FAQ / frequently asked questions

Air pollution refers to a mixture of harmful particles and gases found in the air we breathe. Air pollution can be found outdoors and indoors.

Outdoor air pollution can come from human activities such as motor vehicles (due to burning fossil fuels) and emissions from power plants (like from coal-fired plants), and from natural events such as wildfires and dust storms.

Indoor air pollution can come from human activities such as heating and cooking appliances that use wood or coal and smoking tobacco products, and from natural sources such as mold and pet dander.

Yes, outdoor air pollutants can enter buildings such as through open doors, open windows, and cracks in housing structures.

PM2.5 stands for particulate matter that is less than 2.5 micrometers (or microns) in diameter. PM2.5 is a mixture of solid particles and liquid droplets like dirt, soot, and smoke.

PM10 stands for particulate matter that is less than 10 micrometers in diameter and includes particles like dust, pollen, and mold.

Nitrogen dioxide (NO2) is a gas that is commonly released in traffic.

Carbon monoxide (CO) is a toxic gas that is colorless, odorless, and tasteless.

Ozone (O3) at the ground level is found in smog.

Sulfur dioxide (SO2) is a colorless gas with a pungent odor.

Wildfires are a major source of outdoor air pollution like PM2.5. Wildfire smoke can travel thousands of miles to impact local air quality. Some studies have shown that chemicals released during wildfires may be more toxic and create more harmful mixtures of urban air pollution. Wildfire season in Washington State generally lasts from May to October each year.

Health effects of air pollution depend on many factors, including which type of air pollutant you are exposed to, how much you are exposed to, how long you are exposed, and your preexisting health conditions.

For example, PM2.5 particles are small and can be inhaled deep into your lungs and enter your blood stream. PM2.5, NO2, O3, and SO2 can irritate and inflame the lining of your nose, throat, and lungs, which can lead to a flare-up of asthma or COPD and symptoms as well as worsen the severity of symptoms such as discomfort when you breathe, coughing, wheezing, difficulty breathing, and tightness of your chest. These air pollutants can also reduce the amount of air that your lungs can hold.

Studies have shown that higher concentrations of exposures to air pollutants in the short term (such as daily levels) are associated with more people being hospitalized for health problems related to asthma or COPD. There is also a higher likelihood of developing respiratory illnesses like pneumonia and bronchitis.

Long-term exposure to high levels of PM2.5 have been associated with increased risk of developing lung cancer, heart disease, stroke, and death.

• ​American Thoracic Society

  • Wildfire guidance

  • Outdoor air pollution​

• Environmental Protection Agency

  • Indoor air pollution

  • Air quality education for health care workers​

• World Health Organization

  • Outdoor air pollution​

  • Indoor air pollution

  • Training for health care workers​​

• Washington State Department of Health: Air Quality​

• Scientific American: Wildfire Smoke Reacts with City Pollution, Creating New Toxic Air Hazard

• ​Wildfire Smoke Impacts Respiratory Health More than Fine Particles from Other Sources: Observational Evidence from Southern California

• Association between Wildfire-Related PM2.5 and Epigenetic Aging: A Twin and Family Study in Australia