Serum concentrations of selected perfluoroalkyl substances for US females compared to males as they age.

Gender-age specific linear statistical models were fitted to analyze gender-based differences in serum concentrations of PFOA, PFNA, PFHxS, and PFOS for US adults and adolescents (N = 17,932) and children age < 12 years (N = 637) using nationally representative data for US for 2003-2018. Around the age of about 11-12 years for PFOS, PFNA, and PFNA, and around 15 years for PFOA, females begin to have reliably lower serum PFAS than males. This divergence is maximized around the ages of about 35 to 40 years for the alkylate compounds PFOA and PFNA, and from around 24-52 years for the sulfonate compounds PFOS and PFHxS. For example, for PFOS, gender divergence was 1.15 ng/mL at age 15, compared to 5.6 ng/mL at the age of 37 years. Uniquely, PFOS remained lower in females in most years after age 56, a contrast to the convergence in other PFAS studied. For males, increasing patterns were followed by somewhat decreasing patterns of concentration for most PFAS, the reverse was observed for females. The findings have implications for study design. Based on the results provided in detailed tables and figures for this study, we recommend separate analyses of male and female data. In addition, female serum concentration data should be considered for stratified analysis for pre- and post-menopausal time periods. From a mechanistic perspective, the data add support to existing questions about influences on gender differences in serum PFAS that may be attributed to causes other than menstruation, pregnancy, and lactation. These are amenable to further study.