The study by researchers Peking University, Tsinghua University, University of California Irvine, Argonne National Laboratory, the University of Illinois at Urbana-Champaign, and the University of Leeds in England is the first to quantify how much of the pollution reaching the American West Coast is from the production in China of cellphones, televisions and other consumer items imported here and elsewhere.

We’ve outsourced our manufacturing and much of our pollution, but some of it is blowing back across the Pacific to haunt us. Given the complaints about how Chinese pollution is corrupting other countries’ air, this paper shows that there may be plenty of blame to go around.

When you buy a product at Wal-Mart, it has to be manufactured somewhere. The product doesn’t contain the pollution, but creating it caused the pollution.

—Steve Davis, UC Irvine Earth system scientist and co-author

Maximum daily percentage of sulfate pollution in US related to Chinese exports. Lin et al. Click to enlarge.

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 analysis found.

On other days, as much as a quarter of the sulfate pollution on the US West Coast is tied to Chinese exports. All the contaminants tracked in the study are key ingredients in unhealthy smog and soot.

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.

The study authors suggest the findings could be used to more effectively negotiate clean-air treaties. China’s huge ramp-up of industrial activity in recent years, combined with poor pollution controls, has unleashed often fierce international debates.

International cooperation to reduce transboundary transport of air pollution must confront the question of who is responsible for emissions in one country during production of goods to support consumption in another.

—Lin et al.

Jintai Lin of Beijing’s Peking University is the paper’s lead author. Others are Da Pan, also of Peking University; Qiang Zhang, Kebin He and Can Wang of Beijing’s Tsinghua University; David Streets of Argonne National Laboratory; Donald Wuebbles of the University of Illinois at Urbana-Champaign; and Dabo Guan of the University of Leeds in England.