"They know the water isn't suitable for swimming if we look at the quality, but they want to push people to pay more attention to water protection," says Li Shiyu, dean of environmental science at Zhongsan University in Guangzhou.

Such political grandstanding is nothing new in China, though the focus on the environment is. In part, it reflects the greater visibility of such issues in Beijing in the wake of a series of industrial accidents and health scares, including a toxic chemical spill last November in the Songhua River.

China's sulfurous skies, filled with emissions from coal-fired plants and an expanding auto industry that sells 24,000 new units a day, also have a global impact. Some predictions say China will overtake the US as the largest producer of greenhouse gases within 20 years.

Ever alert to their own hold on power, Chinese policymakers have cited a risk of further social unrest if local officials fail to regulate industries properly. While land disputes are perhaps the common flashpoint in China, rural residents have also vented fury over the contamination of drinking water and farmland by factories and mines.

Beijing now says it will weigh economic growth in provinces against environmental protection. But enforcement of environmental laws is spotty. In theory, China's State

Environmental Protection Agency (SEPA), a national agency with provincial offices, should be a check on local officials. But that is rarely the case, say critics.

"[SEPA's] function is to monitor provincial operations, but they are actually funded by the provincial government whose main concern is economic growth, so it's difficult for [SEPA] to really function," says Yang Ailun, a Greenpeace activist in Guangzhou.

Given its wealth and reputation as the world's workshop, the Pearl River Delta could offer clues on China's ability to balance growth with the sustainable use of natural resources.

While its rivers and skies have taken a pounding, observers say the degradation pales in comparison with other industrialized parts of China that have less money to spend on cleaning up.

Guangzhou has begun collaborating with Hong Kong on monitoring air pollution that often blankets Hong Kong's famed skyline. Guangzhou's middle class is growing more health-conscious, and "green" groups have sprouted on university campuses.

But despite the addition of new water-treatment plants in Guangzhou, experts say that there's a long way to go. A study completed last year on marine life in the Pearl River estuary found high levels of toxic metals. Shrimp contained 16 times the level of recommended cadmium, according to researchers, who identified industrial pollution as the likely cause.

"Factory discharge along the Pearl River is under better control compared with five years ago," says Li Xiangdong, a professor at Hong Kong Polytechnic who coauthored the study. "But even if you control one or two [polluters], the others are still there. It's a widespread problem for water quality."