One recurring subject among Westerners living in Beijing, at least in my circle of friends, is whether we’re harming our kids by choosing to live in a polluted environment.

Beijing is severely polluted. Call me ethnocentric but my experience is that most Chinese have no idea how severe the pollution is. They’ve rarely or never been outside of China, and they’ve grown accustomed to the haze and smog. We Westerners are not. Yet we choose to live here, often for very good job reasons, even enjoying ourselves greatly. And our kids’ health may suffer in the process. It’s not something most parents want to dwell on.

I spent the morning with Kenneth A. Rahn, an atmospheric chemist retired from the University of Rhode Island. He’s working with Tsinghua University in Beijing, China’s top university in the sciences, to study air pollution.

We discussed the dry air, wind movements in Central Asia, tiny suspended particulate matter, and other factors aggravating the pollution. Then I found myself blurting out the question: How bad is it for my family to live here?

He began by describing the general conditions of air pollution in northern China, saying the blanket of aerosol pollutants stretches not just over urban areas but vast regions stretching hundreds of miles away.

“When you fly out of Beijing, all you see is brown everywhere,” Rahn said. “The levels of most things – ozone, particulates and gases – are six to seven times higher than what we are used to in the West.”

Arriving, many foreigners are surprised at the number of smokers in Beijing. One wag even suggests that smoking through a filtered cigarette is better than breathing the air. News reports sometimes say that living in Beijing is like smoking a pack of cigarettes a day, but Rahn said he couldn’t make such a comparison.

“It’s not going to help your health to live in Beijing. That’s for sure,” he said, discussing the lethargy many foreigners feel when arriving for the first time. “People talk about ‘Beijing crud.’ After a week, your joie de vivre is completely blow. You don’t feel enthusiastic about stuff. … You don’t sleep so well.”

I went to see Rahn partly because of a posting on a blog that suggested environmental protection officials might be fudging numbers so that Beijing can achieve its vaunted target of 245 “blue sky” days this year.

Rahn said he didn’t think officials had had “fun” with the numbers but he scoffed at the concept of  “blue sky” days.

“They take what is really a bad condition and give it a good name,” he said. “The concept is crazy. ... ‘Blue sky’ days in Beijing are not really blue. They are various shades of gray.”

He also dismissed the test in mid-August when Beijing officials forced some one million cars off the road for three days. “The scientists who have looked at the data all agree that there were no detectable changes from the auto experiment,” he said.

Much bigger factors are at play on the air pollution than the cars on the road, he said, and when it comes down to the Olympic Games next summer, there is little authorities can do except hope that a northern wind comes along and blows the smog away.

“What are you going to do? You’re going to pray to the Mongolian weather Gods and hope for Mongolian air,” he said.