Reducing regional haze in scenic areas

We're working to improve visibility in national parks and wilderness areas. We monitor air quality and develop strategies for returning visibility to natural conditions by 2064. Our initial strategies focus on large industrial sources of air pollution and how forest debris is burned.

Measurements show that visibility at Washington's scenic areas has improved over the past two decades.

Regional haze ruins our view

Have you ever looked out expecting to see a breathtaking view of Mount Rainier or the North Cascades, and been disappointed to see an ugly brown or white haze ruining the view? It's called "regional haze" and it's air pollution. Regional haze has reduced scenic views in national parks and wilderness areas from an average of 140 miles down to 35-90 miles in the Western U.S.  In the Eastern U.S., visibility has decreased from an average of 90 miles down to 15-25 miles.

Haze is caused when tiny particles in the air absorb and scatter sunlight between the object we are looking at — such as Mount Rainier — and our eyes. More particles in the air means that more light is either absorbed or scattered, reducing the clarity and color of what we see.

Comparison of a clear day and regional haze

Sources of fine particles

The particles that cause haze come from both natural and human-caused sources. Natural sources include windblown dust and soot from wildfires or other burning. Human-caused sources include motor vehicles, electric utilities, industrial fuel burning, and manufacturing. Haze from these sources can come from as far away as Asia. Some of the particles that cause haze are emitted directly to the air. Others are formed from gases, such as sulfur dioxide and nitrogen dioxide, that can be carried far from their original source. This is why haze is often seen in areas that don't have any major sources of air pollution nearby.

Improving visibility

The federal Clean Air Act requires states to protect and improve visibility in national parks and wilderness areas. The goal is to return visibility in the 156 national parks and wilderness areas to natural conditions by the year 2064. These are "mandatory federal Class 1 areas" where visibility is especially important. All states must submit regional haze plans to EPA about how to reduce air pollutants that affect visibility in these areas.

This map shows the eight Class 1 areas in Washington, including national parks:  Mount Rainier, North Cascades, and Olympic.

Washington's eight Class 1 areas and IMPROVE monitoring network sites


Washington has eight Class 1 areas, totaling more than 3.3 million acres of land. They are:

  • Alpine Lakes Wilderness
  • Glacier Peak Wilderness
  • Goat Rocks Wilderness
  • Mt. Adams Wilderness
  • Mt. Rainier National Park
  • North Cascades National Park
  • Olympic National Park
  • Pasayten Wilderness

Measuring visibility

We measure visibility by collecting and analyzing particles in the air as part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network. We partner with the National Park Service and U.S. Forest Service. In Washington, there are six IMPROVE monitoring sites. One 24-hour air sample is collected at each site every three days, providing up to 121 samples each year from each site.

We analyze the samples for substances like sulfate, nitrate, carbon-containing particles, sea salt, and dirt and sand — all of which affect visibility. We calculate visibility based on the types and amounts of substances in the particles.

We show visibility in one of three ways:

  • Visual range (the number of miles the naked eye can see).
  • Deciviews (the number on a visibility index where the higher the number, the worse the visibility). The human eye can see the difference in visibility of two deciviews.
  • A measure of light scatter using an instrument such as a nephelometer.

Long-term monitoring trends show that visibility is improving somewhat at Washington's national parks and wilderness areas.

Haze reduction agreement

In 2011, the TransAlta power plant agreed to install nitrogen oxide-reducing technology on two coal-fired boilers by the end of 2020 and 2025, respectively. This was a significant step to reduce regional haze.

Plan revisions

In 2010, we revised the regional haze State Implementation Plan (SIP) to identify key sources of air pollution and define a strategy to improve visibility in Washington's Class 1 areas. Modernizing emission technology at large industrial sources and using existing federal and state controls are important steps to make "reasonable progress" toward natural conditions in Class 1 areas.

The next plan — for the period 2018-2028 — is due to EPA by July 31, 2021.

Draft plan documents

We will discuss these revised chapters of the State Implementation Plan and supporting documents with industries and federal land managers affected by the regional haze regulations.

Industry meetings

We are hosting three online meetings in January for specific industries that may be directly affected by regional haze State Implementation Plan actions.

Petroleum refineries
Mon., Jan. 25, 2021, 9 a.m. – noon
Call in: 415-655-0001 or 855-929-3239
Access code: 177 388 3335

Pulp and paper mills
Wed., Jan. 27, 2021, 9 a.m. – noon
Call In: 415-655-0001 or 855-929-3239
Access Code: 177 305 5195

Other industries (aluminum, cement, glass)
Wed., Jan. 27, 2021, 1:30 p.m. – 4:30 p.m.
Call In: 415-655-0001 or 855-929-3239
Access Code: 177 544 8199


We held a workshop on regional haze and Washington’s air quality plan on Dec. 3, 2020. Review the presentation.

Plan timeline

  • Summer 2020 – Chose air pollution sources to analyze potential pollution controls
  • Late summer 2020 – Evaluated air pollution sources using four-factor analysis to determine reasonable controls
  • Sept. – Nov. 2020 – Consulted with federal land managers
  • Dec. 3, 2020 – Held public information session
  • Jan. 2021 – Hold industry-focused meetings
  • April – May 2021 – Post draft plan and start informal public comment period
  • July – Aug. 2021 – Hold public comment period and public hearing
  • Sept. 2021 – Finalize plan
  • Oct. 2021 – Submit final plan to EPA