Yesterday, "Technology Daily" published news, Chen Chao, deputy researcher of the National Environmental Simulation and Pollution Control Key Laboratory of the Environmental College of Tsinghua University, revealed that the experimental team has 155 points in 44 large, medium and small cities and towns in 23 provinces across the country. Including waterworks, household faucets and source water, 164 water samples were collected from which carcinogens, disinfection by-product NDMA (nitrosodimethylamine), were detected. Epidemiological studies have shown that nitrosamines are closely related to cancers in certain areas of the digestive tract.
The detection rate of drinking water nitrosamines cannot be ignored
Due to its carcinogenicity, high detection rate and possible inclusion in water quality testing standards in China, nitrosamine disinfection by-products in drinking water have received unprecedented attention from researchers at home and abroad. Chen Chao, deputy researcher of the National Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, told the Science and Technology Daily on the 12th that a key research work of this group was on the census of nitrosamine disinfection by-products in the national drinking water system. . The result was published recently in the top journal “Water Research†in the municipal and environmental fields. “The problem of nitrosamines in drinking water is urgent and needs to be studied and engineered as soon as possible!†Chen Chao called.
In the past three years, Chen Chao and his team have tested nitrosamine disinfection by-products and their precursors in 44 urban water supply systems. Among the total water samples tested, the average NDMA concentrations in the factory water and faucet water were 11 ng/L and 13 ng/L, respectively, and the average NDMA generation potential in the source water was 66 ng/L. He said that compared with a large-scale census data published by the US Environmental Protection Agency in 2012, the detection rate of nitrosamines in China's factory water and faucet water is 3.6 times that of the United States. The concentration of nitrosamines in drinking water in Western European countries is lower than in the United States. Chen Chao said that among the more than 700 disinfection by-products that have been identified, nitrosamines are one of the health-risk categories of disinfection by-products, especially NDMA.
Closely related to cancer of the digestive tract
In the 1950s, the medical profession discovered that nitrosamines were a class of strong carcinogens. At that time, they mainly studied nitrosamines in food, tobacco and industrial pollution. The study of nitrosamine disinfection by-products in drinking water began in the late 20th century.
“Preliminary epidemiological studies have shown that nitrosamines are closely related to digestive tract cancers in certain parts of China.†Chen Chao said that they have detected that tap water in these areas is contaminated with severe nitrosamines from industrial wastewater. At the same time, this year, a research group of Nanjing University also found serious nitrosamine pollution in the source water of many cities in Jiangsu Province in East China.
"It is reported that according to the results of the toxicology test, the NMG lifetime drinking of a million percent consistent cancer risk concentration is 0.7 ng / L, it is reported that the US Environmental Protection Agency is trying to develop a US nitrosamine concentration standard, the limit may be in the million One to a very limited range of cancer risk concentrations." Chen Chao revealed.
Chen Chao said that the report shows that NDMA is more risky in densely populated and heavily polluted areas. Cities that detect high concentrations of NDMA in faucet water are likely to be contaminated with NDMA precursors from industrial and domestic wastewater.
If the secondary water supply equipment is not cleaned and maintained according to the national regulations on time, there will be serious concerns about water pollution. Since there are more than a dozen households or even dozens of users in a water tank, serious infections such as dysentery may occur. Typhoid fever, etc. Experts from the disease control department suggest that families with conditions can maintain water safety at home by installing water purifiers.
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