Assessment on Health Risk of Urban Water Supply in Shenzhen

Objectives To perform an assessment on the health risk of drinking water in 2012 in Shenzhen.

Methods The monitoring data on the quality of finished water from the outlet of water factories and peripheral tap water collected in 2012 were analyzed, and the health risk on three kinds of genetic toxic substances (hexavalent chromium, cadmium, and arsenic) and twelve non-carcinogenic substances (iron, manganese, lead, fluoride, volatile phenol, cyanide, mercury, ammonia nitrogen, nitrate, copper, zinc and selenium) for adults and children was assessed by risk evaluation models recommended by the U.S. environmental protection agency (US EPA).

Results The quality of all indicators measured in 150 finished water samples and 207 tap water samples were in the limits of the National Standards for Drinking Water Quality (GB 5749-2006) except for manganese in a tap water sample and nitrate in another tap water sample. The health risk (HI) on 12 non-carcinogenic materials for adults and children were 178.04×10^-8/y and 249.96×10^-8/y in finished water samples, and 363.02×10^-8/y and 509.66×10^-8/y in tap water samples, respectively. The harm of lead in finished water and fluoride in tap water was the most serious in all measured indicators. The cancer risks (R) of 3 genetic toxic substances for adults and children were 25.60×10^-6/y and 28.51×10^-6/y in finished water samples, and 23.47×10^-6/y and 26.08×10^-6/y in tap water samples, respectively. The damage of hexavalent chromium was the most among three detected carcinogenic materials. The total health hazard risks, including 3 carcinogenic and 12 non-carcinogenic substances for adults and children were 27.38×10^-6/y and 31.00×10^-6/y in finished water samples and 27.10×10^-6/y and 31.17×10^-6/y in tap water samples, respectively. Genetic toxic substances in drinking water are the main health risk for children than for adults.

Conclusions The health risk (R) of these 15 chemicals in municipal water supply in Shenzhen was in the range of acceptable levels (5.0×10^-5/y) recommended by the International Commission of Radiation Protection (ICRP). The results indicated that the risk of carcinogenic substances was greater in comparing with the non-carcinogenic substances, and the carcinogenic risk of hexavalent chromium was the biggest; lead and fluoride was the most important non-carcinogenic risk substances; and the risk for children was more than for adults.