Per- and polyfluoroalkyl substances in agricultural systems: Human dietary exposure via beef raised on corn stover from a field with contaminated biosolids.

Abstract

Per- and polyfluoroalkyl substances (PFAS) in biosolid-amended soils can transfer and accumulate in crops, cattle, and people. Bioaccumulation factors (BAFs) are often applied to estimate the transfer of contaminants from soil to crops. However, they can vary widely and introduce uncertainty to exposure and risk estimates. We, therefore, aimed to quantify this uncertainty in a case study of an agricultural field with elevated soil concentrations of perfluorooctane sulfonic acid (PFOS) using literature-derived BAF versus measured concentrations of PFOS in corn (Zea mays L.) kernels and stover. PFOS was the predominant PFAS detected in soil and corn stover (<100 and 19 ng/g), and no detectable PFAS were identified in kernels. The median BAF (0.17) for PFOS was similar to that derived from a review of previous studies, while the maximum (0.2) was over an order of magnitude lower. Median PFOS concentrations in stover from our samples were comparable (16.60 ng/g) to those calculated using the literature-based BAF (16.28 ng/g). For cattle consuming stover, median and upper bound concentrations of PFOS in beef (30 ng/g) were similar and 60% lower using measured versus literature-derived BAF concentrations in stover. Finally, the central tendency exposure for children (27 ng/kg-bw/day) was similar using measured versus literature-derived BAF concentrations in stover and higher compared to adults (15 ng/kg-bw/day). Overall, these results indicate that (1) corn kernels accumulate little to no PFAS even when soil concentrations are elevated, (2) direct measurement of PFAS in crops can reduce uncertainty in exposure and risk assessment, and (3) PFOS can biomagnify via the soil-stover-cattle-human pathway and is found to pose a potential risk in our case study.