Abstract: In order to evaluate the safety of beta-cypermethrin applied on cabbage (Brassica oleracea L.), the residue and dissipation dynamics of beta-cypermethrin in cabbage were studied through filed experiments carried out in Shaanxi, Fujian and ten other provinces in China and the dietary intake risk of beta-cypermethrin was assessed. Samples were extracted with acetonitrile. The extract was suction filtrated, salted out, concentrated and then brought to a final volume of 5 mL with n-hexane before analysis by gas chromatography (GC). The results showed that good linearity was found between the concentration of beta-cypermethrin in the range of 0.01–5.00 mg/L and response peak area, with a determination coefficient of 0.999 9. The recoveries of beta-cypermethrin at three spiked levels of 0.05, 0.5 and 5 mg/kg ranged from 83% to 106%, with relative standard deviation (RSD) of 6%–9%. The limit of quantitation (LOQ) of the developed method was 0.05 mg/kg. In filed experiments, 3% beta-cypermethrin microcapsule suspension was applied twice times on cabbage at a dose of 33.75 g/hm2 with an interval of seven days. At seven days after the last application, the residue of beta-cypermethrin in cabbage ranged between < 0.05 mg/kg (less than LOQ) and 0.28 mg/kg, and the supervised trials median residue (STMR) was 0.13 mg/kg. At 10 days after the last application, the residue of beta-cypermethrin in cabbage ranged from < 0.05 mg/kg (less than LOQ) and 0.21 mg/kg, and the STMR was 0.07 mg/kg. Both residue levels were lower than the maximum residue limit (MRL) value of 5 mg/kg. The dissipation process of beta-cypermethrin in cabbage followed a first-order kinetic model. The dissipation half-lives of beta-cypermethrin residues in cabbage from Shanxi, Zhejiang, Hunan and Guangxi were 3.8, 2.0, 2.7 and 3.7 days, respectively, and the correlation coefficients (r) ranged from 0.967 to 0.994. The national estimated daily intake (NEDI) of beta-cypermethrin was 0.575 mg and the risk quotient (RQ) was 45.6%. The results of risk assessment showed that the dietary intake risk of beta-cypermethrin was acceptable.

Key words: beta-cypermethrin; cabbage; gas chromatography; residue; dietary risk assessment