Air Toxics & Hazardous Air Pollutants Sources

Hazardous Air Pollutant Source Categories

Hazardous air pollutants (HAPs) are substances that are known or suspected to cause serious health problems such as cancer. The Clean Air Act defined an initial list of substances, and EPA currently identifies 188 HAPs. The list includes relatively common pollutants such as benzene, chlorine, methanol, and asbestos, as well as numerous less common substances. For details, see the complete list of hazardous air pollutants in the National Emissions Inventory (NEI) database. EPA’s Air Toxics Web site has further information about the sources of HAPs, and a list of the 188 pollutants. (“Air toxics” and “toxic air pollutants” are synonyms for hazardous air pollutants.) EPA has identified a subset of the 188 HAPs that pose the greatest potential for adverse health effects to the majority of the U.S. population living in urban areas. These 33 pollutants are called urban HAPs.

Clean Air Act & Air Toxics/Hazardous Air Pollutants (HAP)

The Clean Air Act defines separates these sources according to four categories:

Major (Point)
Point sources that emit or have the potential to emit at least 10 tons per year of any one HAP, or at least 25 tons per year of a combination of HAPs, are major sources. Examples of major sources are electric utility plants, chemical plants, steel mills, oil refineries, and hazardous waste incinerators. These sources may release air toxics from equipment leaks, when materials are transferred from one location to another, or during discharge through emissions stacks or vents.

Area and Other (Nonpoint)
Area sources are stationary sources that do not exceed the thresholds for major source designation. They emit less than 10 tons per year of a single HAP and less than 25 tons per year of all HAPs combined. Examples of area sources are neighborhood dry cleaners and gas stations. Though emissions from individual sources are often relatively small, collectively their emissions can be of concern, particularly where large numbers of sources are located in heavily populated areas.

Other sources are wildfires and prescribed burning.

Onroad sources include licensed motor vehicles, including automobiles, trucks, buses, and motorcycles.
Nonroad sources include 2- or 4-stroke and diesel engines, nonroad vehicles, aircraft, commercial marine vessels, and locomotives.

Toxic Release Inventory

A federal law called the Emergency Planning and Community Right to Know Act (EPCRA) gives you the right to know about toxic chemicals being released into the environment. The law requires facilities in certain industries, which manufacture, process, or use significant amounts of toxic chemicals, to report annually on their releases of these chemicals.  The U.S. Environmental Protection Agency (EPA) maintains this information in a database called the Toxics Release Inventory (TRI), which is available to the public online at You can also access information on toxic chemicals released in your community at

NLEH Neighborhood Air Toxics Data

Mercury Air Pollution

  • In March, 2004 EHW and the National Wildlife Federation released a report showing that alarming levels of mercury in rain falling on Cleveland, levels up to 31 times higher than the levels EPA considers safe. Read the Akron Beacon Journal’s Editorial
    • Mercury Press Release
    • Mercury Report (pdf, 15pgs)

Cuyahoga County Air Toxics Emissions Inventory (2002)

  • As Part of the Cleveland Clean Air Century Campaign the EPA prepared a detailed inventory and analysis of sources of toxic air emissions for Cuyahoga County.  Separate inventories were also prepared for the St. Clair-Superior and Slavic Village neighborhoods.
    • Inventory Highlights
    • Inventory Summary (pdf, 9pgs)
    • Slavic Village, Cleveland, Ohio (pdf, 4pgs)
    • St. Clair-Superior, Cleveland, Ohio (pdf, 5pgs)
    • Full Inventory Report (pdf, 127pgs)

Air Toxics Exposure Modeling for Cuyahoga County

  • As part of an analysis of the modeling data from the Cumulative Exposure Project (US EPA) for Cuyahoga County, EHW found 14 air toxics estimated to exceed the cancer benchmark. Mobile air toxics had the highest exceedences of the cancer benchmarks, by far with several exceeding the cancer benchmarks by more than 20 times.
    • Estimating Exposure
    • Slides, Tables and Graph
    • Air Quality Monitoring in Cuyahoga County (Cleveland, Ohio)

Comments are closed.