POISONED SLURRY: Workers clean the sewage left by Zijinshan Copper Mine in Shanghang County, Fujian Province, on July 13, 2011 (JIANG KEHONG)

In April 2009, more than 800 children were diagnosed with elevated levels of lead in their blood in Fengxiang, northwest China's Shaanxi Province. Soon afterward, hundreds of children were found to be suffering from lead poisoning in Wugang, central China's Hunan Province. In October that year, almost 1,000 children were diagnosed with elevated lead levels in their blood in Jiyuan, central China's Henan Province.

In July 2009, more than 500 villagers fell sick and two died after being exposed to cadmium that was illegally dumped into the Liuyang River by the Xianghe Chemical Plant in Liuyang, Hunan Province.

In March 2011, more than 160 residents, including 53 children, living near a battery factory in Taizhou, east China's Zhejiang Province, were diagnosed with excessive lead levels in their blood.

Despite receiving more attention from the media and the general public, heavy metal contamination has not diminished. Instead, it becomes more serious with China's rivers, seas and farmland absorbing more and more pollutants daily.

Heavy metal pollution stems from hundreds of different sources, but it mostly comes from the purification of metals during the manufacturing process.

According to the MEP, 72 percent of China's more than 44,600 chemical companies are located on a river bank and 12.2 percent are situated less than 1 km from environmentally sensitive areas, including vital sources of drinking water.

In 2010, a total of 960 of 10,896 companies producing heavy metals were found to be in violation of environmental standards and were ordered to reduce their emissions and enhance safety procedures, the ministry said.

Besides manufacturing, the waste dumped by chemical factories and mines is among the major causes of metal poisoning in the country.

Due to its rapid development, China has seen a steady increase in the amount of industrial waste it produces.

"As of 2012, a total of 19.28 million tons of chromium residue, a hazardous waste material generated during the production of chromium metal and chromium salt, have been released into the country's environment," said Zhou.

Ma warned that the residue had gradually penetrated into underground water sources and farmland.

A case in point is an incident in southwest China's Yunnan Province between April and June last year in which two truckers were accused of dumping more than 5,000 tons of chromium-contaminated waste near a reservoir and on hills around villages in Qujing, causing 77 head of livestock to die and threatening the health of tens of millions of people.

On August 13, 2011, Qujing authorities said in a press release that the illegally dumped chromium slag came from the local Yunnan Luliang Chemical Plant.

Last September, the police arrested five suspects for allegedly dumping the waste.

"Chromium poses great health dangers. Drinking water polluted with it could cause acute poisoning," said Liu Xiaoduan, a researcher with the Chinese Academy of Geological Sciences.

Land pollution

To protect people and the environment from chromium residue, the State Council, China's cabinet, ordered in 2005 all local governments around the country to deal with chemical waste within five years. But to date, this task remains incomplete.

In 2006, a severe case of cadmium contamination poisoned 150 residents in Xinma Village in Hunan. Two villagers died as a result of the contamination.