TEH ENG KOON/AFP/Getty Images

A tale of two cities: Above, Beijing’s National Stadium on August 4. Below, the same stadium on August 2. The difference? The weather.

Foreign Policy: You participated in a 2007 study that emphasized some of the key difficulties with Beijing’s air pollution. According to your research, was Beijing’s air ever going to get clean in time?

David Streets: This is a difficult question because, as we showed in our original work, a lot of the pollution that occurs in Beijing comes from outside Beijing. So, in terms of the ability to clean up the local stuff, yes, they are already doing a lot of that. But the big question is what can be done about the pollution coming in from outside. And we know that our study was used as a basis for the mayor of Beijing to get together with leaders of the surrounding areas and cajole them into getting involved. What we don’t know is exactly what those measures were in other places. This information has not been released to anybody, especially outside China, but it will have a big bearing on the final air quality.

FP: What are the health implications for the athletes who are competing? Will they have long- or short-term problems if the air is too heavily polluted?

DS: Normally in the summertime in Beijing, the air pollution can be bad. It can exceed, say, U.S. air-quality standards and the World Health Organization guidelines by a factor of two and sometimes even three on occasion. We’re concerned about two species mainly, and that’s ozone and fine particles. Particulate matter causes the haze that is often seen in Beijing. These two are known to be damaging to human health, especially to people exerting themselves and especially athletes who are superexerting themselves in events like the marathon.

FP: Will the measures that Beijing has passed become lasting legacies? Do you think Chinese officials are serious about cleaning up the city for good, or do you think it will all disappear when the Olympics leave town?

DS: Some of the measures are obviously just for the period of the Olympic Games, and I’m thinking mainly of the traffic restrictions. They’re going to go away. But China has in place air-quality regulations and they’re adopting new technology at their own rate. They’ve made some significant strides in recent years on some aspects of air pollution, like controlling sulfur dioxide from power plants and worrying about vehicle emissions, and they’re trying to tighten the regulations in major cities. The problem is that most of the measures are generally applied in the major cities, like Beijing, Shanghai, and Guangzhou, and it takes a long time for these kinds of technologies to penetrate smaller cities and the countryside.

FP: Let’s say that Beijing, tomorrow, shuts down all emissions: removes every car and cuts off every industry with high emissions. How long would it take to get back to an acceptable level, by WHO standards?

DS: Well, it wouldn’t take too long to clean up the air, especially particulates. It could be cleared out in a few days. The problem is that they’re mostly dictated by weather. If it’s hot, if it’s humid, if the winds are slow or stagnant, then what happens is that you slowly get build up of these pollutants, and that’s a chemical process and doesn’t have much to do with the actual emissions. It only really gets cleared by rain and wind, so in theory the dispersal could only take a few days, but if the weather was bad it could stick around a lot longer.

FP: In your mind, was the International Olympic Committee aware of how difficult an undertaking Beijing’s air would be? Were they simply oblivious? Did they really think it could be done?

DS: I think it was an honest decision, and that China committed to cleaning up the air for the games. We don’t know whether it’s going to be clean enough or not. We won’t know this until it actually happens. If the weather cooperates, and with reductions in emissions, things might be OK. There may be some days where there will be pollution, and China can do two things. If they see this coming—because you can anticipate this from the meteorological forecasts—they can do a lot more, up to and including shutting all industry and telling everybody to take a vacation for a week or two. They could be much more severe in restricting vehicles. I believe they would consider doing that if it looked bad. The other thing they could do is postpone some events until things looked better.

FP: It seems like we’re hearing about all of these efforts to reduce emissions and improve the air quality only now, a couple of months or weeks before the games. Couldn’t they have tried to improve standards on vehicles in, say, 2005 or 2006?

DS: I think they did. The vehicle standards have been tightened in recent years in several stages. This only applies, though, to new vehicles. If you buy a new vehicle today, it has better performance than one in 2003. But the older vehicles are still on the road, so the only way to stop them [from] polluting during the games is by some kind of restriction. If you have a very poor-performing vehicle, you have to stay outside until the games are over. So they couldn’t really do much better than that.

In terms of factories and power plants, they did start seriously about two years ago. Some of the factories were closed or moved some time ago, and the power plants have either been fitted with controls or switched to gas. Power plants generating electricity for the city during this period are pretty well-controlled.

FP: Given the enormity of the task, how do you think China has done?

DS: Beijing has done a good job, probably about as good as they could do. If it turns out that it wasn’t enough, the problem is that the pollution is not that local. So, in order to really clean up for the games, you’d have had to address all of northeast China, and that is impossible. It takes 10 or 20 years to tackle, and you have to do it through national standards, the way it’s done in the United States and Europe. They’ve done a good job, but weather will determine whether it’s good enough. It’s in the hands of the gods right now—the weather gods.

David G. Streets is a senior scientist at Argonne National Laboratory in Argonne, Illinois.