The presence of PFOS, the so-called forever chemicals that find use in critical applications like nonstick cookware and fire fighting chemicals, are finally being noted as improved quantification methods become available. This study is perhaps the first of its kind quantifying both the presence the persistence of PFOS in the human body. This is no measure of the harm it may be causing to Australian firefighters, but it poses the giant question of whether firefighter pay sufficiently covers their service as guinea pigs in toxicology studies of new chemicals.
Elevated levels of perfluorooctane sulfonate (PFOS) and elevated detection frequency of chloro-substituted PFOS have been reported in Australian firefighters with historical exposure to aqueous-film forming foam (AFFF). The aim of this study is to estimate the apparent half-lives of Cl–PFOS and PFOS isomers in firefighters following the end of exposure to 3M-AFFF. Paired serum samples from 120 firefighters, collected approximately five years apart, were analyzed for 8-Cl–PFOS (8-chloroperfluoro-1-octanesulfonic acid) and PFOS isomers via targeted LC–MS/MS. Apparent half-life was estimated by assuming a first order-elimination model. Cl–PFOS was detected in 93% of all initial serum samples (<LOQ–1.09 ng/mL). The average half-life of Cl–PFOS among the firefighters was 5.0 years. Branched PFOS isomers made up 55% of the total isomer concentration at the initial sampling timepoint. Five years later, the proportion of branched PFOS isomers was greater (65%). The longest average half-life (11.5 years) was estimated for “1m-PFOS”. Other isomers had average half-lives ranging from 4.0 to 7.5 years. Marked differences in half-lives between PFOS isomers suggest that the elimination rate of “total PFOS” (sum of all PFOS isomers) is non-linear. This is the first study to report the serum concentrations and apparent half-life of Cl–PFOS in humans.