The downtown skyline is enveloped in smog shortly before sunset in Los Angeles, California. - 

A new study published in the Proceedings of the National Academy of Sciences says some of that bad air people breath in the American West is imported from China. A lot of the imported pollution has been specifically identified as coming from factories in eastern China that make goods purchased by Americans, which is raising fascinating questions about who is really to blame for the bad air. 

As American manufacturing has largely gone overseas, the prevailing attitude has been that the U.S. has also outsourced the pollution from that manufacturing. But this new study challenges that assertion, says Marketplace China bureau chief Rob Schmitz.

"They've made connections between that very intense pollution that's being emitted in much of China and our own economic role in this very pollution," Schmitz says. "Buying products made in China is not only contributing to China's dangerous air pollution problem, but while those cheap exports are being shipped over the ocean to us, above it all are clouds of pollutants that are also being exported to America."

To hear more about how China's pollution problem is a global problem, click the audio player above.

Follow Rob Schmitz at @rob_schmitz