January 21, 2010

Asian Pollution Drifting To US Skies

Pollution from Asia is causing ozone levels to rise above the western United States, an increase that could make it more difficult for the U.S. to meet Clean Air Act standards for ozone pollution at ground level, according to an international study published on Wednesday.

The study, published in the journal Nature, analyzed large sets of ozone data captured since 1984. It focused primarily on data for ozone in springtime above western North America at an altitude of between two and five miles, reported AFP.

This height is between the stratosphere, where a thin layer of ozone helps to filter out harmful ultra-violet light from the Sun, and at ground level, where ozone can be dangerous for those suffering from cardiac or respiratory problems.

According to the study, ozone levels in the monitored area has risen by 14 percent in springtime from 1995 and 2008.

After taking data for 1984 into consideration, the year with the lowest average ozone level, the increase from that date up to 2008 was 29 percent.

The paper says this boost in levels could only be explained by pollutants that are the precursors to ozone and strong winds pushed them across the Pacific from East and South Asia.

Nitrogen oxides and volatile organic compounds, which are gases that are the byproduct of burning fossil fuels, are the primary man-made sources of ozone. They react with sunlight to produce ozone, which is a triple molecule of oxygen.

Domestic emissions of these precursor gases had decreased during the time of the study.

"In springtime, pollution from across the hemisphere, not nearby sources, contributes to the ozone increases above western North America," said lead author Owen Cooper of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado.

"When air is transported from a broad region of South and East Asia, the trend is largest," he said in a press release.

With previous research indicating that pollution at the altitude in the study can descend and mingle with surface air, such findings are of great importance.

If what researchers suspect is true, experts may find the answer to a question they have been asking for a long time. Even though there has been an increase in ozone levels in parts of the rural western United States, there has not been much road traffic or industry in these regions to justify such a spike in levels.

The paper says the phenomenon could have adversely affect the U.S. as it attempts to deal with smog problems with tough car-exhaust measures and other initiatives.

"The observed increase in springtime background ozone mixing ratio may hinder the USA's compliance with its ozone air quality standard," it says.


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