_Stop Ozone Before It Starts

Atmospheric researchers believe hundreds of lives and hundreds of millions of dollars in crops could be saved with a minimal reduction of the key emissions that form ozone.

_Shannon Capps

Capps is an assistant professor in the Department of Civil, Architectural and Environmental Engineering in the College of Engineering.

What do you get when you mix oxides of nitrogen, volatile organic compounds and sunlight? You get ozone, which harms people and plants. But, policies that limit these precursors could drastically reduce the formation of ozone, according to an international team of atmospheric researchers.

Shannon Capps, an assistant professor in Drexel’s College of Engineering, led the team which traced the precursors of air pollution over space and time across the United States to understand why it forms where it does and what specific steps can be taken to curtail it.

“Having a map of where marginal emissions reductions are expected to benefit human health and crop productivity greater than average is an important new development,” Capps says. “For example, we found that by cutting oxides of nitrogen (NOx) and volatile organic compound (VOC) emitted by humans by just 10 percent, nearly 650 lives could be saved.”


Researchers found that by cutting oxides of nitrogen (NOx) and volatile organic compounds (VOCs) emitted by humans by just 10 percent, nearly 650 lives could be saved.

In urban areas, where NOx are present in high levels from vehicle fuel and exhaust, VOCs are the controlling factor for ozone formation. For instance, in Chicago, St. Louis and Louisville, 10 percent reductions in VOC emissions would not only benefit the health of residents but also the productivity of surrounding soybean producers.

Nitrogen emissions played a larger role in affecting the productivity of plants and crops. For crops like potatoes, soybeans and cotton, a 3-4 percent loss in productivity due to ozone exposure could be reduced by about 5 percent with the prescribed 10 percent reduction of NOx emissions.

The group produced a map that shows were it is most advantageous to reduce VOC and NOx emissions. That is, where would a 10 percent reduction in NOx or human-produced VOCs benefit both human health and crop productivity while also helping states comply with the EPA’s National Ambient Air Quality Standards? Such information has been hard for local regulators to find in the past.

“The tools that we used could be applied by local or state governments to determine how to efficiently protect both human health and crop productivity from ozone exposure,” Capps says.