Wintertime ozone, a relatively new phenomenon that is affecting air quality some of the West's major oil and gas fields, remains a mystery for regulators, in part because the problem is exacerbated by shifting weather patterns. Even so, states like Wyoming and Utah are under growing pressure to ratchet down ozone-forming pollutants from drill rigs. Photo courtesy of NOAA.
The mystery behind the wintertime ozone problem that has plagued parts of the Intermountain West is deepening as pollution levels during the first quarter of 2011 dropped in northeast Utah but increased in southwest Wyoming.
Ground-level ozone exceeded federal health standards in northeast Utah's Uintah Basin on 26 days between January and March, according to air monitoring data compiled by U.S. EPA. That figure was down from 37 days of ozone exceedances recorded in the basin for the first three months of 2010.
But in Wyoming, after two years of clean winter air in the Upper Green River Basin, EPA monitors registered 13 days between January and March when ozone levels exceeded the eight-hour health standard of 75 parts per billion (ppb). That includes a March 2 ozone reading of 124 ppb -- higher than the worst ozone levels recorded last year in Los Angeles.
And even though the Uintah Basin saw fewer bad ozone days early this year, the region did experience significant ozone spikes on days when the pollutant was a problem. That included a Feb. 16 eight-hour average of 146 ppb, nearly twice the federal standard and potentially dangerous for even healthy adults to breath, said Carl Daly, chief of the air permitting, modeling and monitoring unit in EPA's Region 8 office in Denver.