Detection and chronic non-carcinogenic risk assessment of chemicals in urban drinking water in Hebei Province from 2017 to 2021

Background Hebei Province is located in the North China Plain. In view of the influence of geological background and the acute and chronic hazards caused by excessive drinking water toxicological indicators, coupled with the large coverage of water supply in urban areas and the existence of self-built water supply facilities, it is necessary to understand the drinking water sanitation status in urban areas and conduct health risk assessment.

Objective To investigate main indicators affecting the compliance rate of drinking water quality in urban areas of Hebei and evaluate the chronic non-carcinogenic risks of 11 chemicals.

Methods The collection, preservation, and testing of 14299 samples of finished water, tap water, and secondary water supply in urban areas of Hebei Province from 2017 to 2021 were conducted following the Standard examination methods for drinking water (GB/T 5750—2006). A total of 11 chemicals were evaluated according to the Hygienic standards for drinking water (GB 5749—2006). The chronic non-carcinogenic risks of the 11 chemicals in drinking water by oral exposure were assessed using the four-step health risk assessment model developed by the United States Environmental Protection Agency and the Technical guide for environmental health risk assessment of chemical substances (WS/T 777—2021).

Results From 2017 to 2021, the compliance rates of arsenic, cadmium, hexavalent chromium, lead, mercury, selenium, cyanide, chloroform, and carbon tetrachloride in drinking water in urban areas of Hebei Province were all 100.00%, and fluoride and nitrate (N) were the main indicators affecting water quality compliance, with compliance rates of 97.68% and 99.53% respectively. The compliance rate of fluoride increased year by year (χ²=178.06, P<0.05), and the concentration showed a downward trend (χ²=563.49, P<0.05). The compliance rate of fluoride in water samples during the wet season was higher than that during the dry season (χ²=5.06, P<0.05). The median concentrations of fluoride and nitrate in drinking water in urban areas of Hebei Province from 2017 to 2021 were 0.36 mg·L⁻¹ and 3.32 mg·L⁻¹, with hazard quotients of 0.15 and 0.05, respectively, both less than 1, suggesting no chronic non-carcinogenic risks, and no significant gender difference was found. The hazard quotient of maximum fluoride concentration was 1.65, which was greater than 1, suggesting chronic non-carcinogenic risks. The chronic non-carcinogenic risks associated with the maximum concentrations of the remaining 10 chemical indicators were all within an acceptable range.

Conclusions  Nine toxicological indicators in drinking water in urban areas of Hebei Province from 2017 to 2021, except for fluoride and nitrate, are within the national standards. Fluoride and nitrate are the main toxicological indicators that affect the overall compliance rate of water quality, and the chronic non-carcinogenic risks associated with maximum concertration of nitrate and 95% concentration of fluoride are at an acceptable level.