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* CRITICAL FINDINGS
Sierra-wide Status
In northern Sierra Nevada airsheds, and in most remote areas during the winter, air
quality is some of the cleanest in the nation and even in the world. Southern airsheds
on the west side are heavily impacted during spring, summer, and fall by ozone and
small particles derived from Central Valley sources and have some of the poorest air
quality in the nation.
Ozone Damage
Extensive ozone damage occurs to sensitive tree species at low and middle elevations
on the southwest and central-western slopes.
Ozone Standards
The federal ozone standards for human health may be inadequate to protect biota from
air-pollution damage.
Smoke
Smoke from managed fires on the average contributes only modest amounts of small particles
to human lungs compared with other Sierran sources; winter smoke from woodstoves
creates much more severe local air-quality problems.
Visibility
Visibility is severely degraded for much of the western slope of the Sierra Nevada
each spring, summer, and fall by fine-particle sulfates, nitrates, and smoke transported
from the Central Valley.
Dust
Dust storms over the alkali and dry lakes of the eastern Sierra (Mono Lake and Owens
[dry] Lake) create severe episodic health hazards to humans and presumably to plants
and animals as well, when transported into the White and Inyo Mountains and the Sierra Nevada.
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