Comprehensive investigation on organophosphate esters and their metabolites in human milk from China: Occurrence, profile, and health risk assessment.

The contamination of organophosphate esters (OPEs) has increased sharply in China due to the regulation of brominated flame retardants (BFRs) in recent years; however, data on their occurrence in humans are limited. In this study, fourteen OPEs and ten of their metabolites (mOPEs) were measured in pooled human milk samples collected across China between 2016 and 2019. Both OPEs and mOPEs were ubiquitous in the tested 100 samples, with median levels of 2.2 and 1.05 ng/mL, respectively. OPE levels had significantly surpassed those of brominated flame retardants (BFRs) in the tested samples, indicating that the consumption pattern of flame retardants in China has shifted from BFRs to OPEs. The significant correlations between some mOPEs and their parent OPEs, and the relative abundance of mOPEs, suggested that certain OPEs were inclined to transform to mOPEs, while a portion of mOPEs may directly originate from external exposure. The present human milk survey was conducted at the same time and site as the 6th China total diet study, and the intakes of some OPEs through food consumption among lactating women were significantly and positively correlated with their concentrations in human milk, indicating that food consumption might be a main pathway for human exposure to OPEs. The estimated daily intakes (EDI) of OPEs/mOPEs via breastfeeding for the Chinese infants were calculated. Under medium exposure, the EDIs of ∑14OPEs/∑10mOPEs for infants aged 0-6 months, 7-12 months, and 13-24 months were 325/148, 197/89.7, and 139/63.4 ng/kg bw/day, respectively, and the daily intake of OPEs/mOPEs via breastfeeding might not cause significant health risks. However, since most OPEs and all mOPEs lack RfD due to limited toxicology data, the health risks posed by exposure to both OPEs and mOPEs should be continually evaluated.