FRESNO (AP) -- A new study shows frogs in the high Sierra are threatened by airborne pesticides sprayed hundreds of miles away in the Central Valley.

Researchers at Southern Illinois University and the U.S. Geological Survey measured toxicity levels of two pesticides, chlorpyrifos and endosulfan, to Pacific treefrogs and foothill yellow-legged frogs. Both species native to the mountain meadows have seen their populations decline.

The tadpoles developed abnormalities that could increase their vulnerability to predators, flood and drought.

The report said that airborne pesticides catch easterly winds and fall during rain and snow, then are spread by runoff.

The study was published in the August 2009 issue of Environmental Toxicology and Chemistry.