Criteria Air Pollutants

Our job is to ensure the people of King, Kitsap, Pierce and Snohomish counties have clean, healthy air to breathe. We do this in part by ensuring our region meets federal air quality standards for six common air pollutants known as "criteria air pollutants." Criteria air pollutants include: particle pollution, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead.

Our efforts to reduce carbon monoxide, sulfur dioxide, nitrogen dioxide and lead in our air continue, although levels of these pollutants are now well below federal air quality standards.

Criteria Pollutants of Concern

Two criteria air pollutants, however, remain of concern to our region: particle pollution and ozone (smog). Exposure to particle pollution (including diesel exhaust and wood smoke) and ozone can cause heart attacks, strokes, asthma attacks and even premature death. These impacts affect our quality of life and our economy.

Recent studies consistently show that these pollutants cause harm, even at levels that meet national standards. We aim to reduce pollution to levels well below the existing standards to better protect public health.

  1. Particulate Matter
  2. Ozone

Particulate Matter

Dust, dirt, soot, smoke – in air quality lingo are considered “particulate matter,” or “particle pollution.” Particle pollution is one of the six criteria air pollutants monitored and regulated by the Clean Air Agency. 

What is Particle Pollution?Airborne Particle Pollution Diagram

Particle pollution can be described in two subsets: PM2.5 which includes fine particles below 2.5 microns (μm), and PM10 which includes particles below 10 microns in diameter.  PM2.5 is easily inhaled into our lungs and, measuring a fraction the diameter of a human hair, they can enter our bloodstream and cause health problems such as breathing troubles, heart and lung disease, stroke and premature death. Children, older adults and people preexisting health conditions are especially at risk. Particle pollution poses serious public health impacts and is the most important criteria air pollutant challenge facing our region.

How Are Particle Pollution Levels in the Puget Sound Region?

Sources of Wintertime Particle Pollution GraphThough we’ve made progress in reducing PM10 and PM2.5 pollution over the years, we still have work to do to further reduce levels of harmful PM2.5. Wood smoke from wood stoves and outdoor burning continue to be a major source of particle pollution, especially in colder winter months.  On an annual basis, PM2.5 emissions from cars and trucks, other transportation sources, and industry contribute to PM2.5 across our region.  

What Can Be Done to Reduce Particle Pollution?

Opt for alternatives to wood-burning for home heating like natural gas and propane; reduce driving and choose cleaner cars and fuels; and refrain from lighting outdoor fires – these are all steps we can take to reduce particle pollution. Public and private fleets that rely on diesel fuel can look into our Diesel Solutions program for additional ways to reduce particle pollution from fleet operations.

What about ultrafine particles?

The fine particle pollution described above (PM2.5 and PM10) are included in criteria pollutants, with robust monitoring networks and established information on health effects. Ultrafine particles are even smaller (0.1 microns in diameter or smaller) and are gaining attention from the public and research community recently. Ultrafine particles, like fine particles, are mainly from combustion sources. Within the combustion sources, ultrafine particles are primarily from transportation sources.

Some studies have shown adverse cardiac and respiratory effects to ultrafine particles, but results are not yet well understood. As more is known about health impacts and unique sources, we may have more information and actions targeted on this pollutant.