Seasonal Variation of Drinking Water Quality and Human Health Risk Assessment in Hancheng City of Guanzhong Plain, China

This research was conducted to understand the seasonal characteristics of water quality for domestic purpose in Hancheng City of the Guanzhong plain, China. The health risks were also assessed using the water quality monitoring data collected from the Hancheng Center for Disease Control and Prevention. For this study, 48 samples were collected from the drinking water distribution system (chlorinated water and terminal tap water) in the dry and wet seasons, and were analyzed for pH, total hardness (TH), total dissolved solids (TDS), Cl-, SO42-, F-, NH4-N, NO3-N, Cr6+, As, Hg and Mn. The water quality was assessed using the entropy water quality index (EWQI) and the results show that above 80% of the water samples are of good quality which is suitable for drinking and other domestic purposes. The potential non-carcinogenic risks of Cr6+, As, F-, and NO3-N and carcinogenic risks of Cr6+ and As to consumers were assessed by the model recommended by the US Environmental Protection Agency (USEPA). The non-carcinogenic health risks in the dry season are higher than the risks in the wet season for both adults and children. Water quality indicators considered in the risk assessment contribute with different degrees to the total non-carcinogenic risk during the dry and wet seasons. The order of the average non-carcinogenic risk values of the chlorinated water and terminal tap water in the dry season was F- > As > NO3-N > Cr6+, while that in the wet season was F- > NO3-N > Cr6+ > As. People face higher carcinogenic risk in the wet season in terms of terminal tap water consumption, while they face higher carcinogenic risk in the dry season in terms of the chlorinated water. Children face almost twice higher the carcinogenic risks than the adults.