Beijing’s pollution – and how to control it – is an old topic of debate. Now, thanks to a municipal research program aimed at clearing the air for the “Green Olympics,” it’s a USD 3.2 million question. If the task were as easy as shutting down local factories, phasing out coal-fired heating, cleaning up power plants, and restricting traffic during the Games – plans already being carried out by officials – Beijing would be on course. But researchers have come to realize that much of the capital’s dirty air is drifting in from outside the city, so figuring out the different sources of the pollution and what to do about it is much more complicated than anyone expected.

“The general implication is that it’s not going to be so easy to clean up Beijing for the Olympics,” says Kenneth Rahn, a Rhode Island-based atmospheric scientist and visiting scholar at Tsinghua who works with the university’s Air Pollution and Control Institute.

Rahn, who studies aerosols (microscopic particles that create haze and may contribute to health problems), says that much of the pollution is floating in from outside Beijing. He cites metal smelters in Outer and Inner Mongolia and Western Siberia as a primary source, but his team has also discovered another culprit: the coal-fired factories and cars to the south of Beijing. Lying as far away as Shandong, Henan and Shanghai, these areas may also need to be cleaned up ahead of the Olympics. “This is something really new,” he says. Thinking that Beijing alone is responsible for its pollution is an oft-repeated mistake in the annals of atmospheric science, says Rahn. “When the Scandinavians complained about acid rain coming up from the UK and Germany, people laughed at them. But [the Scandinavians] were right.”

During a typical pollution cycle, smog blows in from the northwest. Then, winds from the south begin to pick up and travel across the flat coastal region that Rahn refers to as The Bathtub, for the way dirty air here easily “sloshes” around. As with other cities, when it arrives in Beijing, the migrant smog mingles with local particulate matter until a cold front or rain pushes it away.

But how many days of blue skies will Beijing get during the Games – and will the city meet Olympic air standards as promised? According to Rahn, while Beijing’s pollution cycles become weaker and less frequent in summer, they begin to reappear with moderate strength in August, just when the athletes roll into town. “That means that the degree of air pollution during the Summer Olympics is purely a matter of chance,” he says.

For the future, Rahn suggests China set stricter emissions controls on cars and create policies like the landmark 1970 Clean Air Act in the US, which enforced pollution standards for all new factories and power plants, because, as he sums it up, “It’s not about the Olympics but the next 50 years.” Alex Pasternack