Louisville’s Air Pollution Control District is beginning work on a new air monitoring system that is designed to help pinpoint the causes of ozone pollution.

Ozone is created when pollution cooks in sun. One type of pollution that contributes to ozone is volatile organic compounds, or VOCs. But some cause more harm than others.

“All VOCs are not created equal,” said APCD Executive Director Keith Talley. “Some are more reactive and lead to the creation of additional ozone. Some are less reactive.”

By 2019, Louisville is required to set up Photochemical Assessment Monitoring Stations. Unlike the city’s current air monitors, which measure ozone levels in general, PAMS measures the photoreactivity of volatile organic compounds to determine which are significantly contributing to the city’s high ozone levels.

“This new monitoring will allow us to determine, of the emissions that we have in this city, which ones contribute the most to the creation of ozone in the community, and that will allow us to be more targeted in reducing those emissions that are going to play the biggest role in reducing ozone,” Talley said.

Some larger U.S. cities have been required to have PAMS for decades. But Louisville is one of the smaller cities swept into the program through recent changes to the country’s ozone standards. And as standards get tighter, cities have likely tapped all of the obvious ways to reduce ozone. APCD spokesman Tom Nord said the more precise monitors will allow regulators to figure out where cuts will make the biggest difference.

“We don’t have the days anymore where it’s just soot being measured in buckets,” Nord said. “You have to kind of improve your knowledge of what we’re breathing out there.”

Louisville’s current ambient air monitors measure pollutants including ozone, carbon monoxide, sulfur dioxide and particulate matter. But since toxics monitoring at the University of Louisville’s Kentucky Institute for the Environment and Sustainable Development was stalled in 2013 because of a lack of funding, there are currently no monitors measuring VOCs in the city’s air.