Monitoring air quality
A network of air monitoring stations throughout our jurisdiction helps give us a regional picture of our air quality.
Our agency operates real-time monitors in cities, near industry, and at one rural site in our jurisdiction. We also require larger industries to monitor air quality at their fence lines and send us monthly reports of the data they collect.
The U.S. Environmental Protection Agency has established health-based National Ambient Air Quality Standards for six pollutants: Ground-level ozone (O3), particulate matter (PM2.5), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2) and lead. We determine which of these pollutants to measure at different locations based on what potential sources of pollution are in the area.
For these pollutants, EPA has converted the pollutant concentrations to a scale called the Air Quality Index (AQI) to help us communicate how clean or polluted our air is, and what the associated health effects might be.
The state of Washington uses a separate indexing system called the Washington Air Quality Advisory (WAQA). The WAQA considers lower particulate concentrations more harmful to human health than the federal AQI, but it is the same as the AQI for other pollutants.
Scaled values for both the state and federal systems range from 0-500. A higher value means more air pollution and unhealthier air. Values below 100 are considered acceptable. When values are above 100, air quality is considered to be unhealthy—at first for sensitive groups of people, then for everyone, as values get higher.
How we report air quality information to you
Our agency’s air quality monitors are linked to the state monitoring network. When you click on links for current, local air quality (see box at top right), you’ll see gauges that describe air quality according to the state WAQA scale.
We archive our data and the data we collect from industry monitors in monthly summary tables (see box at right) that report the actual 24-hour average concentrations of pollutants, and are color coded according to the federal AQI scale.