Different transformation of carbosulfan to its higher toxic metabolites in pakchoi (Brassica campestris ssp.) and cucumber (Cucumissativus L.) after field application

Carbosulfan (CAS) is used as an insecticide on vegetables, but its toxicity might increase due to the formation of higher toxic metabolites including carbofuran (CAN), 3-hydroxycarbofuran (3-OH) and 3-ketocarbofuran (3-KETO). In this study, the transformation of CAS to its metabolites in pakchoi (Brassica campestris ssp.) and cucumber (Cucumissativus L.) was investigated in the field in Beijing and Changsha and in a greenhouse in Hangzhou. CAS was metabolised to CAN, 3-OH and 3-KETO in pakchoi but only to CAN and 3-OH in cucumber. In pakchoi, the degradation of CAS (as measured by the DT₅₀ value, the time marking the disappearance of 50% of the pesticide) was the fastest in Hangzhou (0.7 d), followed by Changsha (1.4 d) and Beijing (2.3 d), whereas in cucumber, its degradation was the fastest in Changsha (1.6 d) and Hangzhou (1.6 d), followed by Beijing (2.5 d). These results suggested the monitoring of metabolites should be a prior objective for CAS, and different metabolites should be considered when assessing the risk of CAS in different vegetables.