EPA Grants Clean Data Determination for St. Louis Ozone Standards
Missouri is no longer required to submit certain nonattainment planning documents after the EPA verified the region meets 2015 ozone standards [1].
The Environmental Protection Agency has determined that the Missouri portion of the St. Louis bi-state nonattainment area achieved clean data for the 2015 8-hour ozone National Ambient Air Quality Standard. This determination follows a review of certified ambient air monitoring data for the 2023-2025 design value period.
The 2023-2025 design value of 0.070 ppm meets the 2015 ozone standard. This finding relied on the EPA's concurrence with an exceptional events request submitted by the Missouri Department of Natural Resources on November 3, 2025, which addressed data influenced by uncontrollable natural events.
As a result of this final clean data determination, the State of Missouri is no longer obligated to submit specific nonattainment area planning requirements. This suspension of obligations remains in effect as long as the Missouri portion of the St. Louis area continues to attain the 2015 ozone standard.
The rule becomes effective on September 14, 2026.