Annual PM2.5 NAAQS Lowered!
Posted: February 8th, 2024
Authors: Dan D.
On February 7, 2024, the United States Environmental Protection Agency (U.S. EPA) made the long-awaited announcement that the annual particulate matter less than 2.5 microns (PM2.5) National Ambient Air Quality Standard (NAAQS) will be lowered from 12 micrograms per cubic meter (µg/m3) to 9 µg/m3. A prepublication version of the rule was signed by U.S. EPA Administrator Michael Regan on February 5, 2024, and will be published in the Federal Register (FR) soon. The final rule and lowered annual PM2.5 NAAQS of 9 µg/m3 will become effective 60 days after the rule is published in the FR. Typically, it takes one to two weeks to publish a rule in the FR from when it is finalized. Based on that schedule the final rule is expected to be published by the week of February 19th with the 60-day effective date putting the final lowered annual PM2.5 NAAQS effective date around April 19, 2024. U.S. EPA also indicated in the preamble that they will develop, and release updated guidance on the appropriate PM2.5 annual Significant Impact Level (SIL) before the effective date of the new standard. This was unexpected, and a decrease from the already low 0.2 µg/m3 annual PM2.5 SIL will trigger more multi-source NAAQS modeling analyses, which will be difficult (if not impossible) in some areas of the country with the lowered annual PM2.5 NAAQS.
Despite requests by industry for a longer implementation period or to establish the annual NAAQS at the higher range proposed (10 µg/m3), air quality modeling demonstrations as a part of air permit applications will need to demonstrate compliance with the new lowered 9 µg/m3 annual PM2.5 NAAQS this spring. Only air permit applications that include an annual PM2.5 NAAQS modeling demonstration in the final stages of being approved and finalized have a chance of squeaking in before the estimated April 19, 2024, effective date. However, be aware that some agencies might not allow this.
Once the annual PM2.5 NAAQS takes effect, the 2-year clock starts for states to make and U.S. EPA to approve annual PM2.5 NAAQS attainment designations. Based on current ambient PM2.5 monitoring data summarized on ALL4’s PM2.5 NAAQS Resource Website there will a large amount of new PM2.5 nonattainment areas across the U.S. Areas designated nonattainment with the PM2.5 NAAQS around April of 2026 will trigger nonattainment new source review (NNSR) air permitting requirements instead of Prevention of Significant Deterioration (PSD) air permitting requirements. NNSR air permitting requirements include more stringent implementation of Lowest Achievable Emissions Rates (LAER), purchasing Emission Reduction Credits (ERCs) to offset PM2.5 emissions increases, and development of alternative siting analyses for proposed projects. NNSR permitting can be triggered by increases in direct PM2.5 emissions as well as PM2.5 precursors, nitrogen oxide (NOX) and sulfur dioxide (SO2) and in some locations ammonia (NH3) and volatile organic compounds (VOC). Unlike PM2.5 modeling requirements that become effective immediately, there are still 2 years to obtain an air permit before NNSR requirements (e.g., implementing LAER and purchasing ERCs) become effective. However, it may be easier to implement LAER and purchase ERCs under NNSR than it will be to complete a PM2.5 NAAQS modeling analysis under PSD.
For areas that are currently exceeding the new annual PM2.5 NAAQS that trigger PSD PM2.5 permitting requirements during the 2-year attainment determination period the only modeling option will be to model below the PM2.5 SIL. This will also likely be the only option for states that have minor source NAAQS air quality modeling requirements. Keep in mind that triggering PSD for SO2 or NOX, PM2.5 precursors also triggers the requirement to conduct a direct PM2.5 NAAQS air quality modeling demonstration.
In related news, U.S. EPA also sent a proposal to lower the secondary NOX, SO2, and PM NAAQS to the White House Office of Management and Budget (OMB) on February 6, 2024. A proposed rule is mandated by a consent decree to be signed by April 9, 2024, with a final rule by December 10, 2024. The Secondary NAAQS are designed to protect public welfare as opposed to public health and have historically been set to levels above the primary NAAQS. If the secondary NAAQS were to be set lower than the primary NAAQS there is no precedent for how air permitting would be impacted.
ALL4 has substantial experience in PM2.5 air quality modeling demonstrations and NNSR PM2.5 permitting. For more information about how a lowered PM2.5 NAAQS will affect your facility and how ALL4 can help check out ALL4’s PM2.5 NAAQS Resource webpage or contact Dan Dix at ddix@all4inc.com or (610) 422-1118.
