Lanzhou is known for its colorful ethnic mix, its super-spicy beef noodles, and its historic perch on the Silk Road. But it has another distinction. In 2011, the World Health Organization named Lanzhou as the city with the worst air quality in China. In spring, sandstorms choke the city - a product of deforestation, overgrazing and urban sprawl.

"If the sandstorm is very strong, I can't go outside, sometimes I can't even breathe, " says Li Xiao, a university student in Lanzhou. And winter, she says, is not much better. That's when the thermal power stations fire up, to heat homes. They run on coal - one of the dirtiest fuels around. For Li Xiao that means "Putting a mask over my head to protect myself." And: keeping keen eyes on the road, as pollution reduces vision to a minimum: "At the worst time, it's somewhere between 10 and 20 meters," he says.

Lanzhou sits in a valley, so there is little air flow to carry pollutants away. But a big part of the problem is man-made. The area is home to petrochemical plants, coal mines and heavy industry.

Soaring pollution and rising health issues

And Lanzhou is hardly an anomaly. Most of China's major cities are shrouded in smog. Like Lanzhou, they're facing huge environmental strains, like the break-neck pace of urbanization. Adding up to that, are tidal waves of newcomers from the countryside, about 20 million a year. That means more roads, more cars, more steel, more smelters - and more pollution.

Meanwhile, China still relies on coal for three-quarters of its energy needs. Coal-burning power plants have helped make it the world's No. 1 greenhouse gas polluter. It is a reminder that China's show-stopping economic rise has come at a huge cost to the environment.

But analysts say attitudes are shifting. People are drawing a line, especially when it comes to their health.

Dr. Jiang Fang is a respiratory specialist with 20 years experience in Lanzhou. Outside her office, patients wander the halls with chest x-rays in hand. She runs through some of the ailments caused by dirty air: runny nose, asthma, lung cancer, cardiovascular disease. “We tell our patients to decrease activities outdoors in spring and winter. Second, we advise them to pay attention to the air flow indoors. We advise the elderly to do exercise in a gym,” Dr. Jiang says.

Small things that matter

Two years ago, the U.S. embassy in Beijing began doing something the Chinese government refused to do: it posted air quality readings - from a monitor on its roof to Twitter. Eventually, the Chinese government gave into public pressure and began publishing its own data.

A few cities have even begun to track tiny particulate matter, meaning dust that is 2.5 microns in diameter or less. This is especially important because these smaller particles can easily penetrate the lung and enter the bloodstream. And although they're extremely hazardous, until recently they were absent from the official data.

Tom Young is a biologist in Shanghai. But his hobby is to crunch the numbers on air pollution. On his website, he funnels public data into tidy graphs for anyone to see and understand. “I think it's a general trend that the wider population is now equipped with better knowledge of their living environment. I think it's a good trend.”

Development not at all costs

Young says he hopes his site will help people decide when to exercise. It might even reveal trends. While he crunches his numbers, China's environmentalists are getting bolder. There has been an uptick in mass protests over health risks related to industrial projects. Some have turned violent. Experts say the government has gotten the message. But it remains to be seen whether China's new generation of leaders can rein in polluters and still deliver the amazing economic growth the Chinese have come to expect.

Young says the Chinese are ready to make some sacrifices. “The issue of environmental protection in general is stronger, and I don't think it can be stopped or muffled, because it's a genuine awakening among the average Chinese citizen. They may be more willing to sacrifice some economic growth in exchange for a more green economy in China.”

After all, not only analysts note that, at the end of the day, China's environmentalists and China's leaders all have to breathe the same air.