Toxic chemicals pose threat

Recent research at the School of Forestry & Environmental Studies shows that an unusual phenomenon of deformed frogs in local wetlands may indicate a serious environmental problem that could threaten human health.

An ongoing study led by ecology professor David Skelly has found that a major outbreak of deformities in local amphibians might be linked to toxic chemicals in the environment. Since 2001, Skelly has led an investigation of the increasing number of frogs born with limb disfigurements in the Vermont and Connecticut wetlands.

Frogs in local wetlands and ponds, like New Haven’s Beaver Pond Park, have been turning up with an increased number of bodily deformities, which are likely caused by high concentrations of toxic chemicals in the environment.
Amy Ly
Frogs in local wetlands and ponds, like New Haven’s Beaver Pond Park, have been turning up with an increased number of bodily deformities, which are likely caused by high concentrations of toxic chemicals in the environment.

The study found evidence that the defects are not caused by a parasite, as was previously believed, but rather by pollutants which could come from agricultural pesticides.

“If you asked scientists before what the common cause of these deformities is, most would say a parasite,” Skelly said. “[But] we tested 42 different wetlands and found no evidence of the parasite.”

After disproving the parasite theory, Skelly’s lab started testing different hypotheses in order to determine the actual cause of the deformities, collaborating with Ecology and Evolutionary Biology chair Gunter Wagner. Because a higher proportion of the affected frogs came from suburban and agricultural areas as opposed to urban environments, Skelly said, the most likely cause is pesticides.

Skelly’s lab is continuing to investigate the deformities in order to pinpoint the specific chemical agent causing this outbreak. He said humans and frogs share many genes, so it is important to understand the genetic cause of these missing limbs before it starts to have effects on humans. Although it is unlikely that humans could start losing limbs, he said, the mutations might cause different problems, such as reproductive disorders.

The study also aimed to determine what the most common deformities are and where they are happening, Skelly said. The research shows that most of the affected frogs are missing limbs or limb pieces — rather than having additional body parts — and that Vermont frogs experience more deformities than those in Connecticut.

While 20 percent of Vermont frogs showed defects, Skelly said that relatively few in Connecticut were deformed, indicating a much cleaner wetland environment.

“We did exactly the same sampling in both states and we found very few deformities here,” Skelly said. “That’s pretty interesting because our sites in Connecticut were only about an hour and a half from our sites in Vermont.”

Officials at the Connecticut Department of Environmental Protection said the findings of the study were surprising. Although Connecticut has made efforts in recent years to improve the environment, they said it was shocking to hear that the state fared better than Vermont in a scientific study on the effects of pollutants.

“It’s sort of counter-intuitive,” Communications Director Dennis Schain said. “You’d think Vermont would be much more pristine than us.”

Some students said that even though Connecticut did relatively well in the study, they are concerned by the outbreak of diseased amphibians. If the cause is a chemical used in agriculture, it makes sense for people in affected areas to start worrying about locally grown food, environmental studies student Rebecca Toseland ’07 said.

“We should probably think about what’s on the produce that we’re eating,” she said. “When we see these deformities in animals coming from our agricultural chemicals, that should definitely make us think twice.”

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