Is Indirect Exposure a Significant Contributor to the Burden of Perfluorinated Acids Observed in Humans?

Abstract

In comparison to other persistent organic pollutants, human fluorochemical contamination is relatively complicated. This complication arises at least in part from a disparity between the chemicals used commercially and those measured in the environment and humans. Commercial fluorochemical products are dominated by fluorinated polymers used in textile or carpet applications, or fluorosurfactants used in applications ranging from personal care products, leveling and wetting agents, to greaseproofing food-contact materials. Investigations into environmental and human fluorochemical contamination have focused on perfluorinated acids (PFAs), either the perfluorinated carboxylates (PFCAs) or sulfonates (PFSAs). In this review we will present an overview of data related to human fluorochemical exposure including a discussion of fluorochemical production, concentrations in exposure media, biotransformation processes producing PFAs, and trends in human sera. These data will be presented in the context of how they can inform sources of human PFA contamination, specifically whether the contamination results from direct PFA exposure or indirect exposure via the biotransformation of commercial fluorochemicals or their residuals. Concentrations of both perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) began to decrease in human sera around the year 2000, a change that mirrored the 2000-2002 phase-out of perfluorooctane sulfonyl fluoride (POSF) production. These temporal trends suggest exposure to current-use POSF-based materials was a significant source of PFOA and PFOS exposure prior to 2000. Relatively slow PFOA elimination and increasing concentrations of the C9 and C10 PFCAs in human sera suggest continued PFCA exposure, without similar exposure to PFOS, which is consistent with indirect exposure via the biotransformation of fluorotelomer-based materials. Conversely, human exposure models have suggested direct exposure to PFAs present in food items is the major source of human contamination. The data set presented here cannot unequivocally delineate between direct and indirect human exposure, however temporal trends in human sera and exposure media are consistent with indirect exposure representing a significant portion of observed human PFA contamination.

Biotransformation of 8:2 fluorotelomer alcohol by recombinant human cytochrome P450s, human liver microsomes and human liver cytosol

“…45,47 People with a higher expression of CYP2C19 may produce higher levels of 8:2 FTAL and thereby, yield more downstream PFAAs and induce higher health risk. Additionally, D'Eon et al 2 found that the elimination half-life of PFOA aer the ECF phase out in 2000-2002 was longer than that in Olsen's results 48 and implicated that 8:2 FTOH metabolism may be of signicance for PFOA exposure. However, some other studies claimed that 8:2 FTOH metabolism has a minimal contribution.…”

Per- and polyfluorinated substances (PFASs): Environmental challenges

“…For the general population the major source of contamination arises from food and sometimes drinking water (> 90%) [35,58,61,70,71,[148][149][150][151][152][153]. PFOS is generally the most abundant PFAS found in humans, the second usually being PFOA, and PFHxS the third [70].…”

Identification, Tissue Distribution, and Bioaccumulation Potential of Cyclic Perfluorinated Sulfonic Acids Isomers in an Airport Impacted Ecosystem

“…Although the mean BAF whole-body values in Crucian carp did not exceed common regulatory criteria for bioaccumulative substances, it has previously been shown that elimination half-lives in humans for perfluoroalkyl acids are not always correlated to bioaccumulation factors in fish due to differences in elimination mechanisms. 48 For instance, PFOA and PFHxS have been found to have long elimination half-lives in humans (3.5 and 7.2 years respectively) 54 despite that they have low BAFs in the fish. Considering the current efforts to investigate PFAS contamination around airports we believe that inclusion of cyclic PFASs in the list of analytes is needed to better characterize human exposure to PFASs and help to close the mass-balance of organofluorine compounds.…”