The rehabilitation of Dichloro-Diphenyl-Trichloroethane
Good article at the
New York Times about DDT's rehabilitation and use, not only as an insecticide but also as a repellant:
A New Home for DDT
DDT, the miracle insecticide turned environmental bogeyman, is once again playing an important role in public health. In the malaria-plagued regions of Africa, where mosquitoes are becoming resistant to other chemicals, DDT is now being used as an indoor repellent. Research that I and my colleagues recently conducted shows that DDT is the most effective pesticide for spraying on walls, because it can keep mosquitoes from even entering the room.
The news may seem surprising, as some mosquitoes worldwide are already resistant to DDT. But we’ve learned that even mosquitoes that have developed an immunity to being directly poisoned by DDT are still repelled by it.
Malaria accounts for nearly 90 percent of all deaths from vector-borne disease globally. And it is surging in Africa, surpassing AIDS as the biggest killer of African children under age 5.
A bit more:
In our studies, in which we sprayed DDT on the walls of huts in Thailand, three out of every five test mosquitoes sensed the presence of DDT molecules and would not enter the huts. Many of those that did enter and made contact with DDT became irritated and quickly flew out.
The mosquitoes we used were the kind that carry dengue and yellow fever, not malaria. But there is ample evidence that malaria-carrying mosquitoes respond similarly to DDT. Several malaria-carrying species are even more sensitive to DDT’s repellent effects.
When we sprayed the huts with either dieldrin or alphacypermethrin, in contrast, all the test mosquitoes entered. Alphacypermethrin acted as a contact irritant, and it killed others that lingered on a treated surface. Dieldrin worked only as a poison — a powerful one, killing 92 percent of mosquitoes that made contact with it, far more than alphacypermethrin or DDT.
But dieldrin’s strong toxicity means that mosquitoes quickly develop resistance to it. Its use against malaria was short-lived, ending in the 1950s, because it so quickly became powerless.
I didn't know about the repellant properties. And again, when it was used earlier, we were marinating in it. Intelligent use of DDT would prevent millions of deaths each year.
Posted by DaveH at August 20, 2007 9:11 PM