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Air Quality

Maximum Achievable Control Technology (MACT)


Since 1970, the Clean Air Act has provided the primary framework for protecting people and the environment from the harmful effects of air pollution. In the 1990 Clean Air Act Amendments, Congress directed the Environmental Protection Agency (EPA) to use a 'technology-based' and performance- based approach to significantly reduce emissions of hazardous air pollutants (HAPs) from major sources of air pollution, followed by a risk-based approach to address any remaining, or residual risks. Under the 'technology-based' approach, EPA develops standards for controlling the 'routine' emissions of HAPs from each major type of facility within an industry group (or 'source category'). These standards, known as "maximum achievable control technology (MACT) standards" are based on emissions levels that are already being achieved by the better-controlled and lower-emitting sources in an industry sector. Eight years after each MACT standard is issued, EPA must assess the remaining health risks from sources categories. If necessary, EPA may implement additional standards that address any significant remaining risk.

Most HAPs originate from human-made sources, including mobile sources (e.g., cars, trucks, buses) and stationary sources (e.g., factories, refineries, power plants), as well as indoor sources (e.g., building materials and activities such as cleaning). Some HAPs are also released from natural sources such as volcanic eruptions and forest fires. There are two types of stationary sources that generate routine emissions of HAPs:

Major Sources Area Sources
Major sources are medium to large industrial facilities that emit 10 tons per year of any of a single HAP, or 25 tons per year of a combination of HAPs. These sources may release HAPs from equipment leaks, when materials are transferred from one location to another, or during discharge through emission stacks or vents.
Area sources consist of smaller-size facilities that release lesser quantities of HAPs into the air. Area sources emit less than 10 tons per year of a single HAP, or less than 25 tons per year of a combination of HAPs. Though emissions from individual area sources are often relatively small, collectively their emissions can be of concern - particularly where large numbers of sources are located in heavily populated areas. Area sources include, but are not limited to, dry cleaners, gas stations and paint and body shops.

The Department's Bureau of Air Quality is responsible for implementing the MACT standards in South Carolina. The current MACT standards include standards covering over 80 categories of major industrial sources, such as chemical plants, oil refineries, aerospace manufacturers, and steel mills, as well as categories of smaller sources, such as dry cleaners, commercial sterilizers, secondary lead smelters, and chromium electroplating facilities. When fully implemented, these standards are projected to reduce annual HAP emissions by about 1.5 million tons nationwide - 15 times the reductions achieved prior to 1990.

For more information please contact us at (803) 898-4123 or by email.