Beyond static loading: a dynamic, multifactorial assessment of dermal exposure to organophosphate esters

Dermal contact is a significant yet underexplored pathway for human exposure to organophosphate esters (OPEs). This study provides a multifactorial assessment of dermal OPE exposure across participants aged 2 - 78 years by analyzing 29 OPEs in skin wipes from four body sites and personal smartphones. Results showed that directly exposed skin areas (hands, forehead, forearms) (range: below method detection limit (2) had significantly higher loads than clothed areas (back) (range: 2). Children aged 2 - 6 years exhibited the highest dermal burden. A strong positive correlation linked skin OPE levels to those on smartphones, identifying phones as a key interface for OPE transfer to skin. Outdoor activity and lower body mass index (BMI) were associated with higher dermal loads, while exercise-induced sweating promoted OPE transfer to the skin surface. Calculated daily intake via dermal absorption was highest in young children (the total dermal exposure of OPEs: 3295 pg/kg bw/day), significantly exceeding that of older children and adults (837 - 1679 pg/kg bw/day). Although subsequent risk assessment indicated low carcinogenic and non-carcinogenic risks under current guidelines, the elevated exposure in vulnerable groups underscores the need for precautionary measures. These findings reveal dermal OPE exposure as a dynamic process shaped by behavior, physiology, and personal item use.