Abstract:
Background Drinking water contains a variety of chemicals that may pose certain health risks to the human body.
Objective To evaluate carcinogenic and non-carcinogenic health risks of chemical pollutants in drinking water in Nanjing from 2014 to 2022.
Methods According to the Standard examination methods for drinking water (GB/T 5750-2006) and the Standards for drinking water quality (GB 5749-2006), the conventional water quality indexes of finished water, tap water, and secondary water supply in Nanjing from 2014 to 2022 were monitored. The health risk assessment model recommended by the United States Environmental Protection Agency (US EPA) was used to assess the health risks of 16 chemicals arsenic, cadmium, chromium (hexavalent), lead, mercury, selenium, cyanide, fluoride, nitrate nitrogen, trichloromethane, carbon tetrachloride, aluminum, iron, manganese, copper, and zinc in drinking water through different routes (drinking water and skin contact) in different populations (adult males, adult females, and children). Region (urban and rural), water period (dry period and wet period), and water sample type (finished water, tap water, and secondary water supply) were stratified for analysis.
Results From 2014 to 2022, a total of 4198 samples of drinking water were monitored in Nanjing, including 483 samples of finished water, 3313 samples of tap water, and 402 samples of secondary water supply. The pass rates of all indicators were above 99%. The health risk assessment results showed that the carcinogenic/non-carcinogenic risks of arsenic and lead presenting a trend of first increasing from 2015 and 2016 respectively, remaining relatively high for 3 and 4 consecutive years respectively, and then decreasing from 2018 and 2020 respectively before remaining stable; the carcinogenic risk of cadmium was much higher than that of other chemicals, and the risk was greater than 1.00×10−4 except for 2018 and 2019. The non-carcinogenic risks of drinking water in different populations (adult males, adult females, and children) under different exposure modes (intake of drinking water and skin contact) were less than 1. The values of carcinogenic risk via drinking water in total population and of cadmium intake via drinking water in all sub-groups (adult males, adult females, and children) were greater than 1.00×10−4. The carcinogenic/non-carcinogenic risk of drinking water was the highest in children, and the carcinogenic/non-carcinogenic risk via drinking water ingestion was higher than that via skin contact. The stratified analysis showed that the carcinogenic/non-carcinogenic risks of arsenic and cadmium in urban drinking water were higher than those in rural drinking water (P<0.05); the carcinogenic/non-carcinogenic risks of arsenic and trichloromethane in wet season were higher than those in dry season (P<0.05); the carcinogenic risks of cadmium in different types of water were all greater than 1.00×10−4; the health risks varied by chemicals and water sample types for the other chemicals, but all were within an acceptable level.
Conclusion The non-carcinogenic risks and carcinogenic risks of selected chemical pollutants in drinking water in Nanjing City from 2014 to 2022 show decreasing or stable trends. Among the 16 chemicals, the carcinogenic risk of cadmium exceeds the acceptable range recommended by the US EPA, and the carcinogenic/non-carcinogenic risks of the remaining chemicals are within the acceptable ranges. Cadmium should be given priority attention in future risk management of drinking water.
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