Comparison of Combined Dissipation Behaviors and Dietary Risk Assessments of Thiamethoxam, Bifenthrin, Dinotefuran, and Their Mixtures in Tea

Abstract

Insecticides are often used in combination during tea cultivation, however, the residue risk due to combined use is still mainly unexplored. In this study, three representative insecticides, thiamethoxam, bifenthrin, and dinotefuran were selected to explore their dissipation behaviors and dietary risks at single and combined application. The dissipative behavior of thiamethoxam, bifenthrin, and dinotefuran followed first-order kinetics, with half-lives of 5.44, 9.81, and 10.16 days, respectively. After joint application, the dissipation half-lives and finial concentrations were significantly affected. Thiamethoxam in combination with bifenthrin or dinotefuran exhibited a longer dissipative half-life, ranging from 5.58 to 5.97 days, than thiamethoxam alone. The thiamethoxam combined with dinotefuran had the longest half-life, with a final residual that was 1.64 times that of the single application after 28 days. Chronic and acute risk quotients (RQc and RQa) were elevated by 1.86 and 1.88 times, respectively, according to the risk assessment of dietary intake. The dissipative half-life of bifenthrin combined with thiamethoxam was longer than bifenthrin alone, prolonged to 10.50 days, and the ultimate residual after 28 days of combined application was 1.29 times that of the single. RQc and RQa were 1.29 and 1.44 times higher, respectively. Different combinations of pesticides affect pesticide residue concentration and dissipation behavior, which were related to the structure of pesticides and their effects on metabolic processes and microbial communities. Overall, the dietary risks of thiamethoxam, bifenthrin, and dinotefuran were less than 50% for both single and combined use, which were acceptable for human health, but the cumulative risks of pesticide mixtures from multiple dietary sources cannot be ignored. This research would provide recommendations for the joint application and risk evaluation of typical pesticides in tea.

Keywords: tea, Thiamethoxam, Bifenthrin, Dinotefuran, Joint application, risk assessment