Published: May 28, 2012 4:33 PM EDT

SEQUOIA NATIONAL PARK, Calif. (AP) - The Sierra Nevada forest that is home to the biggest and oldest living things on earth - the giant Sequoia redwoods - also suffers a dubious distinction. It has the worst air pollution of any national park in the country.
    
Mountaintops that should offer awe-inspiring views of California's geologic grandeur often are muddled by a disorienting gray soup of smog.
    
Ozone levels in the Sierra Nevada park are comparable to those in Los Angeles. The pollution comes from the San Joaquin Valley, one of the worst air basins in the country.
    
Ozone is weakening many of the park's Jeffrey and ponderosa pines, leaving telltale yellowing of their long needles.
    
Weakened trees are more susceptible to drought and pests. Scientists say the long-term impact on the giant redwoods is unclear.

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