Deposition, bioaccumulation and depletion of organophosphate triesters (tri-OPEs) and their organophosphate diester metabolites (di-OPEs) from feed to laying hens’ eggs

Abstract

Although organophosphate triesters’ (tri-OPEs) large application and potential toxicity has aroused public concern of human dietary exposure, no study has evaluated their deposition, bioaccumulation and depletion in farm animals yet, limiting our understanding about their behavior and further regulation. In this study, we fed 135 laying hens (control group, low-level group (LLG) and high-level group (HLG)) with chlorinated alkyl-, alkyl- and aryl-tri-OPEs for 14 days and followed by a 28-day depuration period to investigate in ovo transfer. Feeding at environmentally-relevant levels, concentrations of tri-OPEs clearly increased during exposure period and decreased during the depuration period in eggs. Tri-OPEs were 5.95–10.8 times higher in HLG feed than LLG feed, but only 1.41–2.52 times higher in HLG eggs than LLG eggs. Half-lives of tri-OPEs in eggs were between 11.3 and 106 d and transfer rates were between 0.22% and 4.22%. As the major metabolites, organophosphate diesters (di-OPEs) were simultaneously studied. Taking di-OPEs into consideration would increase the transfer rate by 64.1%. Both tri-OPEs and di-OPEs mainly deposited in egg albumen. The molecular docking showed that strong combination between OPEs and egg albumen might be responsible for the maternal transfer. The average ratios of di-OPEs to tri-OPEs (Rdi/tri) were 16.7% and 67.2% in LLG and HLG albumen, and were 438% and 517% in LLG and HLG yolk, respectively. Chlorinated alkyl-di-OPEs showed higher in ovo transfer than other di-OPEs. Different distribution patterns of tri-OPEs and di-OPEs were controlled by combination to egg protein, egg formation, metabolic organs and congener-specific properties.