Objective To investigate the contaminant level of disinfection by-products (DBPs) of sodium hypochlorite in drinking water and to estimate their health risks in Jiangsu Province, China.

Methods A total of 53 finished water samples disinfected by sodium hypochlorite were collected from water plants in 2017 to 2020. The mass concentrations of DBPs including trihalomethane (trichloromethane, chlorodibromomethane, bromodichloromethane, and tribromethane) and haloacetic acid (dichloroacetic acid and trichloroacetic acid) in the samples were measured. The health risks of DBPs (trihalomethane and haloacetic acid) exposure in drinking water for adults were assessed using the health risk assessment method recommended by US EPA.

Results Chlorodibromomethane and bromodichloromethane contributed the highest carcinogenic risk of the total carcinogenic risk. The carcinogenic risk of chlorodibromomethane exposure through drinking water was 1.2×10^-5 (1.4×10^-7-5.1×10^-5) for adult males and females. The carcinogenic risk of bromodichloromethane exposure through drinking water was 8.2×10^-6 (5.0×10^-7-5.7×10^-5) for adult males, and 8.3×10^-6 (0.50×10^-6-5.74×10^-5) for adult females. The carcinogenic risk of DBPs in drinking water was higher in Taihu Lake water source than that in river water source. The non-carcinogenic risks of adult men and adult women were far less than 1, respectively.

Conclusion The carcinogenic and non-carcinogenic risks of trihalomethane and haloacetic acid in drinking water are accepted in Jiangsu Province. Chlorodibromomethane and bromodichloromethane are key indicators for risk management of DBPs in drinking water disinfected by sodium hypochlorite.