PITT NEWS (Pennsylvania) 14 September 05 Pitt professor finds herbicide kills frogs (Tasha Webb)
A Pitt researcher found this summer that the most common herbicide in the world could be more fatal to frogs and tadpoles than previously thought.
Rick Relyea, Pitt researcher and biology professor, discovered that Roundup — the second-best selling herbicide in the United States, No. 1 in the world — kills frogs and amphibians at lower concentrations than previously believed.
Before 1999, Roundup’s effects on frogs and tadpoles were largely unknown — in part, because the Environmental Protection Agency’s policy did not require amphibian or reptile testing.
But when a team of Australian researchers tested the herbicide to determine if it could be used in their forests, they found that it was moderately lethal to the indigenous frogs.
Relyea’s study found that North American frogs are even more sensitive to Roundup.
An alternative type of Roundup, which Relyea said would be less harmful to frogs, now exists in Australia.
A representative of Monsanto, the largest producer of the active ingredient in Roundup, said that the study does not represent real-world use of Roundup.
“We think that they don’t represent the realistic ways the products are used,” spokeswoman Mica DeLong said. “We stand behind the safety of our products.”
DeLong listed several factors that could have influenced Relyea’s study negatively.
She said, however, that primarily Relyea’s method of applying Roundup directly to the water was probably the reason for the high rate of fatalities.
Relyea said that his study was different from those done by other researchers, who studied amphibian behavior by placing a single species in about 10 quarts of water.
“We try to simulate a real pond using big outdoor tanks,” Relyea said. “So we have lots of the components of a real pond in a wetland like algae, soil, leaf litter, snails, tadpoles, insects.”
He used about 25 species of animals, five of which were amphibians, in 300-gallon tanks.
“This represents nature more than the experiment in the lab does,” Relyea said.
He then used the maximum concentration of Roundup, as predicted by Monsanto, to mimic a “worst case scenario.”
He discovered that two species of frogs died off entirely, one species became nearly extinct and the two other species were not affected.
Relyea then used one-third of the maximum concentration and found it could still eliminate 71 percent of a species of American tadpoles.
DeLong conceded that some individual users may inadvertently spray Roundup into water, but added that concentrations as high as the one used by Relyea would almost never reach bodies of water.
Roundup products have labels on them that explicitly forbid spraying directly onto water. DeLong said that since the labels are approved by government regulatory agencies, it would be a crime to go against them.
She added that Roundup has a low chance of runoff because it contains a chemical that has a unique characteristic that causes it to bind to soil.
“[Roundup] needs to be tested in the real world,” DeLong said. “We don’t believe that we would see those same results.”
The best-selling version of Roundup contains two parts.
The active ingredient, glyphosate, shuts down photosynthesis in weeds and acts as the binding agent with soil.
The other part, a surfactant, penetrates the plant’s waxy surface.
It is the surfactant that is lethal to frogs.
In Australia, a change in the country’s national risk assessment policies resulted in a higher standard.
DeLong said that many herbicides — Roundup included — didn’t meet the new criteria.
Monsanto developed a version of the herbicide, Roundup Biactive, with a new surfactant. However, it is not available in the United States.
Relyea said the switch to a new surfactant wouldn’t happen in America unless the people call for it.
“It is up to the public to decide if the costs outweigh the benefits,” he said. “If there is sufficient public concern there will be Roundup Biactive here. If not, we won’t.”
DeLong said that bringing in Roundup Biactive wouldn’t necessarily mean any less or more harm to frogs.
“It wasn’t changed because it was any safer per se,” she said.
She added that Roundup Biactive hasn’t been brought to the North America for reasons other than environmental concerns.
“In different parts of the world, you have different weed pressures,” DeLong said. “It wasn’t as effective at killing weeds in the United States.”
Monsonto’s supplier also determined that the switch would not be cost-effective, according to DeLong.
Pitt professor finds herbicide kills frogs