Filthy emissions from China’s export industries are carried across the Pacific Ocean and contribute to air pollution in the Western United States, according to a paper published Monday by a prominent American science journal. http://www.nytimes.com/2014/01/21/world/asia/china-also-exports-pollution-to-western-us-study-finds.html?ref=world&_r=0

The research is the first to quantify how air pollution in the United States is affected by China’s production of goods for export and by global consumer demand for those goods, the study’s authors say. It was written by nine scholars based in three nations and was published by Proceedings of the National Academy of Sciences, which last year published a paper by other researchers that found a drop in life spans in northern China because of air pollution.

The latest paper explores the environmental consequences of interconnected economies. The scientists wrote that “outsourcing production to China does not always relieve consumers in the United States — or for that matter many countries in the Northern Hemisphere — from the environmental impacts of air pollution.”

The movement of air pollutants associated with the production of goods in China for the American market has resulted in a decline in air quality in the Western United States, the scientists wrote, though less manufacturing in the United States does mean cleaner air in the American East.

Jintai Lin, the lead author of the paper, said in an interview that he and the other scientists wanted to examine the transborder effects of emissions from export industries to look at how consumption contributes to global air pollution.

Powerful global winds called westerlies can carry pollutants from China across the Pacific within days, leading to “dangerous spikes in contaminants,” especially during the spring, according to a news release from the University of California, Irvine, where one of the study’s co-authors, Steven J. Davis, is an earth system scientist. “Dust, ozone and carbon can accumulate in valleys and basins in California and other Western states,” the statement said.

Black carbon is a particular problem because rain does not wash it out of the atmosphere, so it persists across long distances, the statement said. Black carbon is linked to asthma, cancer, emphysema, and heart and lung disease.

“Los Angeles experiences at least one extra day a year of smog that exceeds federal ozone limits because of nitrogen oxides and carbon monoxide emitted by Chinese factories making goods for export,” the statement said.

Using a modeling system called GEOS-Chem, the scientists estimated that in 2006, sulfate concentrations in the Western United States increased as much as 2 percent, and ozone and carbon monoxide levels also increased slightly because of the transportation of pollutants from emissions that resulted from the manufacture of goods for export to the United States.