Organophosphate di-ester/tri-ester ratio as a novel interspecific metabolic biomarker: Dual sources and differential metabolism in terrestrial and aquatic organisms.

Organophosphate tri-esters (tri-OPEs) and their di-ester metabolites (di-OPEs) contaminate food chains, while di-OPEs also have independent industrial sources. Interspecific differences in tri-OPE metabolism and the utility of the di-OPE/tri-OPE ratio across terrestrial and aquatic organisms remain poorly understood. This study investigated 24 tri-OPEs and 6 di-OPEs in 240 animal-derived food samples (eggs, meat, fish, shrimp, and shellfish) collected from South China. Aryl tri-OPEs dominated in eggs and terrestrial meat, whereas di-OPEs prevailed in aquatic products. Two metabolite-parent pairs (DPHP/TPhP and BDCIPP/TDCIPP) exhibited striking interspecific ratio variations: eggs showed extremely low values of 2.00 and 0.15, indicating weak hepatic biotransformation and oviparous excretion in poultry; shellfish exhibited markedly higher ratios (23.09 and 2.51), reflecting efficient metabolic capacity of aquatic invertebrates. Source apportionment identified that contamination in meat primarily originated from feed and rearing environments, whereas aquatic products were mainly affected by wastewater, e-waste leachate, marine oils, and plastic degradation. Despite children exhibiting the highest exposure via egg consumption (total estimated daily intake: 12.8×10-3 μg/kg BW/day), probabilistic risk assessment (Monte Carlo simulation) confirmed negligible non-carcinogenic and carcinogenic risks for all populations. These findings clarify the dual sources of di-OPEs and highlight the di-OPE/tri-OPE ratio as a novel interspecific indicator, supporting food safety monitoring.