The St. Louis and Kansas City areas, along with part of southeast Missouri, have violated 2008 air quality standards and may be forced to impose new restrictions, the state said Thursday.
The Missouri Department of Natural Resources said ozone levels in St. Louis, Kansas City and Ste. Genevieve County were above the eight-hour standard at some points during the April 1 to Oct. 31 ozone season.
St. Louis and Kansas City already are under ozone control measures because of air quality.
Violations typically require additional restrictions to cut pollutants created by trucks, cars, power plants and other businesses.
But because the U.S. Environmental Protection Agency is reconsidering the standard for smog and may make them more stringent, the states are in a holding pattern, DNR spokeswoman Renee Bungart said.
The EPA is expected to propose revised smog standards to protect health and the environment in late December.
Last year, the EPA under the Bush administration set a maximum airborne concentration for ground-level ozone at 75 parts per billion.
EPA's science advisory board _ and most health experts _ had recommended a limit of 60 to 70 parts per billion to adequately protect the elderly, people with respiratory problems and children.
Prior to last year, the last EPA standard for ozone was 85 parts per billion set in 1997.
The St. Louis region had succeeded in attaining the 1997 standard of 85 ppb, with reformulated gasoline, gasoline vapor recovery nozzles, industrial regulations and mandatory inspection of autos. Meanwhile, the Kansas City region has hovered just below it, DNR said.
Smog is a respiratory irritant that can aggravate asthma and has been linked to heart attacks.
On the Net:
Missouri Department of Natural Resources, ozone designations: http://www.dnr.mo.gov/env/apcp/ozone/finalmap-08ozone.pdf