Nitrosamines such as nitrosodimethylamine(NDMA) in drinking water have recently attracted great attention because of their high carcinogenicity and high detection rate. Nitrosamines have also been repeatedly detected in drinking water in our country, leading to a lot of concerns about our drinking water safety. However, China has not yet formulated the relevant drinking water safety standards. In order to evaluate the health risks caused by NDMA in drinking water and to provide recommendations for the development of drinking water safety standards, the method of disability-adjusted life years(DALYs) and the two-stage disease model were used to estimate the health risk of liver cancer caused by intake of NDMA in drinking water. The data of this study were collected from two large-scale water quality surveys conducted in 35 cities in China from November 2009 to May 2012, and the detection conducted by Chen Chao et al. in 23 cities in China from 2012 to 2014, with a total of 146 water plants data. The results showed that mean(8.97 ng·L-1) and median(2.90 ng·L-1) NDMA concentrations were both not very high except in some special areas. The incidence of life-long cancer was 5.69×10-6 and 5.69 times as high as the negligible risk value(1×10-6) specified by the US EPA. The total disease burden of NDMA was 844.15 person-years, of which the death loss was 818.31 person-years, accounting for 96.9%. The incapacity loss was 25.84 person-years, accounting for 3.1% in comparison. Death loss was greater than the loss of incapacity. The disease burden was highest in the age group of 55-60 years(129.40 person-years), followed by 45-50 years(120.44 person-years). The burden of disease was higher in middle-aged and elderly people. The averaged loss was 6.27×10-7 DALYs per person per year in our country. Only considering the health risk factors, NDMA concentration safety standards should be 6.12 ng·L-1. According to the specific national conditions, the NDMA safety standard in the range of 6-40 ng·L-1 was recommended. On one hand, we can control the concentration of NDMA in drinking water, to reduce health risks as far as possible, and on the other hand, we can also ensure the effectiveness of disinfection of drinking water treatments. China's economic and water treatment technological level and other factors should also be taken into consideration in the near future. In view of potential health risks of NDMA, it's necessary to adopt more effective, economical and also environmental water treatment techniques and develop reasonable safety standards to ensure the quality of drinking water and people's health.
Keywords: N-nitrosodimethylamine(NDMA); disability-adjusted life years(DALYs); drinking water safety; drinking water safety standards; health risk.