Residues and dietary intake risk assessment of flonicamid and bifenthrin in peach

Abstract: 【Objective】To provide the basic data for rational use of flonicamid and bifenthrin, the residual characteristic of the two pesticides used in peach were studied, and the chronic risk assessment of long-term dietary intake of the two pesticides were evaluated. The maximum residue limits(MRLs) of flonicamid and bifenthrin in peach were recommended, and the comparisons with the international MRLs were analyzed.【Methods】An analytical method was established to simultaneously detect the residues of flonicamid and bifenthrin in peach. The samples were extracted with ethyl acetate, purified with QuEChERS method, detected with gas chromatography-electron capture detector(GC-ECD), and quantified with external standard method. The digestion patterns and the final residues of flonicamid and bifenthrin in peach were analyzed. The national estimated daily intake(NEDI) or theoretical maximum daily intake(TMDI) were calculated by using the supervised trial median residue(STMR) or maximum residual limit(MRL), and the chronic risk quotient(RQc) was calculated according to the acceptable daily intake(ADI). The pre-harvest interval(PHI) and MRLs for the two pesticides were recommended.The protection level(CPLc) of recommended MRLs and international standards for the two pesticides in peach were evaluated separately and compared.【Results】At the spiked level of 0.01, 0.1 and 1.0 mg·kg-1,the recovery rate of flonicamid ranged from 86% to 104%, and the relative standard deviation(RSD)ranged from 1.5% to 5.5%. At the same spiked concentrations, the recovery rate of bifenthrin was between 82% and 92%, and the RSD was between 1.9% and 2.2%.The limits of quantitation(LOQ) of both pesticides in peach were 0.01 mg · kg-1. The field trials for final residue were conducted in eight provinces in 2018, including Shandong, Hebei, Henan, Zhejiang, Shanxi, Sichuan, Liaoning and Hubei provinces. The dynamic digestion experiments were carried out in Liaoning, Hubei, Hebei and Zhejiang provinces. The degradation patterns of flonicamid and bifenthrin in peach accorded with the first-order reaction kinetic equation, and the half-life was 2.5-5.6 d and 1.6-6.7 d, respectively, proving that the two pesticides are easily digested. The original deposition amounts were slightly different in different regions, and the experimental site in Liaoning province was relatively low. The high single fruit weight of peach, which was 2-4 times of that of other varieties on average was speculated. The application of pesticides in the fruit expansion stage had a greater dilution effect on pesticides compared with other varieties. 15% bifenthrin · flufenthrin suspension concentrate(SC) was applied twice in accordance with the highest recommended dosage(37.5 mg · kg-1) in peach trees. At 14 days after the second application, the final residue range of flonicamid was from less than 0.01 mg · kg-1 to 0.033 mg · kg-1 with the STMR of0.015 mg·kg-1, and the final residue range of bifenthrin was from less than 0.01 mg·kg-1 to 0.029 mg·kg-1 with the STMR of 0.012 mg · kg-1. At 21 days after the second application, the final residue range of flonicamid was from less than 0.01 mg · kg-1 to 0.024 mg · kg-1, and the final residue range of bifenthrin was from less than 0.01 mg · kg-1 to 0.025 mg · kg-1, which both with the STMR of lower than LOQ in the analyzed samples. The final residual quantity decreased with the extension of sampling interval. PHI was recommended to be 14 d. Flonicamid was registered on seven edible crops such as rice, cucumber,potato, apple and tea, while bifenthrin was registered on twelve edible crops such as wheat, tomato, cucumber, apple, cotton, sugar cane and tea. According to GB 2763, the ADI values of flonicamid and bifenthrin are 0.07 mg · kg-1 bw and 0.01 mg · kg-1 bw, respectively. The dietary intake risk assessment showed that the chronic risk quotient of long-term dietary intake for the general population to flonicamid and bifenthrin was 18.0% and 45.1%, respectively, to which, the contribution of peach was 0.09%and 0.2%, respectively. The results suggested that flonicamid and bifenthrin generally does not pose an unacceptable chronic risk of long-term dietary intake on the general population, and peaches were only a small percentage of the total dietary intake risk. According to HR, the MRL values of the two pesticides on peaches were both recommended to be 0.1 mg · kg-1. The TMDI of flonicamid and bifenthrin were calculated to be 0.798 1 mg and 0.288 0 mg, and the CPLc was 5.53 and 2.19, respectively. According to the MRLs in USA, the TMDIs of flonicamid and bifenthrin were calculated to be 0.821 0 mg and 0.306 3 mg, and the CPLc was 5.37 and 2.06, respectively. The MRLs recommended in this study would be stricter than the USA MRLs, but they had a relatively consistent protection against the chronic dietary risk for Chinese consumers. The reason might be the lower risk contribution of peach.【Conclusion】The improved ethyl acetate QuEChERS-GC-ECD method was convenient and fast for simultaneous detection of flonicamid and bifenthrin. In accordance with the recommended use of PHI, the RQc of the two pesticides in peach were acceptable. The MRLs recommended in this experiment for peach are stricter than those in USA, but the protection levels against the chronic dietary risk for Chinese consumers are similar.