Changing on the Concentrations of Neonicotinoids in Rice and Drinking Water Through Heating Treatment Process: An Unusual Increase in Imidacloprid

Abstract

Neonicotinoids (NEOs) have become the most widely used insecticides in the world since the mid-1990s. According to Chinese dietary habits, rice and water are usually heated before being consumed, but the information about the alteration of NEOs before and after the heat treatment process is very limited. In this study, the parents of NEOs (p-NEOs) accounted for >99% of ∑NEOs in both uncooked (median: 66.8 ng/g) and cooked (median: 41.4 ng/g) rice samples, while the metabolites of NEOs (m-NEOs) accounted for less than 1%. Significant reductions in acetamiprid, imidacloprid (IMI), thiacloprid, and thiamethoxam (THM) have been observed after the heat treatment of the rice samples, while the reductions in the water samples were insignificant, except for those of THM and dinotefuran. These results indicate the degradation of p-NEOs and m-NEOs in the rice samples during the heat treatment process. However, the concentrations of IMI increased in the high-concentration-spiked water samples after boiling, suggesting the presence of potential IMI precursors. The concentrations of NEOs in rice and water can be shifted by the heating treatment process, so this process should be considered in relevant human exposure studies.

Keywords: neonicotinoids, diet intake, heating treatment, imidacloprid