(Beyond Pesticides, May 28, 2008)
Researchers have begun preliminary work to find suitable and safe alternatives to the widely used mosquito repellent DEET. Several possibilities have been identified, which repel mosquitoes for longer periods of time, but their safety for use on humans still needs to be investigated. Researchers, with funding from the Department of Defense, set out to determine what makes insect repellents work, and then to use that information in finding more effective ways to chase away disease-carrying insects. Insect repellents are used to repel biting insects such as mosquitoes and ticks that spread diseases such as encephalitis, Lyme disease, Rocky Mountain spotted fever, malaria and dengue fever.
Ulrich R. Bernier, PhD, co-author of this study published online in the Proceedings of the National Academy of Sciences http://www.pnas.org/ and research chemist at the Agriculture Department’s mosquito and fly research unit in Gainesville, Fla., remarked that several of the new chemicals reviewed were “just phenomenal.”
Using previous USDA data on hundreds of chemicals collected over 50 years, the researchers rated chemicals from “1≥ to “5≥ on ability to repel insects, and then focused on what the most effective ones the 5s had in common. They were able to narrow the study down to 34 molecules, 23 that had never been tested before and 11 that had been tested, with a focus on a class of chemicals known as N-acylpiperidines.
Tests conducted using cloth treated with the chemicals were very promising. Some of the chemicals repelled mosquitoes for as long as 73 days and many worked for 40 to 50 days, compared to an average of 17.5 days with DEET. The 10 most effective were narrowed down to seven, with eliminations based on concerns about toxicity and high cost to produce. Safety testing to make sure these chemicals are safe to be applied on human skin is expected to begin this summer.
DEET (N,N-diethyl-meta-toluamide) is commonly used as an insect repellent but its use has become highly controversial. Scientists have raised concerns about the use of DEET and seizures among children, even though the U.S. Environmental Protection Agency (EPA) claims that there is not enough information to implicate DEET with these incidents. DEET is quickly absorbed through the skin and has caused adverse effects including severe skin reactions including large blisters and burning sensations. Laboratory studies have found that DEET can cause neurological damage, including brain damage in children
Its synergistic effect with other insecticides is also a major health concern. DEET, when used in combination with permethrin – a synthetic pyrethroid insecticide, likely facilitates enhanced dermal absorption of permethrin and induces symptoms such as headache, loss of memory, fatigue, muscle and joint pain, and ataxia, which causes an inability to coordinate muscular movements. Several studies done by a team of Duke University researchers lead by Mohammed Abou-Donia suggest that DEET in conjunction with permethrin-impregnated clothing may be linked to Gulf War Syndrome. (See Review of Study.) DEET was originally developed for military use in 1946 and was then registered for use on the general public in 1957. According to the EPA, more than one third of the U.S. population uses DEET-containing products every year.
Safer alternatives to DEET include picaridin, citronella and other essential oils, like oil of lemon eucalyptus. For more information on safer methods to protect yourself from mosquitoes and other insects, please visit Beyond Pesticides’ fact sheet on mosquito repellents.
Source: Associated Press