Recommendation for PM 2.5 designation and exceptional event demonstration

• Washington meets the updated air quality standard for fine particles (PM_2.5).
• Particle pollution from 2023 wildfire smoke in Colville was beyond our control, so that data should be excluded as an exceptional event.

We recommend all counties in Washington be designated as meeting the PM_2.5 air quality standard ("attainment") or not enough information ("unclassifiable"). We tentatively recommend Omak be designated as meeting the PM_2.5 air quality standard ("attainment") based on preliminary 2024 air monitoring data. Our recommendations are based on the most recent (2021-2023) certified air monitoring data. We also considered preliminary 2024 data because EPA expects to make final designation decisions based on the 2022-2024 monitoring data.

Documents for review

• Proposed designation letter to EPA
• Exceptional event demonstration report for 2023 wildfire smoke in Colville
• Flagged data for 2021 wildfire smoke in Colville, Toppenish, and Yakima

After the public comment period, we will submit the report to EPA.

Online information session

• Register for the webinar to get your access code and password.
• To hear the webinar better, use your phone (instead of the computer) to call 253-215-8782.

Background

State Implementation Plan

A State Implementation Plan (SIP) is a general cleanup plan for air. It describes how Washington carries out, maintains, and enforces national air quality standards.

The SIP explains how Washington will lower air pollution from sources like transportation, wood smoke, and industry. Sections of the plan are customized to meet regional air quality needs.

Designation recommendation

EPA continually reviews the levels of air pollution from six common pollutants ("criteria pollutants") and sets levels based on how much is safe for people's health. One of those pollutants is fine particles (PM_2.5), which are particles that are smaller than 2.5 micrometers that easily get into the lungs and cause health problems.

In February 2024, EPA strengthened the primary annual PM_2.5 standard to be more protective of health. The standard changed from 12 μg/m³ to 9 μg/m³. Under the federal Clean Air Act, Washington must show EPA that the state meets the updated air quality standard.

When EPA changes the level of air pollution, they also look at every area of the country to determine if it meets the new standard. If an area's air pollution from that pollutant (in this case, PM_2.5) is below the new level, that area is considered to be meeting (attaining) the standard or in attainment. If the area's pollution is higher than the new level, it is considered to be in nonattainment or not meeting the standard.

Before EPA designates an area as attainment or nonattainment, it allows states to recommend whether areas of the state are meeting the standard or not.

Exceptional event demonstration

An exceptional event is an unusual or naturally-occurring event that can make air quality unhealthy, but cannot be controlled.  Examples of an exceptional event are wildfire smoke, dust storm, volcano ash, and when good ozone goes bad (“stratospheric intrusion”).

Under the federal Clean Air Act, exceptional events are regulated differently than other sources of air pollution. For example, if a storm causes air monitor readings to go over the federal standard and EPA agrees the readings were beyond our control, then the high readings would be considered an exceptional event. The high readings would not count when determining if an area meets air quality standards.