Determining if areas in Washington meet national air quality standards

We focus our work on six common air pollutants (called "criteria air pollutants") which EPA sets in National Ambient Air Quality Standards (NAAQS):

• Carbon monoxide (CO)
• Lead (Pb)
• Nitrogen dioxide (NO₂)
• Ozone (O₃)
• Particle pollution (PM _2.5 and PM₁₀)
• Sulfur dioxide (SO₂)

Using air monitoring data, we must determine whether an area meets each air quality standard. This is called a designation. Then we recommend that designation to EPA.

Under the federal Clean Air Act, there are three ways to classify — or "designate" — an area's air quality:

• Attainment — meeting an air quality standard
• Nonattainment — not meeting an air quality standard
• Unclassifiable — not enough information to determine whether an area meets or doesn't meet an air quality standard

Each designation is made for a specific air quality standard. An area can be in attainment for one standard, and be in nonattainment or unclassifiable for another. If an area does not meet a standard, then we must follow a state implementation plan to bring that area back into attainment. When EPA sets or revises an air quality standard, we must determine if the state meets the new standard and if the designation has changed.

Read more about how we are working to prevent nonattainment.

Maintaining clean air

Most areas of Washington, except a small area in Whatcom County, currently meet air quality standards. Several areas are being watched closely. We and other clean air agencies monitor the air using Washington's air monitoring network at 55 locations.

• 22 are in urban areas (the Puget Sound region, the Tri-Cities, and Vancouver, Spokane and Yakima counties).
• 19 are in small communities outside of urban areas that have local sources of PM_2.5 pollution.
• 7 are in agricultural areas, to help us make decisions about agricultural burning.
• 7 are in tribal areas.
• 1 is in a natural rural location (Olympic Peninsula).

Areas of concern for criteria air pollutants