Residue behavior and dietary risk assessment of zineb and its metabolite ethylene thiourea in edible lily

At present, zineb has not been registered on edible lily in China, and the lack of pre-harvest intervals and other relative information may lead to irrational use of pesticides and high residue risks. In order to determine the residue risks of zineb on edible lily, the residue dissipation and dietary risks of zineb residues were evaluated in field trials. The results showed that the degradation of zineb in lily conformed to the first-order kinetic equation, and the half-lives in Jiangsu and Hunan Provinces were 5.9 and 3.8 days, respectively. To investigate the terminal residues in the field trial, the recommended dosage (3000 g a.i./hm²) and 1.5 times recommended dosage (4500 g a.i./hm²) of 65% zineb wettable powder were sprayed three or four times on lily crops at four locations. At 7, 14 and 21 days after the last application, the maximum residues of zineb (calculated by CS₂) in harvested fresh lily and dried lily were 0.260 mg/kg and 1.290 mg/kg, respectively, both of which were lower than the maximum residue limits (MRL) of zineb in China on fresh lily (0.5 mg/kg) and dried lily (2 mg/kg). Because zineb is easily degraded to ethylene thiourea (ETU), and the ETU was detected in the samples of fresh lily, the dietary intake risks of zineb and its metabolite ETU in lily were analyzed. The results of the dietary risk assessment suggested that the ratios of dietary intake risk of zineb to the acceptable daily intake (ADI) in fresh and dried lilies were 0.014% and < 0.014%, respectively, which contributed very little to the overall dietary exposure. These results showed that the residues of Zineb in edible lily would not have an unacceptable risk to Chinese people when Zineb formulation was applied at the recommended dose.