Heavy metals and per- and polyfluoroalkyl substances in breast milk: associations with infant birth outcomes in an E-waste recycling area.

Many environmental pollutants are released during the dismantling of electronic waste (e-waste). Per- and polyfluoroalkyl substances (PFAS) and heavy metals are representative pollutants of persistent and hazardous contaminants that are known to pose threats to human health. In an e-waste dismantling area, 149 mothers with singleton births and their infants were recruited in 2021 to investigate associations between heavy metals and PFAS concentrations in postpartum breast milk and infant birth outcomes. The concentrations of six heavy metals and six PFAS compounds were measured in breast milk. The median concentration of chromium (Cr) in breast milk was 1.27 μg/L, whereas the median perfluorooctanoic acid (PFOA) concentration was 0.28 ng/mL. Birth weight and length were recorded and were subsequently used in stratified analyses via multiple regression models. Exploratory evidence suggests that higher log-transformed Cr (β = 0.371, 95% CI: 0.082-0.660) and PFOA (β = 0.163, 95% CI: 0.009-0.317) concentrations in breast milk were associated with greater birth length among female infants. These findings suggest that concentrations of Cr and PFOA in breast milk are associated with sex-specific infant growth patterns. Furthermore, quantile g-computation analyses did not identify any statistically significant mixture effects. However, the cross-sectional design and the sample size both limit the interpretation of these results. Therefore, the findings should be interpreted with caution. Larger longitudinal studies are needed to confirm these findings and to clarify their potential biological and health implications.