Defining region-specific soil quality standards for pesticides in China

China is a vast, pesticide-dependent agricultural country. Given that pesticide exposure patterns and dissipation vary across regions, there is a need to establish region-specific soil pesticide standards to protect human health. This study proposed a regulatory framework that can derive pesticide soil standards (PSSs) for the average (PSS_A) and ceiling (PSS_C) values. This framework consists of two components: human exposure assessment and pesticide dissipation. The former computes the region-specific exposure frequency and duration of the children and provides a comprehensive health risk assessment to derive PSS_A. The latter calculates the region-specific pesticide dissipation and pesticide application intervals and determines the relationship between average and ceiling concentration after pesticide application to derive PSS_C. Employing this framework, a spreadsheet-based simulation tool was developed to calculate standards for the four most widely used pesticides in China. The results showed that the simulated PSS_A values of acetochlor, atrazine, carbofuran, and chlorpyrifos varied considerably among different provinces, ranging from 33.3-121.6, 300.7-683.4, 1.9-5.1, and 10.1-33.9 mg kg^-1, respectively. Children in the southern provinces tended to have longer outdoor activity time (i.e., higher outdoor soil exposure frequency) than in the northern provinces due to the warm weather, hence these regions require stricter (i.e., lower) average soil standards. Pesticide dissipation rates in the northern provinces were slower than in the southern provinces. Nevertheless, due to the higher frequency of pesticide applications in the southern regions, the PSS_C values in these areas are still generally lower than in the northern regions. In addition, a comparison was conducted between the current standards and simulated values for 13 regulated pesticides. The results found that there is a lack of ceiling standards in China to manage pesticide application patterns and the existing standards for some pesticides (e.g., chlordane, HCB, and lindane) may be too lenient for certain southern provinces to protect human health. Taken together, it is recommended that China's environmental agencies update the pesticide standard system. The regulatory framework and simulation tool proposed in this study are expected to provide scientific and reasonable support for establishing region-specific standards.