Hazardous Air Pollutants (HAP) Standards

Overview of HAP Standards

Hazardous Air Pollutants (HAP) are air pollutants known to cause cancer and other serious health effects, including birth defects, reproductive disorders, and respiratory illness. These pollutants are emitted from a wide range of sources such as industrial operations, power plants, and waste treatment. Emission sources refer to any facility, equipment, or operation that releases pollutants into the air. The Clean Air Act divides these sources into two primary categories based upon annual HAP emissions:

• • Major sources: Facilities that emit 10 tons/year of any single HAP, or 25 tons/per year of any combination of HAPs.
  • Area sources: Facilities that emit smaller quantities of HAP but still subject to EPA control standards.

Many facilities emitting HAP are subject to Title V permitting requirements to ensure compliance with applicable emission limits, monitoring, and reporting obligations. As of 2022, the EPA regulates 188 HAP, including 30 urban air toxics and 68 area source categories listed in Section 112(b) of the Clean Air Act. Common examples of HAPs include benzene (often found in gasoline), metals such as mercury, chromium, and lead compounds, chlorine, and asbestos. For the complete list of compounds determined to be a HAP, click the link to the EPA website (Initial List of HAPs with Modifications).

Regulations of HAP Under the Clean Air Act

The regulations of HAP are governed by Title III of the Clean Air Act Amendments of 1990 where emissions from large industrial facilities are controlled by a two-phase approach:

1. • Phase 1: “Technology-based Standards” – What Is Feasible for Industry Sources
     This approach uses EPA developed standards to control air pollution from industry groups or “source categories,” using MACT standards. The maximum achievable control technology (MACT) standards are based upon emissions levels already implemented by similar sources in an industry. The minimum standard that industries must meet to comply with MACT requirements is known as “MACT floor,” which is based on the average emissions performance of the top-performing 12 percent of similar sources.
   • Phase 2: “Risk-based” – Continued Protection of Communities
     The second phase (or residual risk) approach is where EPA re-evaluates the health and environmental risks from sources. Within the 8 years after MACT standards are established, the EPA conducts the Residual Risk and Technology Review (RTR) to determine whether additional risk-based standards need to be enforced related to a HAP to protect public health against adverse environmental impacts.

HAP standards are implemented under the regulation and framework of National Emissions Standards for Hazardous Air Pollutants (NESHAPs) through either MACT for major sources or Generally Available Control Technology (GACT) for area sources.

Monitoring & Ensuring Compliance with HAP Standards

Staying compliant with the HAP standards requires ongoing monitoring, recordkeeping, and reporting of facility emissions. This includes ensuring that appropriate control technologies, under MACT or GACT, are implemented and periodic performance testing to monitor the environment. SEC supports facilities through every step of the compliance process – from coordinating emissions testing to adequately preparing all necessary reports.