PITTSBURGH,
Pennsylvania, August 15, 2005: As amphibians
continue to mysteriously disappear worldwide, a University
of Pittsburgh researcher may have found more pieces
of the puzzle. Elaborating on his previous research,
Pitt assistant professor of biological sciences Rick
Relyea has discovered that Roundup, the most commonly
used herbicide in the world, is deadly to tadpoles at
lower concentrations than previously tested; that the
presence of soil does not mitigate the chemical's effects;
and that the product kills frogs in addition to tadpoles.
In two articles published in the August 1 issue of the
journal Ecological Applications, Relyea and his doctoral
students Nancy Schoeppner and Jason Hoverman found that
even when applied at concentrations that are one-third
of the maximum concentrations expected in nature, Roundup
still killed up to 71 percent of tadpoles raised in
outdoor tanks.
Relyea also examined whether adding soil to the tanks
would absorb the Roundup and make it less deadly to
tadpoles. The soil made no difference: After exposure
to the maximum concentration expected in nature, nearly
all of the tadpoles from three species died.
Although Roundup is not approved for use in water,
scientists have found that the herbicide can wind up
in small wetlands where tadpoles live due to inadvertent
spraying during the application of Roundup.
Studying how Roundup affected frogs after metamorphosis,
Relyea found that the recommended application of Roundup(r)
Weed and Grass Killer, a formulation marketed to homeowners
and gardeners, killed up to 86 percent of terrestrial
frogs after only one day.
"The most striking result from the experiments
was that a chemical designed to kill plants killed 98
percent of all tadpoles within three weeks and 79 percent
of all frogs within one day," Relyea wrote.
Previous studies have determined that it is Roundup's
surfactant (polyethoxylated tallowamine, or POEA, an
"inert" ingredient added to make the herbicide
penetrate plant leaves) and not the active herbicide
(glyphosate) that is lethal to amphibians.
This research was funded by the National Science Foundation,
Pitt's McKinley Fund, and the Pennsylvania Academy of
Science.
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