How Much Is U.S. to Blame for “Made-in-China” Pollution?

China has some of the dirtiest air in the world, but a large share of the country's pollutants are generated during the manufacture of goods destined for countries like the United States, according to a new study. (See related story: "Coal Burning Shortens Lives in China, New Study Shows.")

The research also found that by catching a lift on strong air currents, some of the emissions from China's manufacturing industry are making their way across the Pacific to contribute to smog in the western United States.  (See related "Pictures: A Rare Look Inside China's Energy Machine.")

In the study, detailed in this week's issue of the journal Proceedings of the National Academy of Sciences (PNAS), researchers led by Jintai Lin at Peking University in Beijing found that, in 2006 alone, about a fifth to a third of China's air pollutants—which include sulfur dioxide, nitrogen oxides, and carbon monoxide—were associated with the production of goods for export, and that about a fifth of those amounts were linked to the production of goods for the United States. (See related interactive map: "Four Ways to Look at Global Carbon Footprints.")

The findings come at a time when concern about China's air pollution is increasing. China is now the world's leading contributor to greenhouse gas emissions, and its largest cities are choked with some of the worst smog on the planet. (See related story: "Harbin Smog Crisis Highlights China's Coal Problem.") A new study published this week in Nature Communications even says that Asia's pollution might be having climactic effects far greater than previously quantified, contributing to more intense cyclones over the northwest Pacific Ocean.

The PNAS study places responsibility for China's pollution on both sides of that ocean. (See related story: "Three Ways U.S.-China Conflict Is Helping on Climate Change.") National Geographic News spoke with study co-author Donald Wuebbles, an atmospheric scientist at the University of Illinois at Urbana-Champaign, about his team's findings and the questions they raise about blame for air pollution emissions. The research concludes that both producing and consuming nations share responsibility for emissions generated during the production of export goods.

How did your team reach its conclusions?

Our team was comprised of people who do numerical modeling of the Earth's climate and air quality systems, experts in the emissions of various gases and particles into the atmosphere, and economists.

Analyses were done to evaluate the emissions occurring in China, and then those results were combined with numerical models that allowed us to look at how those various gases and particles are transported to the U.S. through chemical and physical processes in the atmosphere.

The other big aspect of the study is looking at how one should view these emissions. In terms of international policy, should you be looking at emissions in terms of just the emissions [that are] produced in the given country like China? Or should you also be considering the consumer? If the latter, then the U.S. is a major consumer of goods from China. This part of the analysis tells us that we should really be doing a consumer-based analysis to fully account for who's responsible for emissions. (See related story: "In China's Icy North, Outfitting Buildings to Save Energy.")

How do the emissions produced in China reach the western United States?

Strong aloft winds, including those associated with the jet stream, can carry the gases and particles across very long distances, including to the U.S. (See related story: "Climate Change Action Could Save 500,000 Lives Annually, Study Says."

Which parts of the United States are affected?

It depends on the time of year and which years you're looking at, but it's pretty much up and down the West Coast.

Is it possible to say how much the United States and other consuming countries are responsible for the air pollution in China?

About a quarter to a third of the emissions in China are related to the manufacture of goods for other countries, and about 20 percent of that was attributable to goods going to just the U.S. (See related blog post:  "China Puts Kibosh on New Coal Plants (in Three Regions).")

What are some of the challenges of sorting out who is to blame?

One [challenge] was having a good understanding of what goods are going where and trying to analyze that aspect. That's where the economists working with us were really useful. That's what led us to this conclusion that a consumer-based way of looking at pollution is better than just looking at who's producing it.

Why is it important to look at the connection between producing and consuming countries and pollution?

I think it puts responsibility on those who are also consumers as well as those who produce emissions. That means we have to bear some fraction of the responsibility [for emissions produced in other countries].

Follow Ker Than on Twitter.

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.