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 protocol

Abstract

Background: There is a growing concern in Sweden and elsewhere that continued emissions of per-and polyfluoroalkyl substances (PFASs) may cause environmental as well as human health effects. PFASs are a broad class of man-made substances that have been produced and used in both commercial products and industrial processes for more than 60 years. Although the production and use of some PFASs has been phased-out in some parts of the world, it is not known what effect these actions to date have had on PFAS concentrations in the environment. Owing to the wide diversity of PFASs, it is difficult to generalize their properties, environmental fate and production histories. However, the strength and stability of the C-F bond renders the perfluoroalkyl moieties resistant to heat and environmental degradation. Several PFASs are now occurring even in very remote areas in large parts of the world, but the environmental transport and fate of substances within this group is not well understood. A systematic review may be able to determine whether the concentrations of these substances in different environments are changing in any particular direction with time, and whether the phase-outs have had any effects on the concentration trends. Methods: Searches for primary research studies reporting on temporal variations of PFAS concentrations in the environment will be performed in the scientific literature as well as in other reports. Relevant samples include both abiotic and biological samples including humans. No particular time, document type, language or geographical constraints will be applied. Two authors will screen all retrieved articles. Double screening of about 10% of the articles will be performed by all authors at both title/abstract and full-text levels. Kappa tests will be used to test if the screening is consistent. Relevant articles will be critically appraised by four authors (double checking of 25% of the articles). Quality assessment will focus on selection bias, dating of samples, sample integrity and analytical procedures. Data synthesis will be based on statistical analysis of temporal concentration trends.

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

“…This relative trend was similar to what was observed in Norwegian males, where a significant change-point was observed in 1993 [92]. The shape of these two human temporal trends [92,137] closely mirrors the trend in annual production volumes of PFOS reported by Paul et al [5] and as plotted in our associated review protocol [9]. Three datasets from Swedish dietary items [99] were also analyzed for change points, but no change points were detected.…”

“…In contrast to what was set out in the protocol [9], we chose not to perform meta-analyses. This is because there were too many sources of heterogeneity to allow for any meaningful meta-analysis.…”

“…In the review protocol [9] also food web changes over time were listed as an effect modifier, but information about that was not reported in any of the included studies so could not be evaluated in this review. Potential effect modifiers and reasons for heterogeneity were evaluated qualitatively by assigning the studies to different categories and assessing whether the results of a particular category deviated from the rest.…”

“…A list of abbreviations used in this review is provided in Additional file 1: List of abbreviations. A more detailed review of PFASs can be found in the protocol for this study [9].…”

Receptor research on xenohormone effects of human serum extracts containing the actual mixture of perfluorinated alkyl acids: a short review

“…In 2000, the PFAS manufacturer 3M started phasing out the production of C6, C8 and C10 PFAAs including PFOS and PFOA [18] . The compounds are however still detected in human serum.…”