Integrated Biomonitoring of Organophosphate Mixtures Reveals Food-Driven Exposure and Hormetic Oxidative Responses in Urban Adults

Dietary exposure to organophosphate (OP) pesticides remains a growing concern in urban environments. In this study, six urinary OP metabolites and four oxidative stress biomarkers (OSBs) were quantified in a cohort of urban Chinese adults. Dimethylthiophosphate (DMTP), diethyl phosphate (DEP), and dimethyl phosphate were detected in nearly all individuals, with DMTP exhibiting the highest mean concentration (6.18 ng/mL). Multivariate analysis identified pork and poultry as primary dietary contributors, collectively explaining over 36% of variability in urinary OP metabolites, while processed food intake was positively associated with dimethyldithiophosphate (DMDTP) and diethyldithiophosphate, consistent with OP residues, preformed dialkyl phosphates (DAPs), and organophosphate esters in packaged products. Reverse dosimetry of urinary DAPs indicated that phorate and dimethoate were major contributors to estimated daily intake, with hazard quotients exceeding 1 in certain individuals. Multiple mixture models revealed significant inverse and nonlinear associations between OP mixtures and OSBs, particularly 8-hydroxy-2'-deoxyguanosine and o,o'-dityrosine, suggesting a potential low-dose hormetic response and adaptive oxidative stress mechanisms. DMDTP and DEP emerged as key drivers across the models. Collectively, these findings provide integrative evidence linking specific dietary OP sources to systemic oxidative stress in nonoccupational populations, highlighting complex exposure-response dynamics and the need for targeted dietary risk management and biomonitoring.