Exceptional Event Demonstration Public Comment period
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The Minnesota Pollution Control Agency (MPCA) is inviting the public to provide their comments on its exceptional events demonstration for the purpose of meeting the annual National Ambient Air Quality Standard (NAAQS) for particulate matter less than 2.5 micrometers in diameter (PM2.5).
On February 7, 2024, the U.S. Environmental Protection Agency (EPA) finalized a newly revised annual NAAQS for PM2.5 at 9.0 μg/m3. EPA did this to better protect human health based on the latest scientific information. After EPA finalizes a new or revised NAAQS it must designate all areas in the country as either meeting (attainment) or not meeting (nonattainment) those standards. Three years of monitoring data are used to calculate a “design value” that determines annual PM2.5 NAAQS attainment designation status. On January 16, 2025, the MPCA recommended to EPA that all Minnesota counties be designated as meeting (attainment) the revised PM2.5 standard based on design values using 2021-2023 monitoring data, the most recent finalized data available at the time. The EPA has not yet made (non)attainment designations, now expected in February 2027. The EPA may therefore designate areas based on design values using 2023-2025 monitoring data. Minnesota would be in attainment of the revised annual PM2.5 NAAQS if not for Canadian wildfire smoke transported into Minnesota. Under the Clean Air Act, states can request that EPA exclude air quality data affected by certain exceptional events, such as natural wildfire smoke, when those events are not reasonably controllable or preventable.
For this reason, the MPCA is submitting an exceptional event demonstration to EPA for wildfire smoke that occurred in 2025. The MPCA proposes to exclude from the design value calculation, data from one day at one metro-area monitor due to an exceptional event that resulted in “Unhealthy” and “Very Unhealthy” air quality across the state due to wildfire smoke. Design values calculated from data years 2023-2025 show one monitor, Apple Valley (monitor site number: 27-037-0470), above the annual PM2.5 NAAQS. The PM2.5 design value at the Apple Valley site including July 12, 2025 is 9.1 μg/m3. Excluding data for the day will reduce the design value to 9.0 μg/m3. This will allow all areas within Minnesota to remain designated attainment of this standard. The MPCA must submit an exceptional event demonstration to exclude from the design value calculation, monitoring data on July 12, 2025 at the Apple Valley monitor.
The MPCA is inviting the public to review the report and submit comments by September 30, 2026.
The Minnesota Pollution Control Agency (MPCA) is inviting the public to provide their comments on its exceptional events demonstration for the purpose of meeting the annual National Ambient Air Quality Standard (NAAQS) for particulate matter less than 2.5 micrometers in diameter (PM2.5).
On February 7, 2024, the U.S. Environmental Protection Agency (EPA) finalized a newly revised annual NAAQS for PM2.5 at 9.0 μg/m3. EPA did this to better protect human health based on the latest scientific information. After EPA finalizes a new or revised NAAQS it must designate all areas in the country as either meeting (attainment) or not meeting (nonattainment) those standards. Three years of monitoring data are used to calculate a “design value” that determines annual PM2.5 NAAQS attainment designation status. On January 16, 2025, the MPCA recommended to EPA that all Minnesota counties be designated as meeting (attainment) the revised PM2.5 standard based on design values using 2021-2023 monitoring data, the most recent finalized data available at the time. The EPA has not yet made (non)attainment designations, now expected in February 2027. The EPA may therefore designate areas based on design values using 2023-2025 monitoring data. Minnesota would be in attainment of the revised annual PM2.5 NAAQS if not for Canadian wildfire smoke transported into Minnesota. Under the Clean Air Act, states can request that EPA exclude air quality data affected by certain exceptional events, such as natural wildfire smoke, when those events are not reasonably controllable or preventable.
For this reason, the MPCA is submitting an exceptional event demonstration to EPA for wildfire smoke that occurred in 2025. The MPCA proposes to exclude from the design value calculation, data from one day at one metro-area monitor due to an exceptional event that resulted in “Unhealthy” and “Very Unhealthy” air quality across the state due to wildfire smoke. Design values calculated from data years 2023-2025 show one monitor, Apple Valley (monitor site number: 27-037-0470), above the annual PM2.5 NAAQS. The PM2.5 design value at the Apple Valley site including July 12, 2025 is 9.1 μg/m3. Excluding data for the day will reduce the design value to 9.0 μg/m3. This will allow all areas within Minnesota to remain designated attainment of this standard. The MPCA must submit an exceptional event demonstration to exclude from the design value calculation, monitoring data on July 12, 2025 at the Apple Valley monitor.
The MPCA is inviting the public to review the report and submit comments by September 30, 2026.
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