After exceeding the standards for ground-level ozone just three times last year, the Perry County monitor has posted 14 exceedances since May.
The current standard, set by the U.S. Environmental Protection Agency, is 75 parts per billion, but the monitor in Farrar, Mo., registered as high as 89 parts per billion June 29, when the temperature hit 107 degrees.
"The heat wave got us. Hot days, still air, lots of sunshine equal the perfect recipe for ozone formation," said David Grimes, deputy director of the Southeast Missouri Regional Planning and Economic Development Commission in Perryville, Mo., who coordinates the regional air quality task force. Other ozone monitors across the state are also recording high ozone values, with Bonne Terre, Mo., monitor in Ste. Genevieve County showing seven exceedances and many monitors in St. Louis and Kansas City, Mo., posting readings above the standard as well, according to the Missouri Department of Natural Resources weekly ozone report released Monday.
The ozone monitor with the most exceedances this year is in Maryland Heights, Mo., with 21 since May.
Counties that fail to meet ozone standards are considered "nonattainment zones" and businesses there face restrictions on their emission of pollutants that contribute to the formation of ozone, such as nitrogen oxide and volatile organic compounds. Exposure to ozone causes a variety of respiratory problems for people and can damage vegetation and upset ecosystems, said Renee Bungart, director of communications at the Missouri Department of Natural Resources.
The designation is based on a three-year rolling average of ozone readings called a design value. The Farrar monitor's design value is currently 77 parts per billion, but the ozone season continues through October. As of Monday, 10 out of the state's 23 ozone monitors had design values above the current standard and two at 75 parts per billion, according to DNR records.
"This is particularly troublesome for us since the Farrar monitor is, at this point, out of compliance for the year and the Bonne Terre monitor is right on the cusp at 75 parts per billion," Grimes said. "When the EPA review of the National Ambient Air Quality Standards for ground-level ozone gets going next year I expect, worry and fear that the new standard will be lower still."
Using air modeling programs, Grimes said, the air on high reading days is coming to this area from the Chicago area across the Ohio River Valley, which has lots of electricity-generating utilities using the Ohio River to import their coal.
There were no exceedances recorded on the Farrar or Bonne Terre monitors last week, as temperatures returned to normal for this time of year.
But Mike York, meteorologist with the National Weather Service in Paducah, Ky., said the next four to eight days will bring the return of above-normal temperatures.
"There's been a persistent upper-level high over a large part of the country that has been responsible for the heat and the dry weather. Really it started in our area in the spring," York said.
On three of the 14 days when exceedances were recorded the high temperature was over 100 degrees, according to National Weather Service data. The temperature was above 90 on every exceedance day except one.
The U.S. Environmental Protection Agency is scheduled to review the ozone standard and boundary designations again in 2013, Bungart said. As part of that review, the EPA will also evaluate all of the monitors that have violated the current standard. The EPA could require states to implement additional control measures to address the violations in order to bring the area back in to compliance, she said.
"If we don't get a cool summer next year, it is likely that both monitors would be out of compliance with the result that sometime in 2014 at least Ste. Genevieve and Perry counties would be designated as nonattainment areas," Grimes said.