Scientists have been documenting the phenomenon of pollution crossing the Pacific Ocean since the 1990s. Most research so far has focused on how imported emissions affect average pollution levels, but the latest analysis goes further, says Meiyun Lin, an atmospheric chemist at Princeton University in New Jersey, who is the lead author of the study. "We show that Asian emissions directly contribute to ground-level pollution in the United States."
Using chemical modeling, Lin and her colleagues distinguished between locally generated pollution and that arriving from thousands of miles away. They analzsed air-quality data from satellites and ground measurements to track the passage of ozone from Asia's churning factories to the western United States over the course of a few days in mid-2010.
They found that the majority of US ground pollution came from local sources, but as much as 20 percent was attributable to Asian emissions.
So the Chinese get our bitumen, refine it into petroleum products, burn those for energy needed to flood Wal-Mart shelves with their wares, and send us ozone as a free bonus.