Overview of MACT Standards

Under the Clean Air Act (CAA) Amendments of 1990, Congress listed 189 pollutants. that it identified as hazardous air pollutants (HAPs), also referred to as "air toxics." The U.S. Environmental Protection Agency (EPA) is required to regulate emissions of these hazardous air pollutants through a two-step process.

The first step is the development and promulgation of technology-based standards based on the best-performing facilities in operation. These are known as maximum achievable control technology (MACT) emission standards. While EPA was to have issued all the MACT standards by November 2000, it missed this completion target.

After the MACT standards are issued, the second step is determining whether health-based regulations are needed. This is known as the "residual risk" analysis. EPA is required to assess the risk posed by HAP emissions after facilities have implemented the MACT standards. If the risk is unacceptably large, EPA is to issue health-based standards for that source category to further reduce HAP emissions and ensure an "ample margin of safety" for the public. In addition, EPA is required to set more stringent standards if necessary to prevent adverse environmental effects, considering energy, costs and other relevant factors. The EPA must set residual risk standards within nine years after promulgation of each MACT standard, which would be between 2001 and 2008, if EPA had issued the standards on time.

EPA develops MACT standards based on the industrial sectors responsible for the bulk of emissions of a particular HAP or group of HAPs. These industrial sectors are called "source categories" by EPA and the Agency issued a list of HAP source categories in 1992. Source categories usually are defined by North American Industrial Code (NAIC) numbers, which have replaced Standard Industrial Code (SIC) numbers.

The Clean Air Act provisions governing air toxics divides facilities into two groups based on the size of their air toxic emissions. These are "major sources" and non-major or "area sources."

A facility is a "major source" if it has the potential to emit (PTE) 10 tons per year or more of a single HAP or 25 tons per year or more of total HAP emissions. 42 U.S.C.A. § 7412 (CAA § 112). Any facility with a potential to emit below the major source level is an "area source."  EPA can regulate area sources that emit hazardous air pollutants. One example is the MACT standard for your neighborhood dry cleaning operations.

A. What is a MACT Emission Standard?

Section 112 of the CAA includes provisions for the promulgation of national emissions standards for hazardous air pollutants (NESHAPs). The standards require the maximum degree of emission reduction that the EPA determines to be achievable by each particular source category listed under the CAA § 112(b), taking into account cost of achieving the reduction and non-air quality health and environmental impacts and energy requirements.

To establish a MACT standard, EPA typically establishes a "MACT Floor" by assessing the performance of the best controlled 12 percent of facilities in the source category. Once the MACT floor has been set, EPA investigates regulatory alternatives that are at least as stringent as the MACT floor. Based on technical achievability, a standard then is chosen that represents the MACT, and it is issued as a proposed regulation subject to notice and opportunity for comment. EPA issued "general provisions" to address requirements such as those just described that apply to all air toxics rules on March 16, 1994. 59 Fed. Reg. 12,430; 40 CFR part 63.

MACT standards apply to new and existing sources, but the EPA may distinguish between classes, and types and sizes of sources within a category. For "area sources," the Agency can require less stringent standards, known as generally available control technology (GACT) standards rather than MACT standards.

B. What is a MACT Hammer?

In 1990, Congress set a timetable for EPA's promulgation of MACT standards. The schedule was divided into four groups that signified when the NESHAP should have been promulgated between 1992 and 2000: 2-year, 4-year, 7-year, and 10-year standards. EPA subsequently issued a MACT schedule that it has struggled to meet.

Because Congress did not trust EPA to meet the MACT standard timetable, it included a provision known as the MACT "hammer" under the CAA § 112(j). If EPA fails to promulgate a standard for the relevant source category or subcategory within 18 months of its statutory schedule, the state or federal permitting authorities must incorporate "equivalent emission limitations" into operating permits for new and existing major sources of HAPs. In other words, the owner or operator of each major source with emission units in that category must apply for a case-by-case MACT determination by the Title V permitting authority.

Permitting authorities try to determine what limit EPA would have established for the source category had the federal MACT standard been promulgated. If the EPA has proposed a MACT standard for the source category, the permitting authority should consider it. Section 63.55(a)(1) of the CAA regulations require that in the absence of a supportable alternative, the equivalent emission limitation should be at least as stringent as any such proposed rule. The process is more complicated if a proposed standard has not been issued. In that case, the regulations dictate that the case-by-case MACT determinations are consistent with the requirements described under the CAA § 112(d), i.e., establishment of a "MACT floor" by assessing the performance of the best controlled 12 percent of facilities in the source category. Recognizing the impracticality of having several state permitting authorities try to establish the appropriate "MACT floor," EPA takes responsibility for setting the MACT floor. If, however, EPA fails to do so, the state permitting authority will have to make the determination and/or the Title V applicant can make a recommendation. These actions are to be coordinated with the EPA so that the information can be shared with other permitting authorities.

C. When must I comply with MACT Standards?

• New sources, which are sources that start construction or reconstruction after proposal of the standard, must comply with the standard immediately upon start-up with a few exceptions discussed below.
• Sources constructed or reconstructed after the MACT proposal but before promulgation may comply with the proposed standards if the promulgated standards are more stringent. Compliance with the promulgated standard is required for such sources within three years of promulgation.
• Existing sources must comply with the MACT standard no later than three years after promulgation. The EPA or a state with an approved Title V Clean Air Act program may grant individual sources a 1-year extension if necessary for the installation of controls.
• The Early Reductions Program allows a qualifying facility to defer compliance with MACT standards for up to six years if it reduces HAP emissions by 90% (95% for hazardous particulate emissions) before the applicable MACT is proposed.

D. How are 'Area Sources' Affected?

Under Title III of the CAA, EPA must identify and list not less than 30 HAPs from area sources that present the greatest threat to public health. EPA also must identify and list the categories of area sources accounting for 90 percent or more of all area source emissions of those hazardous air pollutants. An area source is any area that is not a "major source," including any building, structure, or installation that emits or may emit hazardous air pollutants. As mentioned above, an area source may be subject to MACT standards or GACT standards at EPA's discretion.

Under section 112(k) of the Clean Air Act, EPA also is required to develop a national strategy to control HAPs from area sources in urban areas. This strategy is known as the "Integrated Urban Air Toxics Strategy." As part of the Strategy, under the National-Scale Air Toxics Assessment, EPA identified 33 air toxics that present the greatest threat to public health in the largest number of urban areas. Of those 33 air toxics, EPA culled 30 with the greatest contribution from smaller commercial and industrial "area sources."  In July 1999, EPA then identified 29 "area source" categories that contribute to the emissions of these 30 listed air toxics, and in November 2002, identified 23 additional area sources for regulation.  EPA planned to propose regulations for a majority of the area source categories listed in the Strategy in 2003 and 2004.

E. What are the MACT Standards that may Impact Plastic Processors?

A comparison chart presents in greater detail four key MACT standards for plastic processors: (1) Misc. Metal Parts and Products (Coating); (2) Paper and Other Web Coating; (3) Plastic Parts and Products (Coating); and (4) Printing and Publishing. In addition, identified below are other MACT standards that may affect the plastic processors' industry (a complete list is available):

• Degreasing Organic Cleaners (Halogenated Solvent Cleaning). Final Rule, 59 Fed. Reg. 61,801 (12/02/94).
• Flexible Polyurethane Foam Production. Final Rule, 63 Fed. Reg. 53,980 (10/07/98).
• Boat Manufacturing. Final Rule, 65 Fed. Reg. 43,841 (7/14/2000).
• Flexible Polyurethane Foam Fabrication Operation. Final Rule,  68 Fed. Reg. 18061 (4/14/03).
• Reinforced Plastics Composites Production.  Final Rule, 68 Fed. Reg. 19375 (04/21/03).
• Generic MACT standards for certain small source categories involved in acetal resins production, acrylic and modacrylic fiber production, hydrogen fluoride production and polycarbonate(s) production. Final Rule, 64 Fed. Reg. 34,953 (6/29/99).
• General provisions including amendments to CAA § 112(j).

F. Does being in a Nonattainment Area change the MACT Standard?

A common question is whether a source in a nonattainment area is subject to more stringent MACT emission standards than similar sources located in attainment areas. The terms "attainment area" and "non-attainment" relate to the regulation of so-called "conventional" air pollutants, such as ozone and particulate matter, under different provisions of the Clean Air Act. Many sources are subject to both conventional and hazardous air pollutant regulations.

MACT standards are uniform nationally and do not vary based on a facility's location. But, many HAPs may also be ozone-precursors and facilities may have obligations to meet MACT standards and, for example, rules relating to the national ambient air quality (NAAQ) standard for ozone under the CAA Title I. EPA has issued guidance on this issue, but typically facilities are required to apply the most stringent provisions of the applicable rules.

G. Conclusion

EPA will continue to issue MACT standards as it attempts to close out the MACT promulgation process.  At the same time, the Agency will continue its residual risk analyses of existing MACT standards.  SPI member companies need to keep track of new, applicable regulations, particularly as they prepare for air operating permit renewals.

Back to Top

More Public Policy:   Worker Safety . Transportation . Codes and Standards . Food, Drug,and Cosmetic Packaging . International Trade . Other Issues