Mohamed Abou-Donia, Ph.D. has also called for further government testing of the chemical's safety in short-term and occasional use, especially in view of Health Canada's recent decision to ban products with more than 30 percent of the chemical. Every year, approximately one-third of the U.S. population uses insect repellents containing DEET, available in more than 230 products with concentrations up to 100 percent.

While the chemical's risks to humans are still being intensely debated, Abou-Donia says his 30 years of research on pesticides' brain effects clearly indicate the need for caution among the general public.

His numerous studies in rats, two of them published last year, clearly demonstrate that frequent and prolonged applications of DEET cause neurons to die in regions of the brain that control muscle movement, learning, memory and concentration. Moreover, rats treated with an average human dose of DEET (40 mg/kg body weight) performed far worse than control rats when challenged with physical tasks requiring muscle control, strength and coordination. Such effects are consistent with physical symptoms in humans reported in the medical literature, especially by Persian Gulf War veterans, said Abou-Donia.

"If used sparingly, infrequently and by itself, DEET may not have negative effects the literature here isn't clear," he said. "But frequent and heavy use of DEET, especially in combination with other chemicals or medications, could cause brain deficits in vulnerable populations."

Children in particular are at risk for subtle brain changes caused by chemicals in the environment, because their skin more readily absorbs them, and chemicals more pote
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Contact: Rebecca Levine
levin005@mc.duke.edu
919-684-4148
Duke University Medical Center
1-May-2002