Air Quality

  1. Particulate Matter
  2. Ozone

Data Tables


Thurston County has excellent air quality. Concentrations of the four main pollutants of concern in our region — ozone, carbon monoxide, particulate matter less than 2.5 microns in size (PM2.5), and particulate matter less than 10 microns in size (PM10) — are all below federal air quality standards set by the Clean Air Act.

This has not always been true. In the 1980s, the region suffered from high levels of PM10 — a pollutant that can become trapped in the lungs and reduce their ability to absorb oxygen. Residential wood stove combustion was a major source of the emissions. In response, the Olympic Region Clean Air Agency launched an aggressive campaign to reduce emissions through the use of more efficient wood stoves and restrictions on outdoor burning. As a result, the region experienced a steady decrease in PM10, falling below the national standard in 1990 and remaining well under the standard today.

To view real time air quality data throughout the state, please visit: Department of Ecology Air Quality Monitoring

Air Quality Standards

The Clean Air Act identifies two types of air quality standards. Primary standards provide public health protection, including protecting the health of sensitive populations such as people with asthma, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.

PollutantStandardAveraging TimeLevelForm
OzonePrimary & Secondary8 hours0.075 ppmAnnual fourth-highest daily maximum 8-hr concentration, averaged over 3 years
Particulate Matter (PM2.5)PrimaryAnnual12 μg/m3Annual mean, averaged over 3 years
SecondaryAnnual15 μg/m3Annual mean, averaged over 3 years
Primary & Secondary24 hours35 μg/m398th percentile, averaged over 3 years
Particulate Matter (PM10)Primary & Secondary24 hours150 μg/m3Not to be exceeded more than once per year on average over 3 years
Carbon MonoxidePrimary8 hours9 ppmNot to be exceeded more than once per year
Primary1 hour35 ppmNot to be exceeded more than once per year


  • Washington State Department of Ecology
  • Olympic Region Clean Air Agency (ORCAA)
Sustainable Thurston Report Card

The Sustainable Thurston Report Card tracks how well the Thurston Region is doing at maintaining good air quality. The goal includes targets for meeting state and federal air quality standards, including:

  • PM2.5: 12 micrograms per cubic meter of air (annual average)
  • Ozone: 0.075 parts per million (8-hour average)