Biologists have since produced deformed frog embryos by mixing newly fertilized eggs with water from at least two sites in Minnesota, suggesting a contaminant in the water is to blame. The Minnesota researchers say their findings are preliminary and haven't been reviewed by other scientists or replicated. The California researchers, meanwhile, have zeroed in on the effects of methoprene, a pesticide used against mosquitos, flies and fleas. In 1996, the Minnesota Pollution Control Agency received about 180 reports of deformed frogs in 54 of the state's 87 counties, including 26 sites where the deformities were confirmed. Significant numbers of deformed frogs also have been reported in more than two dozen states and two Canadian provinces.
Biologists are alarmed by the discoveries because frogs are like environmental sponges.
Their skin soaks up whatever is in the water or in the air. I think the problem is real. The MPCA is not sure whether the water represents a human health threat, but the agency has alerted nearby residents and offered them bottled water as a precaution. The agency refused to identify the area, citing scientific reasons. The project identified about 14 sites in Minnesota, half of which produced deformed frogs in 1996 and 1997, and half of which didn't.