Air quality recommendation for sulfur dioxide designation

Based on ambient air quality monitoring data, emissions inventories, and air quality trends:

• All areas with sulfur dioxide monitoring meet the standard (attainment).
• In unmonitored areas, available information shows the standard is also being met (unclassifiable).

Document for review

• Washington State Air Quality Designation Recommendation:  2024 Annual Sulfur Dioxide National Ambient Air Quality Standard report

Tentative public hearing

(if requested by February 12, 2026, 11:59 p.m.)
Thursday, February 26, 2026, 11 a.m. online

We will hold an online public hearing if we receive a written request. If we hold a public hearing, the public comment period will be extended through February 27, 2026, 11:59 p.m. If you request a public hearing, please tell us if you need interpretation in a language other than English.

If we do not receive a written request for a public hearing by February 12, 2026, then the public hearing will be cancelled. We will update this web page cancelling the public hearing or with a link to register for the public hearing.

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

Background

Sulfur dioxide (SO₂) is a colorless gas with a strong smell. It gets into the air when fuel that contains sulfur is burned. Sulfur dioxide is a criteria air pollutant because of its health and environmental impacts.

Sulfur dioxide can make it harder to breathe by irritating the lungs and narrowing airways. High levels can damage trees and plants. It also helps form acid rain that harms sensitive ecosystems. In the air, it can create haze that reduces visibility.

Determining if areas meet national air quality standards is called "area designation." An area designation tells us if we need to adjust our rules or permits to meet the national air quality standard for sulfur dioxide. If an area is “attainment/unclassifiable,” it means our current, EPA-approved plan (the Washington State Implementation Plan, or SIP) is working. A State Implementation Plan (SIP) is a cleanup plan for air. It includes state and local rules, programs, and permits needed to meet, maintain, and enforce 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.