Be Aware of Organophosphate Diesters as Direct Sources in Addition to Organophosphate Ester Metabolites in Food Supplies

The substantial application of organophosphate triesters (tri-OPEs) may lead to a concentration escalation of their major metabolites, organophosphate diesters (di-OPEs) in animal-derived and plant-derived animal protein supplement feeds (APFs). APFs are major food for raised animals and may bring OPEs into the food supply. In the present study, the concentrations of Σ8di-OPEs in animal-derived and plant-derived APFs were in the range of 1.98–182 ng/g dw (average: 39.2 ng/g dw). Meat meal had the highest average concentrations of di-OPEs (52.1 ng/g dw), followed by blood meal (49.9 ng/g), feather meal (23.3 ng/g dw), and plant-derived feeds (18.3 ng/g dw). The concentrations of di-OPEs were at the same order of magnitude as those of tri-OPEs in APFs. Bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) was the major contributor in blood meal, feather meal, and plant-derived APFs, while dimethyl phosphate dominated in meat meal. The ratios of di-OPEs/tri-OPEs (Rdi/tri) displayed large variability, ranging from 0 for the bis(2-chloroethyl) phosphate–tris(2-chloroethyl) phosphate pair to 175 for the BDCIPP–tris(1,3-dichloroisopropyl) phosphate pair, which indicated that the metabolism capacities and environmental sources for di-OPEs are diverse in APFs. Different Rdi/tri between APFs and similar food matrices implied that di-OPEs may have different environmental sources. The similar Rdi/tri values for some of the di-/tri-OPE pairs among APFs and dust samples indicated that dust may be a direct exogenous source of OPE exposure in some APF matrices. Future studies should simultaneously focus on tri- and di-OPEs, together of which may reflect the actual exposure to OPEs through the food supply.