Harbin's troubles were caused by an explosion at a petrochemical plant up-river, which spilt cancer-causing toxins into the water, but is symptomatic of wider problems.

China's water is dirty or vanishing -- 70 percent of its rivers are contaminated, over a third of the country is plagued by acid rain, and in the past 50 years it has lost more than 1,000 lakes, the official Xinhua agency says.

Its skies are choked too. Home to seven of the world's 10 most-polluted cities, its urban smog causes over 400,000 early deaths a year, the International Energy Agency says.

Factory and power stations often ignore environmental rules in the hunt for profits or market share, pumping effluent into rivers or skies, while even those who fit equipment to process waste sometimes leave it unused to cut costs.

Others run equipment for too long, risking accidents from human error or faltering machinery.

This may be particularly tempting in the petrochemical sector, which supplies the building blocks of everything from fertilizer to drugs, and is racing to keep up with demand.

Imports are high and multinational firms like Germany's BASF are pouring billions of dollars into Chinese plants.

"The Chinese system has its standards to follow and they argue that these are comparable to international levels," said analyst Victor Shum at Purvin & Gertz in Singapore.

"I think this is true, but the question is how closely on a day-to-day basis you follow those rules. Where you're under a lot of pressure there may be a temptation to cut corners."

Apart from the risk of damaging spills, the petrochemical industry is one of several energy-intensive sectors which are consuming vast amounts of dirty-burning coal.

GREEN GROWTH?

As problems spread, people once content with earning more money are now worrying about quality of life. In some cases that has led to the social unrest and economic troubles Beijing is so keen to stave off with growth.

This summer hundreds of angry farmers rioted in eastern Zhejiang province about effluent from a pharmaceutical plant they said had ruined crops.

A top environment official has said pollution costs China 8-15 percent of its gross domestic product.

Even efforts to keep the population fed after decades of shortage last century -- exacerbated by a lingering Maoist desire for self-sufficiency -- are chased in an unsustainable way. "China's use of fertilisers per hectare is almost three-fold higher than the global average ...(which) creates a large number of environmental problems," the OECD said in a recent report.

The State Council, or cabinet, this week set the ambitious target that by 2020, the country's environmental quality should have improved significantly, and said the current situation was "grim", Xinhua reported.