About Urban Air Toxics

What are urban air toxics?

Air toxics, also known as toxic air pollutants or hazardous air pollutants, are those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects. Learn more about air toxics.

The Clean Air Act identifies 187 hazardous air pollutants (HAPs) that EPA is required to control to protect public health. More specifically, to address HAPs in urban areas, section 112(k) of the Clean Air Act directs EPA to:

  • Identify a subset of 30 HAPs that present the greatest threat to public health in the largest number of urban areas. These 30 HAPs are known as the 30 urban air toxics.
  • Identify area sources that represent 90 percent of the combined emissions of the 30 urban air toxics, and subject these sources to regulation. The EPA identified 68 area source categories of urban air toxics.

Health effects of urban air toxics

Air toxics tend to pose greater risks in urban areas because these areas have large populations and a higher concentration of emission sources. Combined exposures from all sources of air pollution, including major stationary sources, smaller area sources, indoor sources and mobile sources can increase public health risks from air toxics. Low-income neighborhoods, tribal populations and communities of color that live in urban areas may be disproportionately exposed to air pollution, which is a barrier to economic opportunity and security.