James Fallows is back from his sojourn in China. His reflections on the health risks of living in a Chinese city are sobering. Sample:

The health situation for ordinary Chinese people is obviously no joke. After stalling, the Chinese government recently accepted a World Bank estimate that some 750,000 of its people die prematurely each year just from air pollution. Alarming upsurges in birth defects and cancer rates are reported even in the state-controlled press.

How long could outsiders live in big, polluted Chinese cities before facing the same actuarial risks as the people who’d grown up there? Now that foreigners have business, cultural, and sheer-fascination reasons to spend time in China, should those opaque skies scare them away? While we were in China, my wife and I joked with friends that now was the time to take up smoking, since our lungs would never know the difference. After returning to the U.S., I decided to ask doctors and public-health experts how much long-term damage foreigners do themselves in exchange for the experience and opportunity of China. This was no one’s idea of a comprehensive survey—and informants still working in China asked me not to use their names—but I was struck by three recurring themes.

The first one was, It’s really bad! As a foreign-trained doctor in Beijing put it, “Just using your eyes, you know this can’t be good for anybody.” Another way to know this is via a clandestine air-quality station that the U.S. Embassy has built in Beijing. The Chinese government does not report, and may not even measure, what other countries consider the most dangerous form of air pollution: PM2.5, the smallest particulate matter, tiny enough to work its way deep into the alveoli. Instead, Chinese reports cover only the grosser PM10 particulates, which are less dangerous but more unsightly, because they make the air dark and turn your handkerchief black if you blow your nose. (Spitting on the street: routine in China. Blowing your nose into a handkerchief: something no cultured person would do.) These unauthorized PM2.5 readings, sent out on a Twitter stream (BeijingAir), show the pollution in Beijing routinely to be in the “Very Unhealthy” or “Hazardous” range, not seen in U.S. cities in decades. I’ve heard from friends about persistent coughs and blood tests that show traces of heavy metals. “I encourage people with children not to consider extended tours in China,” a Western-trained doctor said. “Those little lungs.”