suggesting that declining PFOS, PFOS-precursor and PFOA concentrations in humans likely resulted from removal of certain PFASs from commercial products including paper and board used in food packaging. Increasing concentrations of long-chain PFCAs in most matrices, and in most regions, is likely due to increased use of alternative PFASs. Continued temporal trend monitoring in the environment with well-designed studies with high statistical power are necessary to evaluate the effectiveness of past and continuing regulatory mitigation measures. For humans, more temporal trend studies are needed in regions where manufacturing is most intense, as the one human study available in China is much different than in North America or Europe.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review finds that human concentrations of PFOS, PFDS, and PFOA generally declined after phase-outs, while PFHxS increases have begun to level off and longer-chain PFCAs generally increase or show insignificant trends. Environmental abiotic and biological samples show no clear global declines, with most trends insignificant and underpowered.

Key findings

  • Human PFOS, PFDS, and PFOA concentrations generally declined, and rapid declines were consistently observed for PFOS precursors such as FOSA; previously increasing PFHxS concentrations began to level off. In contrast, limited data from China indicated increasing human PFOS and PFOA, with >40% and >20% annual changes respectively in Shenyang serum.
  • Human concentrations of longer-chain PFCAs with 9–14 carbons generally increased or showed insignificant trends with too little power to detect a trend; no evidence supported significantly declining trends globally.
  • For abiotic and biological environmental samples, there were no clear patterns of declining trends; most substances showed mixed results, and a majority of trends were insignificant with low power. Some coastal surface waters showed significant PFOS and PFOA declines, while many sediment cores showed increasing trends.
  • The review included 92 articles and 227 time trend datasets, extracting data for 42 different PFASs or precursors; PFOS was the most frequently analyzed substance, followed by PFOA.

Methods

  • Systematic review with PICO elements: population/subject was abiotic and biological samples including general human populations; intervention was legislative or voluntary phase-out of long-chain PFASs starting in 2000; comparator was before intervention; outcome was change in concentrations of phased-out substances, precursors, and substitutes.
  • Searches were run in seven bibliographic databases and Google Scholar, plus grey literature, specialist websites, and stakeholder contacts; searches had no time, document type, language, or geographical constraints, but articles in languages other than English, French, German, and Scandinavian languages were excluded during screening. Searches identified 10,170 unique records; 564 were screened at full text; after critical appraisal and removal of redundant articles, 92 articles remained, yielding 227 time trend datasets.
  • Two reviewers screened all articles, with 10% double-screened at title/abstract and full-text levels and kappa tests for consistency; four reviewers critically appraised studies, with 20% double-checked. Meta-analysis was judged inappropriate due to heterogeneity, so results were narratively synthesized and independently reanalyzed using log-linear regression and change-point detection, with statistical power assessed for detecting a 10% annual trend.

Limitations

  • The paper states that searches used a limited number of languages and specialist websites in a limited number of countries, so evidence may have been overlooked, especially from Asia and the southern hemisphere; all identified grey literature was excluded during critical appraisal due to lack of methodological detail. The evidence base itself is limited in Asia and the southern hemisphere, has little data on alternatives to phased-out long-chain PFCAs and PFSAs, and many studies have low power to detect trends due to short study periods and low sampling frequency.
  • The paper also states that different authors used different statistical methods, making trends difficult to compare; there is no proper baseline throughout study periods, so only before-and-after comparisons are possible, not what would have happened without intervention. The review lacked quantitative synthesis because meta-analysis was not feasible.
  • Evident from the text: many extracted datasets were not independent (e.g., same individuals or overlapping studies), and the review’s independent reanalyses sometimes diverged from original authors’ reported trends, illustrating sensitivity to statistical method choice.

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Integrity signals

Registry

Crossref · 10.1186/s13750-017-0114-y

Cites

140 of 140 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

106 Not checked yet · 51 No basis given · 50 Own interpretation · 49 Own result · 26 Own method

Verify all 99 references — free account

Show all 135 claims

  • The quote only partly states this claim. 2
  • It may state two separate claims as one. 96
  • Probably not a substantial claim. 67
147 of 147
  • The authors state this as an assumption.

    The effect of phase-outs on PFAS concentrations will be smaller in regions close to present sources than in regions close to past sources where interventions have been implemented.

    “Since the interventions are not yet implemented globally, it is reasonable to assume that the effect will be smaller in regions close to present sources compared to regions close to past sources where the interventions have been implemented.”
  • The authors state this as an assumption.

    There is a time lag between phase-out interventions and measurable effects on PFAS concentrations in the environment.

    “It is reasonable to assume that there is a time lag between the interventions and any measurable effects in the environment.”
  • The paper relies on this without support.

    The relative importance of direct and indirect sources of PFCAs to the environment is temporally variable, specific to each substance, and not well quantified.

    “Overall, the direct and indirect sources (i.e.precursor degradation) of PFCAs to the environment are various, and the relative importance of each source is temporally variable, specific to each substance and not well quantified.”
  • The paper relies on this without support.

    Plasma and serum are equivalent matrices for monitoring time trends of PFASs.

    “Plasma and serum are considered equivalent matrices for monitoring time trends of PFASs.”
  • The paper relies on this without support.

    The 3M Co. phase-out of PFOS and related chemicals occurred by 2002.

    “Overall, the declining trends for PFOS generally coincide with the timing of the 3M Co. phase out by 2002.”
    “Overall, most temporal data for PFOS precursors in human samples show declining concentrations consistent with the time of the 3M Co. phase-out of these chemicals by 2002.”
  • The paper relies on this without support.

    Temporal trends in PFAS concentrations can be used to assess the effect of phasing out long-chain PFASs.

    “Thus, PFOS concentrations do not yet appear to be declining on a global scale after the phase outs.”
  • The paper relies on this without support.

    The change point analysis method used in this review is valid for detecting changes in temporal trends.

    “For PFOS in abiotic samples, change points were detected in a snow core sampled in Tibet [38] and in three sediment cores sampled in Canada in two separate studies [93] (Fig. 8).”
  • The paper relies on this without support.

    The included studies' temporal trend data are comparable across studies and can be synthesized.

    “This illustrates the difficulties in choosing proper statistical methods in temporal trend studies that make it possible to compare the results of different studies.”
  • The paper relies on this without support.

    The phase-out of long-chain PFASs is the main driver of observed temporal trends in PFAS concentrations.

    “Thus, PFOS concentrations do not yet appear to be declining on a global scale after the phase outs.”
  • The paper relies on this without support.

    Different PFASs have different production histories and properties.

    “different PFASs have different production histories and properties.”
  • The paper relies on this without support.

    The phase-outs and regulations have not been implemented in China, but the production of these substances has rather increased during recent years.

    “The phase-outs and regulations have not been implemented in China, but the production of these substances has rather increased during recent years”
  • The paper relies on this without support.

    Production of PFASs has been picked up in regions with weaker voluntary phase-outs and regulations.

    “production of PFASs has been picked up in regions with weaker voluntary phase-outs and regulations”
  • The paper relies on this without support.

    Due to very limited degradation of PFAS in the environment, ecosystems continue to be exposed to PFASs already released.

    “due to the very limited degradation of PFAS in the environment, ecosystems continue to be exposed to PFASs already released”
  • The paper relies on this without support.

    The stewardship program consisted of gradual phase-outs until 2015.

    “the stewardship program consisted of gradual phase-outs until 2015”
  • The paper relies on this without support.

    The interventions are widely implemented and potentially have a global impact.

    “the interventions are widely implemented and potentially have a global impact”
15 of 15

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Each contradiction between two passages listed here was confirmed by an independent check.

5 of 5

Citations

Cites

Research works printed but not linked: 11

  1. Kissa E. Fluorinated surfactants and repellents, vol. 97. 2nd ed. New York: Marcel Dekker, Inc.; 2001.
  2. Smart BE, Dixon DA. Bond-energies and stabilities of poly(perfluoroethers). In: Abstracts of papers of the American chemical society, vol. 207. 1994. p 31–FLUO.
  3. Land M, de Wit CA, Cousins IT, Herzke D, Johansson J, Martin JW. What is the effect of phasing out long-chain per- and polyfluoroalkyl substances on the concentrations of perfluoroalkyl acids and their precursors in the enironment? A systematic review protocol. Environ Evid. 2015;4(3):1–13.
  4. EFSA. Opinion of the scientific panel on contaminants in the food chain on perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts. EFSA J. 2008;653:1–131.
  5. 3M. Letter to US EPA Re phase-out plan for POSF-based products (226-0600). US EPA Admin Record. 2000;226:1–11.
  6. Ritter S. Fluorochemicals go short. Chem Eng News. 2010;88:12–7.
  7. Johansson JH. Sources, transport and fate of perfluoroalkyl acids in the atmosphere. PhD thesis. Stockholm: Stockholm University; 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-142116. ISBN 978-91-7649-700-5.
  8. Hu JY, Yu J, Tanaka S, Fujii S. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in water Environment of Singapore. Water Air Soil Pollut. 2011;216(1–4):179–91.
  9. Sturludottir E, Gunnlaugsdottir H, Nielsen OK, Stefansson G. Detection of a change-point, a mean-shift accompanied with a trend change, in short time-series with autocorrelation. In: Statistical analysis of trends in data from ecological monitoring (PhD thesis). School of Engineering and Natural Sciences, Faculty of Physical Sciences, Reykjavik; 2015.
  10. Petreas M, Park JS, Wang M, Wang Y, Guo W, Tarrant D, Rhee A, Harwani S. The california biomonitoring program: persistent organic pollutants in archived and contemporary serum. Glob Nest J. 2012;14(1):80–5.
  11. AMAP. Assessment 2015: temporal trends in persistent organic pollutants in the Arctic. Oslo: Arctic Monitoring and Assessment Programme; 2016.

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Metadata

Authors
Land, M., de Wit, C. A., Bignert, A., Cousins, I. T., Herzke, D., Johansson, J. H., & Martin, J. W.
Affiliations
  • Stockholm Environment Institute (SE)
  • Swedish Museum of Natural History (SE)
  • Stockholm University (SE)
  • The FRAM Centre (NO)
  • University of Alberta (CA)
Corresponding author
Land, Magnus
Venue
Environmental Evidence
Published
2018-01-22
Volume
7
Issue
1
ISSN
2047-2382 (ISSN-L)
OpenAlex
W4210977565
Cited by
219
References
141
Citations by year
2026: 14 · 2025: 29 · 2024: 31 · 2023: 27 · 2022: 40 · 2021: 31 · 2020: 31 · 2019: 13 · 2018: 3
FWCI
1.65
Type
journal article
Language
en
Open access
Locations
  • Environmental Evidence (publishedVersion, cc-by)
  • DiVA (Linkoping University) (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
Funders
  • Stiftelsen för Miljöstrategisk Forskning
  • University of Alberta
  • Stockholms Universitet
Topics
  • Physical Sciences › Environmental Science › Environmental Chemistry › Per- and polyfluoroalkyl substances research
  • Physical Sciences › Chemistry › Organic Chemistry › Fluorine in Organic Chemistry
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Toxic Organic Pollutants Impact
Keywords
per- and polyfluoroalkyl substances, PFAS regulation, PFOS, perfluorooctanoic acid, PFHxS, perfluorooctane sulfonamide, perfluorinated carboxylic acids, temporal trends, human exposure, environmental concentrations, PFAS emissions

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