Determinants of Serum PFAS Concentrations in Canadian Children: Prenatal Exposure, Breastfeeding, and Temporal Trends in the MIREC Cohort

Abstract

Per- and polyfluoroalkyl substance (PFAS) exposure is widespread among Canadian children, yet determinants of exposure remain incompletely understood. We identified determinants of serum PFAS concentrations in Canadian children, focusing on temporal trends, maternal PFAS concentrations, sociodemographic factors, and breastfeeding-related exposures. We measured serum concentrations of 9 PFAS in 204 children aged 7–11 years from the 2018–2021 follow-up of the Maternal-Infant Research on Environmental Chemicals (MIREC) study. Analyses focused on 5 PFAS detected in >50% of children (PFOA, PFOS, PFHxS, PFNA, PFDA) and their sum (ΣPFAS). Pearson correlations assessed associations with maternal blood and breastmilk PFAS concentrations. Bivariate and multivariable linear regressions estimated percent differences in child PFAS according to potential determinants. Children’s serum PFAS concentrations were moderately correlated with maternal PFAS measured prenatally and at follow-up, strongest for PFHxS (r=0.55–0.58). In multivariable models, child PFAS declined 8–19% per year of sample collection. A 2-fold increase in maternal plasma PFAS concentrations during pregnancy predicted 7–31% higher child PFAS. Higher concentrations were observed among children of mothers with a graduate degree (14–28% higher PFOA, PFOS, PFDA, ΣPFAS), and among those ≤30 years (26% higher PFDA). Children in the highest tertile of PFAS cumulative intake from breastmilk had 13–26% higher PFOA, PFOS, and ΣPFAS. Those breastfed >12 months had 37% higher PFDA than those breastfed <6 months. Child sex, age, birth order, maternal race, and household income were not associated. Prenatal PFAS exposure, maternal sociodemographic characteristics, breastfeeding, and sampling year are key determinants of PFAS body burden in Canadian children.