DECEMBER 23, 1996
In Minnesota, a routine biology field trip resulted in a world-wide scientific investigation when students found frogs with deformed, missing, or extra legs, as well as deformed eyes or other parts. Mutant frogs have been found in several states, even as far as Japan. Is it pollution, or unidentified environmental changes? Investigators have yet to find the answer. Fred De Sam Lazaro looks into the mystery that has the scientific community hopping.
FRED DE SAM LAZARO: About a year ago last summer teacher Cindy Reinitz took her pupils on a nature walk like this one not far from their private school in rural Le Sueur, Minnesota.
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ELAINE FARLEY: We're just catching frogs, just because it'd be neat, and we caught one and I thought I broke its leg because it was sticking straight out. And someone else caught a frog, and they go, you broke its leg too, and we just--so we just started catching more frogs, and they all have broken legs, we thought.
FRED DE SAM LAZARO: Until they began looking more closely at the frogs in this pond. The limbs were not broken but grossly deformed or non-existent. Some animals lacked an eye or had reached adulthood without shedding their tails.
STUDENT: See, this leg is pretty normal, but then this one is totally screwed up.
ANOTHER STUDENT: Here's one with no legs on one side and a bunch on the other.
CINDY REINITZ: If you go in the water and see some of these deformed ones trying to swim, they just can't escape. They just can't swim. We've got some with no hind legs at all.
FRED DE SAM LAZARO: Reinitz quickly notified Minnesota Pollution Control Agency scientist Dr. Judy Helgen.
DR. JUDY HELGEN, Minnesota Pollution Control Agency: I sent our student worker down there because we were involved in something else. He came back at the end of that day, and he just said, you'd better get down there.
FRED DE SAM LAZARO: Dr. Helgen began investigating what seemed the likely cause--chemical or pesticide runoff from farms in this heavily agricultural region. But she soon discovered the problem was not local.
DR. JUDY HELGEN: Cindy called me the next week to say that someone had talked to her, someone who lived across the Minnesota River, over a mile away from this site, that they had abnormal frogs on their farm. So it started even then last summer and fall to expand, and every time I'd get one of these calls I'd get this chill up my back because at first we thought, well, it's just this one wetland, and there's some problem there.
FRED DE SAM LAZARO: To date, Dr. Helegen's agency has received reports of malformed frogs from 54 Minnesota counties. They're widely scattered and some in relatively pristine forested areas in Northern Minnesota, miles from any industry or farming. There have also been reports from states as far apart as California and Vermont, Canadian provinces, and recently, there was one sighting of deformed frogs in Japan.
FRED DE SAM LAZARO: Have you seen anything like this before?
DR. ROBERT McKINNELL, University of Minnesota: Nothing. It's unprecedented in my experience.
FRED DE SAM LAZARO: Dr. Robert McKinnell has 40 years of experience studying frogs. He says normally about one in ten thousand animals may have deformities.
DR. ROBERT McKINNELL: I think we should put this fellow back into the tank. I don't think he's quite ready yet.
FRED DE SAM LAZARO: Dr. McKinnell first looked for cancer, but he dismissed that possibility since he thought the deformities seemed developmental. So, with other biologists, he began testing for abnormal chromosomes. He had experience in this field; 20 years ago he'd worked with residents of New York's Love Canal, site of perhaps the best-known case of toxic environmental contamination in U.S. history.
DR. ROBERT McKINNELL: There were abnormalities reported among the children at Love Canal, as well as cancer, and I said it might very well be that you would expect to find abnormal chromosomes. Thus far, and we're not through with the study yet, thus far, there seem to be no chromosomal aberrations.
FRED DE SAM LAZARO: Dr. McKinnell also examined the DNA or genetic material in blood samples from the deformed frogs, looking for any alterations. Again, none was evident.
DR. ROBERT McKINNELL: That doesn't mean they're not there, but nothing obvious.
FRED DE SAM LAZARO: And there don't seem to be any other obvious answers, though many possibilities have been raised. Scientists have speculated that some form of water pollution may be the villain, perhaps a chemical that's airborne or widely scattered in frog habitats. Others have even suggested the deformities may be triggered by ultraviolet radiation caused by a thinning ozone layer. Still others have suggested parasites, including one found more commonly in water snakes. Whatever the irritant, it almost certainly became active in just the past couple of years. Dr. Helgen says young frogs are widely used as fishing bait, so widespread deformities would certainly have caught people's attention if they'd existed earlier.
DR. JUDY HELGEN: What is it that's different in the environment in the last couple of years, or maybe some period of time briefly before that, whether a year or two years? We're reaching out to people to give us information about what would be new products that are being used. The other aspect is that one person suggested you could actually have--you could have a problem happening and causing abnormal animals, but it didn't--it didn't become evident until they became a significant part of the population because in the past, the predators would have removed them.
DR. ROBERT McKINNELL: As a scientist I must humbly come to you and say I don't know.
FRED DE SAM LAZARO: Scientists worry that frog populations are already being seriously depleted across the world, mostly as a result of human encroachment, but they also are concerned about what the deformities might mean to humans. Because they don't know the cause, they cannot be certain about the implications.
DR. ROBERT McKINNELL: I couldn't say that it is not a threat to human health but, on the other hand, let me tell you there are many toxic things--potentially toxic substances in our environment, and we live very nicely side by side because we do have mechanisms to de-toxify our environment, but then so too do frogs.
FRED DE SAM LAZARO: Dr. McKinnell says the renal systems of frogs and humans use similar enzymes to de-toxify poisons. It's one reason amphibians are considered a sentinel or indicator species.
DR. JUDY HELGEN: They are telling a lot about the whole broad environment. They're in the water, so they're kind of indicating water quality, and they're indicating landscape quality. So from that point of view, for me, as somebody interested in environmental quality, they are a powerful indicator. Whether it translates to human health is just another unknown issue.
FRED DE SAM LAZARO: One big reason the frog deformities may not pose a public health threat is that humans are not as extensively exposed to the frog's immediate environment, ponds or wetlands.
DR. ROBERT McKINNELL: My thought is let's be concerned but let's not be panicked.
FRED DE SAM LAZARO: That seems to be the approach of many residents of La Sueur County, site of the original discovery of deformed frogs, a constant, if low grade, worry.
LINDA QUINTERO: My nephew loves to collect them, and he'd be bringing them home and putting them in a big old fish bowl, you know, and I wonder what they're bringing home, you know, if the frogs actually bring this disease home, and if it's water that's running through our sewers, is it going to get our kids sick, you know.
MICHELLE DAHN: Well, I guess the biggest fear is in the future, you know. Will our children's children be safe and on down the line from there? Those are some of the simplest forms of life, and if they're starting to get deformed, it just moves up the chain.
GUTHRIE SWENSON: It's scary in a way, but it's kind of just being more aware that we're doing something wrong to the environment, and we've got to stop it, and find out the cause so we know what we can't do anymore.
FRED DE SAM LAZARO: For their parts, the kids in La Sueur have become foot soldiers for the state pollution control agency. They created a Web page on the Internet on the subject of frog deformities. It's one of several ways in which the reports are being gathered and registered.
By next spring, researchers hope to have narrowed their search for causes, and they hope that a new generation of frogs may provide some answers on how widespread the affliction is, how it affects the amphibians' reproduction, and whether there's any concern for human health.