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St. Louis area makes progress on ozone, but now must meet tougher federal standards

ozone air pollution St. Louis
Missouri Department of Natural Resources

The St. Louis metro area has one of the worst smog levels in the country. In recent years, ozone levels have declined, but the region must  comply with stronger federal air quality standards set last year. 

Credit Provided by Missouri Department of Natural Resources
Recorded ozone levels in the Missouri portion of the St. Louis area.

Under the 2008 standard, St. Charles, St. Louis, Franklin and Jefferson counties had exceeded the Environmental Protection Agency's ozone limit at 75 parts per billion. After 2013, ozone levels in the area dropped and state officials say the counties comply with the 2008 standard. However, a new EPA rule last year lowered the standard to 70 parts per billion. State officials are now asking the EPA to indicate that the region meets the old ozone regulations, but not the new. 

Ozone, a toxic gas that increases on warm, sunny days, can cause respiratory problems for children, the elderly and worsen health conditions people already have. 

Credit Provided by Missouri Department of Natural Resources
The ozone designation is applied to the St. Louis metro area.

The Missouri Department of Natural Resources will host an Aug. 25 public hearing in St. Louis on the new designation that the area does not comply with the 2015 rule. The deadline for public comments is Sept. 1.

If approved, it's likely the redesignation won't be official until early next year.

Eli is the science and environment reporter at St. Louis Public Radio.