Insecticides in the water is the latest explanation for deformed frogs found all across the country.
The Midwest Declining Amphibians Conference, held March 21 and 22 in Milwaukee, pointed to a commercial mosquito spray, called methoprene, as a possible cause of amphibian deformities. These misfit frogs often have missing or extra limbs, missing eyes and missing jawbones.
The spray, commonly used in rural and urban areas around the state, mimics the hormone retinoic acid. Physical development in animals, including humans, is based upon levels of retinoic acid. Many of the deformed frogs were found in areas with a higher or lower than normal amount of the growth hormone.
But Judy Helgen, a wetlands biologist for the Minnesota Pollution Control Agency, said that although the spray has been used in several ponds, it has not been detected in any of the local testing sites.
“However, just because we don’t find it, doesn’t mean it’s not there,” she said.
If it is methoprene, there would be more occurrences in metro area testing sites, she added.
Hillary Carpenter, an environmental toxicologist for Minnesota’s Department of Health, said although methoprene is used extensively in Minnesota, there is no evidence of the chemical where the deformed frogs were found.
“We haven’t pinpointed a cause because there is no common carrier in the testing areas,” Helgen said. “We’re looking for everything.”
Environmentalists say humans have little reason to worry about the spray because of their stronger skin makeup. An amphibian’s physiology allows for an intake of everything in their environment during development, as opposed to the non-porous skin of humans.
“The most likely case of methoprene harming humans is through the drinking water,” said Carpenter. He added that the concentration of the chemical must be kept in mind and that trace amounts would not be detrimental to humans.
Scientists at the conference said pesticides might not be the only reason for the deformities in frogs. Current research also consists of looking at the possibilities of alien metals in the water, or other abnormal hormones, such as thyroids, which control every stage of physical development in frogs.
Last year the state government appropriated $200,000 for investigations into the frog deformities. This year, Greg Knopff, a legislative research analyst for environment and agriculture, said the state government will allot between $375,000 and $500,000 to continue that research.
“With the new funding, the research effort by Minnesotan environmentalists will continue to be very strong,” Carpenter said. Some testing includes measuring amounts of foreign elements in water and comparing water chemistries of different testing sites.