The precise number was only ascertained after a major chemical spill late last year triggered a nationwide survey, said Zhou Shengxian, the head of the State Environmental Protection Administration (SEPA).

"At present, China roughly has 21,000 chemical plants along its rivers or its coastline, and of these more than 50 percent are located along either the Yangtze or the Yellow River," he told a briefing in Beijing.

"In this situation, if a problem arises, the consequences could be unthinkable."

About 400 million people, or nearly one third of the nation's population, live along the banks of the Yangtze, while 100 million are settled in the Yellow River basin.

The issue is one of great political significance because China's rulers have for millennia been expected to provide access to clean water.

Zhou indicated that China's current government may gradually be assuming more of that historic responsibility, after decades of focusing on the economy.

"After the establishment of new China (when the communists rose to power in 1949), to a large extent we sacrificed the environment for the sake of economic growth," he said.

"Now we've entered a stage where we'll try to use environmental protection measures to boost economic growth."

Even so, SEPA did not know the exact number of chemical plants along the nation's waterways until the government kicked off the national count around New Year.

The measure came after China was rattled by a blast on November 13 at a PetroChina chemical plant in the northeast province of Jilin, sending an 80-kilometer-long (50-mile-long) toxic slick down the Songhua river.

The slick caused water supplies to be interrupted for nearly four million residents in the city of Harbin as it passed through, before moving on to the Russian border.

Zhou said the New Year survey uncovered lax safety standards at a large number of chemical plants.

"We have discovered more than 100 enterprises with potential safety problems," he said.

He said the environmental administration was looking into these enterprises and would publish the results later.

While the Songhua river debacle served as a wake-up call to many Chinese, incidents happening in the weeks after showed it was far from the only example of how the nation's water is under threat from rapid economic growth.

Industrial chemical cadmium was released by accident into major waterways in two separate accidents in south China's Guangdong province and central Hunan province.

Observers have warned for years that China, with the world's fastest growing major economy, is facing a water crisis of epic proportions.

Previous government reports have said that more than 70 percent of China's rivers and lakes are polluted, while about 400 of China's 600 largest cities suffer from water shortages.

Related Links