Dietary exposure and risk assessment of imidacloprid and flusilazole residue in greenhouse strawberries

In order to assess the dietary exposure risk of imidacloprid and flusilazole residue in greenhouse strawberry, the final residues and decline trends of imidacloprid and flusilazole used in strawberry were studied. The dietary exposure and risk assessment were conducted based on the supervised field trial data. The results showed that the decline dynamics of imidacloprid and flusilazole accorded with the first-order kinetics in greenhouse conditions with imidacloprid applied at a dosage of 56.25 g(a.i)/hm2 and flusilazole at a dosage of 67.5 g(a.i)/hm2. The half-lives of imidacloprid and flusilazole were 6.3 d and 9.9-11.5 d, respectively. The strawberry was sprayed in 2-3 times at an interval of 7 d with imidacloprid 10% wettable powder at dosage of 37.5 g(a.i)/hm2 and 56.25 g(a.i)/hm2 at the stage of half ripe fruit. At 3, 5, 7, 10 days after the last application, the final residue levels of imidacloprid in greenhouse strawberry at harvesting were 0.022-0.16 mg/kg. The strawberry was sprayed in 2-3 times at an interval of 7 d with flusilazole 400 g/L emulsifiable concentrate at dosage of 45 g(a.i)/hm2 and 67.5 g(a.i)/hm2. At 3, 5, 7, 10 days after the last application, the final residue levels of flusilazole in greenhouse strawberry at harvesting were 0.079-0.30 mg/kg. Chronic and acute risk quotient of imidacloprid and flusilazole were calculated from residue trial data, average dietary intake in all kinds of food and their acceptable daily intake. The results showed that acute risk quotient of imidacloprid and flusilazole in strawberry were about 0.18%-1.01% and 10%-37.7% of their acute reference doses, respectively, indicating that the acute dietary exposure risks of these two pesticides are acceptable. The chronic risk quotient of imidacloprid and flusilazole in strawberry is about 18.6%-85.3% and 68.3%-316.4% of their acceptable daily intakes, respectively. Chronic risk quotient of flusilazole in strawberry for children between 2 and 4 years is about 284.9%-316.4%, indicating chronic risk of flusilazole in baby foods. As exposure risks by strawberry devoted less than 3.2% of the total dietary risks, dietary risk of flusilazole in strawberry may be not the main portion of the whole food dietary. Up to now, no maximum residue limits of imidacloprid and flusilazole in strawberry were set in China. Further, assessments of consumer protection level were carried out based on field trial residues. The results showed that consumer protection levels are acceptable with CPLc of imidacloprid and flusilazole at 18-109, 2-13 and CPLa at 121-725, 6-36. Maximum residue limits at 0.5 mg/kg and PHIs at 3 d, 5 d were recommended for imidacloprid and flusilazole in strawberry, respectively. For 2-4 years old children, the risk of chronic dietary exposure for flusilazole in strawberry could not be ignored.