Understanding National Ambient Air Quality Standards (NAAQS): What Facilities Need to Know

What Are National Ambient Air Quality Standards (NAAQS)?

The Clean Air Act requires the US Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) under 40 CFR Part 50 to protect public health and welfare from air pollution.

EPA has established NAAQS for six principal criteria air pollutants:

  • Carbon Monoxide (CO)
  • Lead (Pb)
  • Particulate Matter (PM)
  • Ozone (O₃)
  • Nitrogen Dioxide (NO₂)
  • Sulfur Dioxide (SO₂)

Under the NAAQS there are two standards:

  1. Primary NAAQS – Designed to protect public health, including sensitive populations such as children, the elderly, and “sensitive” individuals such as those with asthma
  2. Secondary NAAQS – Intended to protect public welfare, including visibility, crops, vegetation, and buildings

EPA’s Menu of Control Measures (MCM) provides state, local, and tribal air agencies with:

  • Proven emission reduction strategies
  • Cost-effectiveness information
  • Tools to develop plans and programs to attain and maintain NAAQS compliance
How EPA Reviews & Revises NAAQS

The Clean Air Act Sections 108 and 109 govern the establishment, review, and revisions of NAAQS. Each review cycle typically takes five years and follows a structured process:

  1. Planning Phase – EPA issues a public Call for Information and develops an Integrated Review Plan (IRP) outlining the scope, schedule, and approach
  2. Assessment Phase – EPA evaluates the most current scientific and technical information through a series of coordinated assessments
  3. Regulatory Decision-Making Phase – Public comment period and hearings along with Final Rule issuance
SEC Experts’ NAAQS Support Services

SEC provides expert support to help facilities understand and respond to air quality planning and permitting requirements that arise from NAAQS implementation by state, local, and tribal agencies. As NAAQS are updated or areas are designated nonattainment, facilities may face new permitting considerations, operational constraints, or planning challenges. SEC supports clients throughout the permitting, compliance, and long-term planning lifecycle.

Our services include:

  • Air Dispersion Modeling
  • Air Permitting & Compliance
    • New Source Review (NSR)
    • Title V
    • PSD Permitting Support
  • Best Available Control Technology (BACT) Analysis – Identification of effective, defensible pollution control technology
  • Health & Risk Assessments – Evaluation of potential impacts related to Hazardous Air Pollutants (HAPs)
  • Regulatory Strategy & Agency Coordination – Support during rule changes, SIP updates, and permitting reviews
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