CHEYENNE, Wyo. (AP) — Itchy eyes and scratchy throats blamed on high levels of wintertime ozone have returned to western Wyoming's gas patch for the first time in six years, and so too has finger-pointing over who's responsible for fouling the air.
The ozone results from atmospheric chemical reactions that occur in just the right mix of cold temperatures, sunlight, snow on the ground and air pollution.
The Upper Green River Basin is home to two of the largest onshore U.S. gas fields, the Jonah Field and Pinedale Anticline operated by Jonah Energy, QEP Resources and Ultra Petroleum. The companies have cut emissions of volatile organic compounds by almost 7,000 tons and nitrogen oxides by almost 2,000 tons since 2008, according to the Wyoming Department of Environmental Quality.
Those reductions in ozone-forming pollutants, coupled with a decline in drilling since last time ozone was a problem, leads John Robitaille with the Petroleum Association of Wyoming to suggest that other pollution sources, such as wood stoves, are to blame.
"We don't currently know how many people were out warming up their vehicles for long periods of time in the mornings. There are multiple things going on out there that I think need to be looked at," Robitaille said Monday.
The focus needs to remain on the gas industry, said Pinedale resident Elaine Crumpley with the group Citizens United for Responsible Energy Development.
"Industry has made some changes and that's well and good. It isn't, obviously, enough," Crumpley said. "They have to come up with some solutions here."
This winter, average ozone levels in the Upper Green River Basin exceeded the federal health-risk standard of 70 parts per billion for the first time since 2011. Eight-hour averages topped the standard on seven days — Jan. 18 and 19; Feb. 14, 15 and 17; and March 3 and 4 — though this year's peak of 85 ppb was well below the 2011 high of 123 ppb.
Ozone above 100 ppb is more consistent with a big city with air pollution problems than a rural area known for migrating big game and a world-famous trout stream. Other gas-drilling hotspots in the West including Utah's Uintah Basin have wintertime ozone problems.
This winter's resurgence in Wyoming happened despite largely voluntary industry efforts in cooperation with state regulators, who declare "ozone action days" when forecasts call for ozone-forming conditions. Companies respond with steps including cutting back on nonessential truck traffic.
"We've been able to reduce the emissions that lead to ozone. And that's a good step forward but we're not done, we realize that. We're still going to focus on this and try to curb those precursor emissions," Wyoming DEQ spokesman Keith Guille said.
Snow cover helps ozone to form by reflecting sunlight back into the atmosphere. A record 15 inches or more of snow covered the basin through much of January and February.
Locals say they go cross-country skiing only to feel congested and wheezy, problems they can't definitively connect to the ozone or a virus. But a cough that afflicted Pinedale resident Dave Hohl during the ozone six years ago was back again this winter, he said.
"I can't be really sure that it was ozone," said Hohl. "It seems like a little more than a coincidence."