Casper and Cheyenne have some of the cleanest air in the country, and Sublette County is among the most polluted counties, according to a study by the American Lung Association.
The group released its annual “State of the Air” study Wednesday. Wyoming’s two most populous cities both ranked highly.
Cheyenne received an “A” from the association for its low levels of average particle pollution for 2012, a measure of how many fine liquids or solids are in the air. The capital city ranked first in the country in the standard, edging out cities in Utah, Arizona and New Mexico.
The Los Angeles and Bakersfield, Calif., metros were named the most-polluted cities for air quality.
Casper also fared well in the rankings, earning an “A” in average particle pollution. Data on ozone levels in Casper and Cheyenne, another criterion measured by the association, wasn’t available.
Of the eight Wyoming counties that did receive a grade, only Sublette County received an “F.”
The county and the surrounding area were recently placed on an EPA “nonattainment” list for excessive levels of ozone, a toxic gas, largely as a result of natural gas drilling. State regulators have announced a plan to address the pollution and bring the area back into compliance by 2015, a federal deadline.
But the county didn’t score exclusively bad marks — it received an “A” in particle pollution.
Association staff compiled the rankings using U.S. Environmental Protection Agency data.
“It was just a few years ago that we learned of the ozone pollution happening during Wyoming winters,” said Renée Klein, president and chief executive officer of the association’s Mountain Pacific Region. “So there’s definitely more work to do to clean up sources of pollution to protect the health of our citizens.”
Of the other counties graded, only Fremont County approached a failing grade in either ranked category, receiving a “D” in ozone and a “B” in particle pollution.
Uinta, Teton, Park, Sweetwater, Crook and Carbon counties all received an A or B in every category. Grades weren’t given to any other Wyoming counties. According to the association, the data needed to award a grade were not available for many counties and cities in Wyoming.