Effective May 2024, EPA tightened the annual health-based National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM2.5) from 12.0 µg/m3 to 9.0 µg/m3. This change was made after a review of the available scientific evidence, technical information, and advice of an independent scientific panel. EPA indicates that lowering the standard will result in significant public health benefits, advance the economy, and improve quality of life.
All areas of North Carolina are in attainment with the previous PM2.5 annual standard (12.0 µg/m3). Based on certified monitoring data from 2021-2023, 19 out of 21 monitoring sites in North Carolina are also meeting the new standard. The 2023 data shows two monitoring sites in the state were slightly above the new standard, which North Carolina believes is due to influences of Canadian wildfire smoke. These sites are in Mecklenburg and Davidson counties. Without the influence from Canadian wildfire smoke, North Carolina contends none of North Carolina's monitors would have exceeded the new standard in 2023.
The North Carolina Department of Environmental Division of Air Quality (DAQ) has recommended that EPA designate all of North Carolina as in attainment with the revised PM2.5 standard, because the Canadian wildfires were exceptional events outside of the state’s control. This would allow DAQ to focus on pollution reduction strategies that are within its control to ensure ongoing attainment with the revised standard. To support that recommendation, the state prepared an Exceptional Events Demonstration that shows that for both the Davidson and Mecklenburg counties’ monitors, Canadian wildfire smoke negatively impacted air quality data. Because this exceptional event was outside the control of the state, a small number of days in June and July 2024 can be removed from the calculation when determining compliance with the revised PM2.5 standard if EPA approves the Exceptional Events Demonstration. Exceptional Events Demonstrations are authorized under the Clean Air Act and EPA governs how states can use these provisions.
When a new air quality standard is announced, the designation process as defined by federal rule takes two years to complete. If the air quality in a geographic area meets or is cleaner than the national standard, it is called an attainment area (designated “attainment/unclassifiable”). Areas not meeting the standard are designated as “nonattainment.” The process includes state input and public comment opportunities.
On February 6, 2025, DAQ submitted to EPA designation recommendations based on certified monitoring data (2021-2023) and other factors, as applicable. EPA will review these recommendations, look at the current monitoring data available at that time (2022-2024), and then make the final designations by February 6, 2026.
EPA has said it will consider impacts from wildfire smoke when making designations if the state submits an exceptional event demonstration for the dates impacted by wildfire smoke for all affected monitors. EPA’s Exceptional Events rule establishes criteria and procedures for use in determining if air quality monitoring data has been influenced by exceptional events such as wildfire smoke. DEQ is reviewing its monitoring data from 2023 in preparation for submitting an Exceptional Events demonstration to EPA for the two monitoring sites above 9.0 µg/m3.
Per EPA, attainment/nonattainment designations will likely be based on PM2.5 monitoring data collected from 2022-2024. Until all 2024 data is collected and reviewed, it is too early to know which, if any, areas of North Carolina may be in nonattainment with the new standard. Keeping PM2.5 levels low in 2024 will be critical for attaining the new standard.
Source: NC Department of Environmental Quality
EPA recently announced that it is going to reconsider the PM2.5 NAAQS. Any change in the standard will have to go through the formal rulemaking process, including the assembly of an administrative record and notice and public comment. It is unclear at this time how this development will affect the above regulatory timeline.
