Review on age-specific exposure to organophosphate esters: Multiple exposure pathways and microenvironments

Organophosphate esters (OPEs) widely exist in the environment, raising increasing concerns about their potential health risks. This comprehensive review surveyed the occurrence of OPEs over the last decade in indoor microenvironments (i.e. residence, in-vehicle, office, and school/daycare center), outdoors, foodstuffs, drinking water, and human-related specimen (i.e. breast milk and urine) with a view to unraveling age-specific exposure to OPEs. Multiple exposure pathways including inhalation, dermal absorption, dust ingestion, and dietary ingestion were considered to prioritize their relative importance. The results showed that dietary ingestion was the main contributor, followed by dust ingestion, regardless of age. A healthy diet with less contaminated food can effectively reduce OPE intake. OPE concentrations in air and dust followed the sequence of in-vehicle and office > school/daycare center > residence > outdoors. Compared to other indoor settings, exposure in schools/daycare centers and offices contributed to a greater OPE intake in non-adults and adults, respectively. The estimated daily intake of OPEs followed the sequence of infants > toddlers > children > teenagers > adults > elderlies. Overall, OPEs posed low health risks to all age cohorts, but infants were vulnerable and subject to the highest risk, largely attributed to breast milk ingestion. This review highlights the need for more toxicity and bioaccessibility studies on OPE mixtures and metabolites to further refine the health risk assessment of OPEs.