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Energy and Environment Cabinet

Photographed by Candy Montgomery

Division for Air Quality
Air Toxics

Air toxics are those air pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive and birth defects. The degree to which a toxic air pollutant affects a person’s health depends on many factors including the quantity and toxicity of the pollutant to which the person is exposed as well as the duration and frequency of exposure.

Air toxics can come from natural sources (e.g., radon gas coming from the ground) or man-made sources such as motor vehicles and industrial processes. Air toxics that deposit onto soil or into lakes and streams can affect ecological systems and eventually human health through consumption of contaminated food.

The federal Clean Air Act targets 187 toxic air pollutants for emissions reduction. These air toxics are known as hazardous air pollutants. Examples include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Other examples are dioxin, asbestos and metals such as mercury, chromium and lead. The Kentucky Department for Environmental Protection ensures that industries in the state comply with the limits on hazardous and/or toxic air pollutant emissions established under the Clean Air Act.

Kentucky Air Toxics Program Overview

The Air Toxics program came into existence in its present form in 2008. The program is implemented under 401 KAR 63:020, which states, “No owner or operator shall allow any affected facility to emit potentially hazardous matter or toxic substances in such quantities or duration as to be harmful to the health and welfare of humans, animals and plants. Evaluation of such facilities as to adequacy of controls and/or procedures and emission potential will be made on an individual basis by the cabinet.”

Air toxics risk assessment is considered the most appropriate means in which to abide by 401 KAR 63:020. The guideline document for conducting Air Toxics Risk Assessment can be obtained on the U.S. EPA Web site at the following address:

The Division for Air Quality is not limited to one particular source for risk values under 401 KAR 63:020. Therefore, the division incorporates the most current risk values drawing upon best science at the time of evaluation.

Air Toxics Screening Analyses

 Air toxics are screened by the division based upon information included in the permit application. A cursory screening is performed for each chemical that has an established value primarily in the U.S. EPA Regional Screening Level (RSL) table located at:  If the screening analysis concentration exceeds the threshold values of one in a million carcinogenic risk or the reference concentration, further refined modeling is conducted by the division to assess the human health impacts posed by the emissions. If the emissions pose a significant threat to human health, the facility will be required to demonstrate as to how the emissions will be reduced to not pose an unacceptable risk. The division can require a risk assessment as part of the demonstration.

 Air Toxics Links of Interest