Air quality in Thurston County has improved substantially over the last 30 years and is considered to be of high quality at present. In the 1980s, the region’s air quality suffered from high levels of PM10 – particulate matter less than 10 microns in size – a pollutant that can become trapped in the lungs and reduce the lungs’ ability to absorb oxygen. In 1985, the region’s maximum readings for PM10 were approximately 250 micrograms per cubic meter over a 24-hour period, exceeding the national standard of 150 micrograms per cubic meter. 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 of these measures, the region experienced a steady decrease in PM10, falling below the national standard in 1990 and continuing well under the standard today.
PM2.5 is particulate matter less than 2.5 microns in size, and this pollutant poses the greatest risk to health. While the annual average of PM2.5 has always met state and federal standards, the 24-hour average often exceeds the standard. Typically the highest PM2.5 days occur in the winter due to wood stove combustion and stagnant winter days, but smoke from wildfires caused large spikes in 2018 - 2020.
Regions that experience persistent air quality problems are designated by the federal government as non-attainment areas. Non-attainment areas are declared for a specific pollutant within a defined boundary, and require controls for the pollutant under the federal Clean Air Act. No pollutants pose persistent air quality problems subject to the Clean Air Act at this time.
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)