Anger at Dead Pigs in Shanghai River

Peter Parks | AFP | Getty Images

Shanghai government officials were scrambling to solve the mystery of nearly 3,000 dead pigs dumped in a suburban river that is an important source of the city's drinking water, the latest environmental crisis to hit a city that is also battling a sudden fall in air quality.

Shanghai residents used social media to air their complaints that the municipal government was slow to respond to the dead pig crisis, which broke on Friday but remained largely unexplained on Monday night.

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"Is this the water we are drinking? And this has happened more than once or twice in the past, I don't know what our 'relevant authorities' are doing!" said one post on Sina Weibo, the popular microblogging site.

Reports of the dead pigs emerged as China's nominal parliament met in Beijing where one of the most politically sensitive topics is air and water pollution. Public opinion polls show rising public dissatisfaction with the quality of China's food supply and environment, with many rich Chinese saying they have considered emigration to avoid the pollution caused by China's rapid economic growth.

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The official Xinhua news agency said on Monday that a pig virus, porcine circovirus (PCV), had been detected in tests on one dead pig from the Huangpu river, the main river that bisects Shanghai and one of the city's primary sources of drinking water. Tests on all other samples were negative. Xinhua was quick to point out that the PCV virus cannot be transmitted to humans.

On Monday night, the Shanghai government appeared to play down the seriousness of the problem, saying tap water from water processing plants in the area qualified as safe under Chinese law, and that water quality in the area before treatment is similar to last year. A preliminary investigation showed that labels tagged to the pigs' ears indicated they came from Jiaxing, in neighbouring Zhejiang province, the government said on its official microblog, adding "No severe animal epidemic has been detected".

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Chinese local media reported earlier this month that a porcine disease had decimated the pig population of a village upstream of Shanghai. Jiaxing Daily newspaper reported that in Zhulin village, more than 10,000 pigs died in January alone, and another 8,000 in February. Local residents said it was not uncommon to see dead pigs floating down the river, but the number of pigs this year was unusual.

Water contamination, caused by fertiliser run-off, chemical spills and untreated sewage, is a significant concern in China. The same district where the dead pigs are turning up now was last month the site of chemical contamination by an Apple supplier, which turned a local stream white because of the pollutant level.