Air Toxics

What are Air Toxics?

Air toxics pollutants, also referred to as hazardous air pollutants (HAPs) by the United States Environmental Protection Agency (EPA), are pollutants known or suspected to cause or contribute to serious health effects. People exposed to air toxics at certain concentrations and durations may have an increased chance of developing cancer or experiencing other serious health problems, including damage to the immune system as well as neurological, reproductive (reduced fertility), developmental, and respiratory problems. The 1990 Clean Air Act (CAA) Amendments require the EPA to regulate air emissions for 187 HAPs. The Virginia Department of Environmental Quality (DEQ) list of air toxics is EPA’s list of HAPs with the exclusion of asbestos, fine mineral fibers, radionuclides, and any glycol ether that does not have a threshold limit value (TLV) as published in 1991-1992 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices (American Conference of Governmental Industrial Hygienists (ACGIH) Handbook). Examples of air toxics include benzene, mercury, formaldehyde, perchloroethylene, and methanol.

Where do Air Toxics Come from?

Air Toxics come from both natural and manmade sources. Natural sources include volcanic eruptions, forest fires, and trees. Man made sources include mobile sources including cars, trucks, buses, trains and airplanes; stationary sources including industrial operations such as refineries and power plants; commercial operations such as gasoline stations, dry cleaners, and auto body shops; institutional operations such as boilers, laboratories, and sterilizers; residential activities such as fireplaces, lawn mowers, and pesticides, and indoor sources such as building materials, paint, and cleaning solvents. Even though some of these activities may release only a small amount of air toxics, the combined effect may be of concern especially in urban areas where multiple sources may exist within a small geographical area.

What is Being Done to Reduce Emissions of Air Toxics in Virginia?

The DEQ air toxics program integrates federal and state air toxics regulations to reduce emissions of air toxics in Virginia. The primary control programs are:

Existing Sources

Existing stationary sources (sources constructed before March 17, 1972 that have not been modified or relocated or that have not commenced reconstruction before December 10, 1976) that emit one or more toxic air pollutants are subject to State Air Toxic Regulations unless the source is regulated or exempted under one of the federal National Emission Standards of Hazardous Air Pollutants (NESHAPs) discussed below. See regulation for specific exemptions.

Preconstruction Review of New and Modified Sources

Proposed projects that emit one or more toxic air pollutants are reviewed for potential health impacts unless the project is regulated or exempted under one of the federal National Emission Standards of Hazardous Air Pollutants (NESHAPs) discussed below. Proposed projects subject to the State Air Toxics Regulation that exceed the corresponding exemption threshold level for a particular air toxic must apply Best Available Control Technology (BACT) to minimize air toxic emissions. Since many of the air toxics are also either volatile organic compounds (VOC) or particulate matter compounds, control measures that reduce these criteria pollutant emissions may be used to reduce air toxic emissions. In addition, the applicant must demonstrate through air dispersion modeling that the concentration of the air toxic does not exceed the corresponding Significant Ambient Air Concentration (SAAC). The SAAC is the concentration of a toxic pollutant in the ambient air that, if exceeded, may have an adverse effect to human health.

EPA’s NESHAPs under 40 CFR Part 61

 The 1970 CAA Amendments required the EPA develop standards to regulate HAP emissions from new and existing sources using a risk based analysis on a pollutant-by-pollutant basis. This approach proved to be a difficult challenge for EPA and only seven HAP standards were promulgated in twenty years.  

EPA’s NESHAPs under 40 CFR Part 63 for Major Sources of HAPs

A major source of HAPs means any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit 10 tons per year or more of any individual HAP or 25 tons per year or more of any combination of HAPs. The 1990 CAA Amendments require a two-phase approach to regulating HAP emissions. The first phase requires EPA to regulate HAP emissions from a published list of industrial "source categories." EPA has identified source categories that must meet technology requirements to control HAP emissions and is required to develop regulations for all industries that emit one or more of the HAPs in specified quantities. These standards are also referred to as Maximum Achievable Control Technology (MACT) standards. MACT standards are based on emissions levels already achieved by best-performing similar facilities and are designed to reduce HAP emissions to a maximum achievable degree, taking into consideration the cost of reductions and other factors.

The second phase, the Risk and Technology Review (RTR) applies a risk-based approach in which EPA assesses how well the technology-based standards have done in reducing the public health and environmental risks. Information on the RTR process and proposed and final action dates for certain source categories can be found on EPA’s RTR website.

EPA’s NESHAPs under 40 CFR Part 63 for Area Sources of HAPs

Area sources of HAPs are stationary sources that are not major. As part of the Urban Air Toxics Strategy, EPA has been developing standards to control certain toxic air pollutants from area sources. The CAA requires EPA to identify a list of at least 30 air toxics that pose the greatest potential health threat in urban areas. EPA identified a list of 33 urban air toxics. EPA has identified a total of 70 area source categories which represent 90 percent of the emissions of the urban air toxics. All of the listed source categories are expected to be promulgated by 2012.

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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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