Residue decline study and risk assessment of thiamethoxam in wheat

In order to evaluate the safety and regular use of thiamethoxam 200 g/L SC,the terminal residue and decline dynamic of thiamethoxam in wheat plant,wheat straw and wheat grain were investigated and the samples were analyzed by HPLC-UVD in Anhui and Jinlin Province.The results indicated that the decline curves of thiamethoxam in wheat plant accorded the first-order kinetics.The half-life of thiamethoxam was 4.6 d in Anhui and 5.9 d in Jinlin.The terminal residue indicated that when the wheat plant was sprayed 2 times with thiamethoxam 200 g/L SC with the recommended dosage of 12.6 g a.i/hm2,and the last application was done 21 d after harvesting,the residue of thiamethoxam in wheat were lower than the MRL of Japan:0.02 mg/kg.By calculating,the intakes of thiamethoxam per man and per day from wheat was 0.035 6 mg.Risk quotient(RQ) was 0.028.The residue could be declined to the safety level.