Laura Erickson's For the Birds

DDT Revisited Part II

Last time I talked about the harmful effects DDT had on the environment, accumulating through the food chain to affect humans. And I cited a 2001 study in which researchers analyzed stored blood samples collected in pregnant women back in the 60s and discovered a high correlation between DDE levels and premature births and low birth weight babies. Understanding the many risks pesticides have, Rachel Carson wrote, “We allow the chemical death rain to fall as though there were no alternative, whereas in fact there are many, and our ingenuity could soon discover many more if given opportunity.”

Although the charges against pesticides listed in her book were borne out, then and today, by a great many researchers, even today, corporate interests continue to vilify Rachel Carson rather than to explore other approaches to insect and disease control and to promote a more nuanced and limited role for pesticides used in disease prevention. Gilbert L. Ross, M.D. Medical Director of the American Council on Science and Health, wrote a widely-quoted letter to U.S. News and World Report, January 31, 2000,

“Ms. Carson’s writings may have been responsible for the chirping of “untold numbers of birds” who owe their lives to her. But, should we not also remember the millions of malaria victims in the third world whose voices have been prematurely stilled due to the banning of the DDT she demonized? It is Ms. Carson’s spiritual cohorts who hope to stifle the potential of food biotechnology to feed the hungry masses, thus following in their mentor’s misguided footsteps.”

Dr. Ross neglects to mention that DDT is still legal in some of the Third World countries where malaria rates are currently increasing, and where other insecticides are heavily applied in the environment as well. Mosquito populations exposed to DDT or other pesticides in the outside environment build up resistances to the toxins much more quickly than do their natural predators, such as dragonflies, which have much longer life cycles and smaller, slower reproductive capabilities. Indeed, DDT’s use in the outdoor environment, for agriculture and other uses, is blamed for the resistance mosquitoes have built up against it, rendering the pesticide ineffective against some dangerous malaria vectors in West Africa, Iran, Pakistan, India, Sri Lanka, Greece, Egypt, Central America, and Columbia (D.R. Roberts, 2000).

But even so, DDT spraying can and should be used in disease-prone mosquito-infested areas, as long as it is safely confined to interior uses, keeping it out of the natural and agricultural food chains. Since first used in the 1940s, the spraying of DDT on house walls has been proven an effective control against the spread of malaria in the Mississippi Valley of the United States, Italy, Venezuela, Guyana, India, and several other countries, with little or no effect on humans and pets. It was this use that wiped out malaria in the Mississippi basin. Rachel Carson’s concerns about the effects of DDT sprayed outdoors were proven absolutely correct, but it also has been proven correct that DDT can play an important role in indoor applications to protect human health where mosquito-borne diseases threaten human lives without entering the food chain, to hurt birds and other wildlife and accumulate in human tissues. But regulation and control of such indoor use of DDT for malaria control should be in the hands of health agencies and the Centers for Disease Control, not the Department of Agriculture, and packaging should include disposable gloves and protective face masks. I’m sure that airborne exposure to DDT can be dangerous—my older brother, who used to chase the DDT truck on his bike when he was a kid, has been treated for prostate and kidney cancer which also involved his adrenal gland. But as long as the spray is directed toward the walls and people leave until it’s dry, and keep all food tightly sealed during the spraying, it presents a far smaller hazard to humans than the diseases mosquitoes carry, and can even contribute to actually wiping out diseases such as malaria in areas where humans are the main carriers.

The application of DDT in the outdoor environment has been a failed experiment, killing far too many birds and insects that feed on mosquitoes, including swallows, flycatchers, and dragonflies, entering natural and agricultural food chains, hurting people, and providing little short-term gain and absolutely no long-term benefits for disease prevention. And as a wide spectrum insecticide, DDT killed enormous numbers of bees and other pollinators, insects essential for producing many of the very crops and fruits that “feed the hungry masses.”

But indoor use of DDT for disease prevention is warranted in third world countries, and even in the United States during serious disease outbreaks. Ironically, keeping humans from getting and spreading West Nile Virus by DDT interior spraying may help save birds in the long run.