Objective To explore the variation rules and health risks of trihalomethane in regional drinking water， and to provide evidence for the innovative water processing technology and the optimization of drinking water quality.
Methods Based on regional drinking water sanitation monitoring， non-parametric rank sum test was used to analyze the effects of residual trihalomethane production in different periods and with disinfection methods. The United States environmental protection agency （USEPA） classic "four-step" health risk assessment model was used to evaluate the carcinogenic risk and non-carcinogenic risk of trihalomethane through drinking water exposure.
Results The yield of trichloromethane in wet season was 6.3 μg·L-1， which was higher than that in dry season. Compared with chlorination pretreatment， ozone pretreatment reduced the content of bromomethane dichloromethane. Compared to liquid chlorine disinfection， sodium hypochlorite treatment incresed the levels of trichloromethane and bromomethane chloride. Although the total carcinogenic and non-carcinogenic risks of trihalomethane in drinking water in the region were at safe levels， they were above the acceptable limits occasionally. The highest carcinogenic risk of trihalomethane were dichlorobromomethane and chlorodibromomethane，and the highest non-carcinogenic risk was trichloromethane. The health risk of children was 1.2 times higher than that for adults.
Conclusion The production of residual trihalomethane in drinking water in this area is relatively low， which is less harmful to the health of adults and children. Monitoring， including other disinfection byproducts， should continue and appropriate disinfection techniques for drinking water should be explored.
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