THE NEXT time you’re in Los Angeles, take a deep breath. A significant portion of the pollution you’ll breathe into your lungs came from across the Pacific Ocean. Decades ago, Angelenos’ respiratory tracts may have been burned by the accumulation of local pollutants in and around Southern California’s valleys and basins. Since then, federal and state pollution controls did much to clean up the air. But a study in the Proceedings of the National Academy of Sciences finds that neither federal nor state authorities can as effectively restrain one pollution source: China. Chinese and American researchers estimated the amount and ultimate destination of smog-forming gases and particulates that Chinese factories pumped out in their production of export goods. Up to a quarter of the sulfate pollution in the western United States wafted over from those factories. Their emissions add a day of substandard air in the Los Angeles area […]