Air pollution from China blows across the Pacific and partly offsets the clean air measures in the western U.S.

Researchers of a new study published in the journal Nature Geoscience on Aug. 10 revealed that over two-fifths of the anticipated benefits of anti-pollution controls in western U.S. were lost as a result of the increasing ozone pollution in China, providing another evidence that domestic pollution problems can have international implications.

Willem Verstraeten, from the Royal Netherlands Meteorological Institute, and colleagues used observations and computer models in their study and found that China's emissions of nitrogen oxide, which come from industrial and vehicle emissions, increased by 21 percent and its tropospheric ozone levels increased nearly 7 percent for a five year period between 2005 and 2010.

They also noted that the increased amount of ozone was being transported to the U.S. offsetting 43 percent of the anticipated air quality benefits from locally adopted measures on the west coast. Verstraeten said that China is in essence exporting its air pollution to America's West Coast.

The findings underscored the need for countries all over the world to work together in efforts to fight air pollution given that its effects can be felt outside of a country's borders.

"Global efforts may be required to address regional air quality and climate change," the researchers wrote. "Air quality and regional climate-change mitigation policies could eventually have limited impact if not considered in a global context."

Although ozone in the upper atmosphere is considered crucial in protecting the Earth from UV radiation, it is actually a harmful pollutant at ground level known to cause respiratory problems in humans as well as damages to plants. It also acts as a planet-warning greenhouse gas in the troposphere.

The study likewise explained why the ozone levels along the U.S. west coast remained the same despite efforts to significantly reduce ozone-forming chemicals in these areas.

"We find that transport from China of ozone and its precursors has offset about 43% of the 0.42 DU reduction in free-tropospheric ozone over the western United States that was expected between 2005 and 2010 as a result of emissions reductions associated with federal, state and local air quality policies," the researchers wrote in their study.  "We conclude that global efforts may be required to address regional air quality and climate change."

Chinese officials acknowledged the air pollution problem of their country and now take measures, which include restricting traffic, shutting down coal plants and bolstering use of renewable energy.

Photo: Kevin Dooley | Flickr 

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