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About Air Toxics and Regulated Sources

  • Air Toxics
  • Current: About Air Toxics and Regulated Sources

Air toxics are substances that are known or suspected to cause cancer and other serious non-cancer health effects. Another term for air toxics is hazardous air pollutants (HAPs). Although there are natural sources of air toxics in the atmosphere such as volcanoes and wildfires, they primarily come from human activities. Examples of common sources of HAPs include large stationary industrial facilities (referred to as point sources), small processes and operations that have low individual emissions but add up to a significant collective impact (referred to as area sources), and mobile sources (such as motor vehicles).

Section 112 of the federal Clean Air Act (CAA) contains requirements for the reduction of air toxics from human sources and provides an initial list of 189 compounds. U.S. EPA has modified this to the current list of 187 regulated air toxics. Common examples include benzene that is found in gasoline, perchloroethylene that is used for dry cleaning, and an industrial solvent called methylene chloride. Regulated compounds also include asbestos (found in certain construction materials and automotive parts), toluene (used to make paint, paint thinners, fingernail polish, glues and more), dioxins (unwanted byproduct from the production of chlorinated compounds, paper manufacturing, combustion processes including waste incineration, and even cigarette smoke).

There are also categories of compounds, such as polycyclic organic matter (POM) from all types of combustion, radionuclides (radioactive materials), and metals such as cadmium, mercury, chromium and lead compounds. These compounds may be in the form of a gas, a particle or a liquid aerosol. Certain compounds are released directly from a source to the atmosphere. Other toxic compounds, known as “secondary pollutants,” form in the air from a chemical reaction between other substances. IDEM’s Air Toxics Program has an important role in understanding air toxics in Indiana, and reducing potential health risks from cumulative effects of combined exposure in urban areas.

Regulations for major stationary sources and area sources of air toxics include U.S. EPA’s National Emissions Standards for Hazardous Air Pollutants (NESHAPs) and state rules at Title 326 of the Indiana Administrative Code (326 IAC) Air Pollution Control Division.

What IDEM’s Office of Air Quality Does Not Do

IDEM’s Office of Air Quality is not responsible for implementing certain programs relating to mobile sources or indoor air quality, but provides resources. U.S. EPA regulates mobile source (motor vehicle) emissions, which are also a source of air toxics in the ambient outdoor air.

IDEM does not address indoor air quality or manage complaints about mold, formaldehyde, radon, lead-based paint removal, or other indoor air quality issues. U.S. EPA’s Indoor Environmental Division and the Indiana State Department of Health’s Indoor Air Quality program provide information and assistance on these issues. Local health departments (listed on ISDH’s website) may also manage indoor air quality issues. IDEM’s Office of Land Quality provides guidance on vapor intrusion, a process in which chemical vapors from contaminated soil or groundwater affect the indoor air quality in a building.