A larvicide spread around Wilton, CT has been linked to deformities in frogs, according to studies done by researchers at the Scripps Institute of Oceanography, La Jolla, California. In June, certified employees for the Dept. of Public Works put the larvicide methoprene in nearly 5,000 catch basins around town. The trade name for the methoprene used in Wilton is Altosid.

In the summer of 1998, Scripps Institute researchers reported that methoprene, an insect-growth regulator introduced in the late 1970s to control fleas and mosquitoes, breaks down into harmful chemical by-products when exposed to sunlight, heat and organic matter. Dr. James LaClair and his associates at Scripps Institute found that fresh methoprene, when exposed to ultraviolet rays of sunlight, produced compounds known as retinoids, which dramatically altered embryo development in frogs. The deformities produced by scientists at Scripps were similar to malformations found in frogs in the U.S. and Canada where methoprene has been used for mosquito control and agricultural applications. Frog deformities included a missing limb (usually a rear leg that did not develop), extra toes and extra legs.

Wilton Health Director Steven Schole, who said he was not familiar with particulars of the study, did question its validity.

"The issue came up before we spread it and I can tell you that the evidence that you are talking about has never been substantiated and there is something wrong with the way they conducted the study to draw those conclusions," Schole said. He also pointed out that there was no such warning on the EPA label.

According to Dr. David Gardiner, a professor of developmental cell biology at the University of California-Irvine, the proper development of frog's legs depends upon small levels of retinoic acid, but excessive amounts of it can cause deformities in any vertebrate animal, including humans. Dr. Bruce Blumberg, formerly with the Salk Institute, and Dr. Gardiner are still studying malformations and they believe that retinoids - a methoprene derivative - may be responsible. In an interview with The Villager Dr. Gardiner said: "We are actively investigating the presence of retinoids in the environment." He said he had not directly tied methoprene to the problem but said, "Whatever chemical agents are disrupting development in frogs could certainly have the same effects on all vertebrates."

Brad Robinson, pesticide program supervisor for the Conn. Dept. of Environmental Protection, said methoprene is safe but, like many, he would not completely rule out its link to deformities in frogs. "Nobody knows for sure; it's a theoretical possibility but, quite frankly, there is only one area in the state where we have found significant numbers of deformed frogs." But according to the North American Reporting Center for Amphibian Malformations (NARCAM), deformed frogs have been reported in many parts of the state including densities in Fairfield County where methoprene has been spread.

The larvicide artificially stunts an insect's development by interfering with the maturation process, making it impossible for baby mosquitoes to mature into adult, biting mosquitoes; it does not, however, affect mosquitoes that already have matured.

According to a spokesman for Wellmark International, the company which manufactures Altosid, the product is safe. Wellmark's director of corporate communications, Mark Nuberg, told The Villager: "Our product is widely used in Minnesota where they have a number of frog deformities, but in the counties where they use our products, they have very few deformities compared to the counties where our products are not used."

Minnesota does report the highest number of deformed frogs and the Minnesota Pollution Control Agency (MPCA) is actively tracking the problem but right behind it -- and 60 miles from Connecticut -- is Vermont with the second-highest number of reported frog deformities. Rick Levey, an aquatic biologist for the state of Vermont, has worked with Dr. LaClair and Dr. Gardiner. He said that although Vermont does not use methoprene, a portion of Lake Champlain in northern Vermont had abnormal numbers of deformed frogs. He sent a sample of the lake water to Dr. LaClair who found concentrations of methoprene by-products in it.

Levy said, "I think any health official would agree that they would not want to see methoprene ending up in anybody's drinking water and I think most also agree that they wouldn't want to see levels of methoprene showing up in our waterways - meaning streams, rivers, lakes or ponds." The Federal Environmental Protection Agency (EPA) has classified methoprene "least toxic" with regard to humans, but scientific research suggests that EPA studies do not routinely evaluate the breakdown by-products of the pesticidal chemicals that the agency has deemed safe Several weeks ago, the Wilton Department of Health began distributing a different larvicide known as Bti to residents who wanted to use it in standing water at their homes. Like methoprene, Bti is a larvicide that is used to control mosquito populations, but unlike methoprene, Bti is a natural bacterium and no studies have linked it to negative impacts on the environment. The methoprene (Altosid XR) that was spread in Wilton in June has a 150-day life span.

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