Air emissions

Scope

EPA is mostly concerned with emissions that are or could be harmful to people. The agency calls this set of air pollutants “criteria pollutants.” The criteria pollutants are:

• Carbon monoxide,
• Lead,
• Nitrogen dioxide,
• Ozone,
• Particulate matter, and
• Sulfur dioxide.

Under the Clean Air Act (CAA), EPA sets limits on certain air pollutants, including how much can be in the air anywhere in the nation. The CAA also gives EPA the authority to limit emissions of air pollutants coming from sources like chemical plants, utilities, and steel mills. Individual states or tribes may have stronger air pollution laws.

The Air Emissions Reporting Rule (AERR) requires state and local agencies to collect and submit emissions data to EPA. Many states voluntarily report air toxics along with the required criteria for air pollutants. AERR first came about in 2008. EPA finalized revisions to AERR in February 2015. Changes included:

• Lowering the current threshold for reporting lead emissions sources as “point sources”;
• Eliminating the requirement for state and local agencies to report emissions from wildfires and prescribed fires;
• Requiring agencies to report the inputs needed to model emissions from mobile sources;
• Removing the requirements for agencies to report daily and seasonal emissions; and
• Clarifying, removing, or simplifying some current emissions reporting requirements.

Regulatory citations

• 40 CFR 51 Subpart A — Air emissions reporting requirements

Key definitions

• Emissions: Describe the gases and particles that are put into the air or emitted by various sources.
• Emission limitation: A requirement established by a state or local government or administrator that limits the quantity, rate, or concentration of emissions of air pollutants on a continuous basis, including any requirements that limit the level of opacity, prescribe equipment, set fuel specifications, or prescribe operation or maintenance procedures for a source to assure continuous emission reduction.
• Nonpoint source: Collectively represents individual sources that have not been inventoried as specific point or mobile sources. These individual sources treated collectively as nonpoint sources are typically too small, numerous, or difficult to inventory using the methods for the other classes of sources.
• Particulate matter: Any airborne finely divided solid or liquid material with an aerodynamic diameter smaller than 100 micrometers.
• Point source: A large, stationary (nonmobile), identifiable source of emissions that releases pollutants into the atmosphere.

Summary of requirements

States must report actual emissions of the following required pollutants for triennial reports of annual (12-month) emissions for all sources and every-year reports of annual emissions for Type A sources:

• Sulfur dioxide;
• Volatile organic compounds;
• Nitrogen oxides;
• Carbon monoxide;
• Lead and lead compounds;
• Primary PM2.5. as applicable, also report filterable and condensable components;
• Primary PM10. as applicable, also report filterable and condensable components; and
• Ammonia.

Remember that states can also optionally report estimates of emissions for additional pollutants like hazardous air pollutants in their emission inventory reports. States must report emissions from the following sources in all parts of the state, excluding sources located on tribal lands:

• Point,
• Nonpoint, and
• Onroad and nonroad mobile.

All states must report two basic types of emission inventories to the EPA:

1. An every-year inventory, and
2. A triennial inventory.

Emission inventory data must be reported in electronic form. Keep in mind that any data that a state submits to EPA under this subpart (40 CFR 51 Subpart A) will be considered in the public domain and cannot be treated as confidential.