Background As an inevitable substance formed during drinking water disinfection, disinfection by-products (DBPs) can not be ignored for their potential carcinogenic and non-carcinogenic risks in populations.
Objective This study is designed to determine the levels of DBPs (halomethanes, haloacetic acids, and haloacetonitriles) in source and finished water in Shanghai and evaluate their health risks.
Methods Water samples from three water plants in Shanghai and from their source water reservoirs were collected (with 6 parallel samples at each point) during September and October, 2020. Gas chromatography equipped with electron capture detector (GC-ECD) were used to detect the concentrations of selected DBPs. The health risk assessment model recommended by the US Environmental Protection Agency (USEPA) was utilized to evaluate the health risks of water DBPs through ingestion, inhalation, and dermal contact among different populations.
Results Trichloromethane, bromodichloromethane, dibromochloromethane, dichloroacetic acid, and trichloroacetic acid were positive in source water. The concentrations of DBPs in finished water met the Standards for drinking water quality (GB/T 5749-2006). The total concentrations of halomethanes, haloacetonitriles, and haloacetic acids in finished water were 8.8-23.5, ND-6.76, and 3.99-14.43 μg·L-1, and the concentration of trichloromethane was the highest, 5.58-12.74 μg·L-1, followed by bromodichloromethane, dichloroacetic acid, and trichloroacetic acid, with concentrations of ND-5.84, 1.72-6.43, and 0.50-5.43 μg·L-1, respectively. Dichloroacetonitrile and bromoacetonitrile were the main haloacetonitrile, with concentrations of ND-2.17 and ND-1.90μg·L-1, respectively. The carcinogenic risks caused by DBPs in the finished water from the three water plants to men, women, and the whole population ranged from 7.25×10-6-2.53×10-5, mainly contributed by bromodichloromethane, trichloroacetic acid, and dibromochloromethane, while the non-carcinogenic risks were 0.03-0.06, mainly from trichloromethane, dichloroacetic acid, and dibromochloromethane. The main risk source was from the ingestion route, accounting for 58%-66% and 55%-61% of the total carcinogenic and non-carcinogenic risks.
Conclusion Trichloromethane, bromodichloromethane, dichloroacetic acid, and trichloroacetic acid are the main DBPs in the finished water of Shanghai water plants. Ingestion route is the main source of lifetime carcinogenic and non-carcinogenic risks. The total carcinogenic risk of various DBPs is higher than the low risk level defined by the US Environmental Protection Agency, which suggests that more attention should be paid to DBPs.
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