Are Flame Retardants Harming Frogs?

Why Study Frogs?

We interviewed Bill Karasov, a UW-Madison Professor and Wisconsin Sea Grant researcher, and his Ph.D. student, Tawnya Cary. Both are interested in wildlife toxicology (the study of how toxins in the environment affect wildlife).

Wisconsin companies make all kinds of products. Companies put chemicals in their products so they are safe, like chemicals so the products don't catch on fire. Those chemicals work really well.

The chemicals do something else, which is hurt the environment and the wildlife living in it. That's what scientists funded by Wisconsin Sea Grant found out.

Dr. William Karasov, with the Department of Forest and Wildlife Ecology at the University of Wisconsin-Madison, and Tawnya Cary, a Ph.D. student at UW-Madison, studied a fire-preventing chemical compound called polybrominated diphenyl ethers (PBDEs for short). They wanted to know what PBDEs do to Northern Leopard frogs. Those frogs live in rivers and forests near Lake Michigan. PBDEs seep into the frogs' environment. The chemicals come from companies' trash or from old products that go into landfills.

In the laboratory, frog tadpoles got food with PBDEs in it. The tadpoles got that food until their front legs began to grow. The scientists especially wanted to find out if PBDEs weakened the frogs' immune systems. That would make them likely to get sick if they lived in the rivers and forests.

Karasov said sometimes large groups of dead frogs have been found in the wild. "We've never really known if a weakened immune system is the problem," he said.

Other scientists have spent a lot of time researching a chemical you've probably heard of —polychlorinated biphenyls, or PCBs. The PBDEs that Karasov and Cary studied have pretty much never been looked at.

"That's where we began. We wanted to get a very fast start on this, because nobody has looked at it yet," said Karasov.

As it turns out, it's a good thing Karasov and Cary did. They found out that the chemical frog food killed some of the tadpoles. Other tadpoles didn't grow right.

The scientists don't think PBDEs hurt the tadpoles' immune systems. But, they want to keep exploring that question.

Their work is on the front lines of a new field of study called immunoecology. That means scientists want to know more about how immune systems keep animals healthy in the environment.

"Frogs play an important role in our ecosystem—they're a key part of our food web," said Cary. "It's a heads-up as to why we should be concerned about this, and how it could affect humans."

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