"Subchronic Dermal Application of N,N-Diethyl m-Toluamide (DEET) and Permethrin to Adult Rats, Alone or in Combination, Causes Diffuse Neuronal Cell Death and Cytoskeletal Abnormalities in the Cerebral Cortex and the Hippocampus, and Purkinje Neuron Loss in the Cerebellum." Ali Abdel-Rahman, Ashok K. Shetty, and Mohamed B. Abou-Donia (Experimental Neurology, Volume 172, November 2001).
The combined use of a popular repellent and mosquito spray can lead to motor deficits and learning and memory dysfunction, according to lead researchers at Duke University. This study is timely because DEET, which is an insect repellent, and permethrin, which is a mosquito spray, are now commonly recommended throughout the U.S. to combat mosquito-borne diseases like West Nile virus.
In this study, researchers sought to determine the effects of these two chemicals on Persian Gulf War (PGW) veterans because they were used extensively in that war. Many PGW veterans complain of chronic symptoms, including headache, loss of memory, fatigue, muscle and joint pain, and ataxia, which causes an inability to coordinate muscular movements.
The authors found that exposure to both DEET and permethrin experienced by service personnel in the PGW has played an important role in causing these illnesses. It is important to note that the animals in this study received the same routes of exposure and doses of DEET and permethrin as the PGW veterans. When used alone, DEET can result in human and animal poisoning including death. Permethrin toxicity can cause tremors, hyperactivity, ataxia, convulsions and paralysis. Other studies conducted by these authors suggest that exposure to DEET and permethrin causes significant sensorimotor deficits and disruption of the blood-brain barrier.
This is a groundbreaking study about the synergistic effects of two commonly used chemicals. When registering a product, the EPA does not evaluate the possible synergistic effects that may be caused by chemical interactions. This type of research is sorely needed in the pesticide field. Abou-Donia warns to be cautious using DEET, and never use on infants or combine with other insecticides, sunscreens, or even over the counter drugs such as antihistamines. While the risk to humans remains in intense debate, Abou-Donia says his 30 years of research on pesticides' brain effects prescribes the need for caution among the general public.
Dr. Abou-Donia spoke at the 20th National Pesticide Forum, April 26-28, 2002 in Seattle, WA.