Clean Air Act

Scope

The CAA calls for states and EPA to solve multiple air pollution problems through programs based on the latest science and technology. The law authorizes EPA to establish air quality standards to protect public health and public welfare and to regulate emissions of hazardous air pollutants from stationary and mobile sources.

Regulatory citations

• 40 CFR Parts 50-99

Key definitions

• Acid rain: Any form of precipitation with acidic components, such as sulfuric acid or nitric acid that falls to the ground from the atmosphere in wet or dry forms.
• Ambient air: The air the general public breathes (not the air in a smokestack or in a warehouse).
• Area source: Any stationary source that is not a major source.
• Criteria air pollutants: Six common air pollutants regulated under the National Ambient Air Quality Standards (NAAQS) program. These are ground-level ozone, particulate matter, carbon monoxide, lead, sulfur dioxide, and nitrogen dioxide.
• Greenhouse gases (GHGs): Gases that trap heat in the atmosphere.
• Hazardous air pollutants (HAPs): One or more of 187 toxic air pollutants that are known or suspected to cause cancer or other serious health effects or adverse environmental effects.
• Haze: A form of air pollution that degrades visibility in cities and scenic areas. Haze is caused when sunlight encounters tiny particles of pollution in the air.
• Indoor air quality: The air quality within and around buildings and structures, especially as it relates to the health and comfort of people in the building.
• Major source: A stationary source or group of stationary sources that emit or have the potential to emit 10 tons per year or more of a HAP or 25 tons per year or more of a combination of HAPs.
• Mobile sources: Moving vehicles. Examples include commercial motor vehicles, passenger vehicles, cars, light trucks, nonroad equipment, and planes.
• Stationary source: A fixed establishment. Examples include manufacturers, processors, refiners, power plants, chemical facilities, and steel mills.
• National ambient air quality standards (NAAQS): The national program requiring states to limit emissions of pollutants considered to be harmful to public health and the environment. There are two types of NAAQS, primary and secondary, that apply to the following six air pollutants: carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone, and sulfur dioxide.
• National emission standards for hazardous air pollutants (NESHAPs): The standards that apply to stationary sources for hazardous air pollutants.
• Nonpoint sources: Smaller sources of air emissions (e.g., residential heating)
• Operating permits (Title V permits): The permit major sources, and some smaller sources, are required to obtain to operate. The permit lists all the clean air requirements the source must meet.
• Point sources: Larger emission sources at a fixed locations (e.g., and industrial facility)
• Risk Management Program: Section 112 of the Clean Air Act. This program covers the prevention of releases to the air of hazardous chemicals in a process.
• Source category: The industry that is emitting pollutants into the air.

Summary of requirements

• Know if you are a major stationary source or an area source of air emissions of any air pollutant.
• Inventory your processes for possible air emissions and work with your state air permitting agency for the permits that may apply to you.
• If you are planning to build a new facility, make major modifications, add equipment or change process that could increase your air emissions, contact your state to apply for preconstruction permits.
• If you own a commercial motor vehicle or transportation-related company, understand the regulations that apply to mobile sources, including state-specific fuel efficiency rules (e.g., California’s Truck and Bus Rule).
• Operate within your permit limitations to avoid enforcement actions.
• Refineries and fuel suppliers, gas stations, and other motor fuel related industries must understand the laws relating to emissions and to renewable fuels.
• If you have refrigerating equipment or are a refrigerator/air conditioner technician, be sure to pay attention to the regulations for ozone-depleting substances.
• If you have a hazardous chemical in a process that could be released into the air, refer to the Risk Management Program (RMP) regulations in 40 CFR Part 68.