Part II. A temporal study of PFOS and its precursors in human plasma from two German cities in 1982-2009

A total of 420 human plasma from two cities (Halle and Münster, Germany) collected between 1982 and 2009, were analyzed for a suite of PFSAs (C4, C6, C8, C10) and selected PFOS precursors (MeFOSAA, EtFOSAA, FOSAA, di-SAmPAP). Among these target analytes, only di-SAmPAP was used in consumer products. PFSAs (C6 and C8), MeFOSAA, EtFOSAA, and FOSAA were detected in over 95% of the samples (<0.0011-116.0 ng/mL), PFDS was detected in approximately 40% of the samples (<0.005-0.0998 ng/mL), and di-SAmPAP was detected in 17% of the samples (<0.005-0.0137 ng/mL). Significant positive correlations were found between PFOS and PFHxS, MeFOSAA, EtFOSAA, and FOSAA. Temporal trends of decreasing concentration were identified for PFOS, MeFOSAA, EtFOSAA, and FOSAA, but not for PFHxS. Di-SAmPAP, a common food-contact paper surfactant and expected PFOS precursor, was detected infrequently (25% in samples prior to 2000) in samples before 2006. Population halving times of PFOS, MeFOSAA, EtFOSAA, and FOSAA were estimated. The observed reduction of these chemicals over time in human plasma is presumably related to the phase-out of POSF-based products beginning in 2000. The detection of di-SAmPAP in human sera is significant because this chemical is expected to be metabolized or degraded to PFOS in humans and the environment. Our detection of di-SAmPAP is the first confirmation of human exposure to this commercially available product which is a plausible source of PFOS in humans.