Ensuring Life, Health and Prosperity for Future Generations

> DDT found in Sierra lakes

Long-banned pesticide surfaces in Sequoia park.
By Mark Grossi / The Fresno Bee /02/27/08 23:02:50

Sequoia National Park officials are warning rangers and hikers that fish in two popular high Sierra lakes are dangerously contaminated by DDT, a pesticide Valley farmers gave up more than a generation ago.The danger was reported this week in the results of a six-year federal study of air contaminants in 20 national parks from Denali in Alaska to Big Bend in Texas.

Researchers found 70 wind-borne contaminants, including mercury, in some of the more remote wilderness locations on Earth.

“National parks are often considered pristine,” said Sequoia spokeswoman Alexandra Picavet. “But national parks are not immune to pollution from hundreds or even thousands of miles away.”

Sequoia officials said they will caution the public about the tainted fish at popular Emerald and Pear lakes. But officials added that the risk is low unless people eat fish daily from the two lakes for perhaps a week or longer.

Sequoia air specialist Annie Esperanza said she and other park scientists need to look more broadly at high Sierra lakes.

“How widespread is this contamination, and is it harming our resources?” she asked.

DDT, or dichloro-diphenyl-trichloroethane, was among the most widely used agricultural pesticides before it was banned in 1972. The chemical can remain in soil for many decades, sometimes moving into water, plants or animals, scientists say.

Environmentalists link DDT to ecological disaster, such as the near extinction of the bald eagle. Federal researchers suspect it causes cancer.

Aside from DDT and other pesticides, researchers found wilderness areas are being showered by dozens of toxins produced by power plants, vehicles, fires, boilers and other industrial activities.

The revelation is a wakeup call for Congress, according to one parks advocacy group.

“We can take steps to reduce mercury emissions from power plants, steps to reduce carbon dioxide emissions that cause global warming,” said Will Hammerquist with the National Parks Conservation Association, which supports funding and improvements for national parks.

The study this week said scientists expected their findings to be dominated by contaminants that blew into North America from Eastern Europe and Asia.

Instead, the bigger problems came from nearby farming and industries.

Sequoia is downwind from a multibillion-dollar farming belt in the San Joaquin Valley.

Sequoia-area environmentalists said it was chilling to think a pesticide banned 36 years ago was found at 9,000-foot-elevation lakes. They wondered where else it could be found in the park.

“If it got into the lake, it would work its way through the food chain,” said Dan Christenson, a retired state biologist who now is an environmental activist in the southern Sierra Nevada. “It would be absorbed by insects and passed throughout the ecosystem.”

Sequoia officials are concerned about their employees. Trail crews, rangers and researchers sometimes spend weeks in the backcountry.

“We will talk to our staff and make sure they understand the possible risks for eating the fish for many days,” said park spokeswoman Picavet.

The study also showed Sequoia’s pine and fir trees had the highest concentration of pesticides of any park surveyed.

Researchers found chlorpyrofos and dacthal in tree needles. Chlorpyrofos is used to kill such pests as aphids; dacthal is used as a weed killer.

Valley farm officials said pesticide practices have changed dramatically over the past 30 years. Fresno County Farm Bureau officials said growers now apply much less pesticide each year, and many prefer to use natural predator insects to prevent infestations in crops.

Sequoia also gets air pollution from Valley metropolitan areas. Each summer, the park has some of the worst air quality among national parks because it is downwind of smoggy cities, such as Fresno and Bakersfield.

Smog damage has been documented in pine trees and young giant sequoias, which grow to be the largest trees in the world.

The Associated Press contributed to this story. The reporter can be reached at or (559) 441-6316.


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