Washington State Air Quality

The links on this page provide access to the Washington State Department of Ecology's Air Monitoring Network, which tracks various air pollutants at more than six dozen sites statewide. Visitors can filter and export historic data using the Site Report tool, and gather traffic-specific air pollutant data from the Seattle and Tacoma monitoring sites linked below.

Data and Resources

Washington State Air Monitoring Network
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Additional Info

Field	Value
Source	https://data.wa.gov/resource/39v6-dykg
Author	ECY DataSync
Last Updated	July 22, 2025, 20:09 (UTC)
Created	July 22, 2025, 20:09 (UTC)
1.	The Department of Ecology and local clean air agencies monitor levels of outdoor air pollutants to make sure concentrations meet federal and state air quality standards. Exceeding these standards can affect sensitive populations.
2.	The time displayed on a Site Information page may be one to two hours old, even though the data is actually current. This is partly because data must only be labeled in Pacific Standard Time (PST), which is an hour behind daylight time. Data are also labeled with the beginning of the hour in which they were collected. Thus, data timestamped with “8:00 AM” was collected from 8:00-8:59 PST, or 9:00-9:59 daylight time.
3.	Two air pollutants are closely tied to traffic circulation: NOx (a combined measure of nitrogen-based pollutants) and CO (carbon monoxide). No standard exists for NOx, but one does exist for a key NOx component, NO2. The hourly average NO2 is not to exceed 100 ppb, a standard exceeded only once at the Seattle-10th & Weller site (established in 2014); site values are typically less than half the standard. The hourly standard for CO is 35 ppm; neither the Seattle-10th & Weller site nor the Tacoma-S. 36th St. site has ever exceeded 3 ppm. Learn more about different air pollutants and standards at https://ecology.wa.gov/Air-Climate/Air-quality/Air-quality-targets/Air-quality-standards
4.	Data from the Seattle-10th & Weller and Tacoma-S. 36th St. monitoring sites are best for tracking traffic-related air pollutants, since the sites are located close to Interstate 5. The Seattle-10th & Weller site was established and began collecting data in 2014, and the Tacoma-S. 36th St. site in 2015.
5.	During the 2020 COVID-19 pandemic, state residents were temporarily ordered to stay home except for essential work and other exceptional circumstances. This affected traffic air pollution. Learn more about COVID-19 at https://www.doh.wa.gov/emergencies/coronavirus
6.	Data Disclaimer - http://www.ecology.wa.gov/copyright.html
Category	Natural Resources & Environment
Metadata Language	English
Originator	Washington State Department of Ecology
Period of Time	2007 to present
Posting Frequency	One time
harvest_object_id	ef7c1636-b9f5-445b-af66-f9e791a5e53d
harvest_source_id	c4128faf-39ff-4aa3-918e-8a395702cab3
harvest_source_title	washington-state