Evaluation of a mother–child dyad toxicokinetic model paired with environmental doses for estimation of serum per- and polyfluoroalkyl substances in early life

Contact-based exposure estimation paired with empirically evaluated toxicokinetic (TK) modeling can complement direct measurements of serum concentrations for characterizing individual exposures and provide a proxy for risk assessment. This study examined whether a mother-child dyad TK model paired with PFAS exposure estimates provide reasonable predictions of serum PFAS concentrations for children. A previously published mother-child dyad TK model was used to estimate the child serum concentrations. We modified the model by updating with recent TK parameter estimates. Background intake rates via food, indoor dust, and indoor air were from published studies. Estimation of child serum PFOA concentrations in PFOA-contaminated regions additionally considered exposure to contaminated drinking water and outdoor air. TK-modeled serum concentrations were then compared with measured serum concentrations from child cohorts for four PFAS (PFOA, PFOS, PFHxS, and PFNA) from other published studies. Individual serum PFOA measurements from the C8 Health Study were compared with modeled serum concentrations using the modified and other published TK models. Modeled child PFAS serum concentrations using the modified dyad TK model were in good accordance with measured serum concentrations. The median model predictions of serum PFOA were highly correlated with the median of measured values and the percentage of TK-modeled serum PFOA within 2-fold and 10-fold of measured values was 34% and 94%, respectively, which was similar or higher than the estimates from the other TK models. The modified dyad TK model can provide reasonable estimates of dynamic serum PFAS concentrations for children when only environmental doses are available.