Abstract
After several decades of widespread use, some per- and polyfluoroalkyl substances (PFASs) were phased-out of use due to concerns raised by their persistent, bioaccumulative, and toxic properties. Our objective was to evaluate temporal trends in serum PFAS levels among 1257 middle-aged and older California women (ages 40-94) during a four year period, beginning approximately 5-10 years after these phase-outs began. An online SPE-HPLC-MS/MS was used to measure 10 long-chain PFASs in serum from blood collected cross-sectionally during 2011-2015 from a subset of participants in the California Teachers Study. Results from multivariable linear regression analyses indicated that serum concentrations of nearly all PFASs declined on average 10% to 20% per year. Serum levels of perfluorohexanesulfonic acid (PFHxS) did not significantly decline. With the exception of PFHxS, the downward trend in serum concentrations was evident for all PFASs across all ages, although declines were comparatively steeper among the oldest women. These findings suggest that the phase-out of some common PFASs has resulted in reduced human exposures to them. The lack of a decline for PFHxS suggests that these exposures may be ongoing and underscores the importance of continued biomonitoring and research efforts to elucidate current pathways of exposure.
Highlights
Sulfonic acids with 6 or more carbons (≥C6) and carboxylic acids with 7 or more carbons (≥C7), which are defined as long-chain perfluoroalkyl acids (PFAAs),[1] have been the target of most of the regulatory and voluntary measures implemented to date
Median serum levels were highest for perfluorooctanesulfonic acid (PFOS), followed by perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS)
PFOS was the predominant polyfluoroalkyl substances (PFASs), comprising, on average, approximately half of the total PFAS measured in sera, followed by PFOA, PFHxS, and PFNA
Summary
Per- and polyfluoroalkyl substances (PFASs) are a large group of synthetic fluorinated chemicals widely used in industrial processes and consumer products since the 1950s.1,2 Owing to their persistent and bioaccumulative properties, some of these compounds emerged during the 1990s as among the most pervasive global environmental contaminants[2−5] and biomonitoring data indicated evidence of human exposures.[6−8] Coupled with accumulating evidence of myriad toxic and potential adverse health effects,[2,9−16] regulatory restrictions and voluntary phase-outs of many of these compounds were enacted shortly after the beginning of the 21st century, internationally as well as within the United States.[2,13,17]Representing a broad class of chemicals, the PFASs encompass a large number of compounds with a diversity of chemical properties that determine their toxicity and their persistence.[1,18,19] manufacturing and use restrictions have been targeted at what are considered the most worrisome chemicals within the class of PFASs. Within the class of PFAAs, the longer chain compounds are more toxic and more resistant to chemical and biological degradation.[1,17] the perfluoroalkyl sulfonic acids (PFSAs), of which perfluorooctanesulfonic acid (PFOS) is the most well-studied, are comparatively more persistent than the perfluoroalkyl carboxylic acids (PFCAs),[17] of which perfluorooctanoic acid (PFOA) is the most notable For these reasons, sulfonic acids with 6 or more carbons (≥C6) and carboxylic acids with 7 or more carbons (≥C7), which are defined as long-chain PFAAs,[1] have been the target of most of the regulatory and voluntary measures implemented to date. In 2006, under the United States Environmental Protection Agency’s (US EPA) 2006 PFOA Stewardship Program, eight of the largest users and producers of PFOA committed to reduce global emissions and use of PFOA, its precursors, and other long chain PFAAs, by 95% by 2010 and completely eliminate them by 2015.23 Some companies reported reaching the complete elimination goal by 2013.24
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