What are EPA MACT Standards?

The EPA developed Maximum Achievable Control Technology Standards, or MACT standards, to reduce the effects of Hazardous Air Pollutants (HAPs) generated by industry.

There is a common misconception that the term "control technology" refers to expensive emission control devices, such as scrubbers, thermal oxidizers and bio-filters. In fact, the term "control technology" can actually mean measures, processes, methods, systems or techniques that are used to limit the emissions of hazardous air pollutants.

MACT standards affect sources (new and old) by making them meet specific emissions limits. These limits are based on the emissions levels already achieved by the best-performing similar facilities.

This straightforward, performance-based approach yields standards that are both reasonable and effective in reducing toxic emissions.

This approach also provides a level economic playing field by ensuring that facilities with good controls are not disadvantaged relative to competitors with poorer controls.

How does the EPA determine these MACT Standards?

The EPA develops MACT standards specific to each source category.

To determine MACT standards, the EPA looks at the current level of emissions that are being achieved by the best-performing similar sources. These emission levels are then used to set a baseline that is known as the "MACT floor" for the new standard.

A MACT standard must, at a minimum, achieve throughout the industry, a level of emissions control that is at least equivalent to the MACT floor.

The EPA can then establish a more stringent standard when this makes economic, environmental, and public health sense. 

The standards that were developed through this MACT approach became known as the National Emission Standards for Hazardous Air Pollutants (NESHAPs). The purpose of these NESHAPs is to protect the public health by reducing discharges of HAPs from major air emission sources.

A "major source" of HAPs is defined as any stationary source (or group of stationary sources) that annually emits, in the aggregate, at least 10 tons of any single HAP or 25 tons of multiple HAPs.

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