Updated PM2.5 Standard: What You Need to Know and How We Can Provide Support

In February 2024, the Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards for Particulate Matter (PM NAAQS)—which officially went into effect in May 2024. Specifically, the EPA updated the primary (health-based) annual standard for PM2.5 (that is, particulate matter with diameters of 2.5 micrometers and smaller) from 12 to 9 micrograms per cubic meter.

Also known as fine inhalable particles, PM2.5 can include soot and smoke. For historical context, the initial primary PM2.5 annual NAAQS of 15 micrograms per cubic meter was introduced in 1997. It was revised to 12 micrograms per cubic meter in 2012.

Public Health Benefits

The EPA’s change stems from scientific research that found the existing NAAQS were not adequate to achieve desired protection of public health and welfare mandated by the Clean Air Act. The goal of the new standard is “to protect millions of Americans from harmful and costly health impacts, such as heart attacks and premature death [due to] particle or soot pollution,” according to the EPA’s website.

In addition, the new standard will yield up to $46 billion in net public health benefits by 2032 and lead to improved health outcomes, including fewer premature deaths and asthma symptoms.

Potential Impact on Facilities

Depending on the emissions’ magnitude and location, the impact of the EPA’s change will vary for facilities emitting PM2.5. There will be little to no impact on facilities:

  • In rural areas (with low background concentration and/or no neighboring facilities)
  • With larger ambient air boundaries; areas inside project boundaries are excluded from NAAQS compliance demonstrations
  • That already show significantly lower PM2.5 ambient concentrations

However, the impact will likely be significant for facilities that have smaller ambient air boundaries and/or are in industrial complexes; pollutant concentrations from neighboring sources’ emissions are considered ambient or background for NAAQS compliance demonstrations.

Obligations for Regulatory Agencies and States

The new PM2.5 NAAQS may also change the attainment status for certain regions, resulting in the creation of non-attainment areas (i.e., those not meeting the new standard)—and permitting new facilities in these areas may require stricter emission standards, controls, and compliance requirements.

Within two years, the EPA will make area redesignation (attainment or non-attainment) determinations. Depending on whether their newly designated non-attainment areas are moderate or serious, states must submit attainment plans within 18 months or six years, respectively.

States must also develop state implementation plans (SIPs) within three years of an official NAAQS update. SIPs must include strategies and programs for adopting the new standard and bringing non-attainment areas into compliance within six to 10 years, depending on the non-attainment level.

All these strategies and programs must be approved by the EPA. If you are unsure whether your facility will be in a non-attainment area and/or whether you might need emission rate or modeling refinements, there is still time to act—and our experienced air quality engineers and scientists can help you review your options.

How Air Sciences Can Offer Support and Expertise

Even though the EPA did not officially update the PM2.5 NAAQS until February 2024, it announced its proposed decision in early 2023.

Since that time, Air Sciences has been proactively consulting with our clients and reviewing projects to identify possible solutions for facilities to demonstrate compliance once the new standard becomes enforceable.

Some potential options for decreasing emissions include:

  • Incorporating new lower-emitting technologies
  • Finding cleaner processes, such as upgrading equipment to reduce facilities’ potential to emit
  • Eliminating redundancies in permitting to more accurately represent actual emissions

We have also been working with our clients to explore creative dispersion-modeling techniques to tackle possible challenges presented by the new standard.

If you have questions on how the updated PM2.5 NAAQS may impact your facility or facilities—or if you want to discuss ways Air Sciences can assist you with demonstrating compliance—contact us today.

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