GREEN RIVER — The potential threat of Sublette County’s air to the health of its residents will be the subject of a meeting Tuesday in Pinedale.

An ongoing study is looking at the risks to Sublette County residents from air toxics and harmful ozone.

Wyoming Department of Environmental Quality spokesman Keith Guille said the air toxics project was commissioned by Sublette County Commissioners in 2008, with the financial assistance and technical oversight of the DEQ.

The two-year study involves data collection on airborne toxics gathered at 16 sites in the county, including five sites that continually monitor for ozone readings.

Most air samples collected during the study are being analyzed for six identified chemicals of potential concern and ozone, according to the DEQ. Sample collection began in February 2009.

The study aims to determine the exposure patterns for residents.

The report will then assess the expected human health risk resulting from exposure of residents to air toxics and ozone measured in the ambient air throughout the county.

Sublette County has experienced wintertime ground-level ozone formations the past few winters that have drawn the ire and concern of residents.

The county has seen ozone levels on occasion that compare with metropolitan cities, where it is commonly found in the summer.

Scientists believe the estimated 4,000 natural gas wells in the Jonah and Pinedale Anticline gas fields have contributed to the ozone problems. They contend emissions from motor vehicle exhaust, industrial facilities and other fossil fuel sources in the fields help create ozone.

At ground level, ozone is a potentially poisonous gas that can cause breathing problems in children, the elderly and in people with respiratory conditions.

Ground-level ozone is created by chemical reactions between nitrogen oxides and volatile organic compounds in the atmosphere in the presence of sunlight.

Dr. Timothy Ryan with the Wyoming Department of Health will discuss the ongoing risk assessment process that is being used in the air toxics project.

The DEQ’s Air Quality Division will also provide a summary of air monitoring results for the first quarter of 2010.

DEQ scientist Jan Lydigsen said validated air toxics data is not yet available for the first quarter of this year.

“Therefore we will provide an overview of air quality monitoring results based on preliminary data for this period,” Lydigsen said.

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Guille said Cara Keslar with the Air Quality Division will also present an update of the 2010 winter ozone season, which ended April 2.

Current efforts by the state and industry to clean up the air in Sublette County seem to be working. There were no ozone advisory warnings this winter.

At the state’s behest, EnCana Oil and Gas Inc. and other operators in the field have taken the lead in recent years to reduce their emissions, including the conversion of hundreds of diesel-powered drilling rigs to run on natural-gas-fired engines.

The industry has also implemented strict contingency plans aimed at curbing ozone-causing pollutants when state officials predict the atmospheric conditions are ripe for ozone formation.

A draft of the air toxics report is expected to be issued in August for public review, according to plans. A final report is scheduled for release in September.

Guille said the meeting will begin at 6:30 p.m. at the Sublette County Library in Pinedale.

Contact Jeff Gearino at

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