The plight of an estimated 190 million Chinese, who regularly drink polluted water, is now in sharp focus due to the benzene slick moving down the Songhua river, causing the suspension of drinking water supply to 3.8 million people in Harbin city.
"In China, freshwater is being threatened from population pressure and rapid economic development," the Worldwide Fund for Nature (WWF) said Thursday.
"In the last half century, China's population has more than doubled and become heavily concentrated along the major river valleys," WWF China said in a statement, adding: "Untreated sewage and industrial waste pollute some 70 percent of China's rivers."
Some 75 percent of rivers are also over-enriched with nutrients flushed into them from agricultural land, according to government estimates.
This year's annual government report on water quality said some 190 million Chinese people were drinking water containing "harmful contaminants" and a total of 300 million lacked access to safe drinking water.
"Freshwater ecosystems are by far in worse condition than forest, grassland, and coastal ecosystems," WWF said.
"Currently, most of China's rivers are menaced with shrinkage, dysfunction, contamination and other problems," Chen Bangzhu, director of a government-run population, resources and environment committee, said at a national conference on lake water quality Wednesday.
"The worsening conditions of these endangered rivers are caused by a booming economy, the expansion of population and irrational development," the government's official Xinhua news agency quoted Chen as saying.
Lack of adequate legislation and poor environmental monitoring were other factors contributing to the increasing pollution of China's rivers and lakes, Chen said.
"Without scientific guidance, some rivers are polluted with illegal discharge of waste and overuse of fertilizers," he was quoted as saying.
The pollution increases the risk of both drought and flood in different areas, as well as the shortage of drinking water, he said.
"Last year, water from half the tested sections of China's seven major rivers was undrinkable because of pollution," the official China Daily quoted Sheng Huaren, a leading official from the National People's Congress (NPC), China's nominal parliament, as saying in the annual report earlier this year.
Five of China's seven major rivers were "seriously polluted" and safe drinking water was a "major issue" in rural areas, the newspaper said.
According to the estimates of the ministry of water resources, more than 300 million rural residents have no access to safe drinking water, and some 190 million people, or 15 percent of China's population, drink water containing harmful contaminants.
In a separate report to the NPC in June, Vice-Premier Wu Yi said water pollution and pesticides had raised a food safety issue in China.
"In some places, vegetables and fruits are grown using polluted water, or harmful pesticides are illegally used," the newspaper quoted Wu as saying.
The estimated 100 tonnes of benzene polluting the Songhua river near Harbin, the capital of Heilongjiang province, leaked into the river after explosions on Nov 13 at a chemical plant in Jilin city, some 500 km upstream.
WWF said the leakage showed the need for China to overhaul safety procedures at chemical plants, and reduce the risks of chemical pollutants to people and wildlife.
"WWF is highly concerned about how the toxic spill in Heilongjiang province will impact the region's people and ecosystem," Li Lifeng, director of WWF China's Freshwater Programme, said in the WWF statement.
Li said China should ensure "improved regulation and monitoring of toxic chemicals, better risk assessment schemes to regularly check the safety of production procedures, and better preventative safeguards such as creating wetland buffer zones".
"We call upon industries and those who regulate them to work together with other stakeholders to prevent this from happening again," he said.