"When you buy a product at Walmart, it has to be manufactured somewhere," said co-author Steven Davis, an earth systems scientist at Irvine, in a press release. "The product doesn't contain the pollution, but creating it caused the pollution."
Air pollution is a major problem confronting China's leaders, who are coping with social, economic and environmental strains resulting from decades of rapid industrialization. A former Chinese health minister recently said that air pollution kills 500,000 people in China every year.
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Most air pollution in the U.S. is produced locally by cars, trucks, refineries and other sources. But powerful global westerly winds can move airborne chemicals across the Pacific in days, according to the researchers.
The incoming dust, ozone and carbon is especially strong in the spring, causing dangerous spikes in contaminants that can accumulate in valleys and basins in California and other Western states, the study said. In Los Angeles, for example, the nitrogen oxide and carbon monoxide from Chinese factories pushes smog levels above U.S. federal ozone limits at least one extra day a year.