By Jessica Mzhickteno and Leslie Fifita, Providence Engineering and Environmental Group LLC
In May 2024, the Environmental Protection Agency (EPA) lowered the primary annual National Ambient Air Quality Standards (NAAQS) for PM2.5[1] from 12.0 to 9.0 micrograms per cubic meter (μg/m3). In August 2024, the Texas Commission on Environmental Quality (TCEQ) identified the potential air quality designations for each Texas county based on preliminary 2023 PM2.5 design values. The TCEQ is one of the first state agencies to issue proposed PM2.5 design value ambient concentrations to monitor, thus giving all states an indication of the impact this lower NAAQS might have. The TCEQ will use this information to propose nonattainment designations for approval by the governor. The governor of each state must submit designations to the EPA of attainment, nonattainment, and unclassifiable areas by February 7, 2025.
The NAAQS were lowered to protect the health of Americans, especially those in sensitive groups such as children, asthmatics and the elderly. The strengthened standards stem from evidence determining that the previous standards were not adequate to protect public health and welfare4. Scientific studies have related high concentrations of PM with health problems such as irregular heartbeat, decreased lung function, nonfatal heart attacks and premature death in people with heart or lung disease2. The environmental impact of PM includes contribution to haze and deposits on water and soil, which leads to the harm of ecosystems and crops.
Figures 1-3 show 2023 monitored PM2.5 concentrations for selected Texas counties compared with population, industrial emissions, and recorded wildfires. The counties with monitored values above the new 9.0 μg/m3 NAAQS include Bowie, Cameron, Dallas, Ellis, Harris, Harrison, Hidalgo, Kleberg, Montgomery, Tarrant, Travis and Webb. Five of these counties (Dallas, Ellis, Harris, Montgomery and Tarrant) are already nonattainment for 8-Hour Ozone NAAQS. Most easy reductions have already been made by facilities to meet the previous standards. The last change in the annual PM2.5 NAAQS occurred in 2012 (lowered from 15 μg/m3 to 12.0 μg/m3). The 9.0 μg/m3 standard will be much more difficult to attain and may potentially create new obstacles for industries.
To better understand these counties and the potential for nonattainment, examination of individual cities and relative locations can provide insight. Harris County has the highest industrial emissions and population combined with the highest monitored value. Harris County includes Houston, Pasadena, Baytown and La Porte; this harbors 4.7 million people and the Bayport Industrial District. The combined factors of population and industrial facility density may be directly correlated with the monitored value. For other counties such as Tarrant and Dallas, both have monitored values above 9.0 μg/m3 with low numbers of recorded wildfires, moderate industrial emissions and comparatively high populations.
The counties can be grouped by proximity such as Bowie and Harrison, and Cameron and Hidalgo which have high monitored values but low populations, industrial emissions and wildfires. These counties are near the Texas state border, which begs the question: how can states meet the requirements given current background concentrations? Apart from Harris County, there is no significant indicator of the source of PM2.5. The lack of a correlation between source and impact eliminates simple answers on what can be done to meet the new NAAQS.
Industry point sources should be the initial focus in air quality improvement. For existing plants, it may become more difficult to obtain the required permits for expansion projects. For new plants, permitting construction in nonattainment areas will be complicated as offsets (reductions elsewhere in the airshed) may become less available to balance new projects. As the TCEQ revises the State Implementation Plan (SIP) to address the new NAAQS, nonattainment areas will face specific targets and new control strategies.
Contributions to PM that are more difficult to control include fugitive emissions and exceptional events. Events such as wildfires contribute to background levels of PM and reduced headroom to demonstrate compliance through dispersion modeling. High background concentrations bring into question the law of diminishing returns: how much more control can industries implement to make effective impacts towards lowering PM2.5 emissions? Future industrial implications could range from shifting energy production further away from fossil fuels to pushing more manufacturing offshore.
The designations of attainment and nonattainment areas have not yet been finalized by the EPA, these designations are expected in February 2026. Discussions about exceptional events and accuracy of monitors may be ongoing; however, it is critical to be prepared for changes involving your company, industry, or facility. Facilities with current projects or planned modifications should consider changing designs to meet the tighter standard. The 2024 PM2.5 primary annual NAAQS are here and now is the time to start planning for its impact on your plant.
The TCEQ data show how difficult PM2.5 causation and reduction will be for areas across the country.
[1] PM2.5 = particulate matter (PM) less than or equal to 2.5 micrometers in diameter, such as fine dust
References
- Federal Register: Reconsideration of the National Ambient Air Quality Standards for Particulate Matter
- Air Pollution from Particulate Matter – Texas Commission on Environmental Quality – www.tceq.texas.gov
- SIP: Introduction – Texas Commission on Environmental Quality – www.tceq.texas.gov
- pm-naaqs-overview.pdf (epa.gov)
About the Authors
Jessica Mzhickteno, EI, is an Air Quality Specialist with Providence Engineering and Environmental Group LLC. She holds a bachelor’s degree in chemical engineering from the University of Kansas.
Leslie Fifita is a Senior Air Modeler at Providence Engineering and Environmental Group LLC with 23 years of experience in air quality consulting. She focuses on AERMOD modeling in support of air permit applications for large industrial clients. She also manages the software team (Providence/ORIS) which provides air dispersion modeling software tools, training, and cloud-based modeling solutions. Her email address is [email protected].
