The distribution and human health risk assessment of eight neonicotinoid residues in agricultural soils from four provinces, south China.

The widespread use of neonicotinoid (neonic) insecticides in China's agricultural sector has led to high residual concentrations in the agroecosystem. Since soil is the primary source of direct pesticide exposure, soil contamination is a significant concern, particularly in regions with extensive agricultural production. This study aims to determine the spatial distribution of neonics in farmlands from four southern provinces that are home to China's crucial commercial grain bases. By combining eight neonics into imidacloprid-equivalent total neonics (IMI) using the relative potency factor method, the ecological risks to humans were also assessed. The results showed that imidacloprid had the highest detection rate (96%-100%), followed by thiamethoxam and clothianidin, which ranged from 44% to 64%. Maximum and average IMI values in soil samples from Zhejiang Province were 277.02 and 46.05 μg kg (dry weight), respectively. Guangdong (maximum = 191.62 μg kg, mean = 39.70 μg kg) and Jiangxi (maximum = 199.13 μg kg, mean = 28.95 μg kg) had comparable IMI while Jiangsu had the lowest level of total neonics, with a maximum of 86.07 μg kg and a mean of 19.49 μg kg. A significant positive correlation between IMI and total organic carbon in soils was also found. The average daily doses of neonics from soil-borne exposure through food intake, soil ingestion, inhalation, and dermal contact calculated for adults and children in each province were all lower than the reference dose (RfD, 57 μg kg d) of imidacloprid. However, the potential health risk to human health cannot be disregarded, given their increasing use and pervasiveness in the environment. Our results help to raise concerns about the safety of the agroecological environment under neonic exposure in the major agricultural provinces of southern China.