Air Toxics

In the 1990 Amendments to the Clean Air Act (CAA), provisions were added to regulate the emissions of about 190 hazardous air pollutants (HAPs) from stationary and mobile sources. To control HAP emissions EPA has established many industry-specific standards, known as National Emission Standards for Hazardous Air Pollutants, or NESHAPs. A key element of this control program is development of the MACT or Maximum Achievable Control Technology - standards. For new sources, the standard is based on the emission levels achieved by the top-performing similar source. For existing sources, EPA sets standards based on the level of performance achieved by the average of the top-performing 12 percent of similar sources. These are known as the “MACT floor.” Eight years following promulgation of a final rule, EPA evaluates the effectiveness of the standard by conducting conservative air modeling and risk analyses to ensure the public is adequately protected.

Major and area sources are the two types of stationary sources. Major sources emit greater than 10 tons per year (tpy) of any single HAP or 25 tpy of any combination of HAPs. The 1990 Amendments also require the installation of technology-based control measures, defined as Maximum Achievable Control Technology (MACT) for all industrial sectors. Most MACT standards affecting the petroleum industry have been promulgated, but EPA reviews and updates MACTS every 8 years if new technology has become available. In addition, CAA Section 112(f) requires EPA to evaluate whether there is any remaining residual risk eight years after each MACT standard is promulgated and to implement additional controls, if necessary, to protect the public health with an ample margin of safety.

The oil and natural gas industry is covered by a large number of regulations, tailored to specific industry categories, or source categories. The industry is subject to the following MACT rules to reduce HAP emissions.

Area sources emit less than 10 tpy of any single HAP or less than 25 tpy of any combination of HAPs. The EPA is expected to set Generally Achievable Control Technology (GACT) for these smaller stationary sources, such as gasoline distribution facilities and oil and natural gas production sites.