Recent analyses of perfluorooctanoate (PFOA) in human blood sera show that the background-exposed population in industrialized countries worldwide exhibits a narrow concentration range; arithmetic means of published studies range between 2 and 8 microg/L PFOA, with the exception of a few outlier studies. The globally comparable human serum concentrations of PFOA and characteristic dominance of PFOA with respect to other perfluorocarboxylate (PFCA) homologues indicate that exposure pathways of humans differ from those of wildlife, where perfluorononanoate (PFNA) is often the dominant homologue. The observed correlations between perfluorooctane sulfonate (PFOS) and PFOA in human serum together with a simultaneous downward time trend of these compounds in human blood sera and blood spots from the year 2000 onward indicate a connection between historical perfluorooctanesulfonyl (POSF) production (phased out by the major manufacturer in 2000-2002) and exposure to both PFOS and PFOA. A comparison of estimated daily intakes to humans based on samples from exposure media (collected post 2000) indicates that food intake is the major contemporary exposure pathway for the background population, whereas drinking water exposure is dominant for populations near sources of contaminated drinking water. A one-compartment pharmacokinetic model used to back-calculate daily intakes from serum levels is shown to provide agreement within a factor of 1.5-5.5 of the daily intakes derived from exposure media, which provides further supporting evidence that dietary exposure is a major ongoing exposure pathway of PFOA to the background population.
ABSTRACT:The incomplete mass-balance of organic fluorine in human serum indicates the existence of unknown per-and polyfluoroalkyl substances (PFASs) with persistent and bioaccumulative properties. Here we characterized human exposure and elimination kinetics of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in metal plating workers (n = 19), high fish consumers (n = 45), and background controls (n = 8). Cl-PFESAs were detected in >98% of the sampled individuals with serum concentrations ranging <0.019−5040 ng/mL. Statistically higher median serum levels were observed in high fish consumers (93.7 ng/mL) and metal plating workers (51.5 ng/mL) compared to the background control group (4.78 ng/mL) (Kruskal−Wallis rank sum test, p < 0.01). Cl-PFESAs could account for 0.269 to 93.3% of ∑PFASs in human serum indicating that this compound class may explain a substantial fraction of previously unidentified organic fluorine in the Chinese population. Estimated half-lives for renal clearance (median 280 years; range 7.1−4230 years) and total elimination (median 15.3 years; range 10.1−56.4 years) for the eight carbon Cl-PFESA suggest that this is the most biopersistent PFAS in humans reported to date. The apparent ubiquitous distribution and slow elimination kinetics in humans underscore the need for more research and regulatory actions on Cl-PFESAs and PFAS alternatives with similar chemical structures.
Following
the global actions to phase out perfluoroctanesulfonic
acid (PFOS) a large number of alternative per- and polyfluoroalkyl
substances, with poorly defined hazard properties, are being used
in increasing quantities. Here, we report on the first detection of
the chlorinated polyfluoroalkyl ether sulfonic acid F-53B in biological
samples and determine the tissue distribution and whole body bioaccumulation
factors (BAFwhole body) in crucian carp (Carassius
carassius). Analysis of fish samples from Xiaoqing River
(XR) and Tangxun Lake (TL) demonstrated a similar level of F-53B contamination
with median concentrations in blood of 41.9 and 20.9 ng/g, respectively.
Tissue/blood ratios showed that distribution of F-53B primarily occurs
to the kidney (TL: 0.48, XR: 0.54), gonad (TL: 0.36, XR: 0.54), liver
(TL: 0.38, XR: 0.53), and heart (TL: 0.47, XR: 0.47). Median Log BAFwhole body values for F-53B (XR: 4.124, TL: 4.322) exceeded
regulatory bioaccumulation criterion and were significantly higher
than those of PFOS in the same data sets (XR: 3.430, TL: 3.279). On
the basis of its apparent omnipresence and strong bioaccumulation
propensity, it is hypothesized that F-53B could explain a significant
fraction of previously unidentified organofluorine in biological samples
from China, and regulatory actions for this compound are encouraged.
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