National air quality standards
We and local clean air agencies monitor and track emissions to make sure levels of outdoor air pollutants meet federal and state air quality standards. We focus on EPA's "criteria" pollutants and other chemicals broadly known as air toxics. Our programs and strategies prevent air pollution from reaching levels that are unhealthy for people or the environment.
Criteria air pollutants
The federal Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants. We monitor these pollutants and take action if levels become unhealthy. The pollutants are:
- Carbon monoxide (CO)
- Lead (Pb)
- Nitrogen dioxide (NO2)
- Ozone (O3)
- Particle or particulate matter (PM)
- Sulfur dioxide (SO2)
Air toxics
EPA established a list of 188 hazardous air pollutants. We regulate over 430 toxic air pollutants from commercial and industrial sources. We prioritized 21 of those toxic air pollutants because of their health risk. To reduce levels of these priority pollutants, we are working to reduce diesel emissions and wood smoke.
Air toxics monitoring
We track air pollution throughout Washington. Since 2000, we have been measuring air toxics at our Seattle-Beacon Hill air quality monitoring station. By comparing long-term trends to current readings, we have determined that most toxic pollutant levels are going down. This shows that driving clean cars helps keep the air healthy.
We also partner with local clean air agencies to identify and monitor pollutants that are the greatest health risk. Reports from some of the studies include:
- Seattle and Tacoma area (2023)
- Seattle Chinatown-International District air toxics study (2018)
- Seattle and Tacoma area (2010)
- Longview (2005) and (2009)
- Vancouver (2005)
- Spokane (2005)
Air toxics dispersion modeling
We rely on EPA’s Air Toxics Screening Assessment (AirToxScreen) to estimate health risks for air toxics. AirToxScreen uses information about air toxics emissions, air movement (i.e., wind), and toxicity to estimate concentrations of air toxics and the risks they pose to people in Washington.
Based on 2019 emissions, AirToxScreen shows that the key sources of air toxics in Washington are on- and non-road vehicles. On-road vehicles are cars and trucks that travel on highways and roads. Non-road vehicles include locomotives, airplanes, ships, and construction equipment. Combined, these sources contribute to about 72% of total cancer risk from air toxics in Washington. Some air toxics also form in the atmosphere after secondary reactions in the atmosphere (secondary formation). Others form naturally from trees, vegetation, or other living things (biogenics). Wood stoves, small commercial and industrial sources (area sources), and major facilities contribute a small amount to air toxics risk in Washington.
Categories of emission sources and their contributions to cancer risk from air toxics in Washington
Based on 2019 emissions, AirToxScreen shows that diesel particles contribute the most (about 66%) to the statewide cancer risk from air toxics. Formaldehyde — which is both directly emitted and forms from secondary reactions in the atmosphere — contributes the second highest portion (about 18%) of air toxics risk. Carbon tetrachloride — which has been banned for decades — still lingers in the atmosphere, contributing about 4% to air toxics risk. Benzene (4%), acetaldehyde (3%), and naphthalene (2%) contribute to the remaining air toxics risk.
Pollutants and their relative contribution to total cancer risk from air toxics in Washington
This map of Washington shows the estimated cancer risk from air toxics in different geographic areas. In general, cancer risk is higher in densely populated areas. The port areas of Seattle and Tacoma are the highest risk locations. Cancer risks shown are only estimates. These estimates do not predict cancers. We use them to help set priorities and focus air toxics reduction work. Note: Risks shown on the map are higher than those reported by EPA. This is because EPA does not estimate cancer risk from diesel exhaust. We adjusted EPA’s AirToxScreen results to account for diesel exhaust risks.
Related links
- Air quality mobile apps
- Air quality map
- Apple: Air Quality WA (classic map)
- Google/Android: Air Quality WA (classic map)
- Air Quality Index (AQI)
- Air quality studies
- State Implementation Plan (SIP)
Contact information
Gary Palcisko
Toxicologist
gary.palcisko@ecy.wa.gov
360-995-3447