Six of the 10 most polluted cities in the world are in China, one MSU researcher said.

This is a problem for Jack Liu, who was born there and now studies the impact of economic growth on the environment.

"Now, more and more people are realizing the importance of the environment to humans," said Liu, the director for MSU's Center for Systems Integration and Sustainability.

Liu said economic development is important, but comes at the expense of the environment. He has been working with the Public Broadcasting Service on a two-part series titled "China on the Inside," the first of which aired Wednesday.

The second part, focusing on the environmental challenges facing China, will appear on Jan. 17.

Some of the most serious problems are the shortage of water and the pollution of rivers by industrial factories, said Dr. Weijun Zhao, director of Office of China Programs.

"The government tries to regulate, but the local government, they are looking for the economic growth," Zhao said. "They want more factories, more products, (which leads to) more people employed."

Air pollution also is a problem.

"If you go to China this time of year, in December, January, the sky is dark and heavy. That presently causes respiratory problems," Zhao said.

Jim Detjen, professor and director of the Knight Center for Environmental Journalism, traveled to China in spring 2002 and said the pollution was obvious.

"It is clear there are very serious environmental problems in China," he said.

"In many of the larger cites of China, the air pollution is dramatically worse than you see in any large American cities.

"There are times, if you are exercising or riding your bike, it's hard to breathe and you feel pains in your lungs."

Chaopeng Shen, vice president of the Chinese Student and Scholar Association, agrees that pollution is a problem in his country.

But, he said, progress is being made.

"During the economic boom, there used to be much more pollution going on, and the environment on the large was deteriorating," Shen said.

Liu said some of the biggest challenges facing China are human health issues, social issues and the threatened long-term sustainability of economic development.

"Development is not constrained," Liu said.

This rampant industrialization has put a strain on natural resources, especially the availability of water.

"With a shortage of water, people cannot live, basically," he said. "In December 2005, there was a big chemical spill from factories, which destroyed water quality in the northern part of China."

Although the water pollution mainly affects China, it also could spread to Japan, Korea and the west coast of the United States, Zhao said.

"It's not only China's own problem, but it's also a global problem," he said. "There's a long way to go for China to solve the problem."

Although he realizes the cause for concern, Yunjie Ding, president of Chinese Student and Scholar Association, said a lot has been done to address environmental problems in his home country.

"It's improving," Ding said. "(China is) starting to put more and more money into environmental protection."

Staff writer Kristi Jourdan contributed to this report.