Puget Sound Clean Air Agency
Air Quality
Today's Forecast
King AQI:Good - Pollutant:PM2.5
Kitsap AQI:Good - Pollutant:PM2.5
Pierce AQI:Good - Pollutant:PM2.5
Snohomish AQI:Good - Pollutant:PM2.5
King AQI:Good - Pollutant:PM2.5
Kitsap AQI:Good - Pollutant:PM2.5
Pierce AQI:Good - Pollutant:PM2.5
Snohomish AQI:Good - Pollutant:PM2.5
Forecast Discussion
Current Air Quality
Data and Reports
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Tips & Trivia
  • If all U.S. households replaced four incandescent bulbs with compact fluorescents, we would reduce as much pollution as if we took 3.5 million cars off the roads! More bright ideas.
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The Air Quality Index

What it is

The Air Quality Index (AQI) is a color-coded tool for reporting daily air quality that tells you how clean or polluted your air is. It provides simple information on local air quality, the health concerns for different levels of air pollution, and how you can protect your health when pollutants reach unhealthy levels.


AQI Values

Level of Health Concern



When the AQI is:

...air quality

...which means you may be affected in this way:

...look for this color:

Air quality is considered satisfactory, and air pollution poses little or no risk.
Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
Unhealthy for
Sensitive Groups
Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Very Unhealthy
Health alert: everyone may experience more serious health effects.
Health warnings of emergency conditions. The entire population is more likely to be affected.


The AQI measures levels of the six criteria pollutants regulated by the Environmental Protection Agency – fine particles, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and lead.  Fine particles and ground-level ozone are the pollutants that show up the most on the AQI for the Puget Sound region.   

As useful a tool as it is, the AQI does not measure two other issues of concern in our region and other parts of the country as well – air toxics and greenhouse gases.   EPA currently has no comparable standards for measuring and reporting air toxics and greenhouse gases.

What it doesn’t tell you

In general, Air Quality Index charts represent some good news for public health.  They show that we generally enjoy clean air in the Puget Sound region, but we still have days when air quality is not in the green.

What the AQI doesn’t tell you is levels of air toxics, pollutants in our area that also pose potential health risk, and greenhouse gases, which cause global climate change.  That’s because there currently are no EPA standards for measuring and reporting air toxics and greenhouse gases in the same way we measure and report criteria pollutants. 

National modeling for air toxics indicates that we share a dubious distinction with other urban areas of the country where traffic is heavy and tailpipes are many – they have high levels of air toxics.  The modeling puts the Seattle metropolitan area among the top 5 percent of the nation for potential cancer risk, like most big cities.  Air toxics monitoring is being done in Seattle to collect data on actual concentrations in the air.


Washington Air Quality Advisory (WAQA)

Many air quality agencies use the Air Quality Index, or AQI, to tell people when air quality is healthy or unhealthy. The AQI uses color-coded categories to show when air quality is “good,” “moderate,” or “unhealthy.”

The Washington State Department of Ecology has developed an enhanced tool similar to the AQI, which we believe better protects public health. This tool is called the Washington Air Quality Advisory, or WAQA. It looks almost exactly like the AQI, but shows that air pollution is unhealthy at lower levels than the AQI does. The Washington State Department of Health developed the health messages WAQA uses to explain the health risks of different levels of pollution.

To find out how WAQA works and why Washington is using it visit: