Local anger boiled over this week with a violent protest at the plant in central Shaanxi province, and tensions remain high in a dispute that demonstrates how environmental degradation caused during the charge for economic growth in China is spawning social unrest.
For decades, many Chinese firms have dumped poisons into rivers and the ground rather than disposing of them safely, counting on the acquiescence of local governments unwilling to damage their economic lifelines.
The resulting problems - from crop losses to cancer - have sometimes prompted violence, but they've also brought a rise in public awareness of environmental safety and health. Since the unrest, the government has promised to close down the Dangling Lead and Zinc Smelting Co. plant in Changqing town until it can be made safe.
That offers at least a temporary victory for the villagers, whose outrage came to a head after some 615 of 731 children in two villages near the plant tested positive earlier this month for lead poisoning. Some had lead levels 10 times that which China considers safe.
On Sunday and Monday, angry residents battled police at the smelter's gates, and stoned trucks delivering coal to the plant.
For now, the plant is closed and security is tight. Associated Press reporters who visited the area on Wednesday were tailed by local government officials, and police officers tried to break up interviews and block access to sick children and their parents.
An apology Monday from Dai Zhengshe, the mayor of Baoji city, which oversees Changqing, seems to have done little to cool villagers' anger. Dai made the promise not to reopen the smelter until it met health standards, according to the official Xinhua News Agency, but villagers said they put little faith in his words.
"You really can't trust what the government tells you," said He Xiaojun, the father of nine-year-old He Haomin, who suffers from nose bleeds and memory problems - common symptoms of lead poisoning. "We want them to move the plant," said He, whose village of Madaokou lies a stone's throw away.
Public distrust has been exacerbated over the years by unmet promises and a lack of government transparency.
Villagers living nearby were supposed to have been given new accommodation even before the smelter opened in 2006, but so far just a few dozen have relocated. Authorities promised to shut the plant on Aug. 6, but villagers - such as Wang, the farmer who likened the plant to a nuclear bomb - insist production continued for days afterward, with smoke coming from the stacks at night.
Officials say that was only to allow time for furnaces to close down without gas explosions. Plans, meanwhile, call for the relocation of all villagers living within 0.6 miles (1 kilometer) of the smelter "as soon as possible," local government spokesman Wang Minmin told The AP.
Official claims that the plant met national standards for ground and surface water, and soil and waste discharge also prompted derision and disbelief from residents, who question how then their children came to have such high lead levels in their blood.
Ma Jun, founder of the non-governmental Institute of Public and Environmental Affairs in Beijing, says that's likely due to outdated standards that don't take into account the cumulative effect of lead and other heavy metals on people and the environment.
"Therefore, even if a given factory had met all the standards on emissions, there would still likely be damage to human health," Ma said.
Lead poisoning can damage the nervous and reproductive systems and cause high blood pressure, anemia and memory loss. It is especially harmful to young children, pregnant women and fetuses, with damage that is usually irreversible, according to the World Health Organization.
On Wednesday at the local Fengxiang County Hospital, about 80 children had been admitted for observation and treatment. They lay on beds, many of them on IV drips, with their parents hovering nearby.
Zha Xiaofang, 41, from Madaokou village, said her 8-year-old daughter has lead levels considered mid- to high-level poisoning. Her daughter has had abdominal pain and memory problems for some time.
"We are anxious because we don't know what will happen next and we don't have any guarantees for the future," she said.
Changqing, about 850 miles (1,380 kilometers) west of Beijing, is just one of scores of places in China where pollution and chemical contamination have sparked opposition and protests, embarrassing the ruling Communist Party and its pledges to pursue clean and sustainable development.
In Wenping township in central Hunan province, angry villagers blocked roads on July 30 after the government refused to close down a manganese processing plant. But last Thursday, the local government announced that it was shutting down the factory because it was operating illegally and had discharged lead excessively. As in Changqing, local officials offered free lead testing for all children under the age of 14 within three miles (five kilometers) of the factory.
Plans for chemical plants and garbage incinerators in urban areas have also drawn protests including marches and petitions - rare in a country where even peaceful dissenters are often punished.
Yet dubious projects continue to receive approval, due in large part to their contribution to local tax bases and employment. According to 2008 media reports, Changqing's Dongling smelter accounted for 17 percent of the county government's revenue and supported more than 2,000 households.
A government stimulus plan is also expediting projects, sometimes shortening their environmental approval times, while a tough government opponent of polluters, vice director of State Environmental Protection Agency, Pan Yue, has recently been sidelined for reasons that are unclear.
Given the lack of trust, greater transparency about major polluting projects was perhaps the only way to head-off future conflicts, said Hu Yuanqiong, a staff attorney with the U.S. Natural Resources Defense Council's China Program.
"The best way to ensure social stability and the sustainability of the economy is to make information open and allow public participation in monitoring emissions and to have a mechanism between the public and the factories to talk things out and resolve disputes," Hu said.