Since the dawn of the satellite era, scientists have been able to watch as vast plumes of particulate matter swirl off of China and move over America. This image from 2001, for instance, shows a vast storm of dust and invisible pollutants traveling from Asia to the United States:
The Asian smog is always coming, especially in the spring. During sporadic surges once or twice a month, it can spread pollution levels over the West Coast of up to 75 percent of federal standards. But Americans can't complain too much about China's interloping smog. Part of it comes from our rabid consumerism, as the factories churning out the foul air are making our TVs, cellphones, and other valued imports.
Now, researchers have found a way of quantifying how the Western world's hunger for cheap Chinese goods influences trans-Pacific air pollution. A team from UC Irvine, writing in the Proceedings of the National Academy of Sciences, explain that the U.S. and Europe are indirectly responsible for one extra day a year of dangerous pollution in Los Angeles. (Specifically, nitrogen oxides and carbon monoxide.) And on bad days, a full quarter of sulfate pollution over the West Coast can be linked to Chinese exports. "Given the complaints about how Chinese pollution is corrupting other countries' air," says Irvine's Stave Davis, "this paper shows that there may be plenty of blame to go around."
This map from the study shows how black carbon relating to exports flows from Asia to North America:
And this one indicates the daily percentages of sulfate pollution in the U.S. that derive from Chinese exports:
It's not easy to shrug off the West's involvement in generating Chinese smog, the researchers explain:
China is not responsible for the lion's share of pollution in the U.S. Cars, trucks and refineries pump out far more. But powerful global winds known as "westerlies" can push airborne chemicals across the ocean in days, particularly during the spring, causing dangerous spikes in contaminants. Dust, ozone and carbon can accumulate in valleys and basins in California and other Western states.
Black carbon is a particular problem: Rain doesn't easily wash it out of the atmosphere, so it persists across long distances. Like other air pollutants, it's been linked to a litany of health problems, from increased asthma to cancer, emphysema, and heart and lung disease....
"When you buy a product at Wal-Mart," noted Davis, an assistant professor, "it has to be manufactured somewhere. The product doesn't contain the pollution, but creating it caused the pollution."
Of course, China's captains of industry could switch to cleaner forms of manufacturing instead of building coal plants all over the place. But that doesn't seem like it will happen soon, with experts predicting that China – despite a government-sponsored anti-smog campaign – will actually use 2.7 percent more coal this year. The researchers suggest that their insights on export-caused pollution one day could be used to negotiate international clean-air treaties, perhaps assigning greater smog-cutting duties to nations that import more fossil-fuel-generated products.
Top image: A man wears a face mask during a hazy day in downtown Shanghai in December, 2013. (Aly Song / Reuters)