Variation and characterization of prometryn in oysters (Crassostrea gigas) after seawater exposure.

Prometryn (PRO) is frequently detected in shellfish of international trade among triazine herbicides because of its wide application in agriculture and aquaculture worldwide. Nevertheless, the variations of PRO remain unclear in aquatic organisms, which affect the accuracy of their food safety risk assessment. In the present study, the tissue-specific accumulation, biotransformation, and potential metabolic pathway of PRO were reported in oyster species Crassostrea gigas for the first time. The experiments were conducted through semi-static seawater exposure with low and high concentrations of PRO (at nominal concentrations of 10 and 100 μg/L) via daily renewal over 22 days, followed by 16 days of depuration in clean seawater. The characterization of prometryn in oysters was then evaluated through the bioaccumulation behavior, elimination pathway and metabolic transformation, comparing with other organisms. The digestive gland and gonad were found to be the main target organs during uptake. In addition, the highest bioconcentration factor of 67.4 ± 4.1 was observed when exposed to low concentration. The level of PRO in oyster tissues rapidly decreased within 1 day during depuration, with an elimination rate of >90 % for the gill. Moreover, four metabolites of PRO were identified in oyster samples of exposed groups, including HP, DDIHP, DIP, and DIHP, in which HP was the major metabolite. Considering the mass percentage of hydroxylated metabolites higher than 90 % in oyster samples, PRO poses a larger threat to aquatic organisms than rat. Finally, the biotransformation pathway of PRO in C. gigas was proposed, the major metabolic process of which was hydroxylation along with N-dealkylation. Meanwhile, the newly discovered biotransformation of PRO in oyster indicates the importance of monitoring environmental levels of PRO in cultured shellfish, to prevent possible ecotoxicological effects as well as to ensure the safety of aquatic products.