Visibility impairment is one of the most obvious indicators of pollution in the air. Air pollution can cause light to be absorbed or scattered, thereby affecting the image we see. The pollution and resulting changes in light are referred to as "haze."

Without haze, the natural visual range would be approximately 140 miles in the West and 90 miles in the East. However, in many parts of the United States, haze caused by air pollution has significantly reduced the range that people can see. In the West, the current range is 33-90 miles; in the East, the current range is only 14-24 miles.

Sawtooth Wilderness Area. Haze impacts how far we can see and how clear the view appears.

Some haze-causing pollutants have been linked to serious health problems and environmental damage. Exposure to very small particles in the air can contribute to increased respiratory illness, decreased lung function, and even premature death. In addition, particles such as nitrates and sulfates contribute to acid rain formation which makes lakes, rivers, and streams unsuitable for many fish, and erodes buildings, monuments, and paint on cars.

Haze also has an economic consequence. Each year, millions of visitors travel throughout the U.S. to our national parks and wilderness areas. Haze affecting these areas obscures the spectacular views they expect. Over time, this could lead to fewer visitors or shorter visits.

To address the public health, aesthetic, and economic impacts of haze, Congress set forth national goals for visibility in 1977. Today, states including Idaho continue to implement these goals to improve visibility.