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[新闻]Chemical spill in Chinese river may pose cancer risk
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Chemical spill in Chinese river may pose cancer risk 18:51 25 November 2005 NewScientist.com news service Shaoni Bhattacharya Exposure to benzene and nitrobenzene from a toxic chemical spill into a river in China could put people at risk of cancer and bone marrow problems, an expert warns. But depriving the 9 million people of water in the region around the city of Harbin, sited on the banks of the polluted river, also creates the danger of ill health by putting elderly people and young children at serious risk of dehydration. A chemical spill of about 100 tonnes of pollutants flooded into the Songhua River on 13 November after an explosion at the chemical plant of the Jilin Petrochemical Company, owned by the China National Petroleum Corporation. The toxic spill has forced cities along the river’s banks to stop taking water. The city of Harbin has 4 million residents in its urban area and stopped drawing water on Wednesday. It is not likely to start again before Saturday, when it is hoped that the pollution will have passed downstream. Stockpiling water The authorities encouraged residents to save water in containers and stockpile bottles of water before the pollutants reached the stretch of the river near Harbin, and before the pipelines were turned off. But many are now trying to flee the city in the face of scant water supplies. But it is difficult to judge the best course of action without a thorough evaluation of the health and environmental effects of the spill, says Alan Boobis, a toxicologist at Imperial College London, UK. He says that dehydration of elderly people and the very young is also a “real concern”. “Whenever these things happen, the immediate response is to get people out of the place, or stop exposing them,” he told New Scientist. “It’s understandable, but from this distance it’s difficult to judge what the right response is.” Nasty compound Boobis says epidemiological evidence shows that long-term exposure to benzene can damage the bone marrow and cause leukaemia. It can also cause a type of anaemia which affects the white blood cells. However, he adds that the leukaemia risk from benzene is very low, with people having to be exposed over years rather than days to be at risk. He says exposure to compounds like asbestos, for example, carry far higher health risks. “Nitrobenzene can be converted to other compounds which could be harmful,” Boobis notes. For example, bacteria can convert it to a “nasty” compound called aniline, he says. The US Environmental Protection Agency says this is classified as “very toxic” in humans and classes aniline as a “probable human carcinogen”. Concentration falling A week after the spill, when the polluted water passed Zhaoyuan, upstream from Harbin, the level of nitrobenzene was 30 times above China's national standard, while benzene was 2.6 times higher, according to Zhang Lijun, deputy director of the State Environmental Protection Administration. He spoke on Thursday to Xinhua, the official Chinese news agency. As the polluted water flows downstream the concentration of pollutants is dropping, with some being deposited along the way. The 80-kilometre-long chemical spill is likely to be further diluted in Harbin as several major tributaries join the river there, Zhang said. At 1300 local time on Friday, 13 days after the spill, the density of nitrobenzene in the water in Harbin was 18 times higher than China’s safety standards dictate, according to the Sifangtai Water Monitoring Station, reported through Xinhua. But the levels of benzene had subsided to below the national standard. But Boobis notes that benzene is “quite a resistant molecule” and could remain in plants and animals for some time. It is also very volatile and could evaporate into the atmosphere. The Chinese government has dispatched a team of investigators from Beijing to Harbin. “The presence of disciplinary officials in the team indicates punishments for irresponsible acts are on the way,” says Xinhua. |
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