New research from Boulder's National Center for Atmospheric Research shows ozone pollution across the U.S. will get worse over the next 35 years due to climate change and rising temperatures.

The NCAR study -- scheduled to be published online this week in the Journal of Geophysical Research-Atmospheres -- shows that the U.S. could see a 70 percent increase in unhealthy summertime ozone levels by 2050 because warmer temperatures and other changes in the atmosphere related to climate change will spur chemical reactions that lead to the creation of ozone.

"It doesn't matter where you are in the United States -- climate change has the potential to make your air worse," said NCAR scientist Gabriele Pfister, the lead author of the new study, in a prepared statement. "A warming planet doesn't just mean rising temperatures, it also means risking more summertime pollution and the health impacts that come with it."

In the study, researchers found that if emissions continue at present-day rates, the number of eight-hour periods in which ozone would exceed 75 parts per billion -- the level considered "unhealthy" by the Environmental Protection Agency -- would increase by 70 percent.

Ozone pollution forms as a result of chemical reactions that take place between nitrogen oxides and volatile organic compounds in the presence of sunlight. Researchers said those chemical reactions occur more rapidly at higher temperatures and plants emit more volatile organic compounds at higher temperatures.

Ground-level ozone can lead to throat irritation and aggravation of asthma, bronchitis and emphysema, and even short periods of unhealthy ozone levels can cause local death rates to rise. Ozone pollution also damages crops and other plants, according to the study.

The study was funded by the National Science Foundation and the U.S. Department of Energy. The University of Colorado, Pacific Northwest National Laboratory and North-West University in South Africa were co-authors on the study.

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