Dissipation of Prothioconazole and Its Metabolite Prothioconazole-Desthio in Rice Fields and Risk Assessment of Its Dietary Intake

Rice is an important food crop, with a long history of cultivation in China, and is one of the important staple foods for Chinese today. However, the occurrence of rice diseases has had a substantial impact on its yield. At present, chemical control is the main means of prevention and control of rice diseases. As a high-efficacy and broad-spectrum fungicide, prothioconazole shows an ideal effect on the prevention and control of common rice diseases, but the residuals that remain after its use may have an impact on human health. In this paper, ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to develop a residue analysis method and explore the dissipation of prothioconazole and its metabolite prothioconazole-desthio in rice grain, rice husk, and rice plants, and the risks of chronic and acute dietary intake of prothioconazole in different Chinese populations were evaluated. The results showed that at a concentration range of 0.005-5.0 μg/mL, prothioconazole and its metabolites showed good linear correlations, and the correlation coefficients were all above 0.9992. The average recoveries of prothioconazole in three matrixes ranged from 80.0% to 99.7%, the RSD was between 1.54% and 11.0%, and the limit of quantitation was less than 0.01 μg/g. The sensitivity, accuracy, and precision of the established method all met the measurement requirements. The dissipation experimental results showed that the parent compound prothioconazole was rapidly metabolized to prothioconazole-desthio in the rice field environment, and the dissipation half-life in rice plants after application was 2.5-10.1 d. According to the results of dietary risk assessment, under the standardized residue test conditions, the residual level of rice at the sampling interval of 7 days was within the acceptable range for the chronic and acute dietary risks of different populations in China. Our research is important for directing the scientific application of pesticides in China.