Temporal trends and determinants of serum concentrations of per- and polyfluoroalkyl substances among Northern California mothers with a young child, 2009-2016.

•PFOA, PFOS, PFHxS, and Me-FOSAA monotonically decreased during the study period.•PFNA, PFDeA and PFUA exhibited mixed trends.•Breastfeeding contributed to the elimination of the common PFAS in lactating mothers.•Our study participants had lower PFAS serum concentrations than NHANES participants.