Building a Better Bug Beater - by Stephen Leahy - 27Jun2003 - Wired News

The key chemical ingredient in effective insect repellents, DEET, was developed for the military in 1946 by the U.S. Department of Agriculture. But soon it will be replaced by something the military likes better: SS220.

For the past 50 years diethylmetatoluamide, or DEET, has been the most widely used insect repellent in the world. While its effectiveness is universally recognized, in recent years, concern has been growing over its safety. Reports have been made of seizures and comas in children, and mental confusion, irritability and insomnia in adults, with repeated and prolonged use.

Those reports have been further substantiated by Duke University Medical Center pharmacologist Mohamed Abou-Donia, who published studies in 2002 showing frequent and prolonged use of DEET caused brain-cell death and behavioral changes in rats.

Abou-Donia suggested those symptoms would look something like Gulf War Syndrome in humans.

The American Academy of Pediatrics recommends repellents used on children contain no more than 10 percent DEET and the EPA is no longer allowing label claims of child safety for products containing DEET. Health Canada (Canada's FDA counterpart) has decided to limit the DEET level of products to 30 percent by December 2004.

Military-issue insect repellents currently contain 33 percent DEET, although they have contained as much as 75 percent as recently as the early 1990s.

Not surprisingly, the Department of Defense found increasing numbers of military personnel weren't using insect repellents. The Defense Department launched a quest to beat DEET three years ago.

But finding a replacement was a real challenge because no one knows why DEET works nor exactly what triggers a mosquito to bite.

The Defense Department, working in collaboration with the U.S. Department of Agriculture, screened hundreds of chemical compounds and products containing citronella, eucalyptus, mint, catnip and other herbs at a special testing facility using the naked arms of human volunteers and disease-free mosquitoes.

While many products have repellent properties, they are short-lived or their effectiveness is limited to certain species. Nothing works as well as DEET, said Jerome Klun, an entomologist at the Chemicals Affecting Insect Behavior Laboratory.

One of the insect-repellent compounds screened was something USDA scientists created in 1978, but it offered protection for only a short period of time. Klun was able to isolate the active ingredient from the mixture and found the stereoisomer, or three-dimensional molecule configuration, that provided exceptional stability.

The new compound, bearing the USDA chemical ID SS220, has piperine, a common black pepper extract, at its core. In human tests at the Walter Reed Army Institute of Research in Silver Spring, Maryland, it outlasted and outperformed DEET.

It's perfectly safe, has a slightly fruity odor, feels good on the skin and isn't sticky, Klun said.

Another big advantage is that SS220 doesn't dissolve common plastics, like eyeglasses or rayon-polyester fabrics, like DEET does. That will make military equipment designers happy.

"SS220 will unseat DEET," Klun predicted, though testing is still needed under real-world conditions and final toxicological testing by EPA is still to come.

Commercialization of SS220 is expected by 2006, although finding a financial partner is a bit of a challenge, as DEET has the twin advantages of market dominance and cheaper manufacturing costs.

The military, which invested $2 million in the project, is very happy, according to Klun. The majority of hospital admissions overseas are related to insect bites, so if the soldiers use the new compound, those numbers should decrease.

Sand flies in Afghanistan and Iraq regions carry Leishmaniasis, a parasitic disease that causes skin sores, enlargement of the spleen and liver and anemia. While local people are immune, chances are good that military personnel will get it without protection, Klun said.

No vaccines exist for Leishmaniasis nor for many of the other diseases transmitted by biting insects.

"Disease has always been the military's biggest challenge throughout history," Klun said.

Yes good news indeed. After having a reaction to DEET that ended with me being airlifted and not remembering anything for 8 hrs. Waking up in the hospital 100 miles away from where I was rock climbing. I would like to get ahold of the new stuff.

[ 07-07-2003, 23:26: Message edited by: p dog shooter ]

Awww...I'm going to miss my ol'friend DEET. Muskol has about 80% DEET I think...

That stuff disolves plastic easily. And when you sweat, whatever you had on your forhead runs into your eyes.

It also helps to give you a nice sunburn, but I am not convinced it wasn't just the DEET burning your skin

It's easy to throw stones at DEET but I would have done FAR less outdoor activities through the years had it not been for that material. I think it's great. I haven't done as much waterfowl photography as I used to but back when I hit it hard it was basically a requirement that I spray myself head to toe to avoid the skeets present in the spring marshes. Of course I was too busy hunting them in the fall to worry about photography.

Nevertheless, I'm hopeful this new material will work at least as well as DEET in repelling insects along with the advantages mentioned.

Reed