A Closer Look at Air Toxics

Air toxics are a group of hundreds of different chemicals which are known or suspected to cause serious health problems. Potential health effects include cancer, lung damage, heart disease, and nerve damage.¹ 

Diesel exhaust contributes most of the health risk from air toxics. Over 80% of the potential cancer risk from air pollution in our region comes from diesel exhaust. Diesel pollution comes from diesel-fueled trucks, cars, buses, construction equipment, rail, marine, and port activities. In industrial areas, hexavalent chromium, a harmful chemical, posed the next highest potential cancer risk at 5%. 

In our region, acrolein is the only air toxic exceeding safe levels for non-cancer health issues. Produced by burning wood, tobacco, or fossil fuels, acrolein irritates the lungs, eyes, and nose.

Although our region’s population has grown by 30%, we have observed a 50% reduction in air toxics levels since monitoring began in 2003.  This significant decrease can be attributed to improved technology standards, including the adoption of cleaner trucks and fuels. 

We also found Black, Indigenous, and other people of color and lower income households in our region have higher potential cancer risks from air toxics due to living near major roadways. 

Overall, we expect continued reductions in diesel exhaust. The largest reduction comes from replacing diesel engines with newer, cleaner engines and electrification. Diesel engine replacement is typically very expensive, and old diesel engines can work for a long time. The Agency leverages grant funding to replace old diesel engines to help speed the transition to improved air quality. New state and federal climate regulations and programs will further decrease air toxics pollution. 

In addition to our work to reduce diesel exhaust, we also actively work on other sources of air toxics pollution. This includes our regular work with industry to comply with regulations through our inspection, permitting, and complaint response programs, as well as programs aimed at reducing wood smoke emissions.  

Resources

• 2023 Tacoma and Seattle Air Toxics Study - The Puget Sound Clean Air Agency completed an EPA-funded study on air toxics in Tacoma and Seattle. The study's purpose was to update air toxics health risks and track trends dating back to 2003. Diesel exhaust continued to be the main contributor to cancer risk from air toxics.
  • Community Report (PDF)
  • Full Report (PDF)
• 2016 Chinatown-International District Air Toxics Study - The Puget Sound Clean Air Agency sampled over 100 air toxics in the community. The study found diesel exhaust is still the primary concern near our major highways. We found 14 other air toxics that were over one-in-a-million potential cancer risk. These toxics and their concentrations were similar to other sites across the country and are consistent with previous air toxics levels in Seattle and Tacoma.
  • Community Report (PDF)
  • Full Report (PDF)
• 2010 Tacoma and Seattle Area Air Toxics Evaluation - Through a study funded by the U.S. Environmental Protection Agency (EPA), the Puget Sound Clean Air Agency and the University of Washington measured the concentrations of toxic air pollutants in Tacoma and Seattle and identified the chief contributors.
  • Executive Summary (PDF)
  • Full Report (PDF)
• 2003 Puget Sound Air Toxics Evaluation - The Puget Sound Clean Air Agency conducted a screening study to identify chemicals and emission sources that posed the greatest potential health risks to citizens in the Puget Sound region. The purpose of the study was to assist the Agency in focusing resources on those emissions and sources that pose the highest risks. The Agency's Diesel Solutions program was created based on the results of this study.
  • Full Report (PDF)