Pollution in Songbai is just the tip of an iceberg of appalling industrial pollution on the Xiang River, environmental experts have warned.
Thanks to tens of thousands of big and small smelters like those of Shuikoushan Nonferrous Metals, the Xiang - a tributary of the Yangtze River that serves as the lifeline for more than 40 million people in Hunan - has been known since the early 1970s as the Chinese river worst affected by heavy-metal pollution.
While industrial countries have focused on recycling to use heavy metal resources more efficiently and reduce environmental hazards, China continued to expand its mining activities while doing almost nothing to control waste and metallurgical slag - which have taken a heavy environmental toll, said Professor Dai Tagen of Central South University.
Leaks of toxic metals such as mercury, lead, chromium and cadmium have been rampant in Hunan province for decades, threatening freshwater supplies and people's health.
Metal poisoning has long been part of everyday life for many river communities.
In Xinma, a village under Zhuzhou city, an industrial hub upstream of the provincial capital, Changsha, people have lived in fear of heavy metal pollution for years. 'There are many cancer victims in our village struggling to stay alive - most of them in their 30s and 40s,' a village cadre said.
At least 20 people died of cancer, and more than a dozen have undergone chemotherapy. More than 400 people showed excessive concentrations of lead in their bodies.
Guo Xiuying's daughter was found to be poisoned by cadmium when she was two years old in 2006. 'My daughter often complains about foot pain and arthritis, just like my fellow villagers who suffered from cadmium poisoning.'
Villagers attributed their suffering to a local smelter, which was allowed to operate for more than 15 years. The factory, with the protection of local authorities, discharged untreated wastewater directly into the Xiang River, locals said.
Although the zinc smelter was closed several years ago, the nightmare was far from over, with more people falling ill. The local government has offered little assistance to help villagers get proper treatment.
'There are people dying of cancer in my village every year. I am really worried about what will happen to my daughter when she grows up,' Guo said.
Despite the hundreds of millions of yuan spent on pollution control over the years, the Xiang's water quality has gone from bad to worse, especially since the 1990s.
This came as little surprise to the experts. Official figures show Hunan topped the list of mainland emitters of mercury, lead, chromium and cadmium in the past decade. It also led other provinces in the volume of its discharges of pollutants, such as arsenic and sulphur dioxide, and in chemical oxygen demand, a measure of water pollution.
An official test of the middle and lower reaches of the river in 2008 found an excessive concentration of toxic heavy metals in vegetables, with arsenic and lead levels exceeding the national standard by over 95 per cent and that for cadmium by nearly 70 per cent.
Weng Lida, former head of the Yangtze River Water Resources Protection Commission, said the water quality in the Xiang, like many polluted rivers, had deteriorated significantly in the past three decades. He pointed to collusion between local government officials and businesses - at the expense of the people.
'There is almost zero government oversight of pollution in rural areas, which helps polluting enterprises at the expense of the environment,' Weng said.
But some positive changes have been brought about in the past few years, with former Hunan Communist Party chief Zhang Chunxian kicking off a war on polluters. Zhang was the first Hunan party boss to inspect the pollution of the Xiang.
This year the central government, in a campaign against metal pollution, listed the Xiang as a national priority. A total of 59 billion yuan (HK$71 billion) has been earmarked for controlling pollution in the waterway in the next five years.
Current Hunan party chief Zhou Qiang promised that the widespread pollution problems along the river would be brought under control within the next decade by cutting pollution sources and upgrading technology.
'The Xiang will turn to the Rhine of the East,' he said.
Despite the pledges and the unprecedented spending spree, experts said Hunan authorities still faced the predicament of trying to balance economic development and environmental protection. Energy-intensive and heavily polluting mining and smelting industries along the Xiang and its tributaries account for up to 70 per cent of local economic output.
Although criminal and environmental laws carry harsh penalties, they have seldom been imposed when pollution violations occur, said Wang Canfa, a professor at the China University of Political Science and Law in Beijing.
'Less than 10 per cent of polluters and officials who violated green laws have actually been held responsible for causing pollution,' Wang said. 'It's not that China's environmental legislation isn't up to scratch. Rather, it's because we never enforce it.'