Air toxics in Minnesota

Air toxics are those pollutants that cause or may cause cancer or other serious health effects or adverse environmental and ecological effects. Air toxics include, but are not limited to, the Hazardous Air Pollutants (HAPs) specified in the Clean Air Act Amendments. The Clean Air Act requires the Environmental Protection Agency to develop National Emission Standards for Hazardous Pollutants to reduce overall air toxic emissions.

The MPCA uses inhalation health benchmarks to assess the health risks associated with air toxics concentrations from these sources: Minnesota Department of Health, EPA’s Integrated Risk Information System (IRIS), California’s Office of Health Hazard Assessment, and the EPA Superfund Provisional Peer Reviewed Toxicity Values for Superfund (PPRTV).

The MPCA works to ensure that concentrations of all air toxic pollutants in Minnesota are below health benchmarks. The MPCA uses air emissions inventory, monitoring and air dispersion modeling data to quantify air toxics concentrations in the environment. MPCA programs such as air permitting, environmental review and other agency air emission reduction programs use this information to prioritize air toxic emission reductions in Minnesota.

Sources of air pollutants

  • Point sources. These are large stationary sources that typically have an air permit; for example, power plants and refineries. There are over 2,000 point sources in Minnesota.
  • Nonpoint sources. Also known as “area” sources, these are smaller but more numerous individual stationary sources. Examples include dry cleaners, gasoline service stations and residential wood combustion.
  • Mobile sources. On-road mobile sources are vehicles operated on highways, streets and roads. Non-road mobile sources include lawn and garden equipment, construction equipment, aircraft and locomotives.


Air emissions are the quantity of air pollutants that are released from an air pollution source. Estimates of the amount of air toxics pollutants released by sources throughout Minnesota can be found at:

  • U.S. EPA National Emissions Inventory — The national inventory of annual air toxics emissions is calculated every 3-years from air emissions data submitted by state, local, and tribal air agencies.
  • U.S. EPA Toxics Release Inventory — The national database that contains information on toxic chemical releases to air, land and water from facilities that manufacture, process or otherwise use toxic chemicals across the country.
  • For information about Minnesota's Air Toxics Emissions inventory, contact Chun Yi Wu or Nate Edel.

Air monitoring provides direct measurements of pollution concentrations in the air at fixed locations. The MPCA monitors air toxic pollutants at more than 20 sites across Minnesota. Air toxics monitoring results are compared to state and federal health benchmarks.

Minnesota monitoring sites

Minnesota Studies and reports

Air modeling

Air modeling provides computer-modeled estimates of pollutant concentrations and risks across Minnesota. Air modeling incorporates air pollution emissions data, facility characteristics and meteorological data to predict air pollutant concentrations. The MPCA uses air modeling to support air permitting, to assess health risks associated with air toxics emissions in Minnesota, and to prioritize emission reduction activities.

Information about air toxics modeling programs and results can be found at:

Air toxics emissions reductions programs at MPCA

The MPCA is responsible for implementing and enforcing federal rules that control toxic releases from industries and certain business activities.

The MPCA has programs that work toward reducing air pollutant emissions with other stakeholders, or through more voluntary and educational approaches.

  • Clean Diesel Grants — An MPCA administered program providing grants or financial assistance to reduce diesel emissions from public or private on-road, non-road, or marine diesel fleets.
  • Project Green Fleet — A community partnership coordinated by Clean Air Minnesota which works with school districts and school bus fleet operators to retrofit buses with diesel emissions control technology.
  • Beyond Regulations — The MPCA provides support for businesses who want to reduce emissions and wastes beyond state and federal requirements.
  • Residential Wood Smoke — The MPCA provides information, advice and external links on limiting air toxics from exposure through residential wood combustion.

MPCA/MDH inhalation health benchmark hierarchy

Air toxics do not have standards. Instead, the MPCA uses a set of inhalation health benchmarks to inform regulatory and environmental decision making. These inhalation health benchmarks are available on the pdf and the MPCA Risk Assessment Spreadsheet (RASS) below.

These benchmarks come from the following hierarchy of sources:

External links for more information on air toxics