Outdoor Air Pollution

Sources of Air Pollution in Washington

The main sources of outdoor air pollution in Washington State are motor vehicles and transportation, outdoor burning, and wood smoke. Gas and diesel-powered equipment, some industries, and wildfires also contribute to air pollution. Air pollution in your community depends mostly on local sources. However, some types of air pollution can travel many miles such as ozone and smoke from wildfires. Air pollution varies by time of year depending on weather and seasonal sources such as woodstoves and wildfires. You can check current air quality conditions and burn bans in your area. Find out more from your local clean air agency.

Fine Particulate Matter (PM_2.5)

PM_2.5 or fine particulate matter, refers to airborne particles 2.5 micrometers or smaller in size. PM_2.5 is one of the most important air pollutants of health concern in Washington.

Major sources of PM_2.5 include wood stoves, vehicles and other transportation, outdoor burning, industrial facilities and power plants, and wildfires.
PM_2.5 can be formed in the environment from other types of air pollutants including sulfur dioxide (SO₂) and nitrogen oxides (NOx).
PM_2.5 can cause regional haze that reduces visibility in some areas.

Health effects: PM_2.5 can be inhaled deep into the lungs, and the smallest particles can cross into the bloodstream and enter systemic circulation, and can exacerbate and lead to many health problems. PM_2.5 has been linked to decreased lung function, increased respiratory symptoms including asthma attacks, exacerbation of existing heart disease, nonfatal heart attacks, irregular heartbeat, premature death among people with existing heart and lung conditions, cognitive impacts, adverse birth outcomes, and negative impacts on mental health.

For more information see Washington Air Quality Guide for Particle Pollution (PDF) and Particulate Matter Pollution, EPA.

Ozone (O₃)

Ground-level ozone is formed in the environment from the reaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of heat and sunlight.
Ozone is the main component of smog and occurs mostly during the summer in Washington.
Ground-level ozone is separate from the ozone layer that protects the earth from UV radiation.

Health Effects of Ozone: Ozone irritates the respiratory tract when you breathe it. Ozone can cause wheezing, shortness of breath, and chest pain; aggravate bronchitis, emphysema and asthma; reduce lung function; and increase susceptibility to respiratory infections.

For more information, see Ground-level Ozone Pollution, EPA.

Nitrogen Oxides (NOx)

Nitrogen oxides refers to a group of compounds that include nitrogen dioxide (NO₂).
NOx contribute to the formation of ozone and PM_2.5 air pollution.
Major sources include vehicle exhaust, power plants (that burn fossil fuel), and non-road equipment including trains, diesel and gas-powered construction equipment and gas-powered lawn and garden equipment.

Health Effects Nitrogen Oxides: NOx is a respiratory irritant and has been associated with asthma attacks, increased hospital visits for respiratory conditions, and other respiratory problems.

For more information, see Nitrogen Dioxide Pollution, EPA.

Other Criteria Air Pollutants

Six air pollutants are highly regulated at the federal level, under the National Ambient Air Quality Standards (NAAQS), due to their ubiquity and level of health concern. These are called Criteria Air Pollutants and include Ozone, Particulate Matter, Carbon Monoxide, Lead, Sulfur Dioxide, and Nitrogen Dioxide. Carbon monoxide (CO), sulfur dioxide (SO2), and lead are no longer pervasive outdoors in Washington.

Air Toxics (also called Hazardous Air Pollutants)

Air toxics consist of 187 pollutants including solvents and other volatile organic chemicals, other industrial chemicals and industrial by-products, combustion products, and metals including mercury.
Air Toxics are regulated differently than EPA's six criteria pollutants (PM, O₃, NO_x, SO₂, CO and lead) because they usually don't impact large regions and come from many different sources.
The major sources of air toxics include vehicle emissions, factories, refineries, and power plants.

Health Effects: Air Toxics include a wide range of air pollutants that are linked to cancer and other serious health problems.

For more information, see Hazardous Air Pollutants, EPA and Air Toxics, Department of Ecology.

People Most Affected by Air Pollution

Air pollution can affect everyone, but some groups are at higher risk of experiencing poor health outcomes. These include:

People with lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD), including chronic bronchitis, and emphysema.
People with current or recent respiratory infections, such as COVID-19, pneumonia, acute bronchitis, bronchiolitis, colds, or flu.
People with existing heart or circulatory problems, such as congestive heart failure or coronary artery disease.
People with a prior history of heart attack or stroke.
People with diabetes because they are more likely to have an undiagnosed cardiovascular disease.
People 18 and younger because their lungs and airways are still developing, and they breathe more air per pound of body weight than adults.
People older than 65 because they are more likely to have unrecognized heart or lung diseases.
Pregnant people because of increased risk of poor health outcomes and pregnancy complications.
People with disabilities because they may not be represented in emergency planning and preparedness.
People who smoke because they are more likely to already have lower lung function and lung diseases.
Outdoor workers because they often spend more time outside and are exposed to smoke longer.
Communities of color because they have often experienced social and economic inequities which contribute to increased risk of poor health impacts from smoke.
Tribal members and Indigenous peoples because they are often among frontline communities impacted first and worst from climate change hazards, including smoke.
People with low income because they are more likely to have higher exposures and are less likely to have access to health care or to be able to afford interventions to reduce exposure.
People who are unhoused or unsheltered because they often experience increased exposure to smoke and may not have access to social and health services.

Check Air Quality in Your Community

Washington Air Quality Map - Check current air quality.
Washington Smoke Blog - During wildfire smoke, check current and forecasted air quality.
Local clean air agencies - Regional agencies who manage air quality.

Ways to Improve Outdoor Air

Follow burn bans for your area.
Replace uncertified wood stoves. Wood stoves must meet both Washington and EPA certification and labeling standards.
Avoid burning yard waste and other vegetation, especially in urban growth areas where burning is banned.
Drive less and don't let your car idle (PDF).
Use electric yard equipment instead of gas-powered equipment.