Criteria Pollutants
The Environmental Protection Agency (EPA) has identified six common air pollutants that are important to measure and track. These are known as "Criteria Pollutants". They are:
- Particle pollution
- Ozone
- Carbon monoxide
- Sulfur dioxide
- Nitrogen oxides
- Lead
Because these pollutants can harm human health and the environment, the EPA has set science-based guidelines for how much of each pollutant should be in the air. These limits, known as National Ambient Air Quality Standards (NAAQS), are designed to help avoid pollution concentrations that could adversely affect our health.
Hazardous Air Pollutants
Also known as air toxics, hazardous air pollutants (HAPs) are pollutants that are known or suspected to cause cancer or other serious health effects. Examples of toxic air pollutants include:
- Benzene
- Perchlorethlyene
- Methylene chloride
- Dioxin
- Asbestos
- Toluene
- Cadmium
- Mercury
- Chromium
- Lead compounds
The EPA has designated 187 hazardous air pollutants. To see the full list, visit the EPA website.
Most HAPs originate from human-made sources, including mobile sources (e.g., cars, trucks, buses) and stationary sources (e.g., factories, refineries, power plants), as well as indoor sources (e.g., some building materials and cleaning solvents). Some HAPs are released from natural sources such as volcanic eruptions and forest fires.
National Emission Standards for Hazardous Air Pollutants (NESHAPs) are EPA set emission limits for air toxics. The standards for a particular type of source (such as dry cleaners or gasoline stations) are known as the Maximum Achievable Control Technology (MACT). Standards for air toxics are authorized under the Clean Air Act, section 112.
ACHD Article XXI §2104.08(PDF, 2MB) PA rules on air toxics including any additions or changes made by the EPA.
In addition, the ACHD's Air Quality program has protocols in place to help regulate and control these toxic air pollutants, as well as respond to new data concerning air toxic “hotspots” and areas of interest.
Our Air Toxic Guidelines, which are followed by the ACHD permit engineers when issuing air permits for new and existing sources of air toxics in Allegheny County, were originally developed in 1988 and have recently been revised by the ACHD.