SCIENCE IN THE SERVICE OF POLITICS

Is There a Place for DDT?: Elimination of the mosquito is the key to preventing an epidemic of West Nile virus, but public policy limits the tools that are available. (HENRY I. MILLER, 8/07/03, NY Times)

In 1972, on the basis of dubious data about toxicity to fish and migrating birds, the Environmental Protection Agency banned virtually all uses of the pesticide DDT, an inexpensive and effective pesticide once widely deployed to kill disease-carrying insects. Allowing political sentiment to trump science, regulators also cited the possibility that DDT posed a cancer risk for humans--an assertion based on studies showing an increased incidence of the illness in mice that were fed extremely high doses of the pesticide.

Not only did government regulators minimize scientific evidence of the safety and effectiveness of DDT, they also failed to appreciate the distinction between its large-scale use in agriculture and more limited application for controlling carriers of human disease. Although DDT can be a toxic substance, there is a big difference between applying large amounts of it in the environment--as American farmers did before it was banned--and applying it carefully and sparingly to fight mosquitoes and other disease-carrying insects. A basic principle of toxicology is that the dose makes the poison.

The regulators who banned DDT also failed to take into consideration the inadequacy of alternatives. Because it persists after spraying, DDT works far better than many pesticides now in use, some of which are toxic to fish and other aquatic organisms. (While its longevity poses risks, they are minimized with targeted use.) Also, the need to spray other insecticides repeatedly drives up costs. For example, budget problems compelled Maryland this summer to turn down requests for spraying from communities badly infested with mosquitoes.

Given the long-term ineffectiveness of other pesticides, DDT remains the best alternative to fighting mosquitoes and the West Nile virus. It's worth recalling that DDT worked before, eradicating malaria from the United States. It's worth recalling, too, that since DDT was widely banned,
insect-borne diseases like malaria and dengue fever have been on the rise worldwide. The World Health Organization estimates that malaria kills about one million people annually, and that there are 300 million to 500 million new cases each year.

Thank you, Rachel Carson. Posted by Orrin Judd at August 12, 2003 8:25 AM