[Distribution and health risk assessment of pesticide pollution in raw water and drinking water within key river basins in China in 2022].

Objective: To investigate the distribution and exposure levels of pesticides in raw water and drinking water in China, as well as to assess the potential health risks associated with long-term consumption.

Methods: A total of 83 typical water plants were selected in key river basins in China to collected samples of the raw water, finished water, and tap water. The online-solid phase extraction coupled with liquid chromatography-tandem mass spectrometry method was used to determine 13 pesticides, including acetochlor, atrazine, dimethoate, malathion, carbofuran, dichlorvos, chlorpyrifos, parathion, trifluralin, isoprothiolane, simetryn, methyl parathion, and metalaxyl, as well as 6 environmental metabolites, including carbendazim, malaoxon, 3-hydroxycarbofuran, deethyl atrazine, deisopropyl atrazine and hydroxy atrazine. The carcinogenic and non-carcinogenic risks of these pesticides were assessed.

Results: The concentrations of total amount of pesticides in the samples ranged from 0.1 ng/L to 1299.4 ng/L, with a median value of 64.7 ng/L. The detection rates of 5 pesticides or their metabolites exceeds 80%, namely acetochlor, atrazine, hydroxyl atrazine, deethyl atrazine, and metalaxyl. More than 6 pesticides or their metabolites were detected in 77.7% of the total 498 samples. The total concentration of pesticides during the wet season ranged from 1.1 ng/L to 1299.4 ng/L, with a median of 69.2 ng/L and a median average daily dose of 2.3 ng/(kg·d). The total concentration of pesticides in the dry season samples ranged from 0.1 ng/L to 543.5 ng/L, with a median of 60.2 ng/L and a median average daily dose of 2.0 ng/(kg·d). Among the 498 samples, the maximum carcinogenic risk of dichlorvos was 2.0×10~(-7), and the maximum carcinogenic risk of trifluralin was 1.1×10~(-10). The non-carcinogenic HI of 19 pesticides and metabolites pesticides was ≤6.0×10~(-3). Among them, the maximum HI of the middle route of the South to North Water Diversion Project, the lower reaches of the Yellow River, the eastern route of the South to North Water Diversion Project, the Liaohe River, and the Songhua River basin was 2.0×10~(-3)-6.0×10~(-3), while the HI of other basins was less than 1.0×10~(-3).

Conclusion: Different concentrations of pesticides have been detected in raw water, finished water, and tap water of key river basins in China, with the highest total concentration of detected reaching 1299.4 ng/L. The carcinogenic risk was lower than 10~(-6) and the non-carcinogenic hazard index of 19 pesticides was less than 1, and both below the acceptable level. Because of the universality and diverse occurrence of these pesticides in drinking water, long-term exposure to pesticides is still a concern.