Wyoming's Department of Environmental Quality (DEQ) announced an ozone action day in the Upper Green River Basin for March 19. That means ozone, a secondary pollutant that can cause respiratory issues, could exceed the federal limit in the area: Sublette, Lincoln and Sweetwater counties.
It marks the ninth time the agency has called for an ozone action day this year. Last year, there wasn't a single one.
Keith Guille, a DEQ spokesman, said favorable weather conditions have made this a big year for ozone. That means lots of snowpack, sunshine and not much wind. He said oil and gas activities are also a contributor.
"We recognize there's gotta be those emission sources that help create ozone. It's not like something that's just already there, it has to be created from your NOx [nitrogen oxide] and your VOC [volatile organic compounds] and sunlight and chemical reaction happens," Guille said.
Nitrogen oxide generally comes from vehicles and causes smog. VOCs include a variety of chemicals that combines with NOx to create ozone. Guille said, this year, increased ozone monitoring doesn't necessarily mean more emissions from oil and gas, but the right kinds of pollutants getting emitted.
The "Action Day" triggers industry to join a voluntary effort to reduce short-term emissions.
"Delaying the refueling of trucks and equipment. Eliminating truck idling whenever possible. Encouraging carpooling or teleworking and then also canceling well venting," Guille said.
He said people with respiratory issues, children, and the elderly should consider holding off on strenuous activities. Of the nine ozone action days, the pollutant exceeded federal limits five times. That's only happened once in the past seven years. In 2017, the federal limit was exceeded seven times.