Occurrence and temporal trends of perfluoroalkyl acids (PFAAs) in occupational workers: Are the half-lives of PFHxS and PFOS shorter than expected?

Perfluorooctanesulfonate (PFOS) has been restricted by the Stockholm Convention, and the reported half-lives of perfluoroalkyl acids (PFAAs) based on human serum concentrations remained some controversial and ranged from... [ view full abstract ]

Perfluorooctanesulfonate (PFOS) has been restricted by the Stockholm Convention, and the reported half-lives of perfluoroalkyl acids (PFAAs) based on human serum concentrations remained some controversial and ranged from several days to decades. Paired serum and urine samples were collected from workers in a fluorochemical plant from 2008 to 2012 (n=302) to investigate the level, temporal trends, and half-lives of PFAAs in workers of a fluorochemical plant. High levels of perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), and PFOS appeared in serum with median concentrations of 764, 427, and 1725 ng mL-1, respectively. There were big difference of PFAAs levels among workers, and PFAA levels were influenced by work assignment and the length of service in the plant, and temporal trends of PFAAs in workers were closely related to the production structure. The elimination of PFAAs was considered to be a first-order model, and the half-lives of PFAAs in workers were estimated by clearance rates of PFAAs and longitudinal data in serum, respectively. The average estimated half-lives for PFHxS, PFOA, and PFOS were, respectively, 17.0 (95% confidence interval (CI), 13.0-20.9), 5.84(4.27-7.42), and 52.0(34.7-69.3) years by the clearance rates, and they were only 3.79(95% CI, 0.541–12.7), 1.68(1.02–1.88), and 1.94(1.70–2.44) years estimated by longitudinal data. The results indicated that there were other important elimination pathways of PFHxS and PFOS other than renal clearance. The half-lives estimated by longitudinal data were the shortest values ever reported, and the intrinsic half-lives might even shorter due to the high levels of ongoing exposure to PFAAs.