Serum half-life of PFOA after end of exposure: a highly exposed community in the Veneto Region

Background and aim. Perfluoroalkyl substances (PFAS) are widely used, ubiquitous and highly persistent man-made chemicals. Groundwater of a vast area of the Veneto Region (North-Eastern Italy) was found to be contaminated by PFAS from a manufacturing plant active since the late 1960s. As a result, residents were exposed to PFAS through drinking water until autumn 2013. The aim of the present study was to estimate the decline rates in serum PFAS, and their corresponding serum half-lives, while characterizing their determinants. Methods. The population investigated in this study is a subgroup of the Regional health surveillance program target population consisting of subjects who enrolled in the second surveillance wave (n=2,619). The two blood samples were collected between January 2017 and December 2021. Four of the twelve measured PFAS were detected in greater than 50% of participants: PFOA (100%), PFOS (99.89%), PFHxS (99.01%) and PFNA (61.82%). Serum PFAS excretion rates and half-lives were estimated based on linear mixed effect models, adjusting for a set of contributing factors on PFAS pharmacokinetics such as age, sex, BMI, smoke-habit and eGFR. Results. Median initial serum concentrations were 62.6 ng/mL for PFOA, (range:0.6-1064), 4.6 ng/mL (range:0.5-142) for PFOS, 4.9 ng/mL (range:0.5-109.2) for PFHxS and, 0.6 (range:0.5-0.8) PFNA, with median declines of 61.18%, 36.96%, 40.82% and 41.67%, respectively. The median estimated PFOA’s half-life was 2.90 years (95%CI:2.83-2.95). We found suggestive evidence that half-lives varied when stratified by gender and tertile of exposure, with more rapid elimination in men and higher tertiles of exposure. Conclusions. Drinking water was the dominant route of exposure for PFOA so this study, the largest on PFOA half-life, offers great potential for studying interactions and risk modifications. Other PFAS longer half-lives than reported in other studies might be due to ongoing exposure to PFAS via other routes. Keywords. perfluoroalkyl substances; contaminated water; half-life.