Environmental protection agency responds to claims of carcinogens in tap water: No impact on health

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The official Weibo account of the Beijing Environmental Protection Publicity Center, @JingHuanZhiSheng, posted a response today to media reports stating that suspected carcinogens were detected in tap water in 44 cities across 23 provinces. Media reports indicate that over a period of 3 years, researchers from Tsinghua University collected 164 water samples from 155 locations in 23 provinces, 44 cities and towns across the country. The water samples included water leaving water treatment plants, household tap water, and source water; this is the largest and most comprehensive survey of its kind conducted in China to date. The researchers tested all 9 known nitrosamine disinfection by-products in the tap water samples, among which NDMA (nitrosodimethylamine) was the most abundant of these nitrosamine compounds. In response to this, @JingHuanZhiSheng clarified that nitrosamine compounds have been classified as Group 2A carcinogens by the International Agency for Research on Cancer, meaning there is clear evidence of their carcinogenicity in animals, but insufficient evidence in humans. It is said that chlorine-based disinfectants are commonly used in water treatment plants for disinfection. Chlorine is the cheapest and relatively safest disinfecting agent, and no alternative to it has been found over the years; as a result, trace amounts of disinfection by-products such as nitrosamines are inevitable, across all countries in the world without exception. The view held by most scholars today is that disinfection by-products in tap water, including nitrosamines, do not have a significant impact on health; however, the risks associated with not carrying out disinfection could be greater. The WHO’s guidelines on drinking water hold the same view. According to the survey conducted by Tsinghua University, the average concentration of NDMA in tap water in China is around 11 ng/L. @JingHuanZhiSheng stated that in this Tsinghua University study, only a very small number of samples exceeded the standards set by Australia or the World Health Organization, while those that exceeded the Canadian standards accounted for about 7%. In other words, according to WHO standards, the vast majority of the water tested is safe. @Jinghuan ZhiSheng also admitted that among the samples in which NDMA was detected this time, the average concentration (median) in China was around 22 ng/L, whereas it was 4 ng/L in the United States. Furthermore, both the variety of nitrosamine compounds detected and their detection rate are more severe in China than in the United States. Compared to Europe and Japan, our gap is even larger. Moreover, researchers from Tsinghua University detected the highest concentration of NDMA in tap water in a county town in the Yangtze River Delta region – the only one out of 44 cities where the level exceeded the World Health Organization’s standard of 100 ng/L. This is ultimately due to pollution at the source, so addressing the issue hinges on controlling pollution at its origin. @Jinghuan Voice concluded by emphasizing that safety does not mean there is no need for improvement. Of course, we should minimize this suspicious carcinogen, nitrosamines, as much as possible, but if we blindly pursue \"high standards,\" it will ultimately harm the interests of all taxpayers.