China detected carcinogens 44 City tap water? Expert: is a bluff | | carcinogens _ tap water news
▌ Source: global times, cloves, doctor
Media recently to check out 44 City tap water disinfection byproducts, or induced by Carcinoma of digestive tract published under the title report, quoted a study of Tsinghua University:
3 years, researchers at Tsinghua University in China's 23 provinces, 44 cities and towns, 155-164 water samples were collected. Water covers water factory, domestic tap water and source water, this is by far the largest one of the most comprehensive research.
Researchers examined water samples of currently known in all category 9 nitrosamines dbps, including NDMA (n-Nitro-dimethyl) is the highest content of nitrosamine compounds.
The report on the Internet "would drink the tap water causes cancer" controversy, and caused panic. In response, Beijing Jia Weilie, Deputy Director of the Institute of ecology civilization, certain media to read too much, "water cancer" is sensational. Tap water containing nitrosamines dbps no effects on health, the public do not need to "drink the tap water will cause cancer" concerns.
1 Why are nitrosamines in tap water?
Nitrosamine compounds by the International Cancer Research Center judged to 2 class a carcinogen, namely "animal carcinogenicity evidence clearly but insufficient evidence of human carcinogenic." In addition, epidemiological studies show that nitrosamine compounds with digestive system cancer has an obvious relevance.
Sounds a bit scary, why nitrosamine substances in tap water?
Nitrosamines are water disinfection by-products. Disinfection usually using chlorine-containing disinfectant water treatment plant, in small amounts of pollutants in water of chlorine disinfection by-products will become, part of organic nitrogen compounds can be turned into nitrosamines such substances.
Chlorine is an inexpensive and relatively safe means of disinfection, has been unable to find alternatives to it, so trace disinfection by-products such as nitrosamines are inevitable, and countries around the world, without exception.
At present, most scholars are: tap water, including nitrosamines dbps is unlikely to cause significant health effects, but if not disinfected, brought harm may be greater.
WHO (World Health Organization) guidelines for drinking water, holds the same view.
Tap water Nitrosamines in the 2 water dangerous? Now that inevitably contain nitrosamines in tap water of such substances, then we'll take a look at dose.
This survey of Tsinghua University:
Average concentrations of NDMA in drinking water in China is about 11 ng/L
East and South China regions, families average concentrations of NDMA in water around about 18 ng/L
Family of NDMA in drinking water of the Yangtze River Delta region average concentration of about 28 ng/L
(Note: 1 ng/L, one-zero, or 0.0000000000001)
So what does the data mean? Note: tap water is undrinkable?
Although nitrosamines in tap water is a hot spot, but only a few countries and regions for it to develop a standard. United States California has developed a particularly exacting standards (10 ng/L), using this measure, tap water has about 1/4 in China exceeded.
But look at other criteria:
Canada Health Ministry guidelines is 40 ng/L
Australia guide value is 100 ng/L
WHO's guideline value is 100 ng/L
By these standards, the Tsinghua University investigation over only a very few samples in Australia or the World Health Organization's standard, and over Canada standard is only about 7%.
According to World Health Organization standards, most of the test water is safe.
Is worthy of note, including nitrosamines in tap water disinfection byproducts have no significant effects on health, in contrast, does not disinfect brings more harm.
Why 3 samples in Yangtze River Delta the highest?
Researchers at Tsinghua Yangtze River Delta a County's leading China's highest concentration of NDMA was detected in water, is the only 44 cities exceeds World Health Organization standard of 100ng/L.
This, after all, is the source of the air pollution problem. Why do you say it?
Although part of nitrosamines in tap water is disinfection by-products, but strictly according to the standard, this is manageable. This study found that if River is a water treatment plant to take water, NDMA concentrations significantly higher than from the reservoir or lake water. This is due to the water of the lakes and reservoirs are relatively closed, less vulnerable to effects of pollutants in the upper reaches.
The Yangtze River Delta region at the end of the main stream of the Yangtze River, accumulation of pollutants in the upper reaches and directly on this, together with local economic development and dense population, pollution emissions, ultimately led to this nitrosamine substances more tap water.
4 China tap water safe?
China's current drinking water standards for the 2007 revision of the drinking water health standards. Water quality project and the selection of indicators, taking into account the actual situation in China, and the World Health Organization guidelines for drinking water quality and to Europe, Japan and other countries drinking water standards. This standard still a gap compared with developed countries, but in developing countries at the forefront.
Although water supply gap with the developed countries, but China's water quality is guaranteed. At the operational level, strictly in accordance with the provisions of the standard water treatment plant in the event of emergencies, water plant will stop the water; once the water plant cannot ensure compliance with national standards, to stop the water. Can responsibly say, finished water water treatment plant is now fully comply with safety standards.
Of course, the water plant was generally in compliance with the standard, but water network and secondary water secondary pollution problems that cannot be avoided. Tap water water distance directly drinking still has larger distance, tap water in the appeared rust, and taste, and color yellow black of situation in many place different degree to exists, due to industrial had fast development produced of pollution has aggravated trend, surface water and groundwater pollution very serious, makes can for people using of quality water constantly reduced; tap water factory of existing process cannot completely removal heavy metal and the organic pollution,, chlorine disinfection and brings side effects.
Beijing Jia Weilie, Deputy Director of the Institute of ecology civilization, completely solve the drinking water safety problem is a huge project, you need to take a long time to complete. From national level see, should speed up governance water pollution of efforts, developed more strictly of drinking water water standard; from enterprise level see, as soon as possible used technology, and new process, speed up tap water factory and lost pipes network of transformation, while perfect environment information disclosure, guarantees public of environment informed right; from public level see, should attention security of itself defense, as installation necessary of water equipment, and participation tap water supply of supervision,.
Responsible editor: Xiang Changming SN123
Article keywords:Water carcinogens
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中国44城市自来水检出致癌物？专家：实属吓唬人|自来水|致癌物_新闻资讯
▌本文来源：环球时报、丁香医生
近日有媒体以《44城自来水检出消毒副产物，或致消化道癌》为题刊登报道，报道援引清华大学的一项课题研究：
历时 3 年，清华大学研究人员在中国 23 个省、44 个城市和城镇、155 个点位采集了 164 个水样。水样涵盖水厂出厂水、家庭自来水和水源水，这是迄今为止国内规模最大最全面的一次调研。
研究人员检测了自来水样中当前已知的全部 9 种亚硝胺类消毒副产物，其中 NDMA（亚硝基二甲胺）是亚硝胺类化合物中含量最高的。
该报道在网上引起“喝自来水会不会致癌”的争议，一时间引起了恐慌。对此，北京生态文明工程研究院副院长贾卫列表示，某些媒体过度解读，“自来水致癌”属耸人听闻。含亚硝胺的自来水消毒副产物对健康无明显影响，公众无需为“喝自来水会不会致癌”担心。
1 自来水中为什么会有亚硝胺？
亚硝胺类化合物被国际癌症研究中心判定为 2A 类致癌物，即“动物致癌证据明确，但人类致癌证据不充分”。此外，有流行病学研究表明，亚硝胺类化合物与消化系统癌症有较明显的相关性。
听起来有点吓人的样子，那为什么自来水中会有亚硝胺类物质呢？
亚硝胺是自来水消毒的副产物。自来水厂消毒通常会使用含氯消毒剂，在氯的作用下水中的少量污染物会变成消毒副产物，其中部分有机氮化物可以变为亚硝胺类物质。
氯是最廉价且相对安全的消毒手段，多年来始终找不到它的替代品，因此亚硝胺等微量消毒副产物也无可避免，世界各国无一例外。
目前大多数学者的观点是：包括亚硝胺在内的自来水消毒副产物并不会对健康产生明显影响，但是如果不消毒，带来的危害可能更大。
WHO（世界卫生组织）的饮用水指南也持同样观点。
自来水 2 水中的亚硝胺危险吗？既然目前的自来水中不可避免地会含有亚硝胺类物质，那么我们就来关注一下剂量。
本次清华大学的调查数据显示：
中国自来水中 NDMA 的平均浓度大约是 11 ng/L
华东、华南地区，家庭自来水中的 NDMA 平均浓度大约在 18 ng/L 左右
长三角地区的家庭自来水中 NDMA 的平均浓度为 28 ng/L 左右
（注：1 ng/L，万亿分之一，即 0.0000000000001）
那么这些数据意味着什么呢？说明这些自来水都不能喝了吗？
虽然自来水中的亚硝胺是一个研究热点，但只有少数国家和地区针对它制定了标准。比如美国加州制定了一个特别严苛的标准（10 ng/L），如果用这个标准衡量，中国自来水有 1 / 4 左右超标。
但是看看别的标准：
加拿大卫生部的指导值是 40 ng/L
澳大利亚的指导值是 100 ng/L
WHO 的指导值也是 100 ng/L
如果用这些标准衡量，本次清华大学的调查中仅有极个别样本超过澳大利亚或世卫组织的标准，而超过加拿大标准的只占 7% 左右。
如果按照世卫组织的标准，这次检验中绝大多数水是安全的。
值得注意的是，包括亚硝胺的自来水消毒副产物对健康没有明显影响，相反，不消毒给人带来的危害更大。
3 长三角地区样本为何含量最高？
清华的研究人员在长三角某县城的龙头水中检出了中国 NDMA 的最高浓度，是 44 个城市中唯一超过世界卫生组织 100ng/L 标准的。
这归根结底，是源头污染的问题。为什么这么说呢？
虽然自来水中的亚硝胺确实有一部分是消毒的副产物，但只要严格按标准来，这是可控的。而这次的研究发现，自来水厂如果以河流作为取水源，则 NDMA 浓度明显大于取自水库或湖泊水源的。这是由于湖泊和水库的水系相对封闭，不易受上游污染物的影响。
长三角地区处于长江干流的末端，上游的污染物不断积累并汇聚于此，加上本地经济发达、人口密集、污染排放多，最终导致了这一地区自来水中亚硝胺类物质偏多。
4中国的自来水安全吗？
中国现行饮用水标准为2007年修订的《生活饮用水卫生标准》。水质项目和指标值的选择，考虑了中国实际情况，并参考了世界卫生组织的《饮用水水质准则》和欧美、日本等国饮用水标准。这套标准与发达国家相比仍有差距，但在发展中国家处于前列。
尽管与发达国家的自来水供应存在差距，但中国自来水的水质是有保障的。在实际操作层面，自来水厂严格依据《标准》规定，一旦发生突发事件，水厂会停止出水；一旦水厂不能保证出水符合国家标准，会停止出水。可以负责任地说，目前自来水厂的出厂水质是完全符合安全标准的。
当然，水厂出水一般符合标准，但输水管网、二次送水产生的二次污染问题无法回避。自来水水质距离直接饮用仍有较大距离，自来水中出现铁锈、有味、颜色发黄发黑的情况在许多地方不同程度地存在，由于工业过快发展产生的污染有加重趋势，地表水和地下水污染非常严重，使可供人们使用的优质水源不断减少；自来水厂的现有工艺不能完全去除重金属及有机污染等，氯消毒又带来副作用。
北京生态文明工程研究院副院长贾卫列表示，彻底解决饮用水的安全问题，是一个庞大的系统工程，需要花较长的时间才能完成。从国家层面看，应加快治理水污染的力度，制订更为严格的饮用水水质标准；从企业层面看，尽快采用新技术、新工艺，加快自来水厂和输水管网的改造，同时完善环境信息披露，保障公众的环境知情权；从公众层面看，应该重视安全的自身防线，如安装必要的净水设备、参与自来水供应的监督等。
责任编辑：向昌明 SN123
文章关键词： 自来水 致癌物
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