Westerly winds can carry air pollution from China across the Pacific Ocean in just a few days.
The study was published in the Proceedings of the National Academy of Sciences by researchers in the United Kingdom, China and the U.S.
And within China, roughly 5 percent of emissions of carbon monoxide, black carbon, sulfur dioxide and nitrogen oxides came from making those exports, according to the report.
Coal-burning factories were the biggest sources of the air pollutants – and greenhouse gases.
The amount of air pollution in the Western United States from China is still very small, compared to the amount we produce here already.
Almost a quarter of China’s economic output came from exports last year.
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