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Hazardous air pollutants (HAPs) are pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. HAPs are often referred to as air toxics. Sources of HAPs include the following: chemical factories, incinerators, motor vehicles, dry cleaners, and auto paint shops.
EPA is required to establish specific requirements for all industries that emit one or more HAPs in significant quantities. Categories of sources that release air toxics have been divided into:
- Major (large) sources, which are required to use maximum achievable control technology (MACT), specified by EPA, to reduce HAP emissions.
- Area (small) sources, which may be required to implement MACT controls or more flexible measures called generally available control technologies (GACT).
Scope
EPA works with states, local governments, tribal governments to reduce air emissions for specific HAPS. The CAA requires EPA to regulate HAPs from large industrial facilities in two phases:
- Phase 1 is technology-based. EPA develops standards for controlling HAPs emissions from sources in an industry group (source category). These are the MACT standards, which are based on emissions levels that are already being achieved by the lowest emitting sources in an industry.
- Phase 2 is a risk-based approach called residual risk. The CAA requires EPA to determine whether more health-protective standards are necessary. Within eight years of setting the MACT standards, EPA must assess the remaining health risks from each source category for the effectiveness of the MACT standards to protect public health with an "ample margin of safety," and against environmental effects.
Every eight years after setting the MACT standards, EPA must review and revise the standards, if necessary, to account for improvements in air pollution controls and prevention techniques. The first eight-year review, when combined with the residual risk review, is called the risk and technology review (RTR).
Regulatory citations
- 40 CFR Part 61 — National emission standards for hazardous air pollutants
- 40 CFR Part 62 — Approval and promulgation of state plans for designated facilities and pollutants
- 40 CFR Part 63 — National emission standards for hazardous air pollutants for source categories
Key definitions
- Adverse environmental effect: Any significant and widespread adverse effect, which may reasonably be anticipated, to wildlife, aquatic life, or other natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental quality over broad areas.
- Area source: Any stationary source of hazardous air pollutants that is not a major source.
- Electric utility steam generating unit: Any fossil fuel fired combustion unit of more than 25 megawatts that serves a generator that produces electricity for sale.
- GACT: Generally achievable control technology.
- Hazardous air pollutant: Any air pollutant listed in the section 112(b) of the Clean Air Act or in the National Emission Standards for Hazardous Air Pollutants (NESHAPs).
- MACT: Maximum achievable control technology.
- Major source: Any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 25 tons per year or more of any combination of hazardous air pollutants.
- Modification: Any physical change in, or change in the method of operation of a major source which increases the actual emissions of any hazardous air pollutant emitted by such source or which results in the emission of any hazardous air pollutant not previously emitted.
- National Emissions Standards for Hazardous Air Pollutants (NESHAPs): Standards for stationary sources of hazardous air pollutants (HAPs).
- New source: A stationary source that will begin construction or reconstruction under an existing NESHAPs has been established.
Summary of requirements
- Determine your industrial source category (e.g., oil and gas, aluminum manufacturing), and whether you are a major or minor source of toxic air emissions.
- Depending on your source category and emissions, compliance will include:
- Performing an initial performance test to demonstrate compliance with the NESHAPs.
- Monitoring and reporting.
- Installing and operating continuous emission monitors (if required).
- Detecting and repairing leaking or malfunctioning equipment.