Occurrence, profiling and prioritization of halogenated disinfection by-products in drinking water of China

The occurrence of 28 disinfection by-products (DBPs), which were divided into 5 groups, in 70 drinking water treatment plants in 31 cities across China was investigated, and the toxic potency of each DBP group was calculated using mammalian cell toxicity data from previous studies for profiling. Of the 28 DBPs, 21 were detected with an average frequency of detection of 50%. Trihalomethanes (THM4) and haloacetic acids (HAAs) were the most predominant species, whose median concentration levels were at 10.53 and 10.95 mu g L-1, respectively. Two of four iodinated trihalomethanes (I-THMs) were detected, and the concentration of the I-THMs ranged from under the detection limit to 5.58 mu g L-1. The total concentration of haloacetonitriles (HANs) in different water samples ranged from under the limit of detection to 39.20 mu g L-1, with a median concentration of 1.11 mu g L-1. Two of four halonitromethanes (HNMs) were detected, and the maximum concentrations of chloronitromethane (CNM) and trichloronitromethane (TCNM) were 0.96 and 0.28 mu g L-1, respectively. HANs were found to be the most potent DBP group in terms of cytotoxicity, and HANs and HAAs had the same level of genotoxic potency. These results indicate that although at a low concentration level, the toxic potency of the unregulated HANs in drinking water may not be neglected.