China Exports Pollution to U.S.

Interconnecting economies across the world has many benefits regarding job production, infrastructure, and revenue/profit. An unfortunate consequence of a global trade market that has recently received attention by the media is the intercontinental movement of air pollution. A negative consequence of such interconnected economies has been analyzed regarding China's exporting infrastructure with the U.S as highlighted in an article in the New York Times (NYT). A report in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) recently analyzed the movement of pollutant emissions from Chinese emissions. These emissions are largely a result  of the the manufacturing of goods in China for foreign consumption.

The New York Times highlights that companies in the U.S. decide to outsource manufacturing to other countries, namely China, for various reasons including the avoidance of the additional emissions of air pollution associated with large manufacturing plants; the true effect of this strategy is commented on by one of the authors of the PNAS article:

"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 NYT article highlights that although there is intercontinental movement of air pollution from China to the US (fig 1), the net reduction of manufacturing in the U.S. does mean cleaner air in the American East. This is easily understood by considering that the movement of pollution approaches the U.S. from the West, leaving the highest concentrations of pollution in the Western half of the U.S. Since the population density is much higher in the Eastern regions of the U.S., this results in decrease of average air pollution when considering the entire country.

The NYT article also highlights that the amount of air pollution in the Western U.S. resulting from emissions from China is a small fraction compared to the amount produced by sources in the U.S. including traffic and domestic industries.

Figure 1. Simulated maximum percentage of Chinese EEE (emissions embodied in export) to daily mean US surface pollution for (A) sulfate, (B) ozone, (C) black carbon (BC), and (D) CO (carbon monoxide).

To better understand how manufacturing goods for export has affected China and the US, consider that in 2006, 36% of anthropogenic sulfur dioxide, 27% of nitrogen oxides, 22% of carbon monoxide, and 17% of black carbon were emitted in China as a result of the manufacturing of goods for export. For each of these pollutants, 21% were a result of China-U.S. trade. Atmospheric modeling showed that export-related Chinese pollution contributed 3 - 10% of annual mean surface sulfate concentrations and 0.5 - 1.5% of ozone over the Western U.S. in 2006 (fig 2). This extra pollution has averaged to one extra day or more of noncompliance with U.S. ozone standard in Los Angeles and even much of the Eastern states.

Figure 2.  Simulated percentage contribution of surface air pollution in 2006 from Chinese EEE for (A) sulfate, (B) ozone, (C) black carbon (BC), and (D) CO (carbon monoxide).

Overall, the NYT article did an excellent job of covering the key points that the PNAS article discussed. The modeling done by the authors was just that, a model, and the NYT article did not make broad assumptions on the data presented. The NYT article also did a great job of highlighting that manufacturing of exported goods is not only harmful to the U.S. but also to regions east of China, a topic that is not discussed as much in the PNAS article. I believe this was a good example of popular media bringing a pressing issue to light using scientific data from a peer-reviewed source.