Image: Hazy view from park
Tracie Cone  /  AP
Sequoia National Park air resource specialist Annie Esperanza explains how ozone diminishes the view from Beetle Rock in Sequoia National Park, Calif.
By
updated 5/29/2012 10:32:52 AM ET 2012-05-29T14:32:52

On a clear day, the view from Beetle Rock in Sequoia National Park extends west for 105 miles across the patchwork of crops in California's agricultural heartland to the Coast Mountains and the Pacific Ocean beyond.

The problem is there are few clear days, even at 6,200 feet.

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 here are comparable to urban settings such as L.A.," said Emily Schrepf of the nonprofit advocacy group the National Parks Conservation Association as she beheld the diminished view. "It's just not right."

This is not the place to take in a whiff of fresh mountain air. Smog is so bad that signs in visitors centers caution guests when it's not safe to hike. The government employment website warns job applicants that the workplace is unhealthy. And park workers are schooled every year on the lung and heart damage the pollution can cause.

Ozone also is to blame for weakening many stands of the park's Jeffrey and ponderosa pines, leaving telltale yellowing of their long needles. Instead of absorbing carbon dioxide, they soak up ozone through the stoma in their needles, which inhibits photosynthesis. Ozone also stresses young redwood seedlings, which already face challenges to survival.

Although weakened trees are more susceptible to drought and pests, the long-term impact on the pines and on the giant redwoods that have been around for 3,000 years and more is unclear.

Slideshow: America's national parks (on this page)

"It's not a great story to tell, but it's an important story to tell because you can look at us as being the proverbial canary in a coalmine," said Annie Esperanza, a park scientist who has studied air quality there for 30 years. "If this is happening in a national park that isn't even close to an urban area, what do you think is happening in your backyard?"

It's a problem in a handful of the nation's 52 parks that are monitored constantly for ozone, including Joshua Tree National Park in California's Mojave Desert and North Carolina's Great Smoky Mountains National Park, which is ringed by power plants and several major highways including Interstate 40, a major tractor-trailer shipping route. But none is in the ballpark with Sequoia and its neighbor, Kings Canyon.

Under the Clean Air Act, the region that encompasses Sequoia and Kings Canyon national parks has been designated a "Class 1 air shed," which means by 2064 it must have pure air with no degradation of visibility. But that apparently didn't take into consideration its proximity to one of the worst air quality basins in the country.

"It does take visitors by surprise," Esperanza said. "On a day it's unhealthy, we ask people if you're going to do a rigorous hike, we recommend early morning. It's limiting, it's quite telling, and it's very sad."

While forest fires create some pollution, the lion's share comes from the San Joaquin Valley, the expanse of farmland that is home to the California's two busiest north-south trucking highways, diesel freight train corridors, 1.7 million dairy cows, food processing plants and tens of thousands of diesel tractors plowing dusty fields. Its trough shape traps pollutants, and high-pressure systems act like a lid on a pot.

Image: Pine needles damaged by smog
Tracie Cone  /  AP
Jeffrey and Ponderosa pines show telltale signs of yellowing, a symptom of ozone toxicity, in Sequoia National Park, Calif.

Smog is created when the sun's rays hit pollutants such as oxides of nitrogen and volatile organic compounds that are in motor vehicle exhaust, solvents, pesticides, gasoline vapors and decaying dairy manure.

"There is no simple answer to ozone pollution," said Thomas Cahill, a researcher at the University of California, Davis who studies air problem in Sequoia and across California.

Breathing ozone at high levels for even a short time can blister the lungs like UV rays blisters skin, scientists agree. The problem in quantifying exposure levels, however, is that some people suffer pulmonary damage at lower doses than others.

Dr. David Lighthall, health science adviser for the San Joaquin Valley Air Pollution Control District, says ozone levels at high altitudes don't drop at night like they do in the valley, which leads to "more cumulative exposure for those who live and work there."

Southerly breezes from the San Francisco Bay collect pollutants and push them to the valley's southern rim, where they bounce back north. Between Fresno and Visalia — just below the park — the warm air hits the cooler air pushing south and gets trapped in a swirling vortex called the Fresno Eddy. The warm, polluted air then rises up the canyons of three rivers that begin in the park.

The only way to improve air in the park is to improve the San Joaquin air basin, something that so far has proved elusive given the myriad sources. Even with hundreds of millions of dollars spent to retrofit diesel engines and replace gasoline lawnmowers with electric ones, residents pay a federal fine for the region's failure to meet even minimal EPA ozone limits.

"We don't create a disproportionate amount of pollution; it's just that we have these natural challenges so that the pollution we do create can take literally weeks or months to clean out. It just builds up over time," said Jaime Holt, spokeswoman for the valley air district.

Already this year, the level of ozone in Sequoia park has exceeded federal health standards, even though it's early in the summer ozone season. During the June-to-September summer season last year, the park violated the National Ambient Air Quality standard at least 87 times, compared with 56 at Joshua Tree and 12 at Great Smoky Mountains.

"It's tragic that the National Park Service is known for clean air, and then you see a sign saying it's unhealthy to breathe," Esperanza said. "It's so contrary to the national parks idea."

Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Photos: America's national parks

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  1. Acadia

    Acadia National Park in Maine boasts the highest mountain on the U.S. Atlantic Coast and was the first national park east of the Mississippi River. Visitors beware: temperatures can vary 40 degrees -- from 45 degrees to 85 degrees in the summer and from 30 degrees to 70 degrees in the spring and fall. (Gareth Mccormack / Lonely Planet Images) Back to slideshow navigation
  2. Rocky Mountain

    Bear Lake, with mountainside aspens changing colors in mid-autumn, is one of the popular attractions in Rocky Mountain National Park in Colorado. (Universal Images Group via Getty Images) Back to slideshow navigation
  3. Badlands

    The climate in South Dakota's Badlands National Park is extreme. Temperatures range from minus 40 degrees in the dead of winter to 116 degrees in the height of summer. Visitors are drawn to the park's rugged beauty as well as the area's rich fossil beds. (Mark Newman / Lonely Planet Images) Back to slideshow navigation
  4. Yosemite

    One of the nation's first wilderness parks, Yosemite is known for its waterfalls, scenic valleys, meadows and giant sequoias. (Robert Galbraith / Reuters) Back to slideshow navigation
  5. North Cascades National Park

    The North Cascades National Park complex offers something for everyone: Monstrous peaks, deep valleys, hundreds of glaciers and phenominal waterfalls. The complex includes the park, Ross Lake and Lake Chelan National Recreation Areas. (David Mcnew / Getty Images) Back to slideshow navigation
  6. Zion

    This spectacular corner of southern Utah is a masterpiece of towering cliffs, deep red canyons, mesas, buttes and massive monoliths. (Mark Ralston / AFP - Getty Images) Back to slideshow navigation
  7. Redwood

    Created in 1968, Redwood National Park is located in Northern California. Today, visitors to the national park can enjoy the massive trees as well as an array of wildlife. (David Gotisha / msnbc.com) Back to slideshow navigation
  8. Joshua Tree

    Joshua Tree National Park is located in southeast California. The area was made a national monument in 1936 and a national park in 1994. Outdoor enthusiasts can go hiking, mountain biking and rock climbing. (Gabriel Bouys / AFP - Getty Images) Back to slideshow navigation
  9. Great Smoky Mountains

    Straddling the Tennessee-North Carolina border, Great Smoky Mountains National Park encompasses more than 800 square miles in the southern Appalachian Mountains. Visitors can expect mild winters and hot, humid summers, though temperatures can differ drastically as the park's elevation ranges from 800 feet to more than 6,600 feet. (AP) Back to slideshow navigation
  10. Arches

    More than 2,000 natural sandstone arches, many of them recognizable worldwide, are preserved in Utah's Arches National Park. Temperatures can reach triple digits in the summer and can drop to below freezing in the winter. (AP) Back to slideshow navigation
  11. Grand Teton

    The Snake River flows through Grand Teton National Park, and the jagged Teton Range rises above the sage-covered valley floor. Daytime temperatures during summer months are frequently in the 70s and 80s, and afternoon thunderstorms are common. (Anthony P. Bolante / Reuters) Back to slideshow navigation
  12. Haleakala

    Visitors watch the sun rise at 10,000 feet in Haleakala National Park in Maui, Hawaii. If weather permits, visitors at the top of the mountain can see three other Hawaiian islands. (The Washington Post via Getty Images) Back to slideshow navigation
  13. Grand Canyon

    Grand Canyon National Park is perhaps the most recognizable national park. Nearly 5 million visitors view the mile-deep gorge every year, formed in part by erosion from the Colorado River. The North and South rims are separated by a 10-mile-wide canyon. (Gabriel Bouys / AFP - Getty Images) Back to slideshow navigation
  14. Yellowstone

    Yellowstone National Park, America's first national park, was established in 1872. The park spans parts of Wyoming, Montana and Idaho. Grizzly bears, wolves, bison and elk live in the park. It is well known for Old Faithful and other geothermal features. (Mark Ralston / AFP - Getty Images) Back to slideshow navigation
  15. Mount Rainier

    Glaciers. Rainforests. Hiking trails. Mount Rainier National Park, located in Washington state, offers incredible scenery and a diverse ecology. The park aims to be carbon neutral by 2016. (National Park Service) Back to slideshow navigation
  16. Hawaii Volcanoes

    Two of the world's most active volcanoes can be found within Hawaii Volcanoes National Park. In 1980, the national park was designated an International Biosphere Reserve; in 1987, it was added as a World Heritage Site. (David Jordan / AP) Back to slideshow navigation
  17. Everglades

    Everglades National Park covers the nation's largest subtropical wilderness. It is also a World Heritage Site, an International Biosphere Reserve and a Wetland of International Importance. Visitors to the park can camp, boat, hike and find many other ways to enjoy the outdoors. (Joe Raedle / Getty Images) Back to slideshow navigation
  18. Glacier

    A view from atop the Grinnell Glacier Overlook trail in Glacier National Park. With more than 700 miles of trails the park is known for its glaciers, forests, alpine meadows and beautiful lakes. (Matt McKnight / Reuters) Back to slideshow navigation
  19. Bryce Canyon

    Located in southwestern Utah, Bryce Canyon National Park is known for its distinctive geological structures called "hoodoos." (Mark Ralston / AFP - Getty Images) Back to slideshow navigation
  20. Crater Lake

    The brilliant blue Crater Lake, located in southern Oregon, was formed when Mount Mazama, standing at 12,000 feet, collapsed 7,700 years ago after a massive eruption. Crater Lake is one of the world's deepest lakes at 1,943 feet. (David Gotisha / msnbc.com) Back to slideshow navigation
  21. Olympic

    Washington state's Olympic National Park offers visitors beaches on the Pacific Ocean, glacier-capped mountain peaks and everything in between. Keep the weather in mind when visiting, though, as roads and facilities can be affected by wind, rain and snow any time of year. (National Park Service) Back to slideshow navigation
  22. Sequoia and Kings Canyon

    A woman stands among a grove of a Giant Sequoia trees in Sequoia National Park in Central California. The trees, which are native to California's Sierra Nevada Mountains, are the world's largest by volume, reaching heights of 275 feet and a ground level girth of 109 feet. The oldest known Giant Sequoia based on its ring count is 3,500 years old. (Mark Ralston / AFP - Getty Images) Back to slideshow navigation
  23. Denali

    Alaska's Denali National Park spans 6 million acres and includes the 20,320-foot Mount McKinley, North America's tallest peak. Many park visitors try to catch a glimpse of the "big five" -- moose, caribou, Dall sheep, wolves and grizzly bear. (National Park Service) Back to slideshow navigation
  24. Kenai Fjords National Park

    The National Park Service considers the 8.2-mile round-trip on Harding Icefield Trail in Alaska's Kenai Fjords National Park to be strenuous, saying hikers gain about 1,000 feet of elevation with each mile. (National Park Service via AP) Back to slideshow navigation
  25. Death Valley

    California's Death Valley encompasses more than 3.3 million acres of desert wilderness. In 1849, a group of gold rush pioneers entered the Valley, thinking it was a shortcut to California. After barely surviving the trek across the area, they named the spot "Death Valley." In the 1880s, native peoples were pushed out by mining companies who sought the riches of gold, silver, and borax. (Gabriel Bouys / AFP - Getty Images) Back to slideshow navigation
  26. Wind Cave

    Bison graze in Wind Cave National Park in the southern Black Hills of South Dakota. Millions of bison were slaughtered by white hunters who pushed them to near-extinction by the late 1800s. Recovery programs have brought the bison numbers up to nearly 250,000. (David McNew / Getty Images) Back to slideshow navigation
  27. Canyonlands

    The Lower Basins Zone is outlined by the white rim edge as seen from the White Rim Trail in Canyonlands National Park, Utah. (Doug Pensinger / Getty Images) Back to slideshow navigation
  28. Shenandoah

    Fall colors blanket the Shenandoah National Park, drawing tourists to Skyline Drive to view the scenery. (Karen Bleier / AFP - Getty Images) Back to slideshow navigation
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  1. Gareth Mccormack / Lonely Planet Images
    Above: Slideshow (28) America's national parks
  2. Image:
    Stephen Saks / Lonely Planet Images
    Slideshow (18) America’s lesser-known national parks

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