Area's ozone levels declining but may not meet new standards

Ground-level ozone has declined in Southeast Missouri in the past five years, but the amount may not be low enough to meet stricter ozone guidelines expected to be announced by the U.S. Environmental Protection Agency by the end of October.

The small Perry County community of Farrar is home to one of 23 air quality monitors in Missouri. There are no monitors farther south.

The EPA uses a complex system of averages, resulting in what's called a design value, to establish which counties fail to meet clean air standards and face additional regulation.

According to readings collected by the Missouri Department of Natural Resources, from 2006 to 2008, the design value in Perry County was 77 parts per billion, slightly higher than the 75 ppb standard set by EPA in 2008. From 2007 to 2009, the design value dropped to 74 ppb and from 2008 to date, the design value has dropped to 72 ppb.

Next month, the EPA is expected to release a new, stricter standard, somewhere between 60 and 70 ppb, EPA spokesman David Bryan said.

Looking at each year's individual average, ozone levels went from 80 ppb in 2006 to 82 in 2007, to 70 in 2008, to 71 in 2009 and edged up again in 2010 to 76 as of Sept. 20.

The Farrar monitor has exceeded the ozone standard of 75 ppb four times so far this year.

"It's not bad," said David Grimes, who heads the Southeast Missouri Regional Planning and Economic Development Commission's air quality committee. "It's not as good as we'd like it. You don't want exceedances, but it's not anywhere near awful."

The Farrar monitor has the highest 2010 average of the 11 monitors outside St. Louis and Kansas City.

Twenty of the 23 monitors have ozone averages that are higher this year than in 2009, according to DNR data through Sept. 20.

The summer's high temperatures may be to blame for higher ozone levels this year.

"Molecules are moving faster when it's warmer, and when they do collide, they're likely to have enough energy to go through the reaction," said Dr. Matthew Fasnacht, who teaches environmental chemistry at Southeast Missouri State University. "The hotter the days, the more likely you're going to have an ozone event."

Wind also affects ozone levels because the particles that react to create it are easily transported in the air. Days with little wind are more likely to be higher ozone days, Fasnacht said.

Nitrogen oxide, a byproduct of combustion, and volatile organic compounds, like evaporated gasoline, react with sunlight and heat to produce ground-level ozone.

"We've had the heat and we've had the sunlight, but we're having reasonable [ozone] numbers. The only conclusion you can draw is there are fewer precursors in the air," Grimes said. "That tells me we've been doing a good job being proactive."

Emissions controls in place in the metro St. Louis area at factories and vapor recovery nozzles at gas stations have helped reduce ozone, Grimes said.

"Ozone has been an issue for more than 20 years in cities; it just hasn't hit the rural communities until now," Fasnacht said.

A voluntary Clean Air Action Plan aimed at further reducing ozone will soon be implemented in the seven counties that make up the Southeast Missouri Regional Planning and Economic Development Commission. The plan includes measures to limit car idling, mowing lawns during the heat of the day and topping off gasoline tanks, which often results in spills.

Ground-level ozone is the same as the ozone found high up in the Earth's atmosphere -- a molecule made up of three oxygen atoms.

"We need stratospheric ozone to shield us from UV rays, but we don't want the ground level because it's an irritant in our lungs," Grimes said.

Health problems associated with ozone include reduced lung function and inflammation of the linings of the lungs, according to the EPA.

mmiller@semissourian.com

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