``We now need to determine if people are at risk.''
Ongoing chemical tests in Michigan areas with deformed amphibians point to the water where the frogs live - but the cause, said Lucier, ``could be chemical contaminants or natural products such as pond plants or algae.''
Wisconsin, Vermont and Oregon - and this summer, the western edge of Delaware - also have seen confirmed clusters of deformities. Most of the frogs have missing or deformed limbs and in some cases, extra legs. But the causes are unknown. And some scientists are now casting doubts on the Minnesota results.
Two common mosquito-control chemicals were rejected as suspects in one study - temephos, an organophosphate, and methoprene, which appears to mimic retinoic acid, a body substance responsible for early development.
Other possibilities range from agricultural chemicals to parasitic worms to increased ultraviolet light from the thinning of earth's ozone layer.
Whatever's going on, it's relatively new. Though an occasional deformed animal is routine, deformities of 40 to 50 percent are not.
For more information: Frog deformities are logged by state and county on the Internet by the North American Reporting Center for Amphibian Malformations at http://www.npwrc.org/narcam.