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Air Quality Program

Regional Haze

Speak up!

Comment on Washington's 5-year progress report and appendices A, B, C, D, E, F.

Public Comment Period:
June 20 - August 1, 2017

Public Hearing:
July 27, 2017 at 6 p.m.
Ecology, 300 Desmond Drive - Lacey

Ecology works 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 mainly on large industrial sources of air pollution and how forestry debris is burned.

Progress report

The Regional Haze 5-Year Progress Report describes our progress to improve visibility since 2010. The report determined that visibility has improved at all Washington's mandatory federal Class I areas. All areas improved at least as much as required by the 2018 visibility goals established in the 2010 Regional Haze State Implementation Plan. However, continued improvement may be difficult due to smoke from wildfires.

Comment on the 5-year progress report and appendices A, B, C, D, E, F.

    Public Comment Period:
    June 20 - August 1, 2017

    Comment on the report:
    Online comment form
    • Mail Anya Caudill
       Air Quality Program
       Washington State Dept. of Ecology
       P.O. Box 47600
       Olympia, WA  98504-7600

    Public Hearing
    Thursday, July 27, 2017 at 6 p.m.
    Ecology, 300 Desmond Drive SE - Lacey

Información en español!
Para información en español, manda un correo electrónico al equipo de español de Ecología a

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 United States. In the eastern United States, 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 means more light is either absorbed or scattered, reducing the clarity and color of what we see.

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 do this in partnership with the National Park Service and U.S. Forest Service. In Washington, there are 9 IMPROVE monitoring sites. One 24-hour air sample is collected at each site every three days, providing up to 121 samples every year from each site.

Once the samples are collected, we analyze them for substances such as 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 or kilometers 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 a change in visibility of even one deciview.
  • Light scatter measurement, using an instrument such as a nephelometer.

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

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 utility and industrial fuel burning, and manufacturing operations. Fine particles 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 source. This is why we often see haze in areas that don't have any major sources of air pollution.

Fine particles have also been linked to serious health problems and environmental damage. Learn more about fine particle pollution.

The photos below show the same view, looking west from the slopes of Mount Rainier, with and without regional haze.

Improving visibility

The federal Clean Air Act requires states to protect and improve visibility in national parks and wilderness areas.  The Clean Air Act has set a goal of returning visibility in these areas to natural conditions by the year 2064. Congress designated 156 national parks and wilderness areas as "mandatory federal Class 1 areas" where visibility is especially important.  All states must submit a plan to EPA to reduce air pollutants that affect visibility in their mandatory Class 1 areas.

Washington has 8 mandatory federal Class 1 areas, totaling more than 3.3 million acres. They are:

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

In 2010, Ecology wrote a Regional Haze State Implementation Plan (SIP) to define a strategy for improving visibility in our Class 1 areas. Through the Western Regional Air Partnership, we worked closely with other states and organizations to write this plan. It documented existing conditions and identified key sources of air pollution. The plan noted that retrofitting emission technology at large industrial sources, and existing federal and state controls are important for making reasonable progress by 2018. Updates to this strategy will occur periodically.

Regional haze reduction results

In 2011, as a result of the 2010 law (Chapter 80.80 RCW), a significant step was achieved in reducing regional haze when the TransAlta power plant in Centralia agreed to install nitrogen oxide reducing technology on two coal boilers.

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