Per- and polyfluoroalkyl substances (PFAS) exposure in the U.S. population: NHANES 1999-March 2020.

Per- and polyfluoroalkyl substances (PFAS), also known as "forever chemicals" because of their persistence in the environment, have been used in many commercial applications since the 1940s. Of late, the detection of PFAS in drinking water throughout the United States has raised public and scientific concerns. To understand PFAS exposure trends in the general U.S. population, we analyzed select PFAS serum concentration data from participants ≥12 years old of nine National Health and Nutrition Examination Survey (NHANES) cycles. Our goals were to a) evaluate concentration changes of four legacy PFAS-perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) from 1999 to 2000 to 2017-March 2020, b) discuss serum concentrations and assess demographic predictors of two PFAS measured for the first time in 2017-2018, perfluoro-1-heptanesulfonic acid (PFHpS) and 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9CLPF), and c) compare concentration profiles of legacy PFAS in NHANES to profiles in exposed communities. We report a decrease in geometric mean concentrations of the four legacy PFAS (16%-87%, depending on the PFAS) from 1999 to 2000, although in 2017-March 2020, more than 96% of people aged 12-19 years, some of whom were born after PFAS production changes started in the early 2000s, had measurable concentrations of these PFAS. An estimated 78% of the U.S. general population had detectable concentrations of PFHpS, and 8% had detectable concentrations of 9CLPF (>44% of whom self-identified as Asian). Comparing profiles in NHANES and people living in communities with PFAS contamination can help identify exposure sources and evaluate and monitor exposures in select areas or among specific population groups. Collectively, our findings highlight the usefulness of NHANES data to help researchers, public health officials, and policy makers prioritize investigations, monitor exposure changes, and evaluate effectiveness of efforts to limit exposures.