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Ground-level ozone down, but STL still not meeting air quality goals

By Matt Sepic, KWMU

St. Louis – Missouri environmental officials say ground level ozone levels in the St. Louis area were lower this summer than in 2005.

Ozone high in the atmosphere helps filter harmful ultraviolet radiation from the sun. But on the ground it can cause trouble for people with asthma and other breathing problems.

This summer St. Louis exceeded the EPA's eight-hour ozone standard on 15 days. That's down from 25 days in 2005.

John Rustige with the Missouri Department of Natural Resources credits the drop in part to better pollution controls. But he said weather is also a factor, and that makes comparisons difficult.

"To say this year is better than last, or this year is different from another year is a little bit hard," Rustige said. "We can look at longer term trends, and that really is showing significant improvement over time."

High ozone levels occur when pollutants from smokestacks and vehicles react with heat.

Tuesday was the last day of the annual ozone measurement season. DNR officials say St. Louis is still out of compliance with federal air quality standards.