Chemical Pollutants Health Risk Assessment of Drinking Water in Fengtai District

Objectives To assess the health risks in rural drinking water safety project and the difference between source well water and treated water, to screen priority pollutants according to the monitoring data in Fengtai district.

Methods Source well water samples and barreled water samples from water supply plants in the rural drinking water safety project were collected and detected in dry and wet season in 2013. An environmental health risk assessment model was applied for risk assessment.

Results The average level of nitrate nitrogen in source well water was 36.96 mg/L, which was higher than the national standard limit; and the level of other pollutants met the requirement of the provisions in "Drinking Water Sanitary Standard"(GB 5749-2006). Chemical carcinogenic contaminants were the most important part of total annual personal health risks, accounting for 99.60% of total annual personal health risks from drinking water. The carcinogenic risks of As, Cr⁶⁺and Cd, both in well water and treated water, were 1.32×10^-5/year, 7.20×10^-6/year and 4.28×10^-6/year, respectively. The proportion of risk from As, Cr⁶⁺, Cd in total carcinogenic risks was 53.48%, 29.17% and 17.34%, respectively. Nitrate(NO₃^-) was the most important non-chemical carcinogenic pollutant in personal annual risks from water, which accounted for 63.86% of total annual risks; the personal annual risk would be falling into 19.21% of the total risk after water being processed. Comparing to well water, the average annual carcinogenic risk of treated water would reduce 0.40%, while the non-carcinogenic risk would reduce 67.09%, and the total risk would reduce 0.40%.

Conclusions The health risk of each pollutant was lower than the maximum tolerable value recommended by ICRP in Fengtai district. Implementation of drinking water safety project would reduce the health risk of drinking water, especially would sharply reduce the health risk of nitrate, which was the non-chemical carcinogenic pollutant. The results indicated that nitrate should be considered as the prior pollutant to be controlled and detected in the protection of drinking water source and barreled water.