See the context of this sign.

Grand Canyon Visibility

In the clean air of the southwestern United States
--some of the cleanest air in the country--a small
amount of air pollution noticeably affects the view.
Air pollution affects Grand Canyon views much
of the time.

Grand Canyon's air pollution appears as haze which
limits how far and how clearly you see. The major
componen of haze is fine sulfate particles, a by-
product of fossil fuel (oil, gas, coal) combustion.
Sulfates also combine with precipitation to form
acid rain.

Where Does it Come From?
Air pollution at Grand Canyon comes from both
nearby and distant sources. Seasonal weather patterns
and local meteorological conditions determine how the
contribution of each source changes over time. In
summer, pollutants often travel great distances from
industrial and urban areas of southern California,
southern Arizona, and northen Mexico. In winter,
local sources and sources in southern Arizona are
usually the main contributors.

The use of modern emission control equipment on
existing pollution sources and careful placement of
new industry can help restore Grand Canyon views.
We can all play a part by conserving electricity,
carpooling, recycling, becoming involved in air
quality issues, and supporting local and national
policy changes.

Notice the canyon during good visibility conditions (photo left); the distant canyon
walls are colorful and clearly visible. But with haze (photo right) the canyon walls
become faded and less apparent. Both photos were taken at about the same
time of morning from the museum roof.

Don't miss the rest of our virtual tour of Grand Canyon National Park in 10803 images.