Occurrence of Multiple Classes of Emerging Synthetic Antioxidants, Including p-Phenylenediamines, Diphenylamines, Naphthylamines, Macromolecular Hindered Phenols, and Organophosphites, in Human Milk: Implications for Infant Exposure

Synthetic antioxidants (AOs) have received increasing attention in recent years due to their environmental ubiquity. However, lactational exposure to these emerging contaminants of current concern remains unknown. In this study, 21 amine antioxidants, 18 macromolecular hindered phenol antioxidants, 3 organophosphite antioxidants, and 2 p-phenylenediamine-derived quinones (PPD-Qs) were integrated into a dedicated screening in human milk from South China. Among all 42 target AOs, 19 were detected, but no PPD-Qs were detected in any of the samples. Eight AOs, including N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), were frequently detected in more than half of the samples. The summed concentrations of all detectable AOs in human milk ranged from 133 to 7,560 pg/mL, with a median of 713 pg/mL. Significant correlations were observed among the concentrations of amine and phenol antioxidants. The preliminary risk assessment revealed that under the high exposure scenario, the overall daily intake of all identified AOs through breastfeeding might pose a non-negligible health risk to newborns. This study is the first to attempt to comprehensively identify a wide range of emerging AOs prevalent in human milk. The findings call for urgent concern for infant exposure to these widely used but less well evaluated chemicals and a possible increased accumulative risk in the future.