Medical journal defends DDT

Published October 1, 2000

Two articles in the July 29 issue of The Lancet, a respected British medical journal, make a surprising and passionate case for DDT, the pesticide banned in the Western world in the 1970s.

Defending DDT

In the Lancet article, “DDT House Spraying and Re-emerging Malaria,” Donald R. Roberts and colleagues from the Uniformed Services University of the Health Sciences in Bethesda, Maryland describe the degree to which malaria cases are increasing, and at an accelerating rate, in Africa. The investigators also describe how malaria is now reappearing in areas from which it had been eradicated, including Korea and central Asia.

Even with the current patchwork application of DDT in epidemic areas, malaria rates are starting to surpass those last seen in the 1940s, affecting additional millions of infants, children, and adults. No public health program without DDT will stop the progression of global malaria.

The authors point out that “claims of risks of DDT to human health and the environment have not been confirmed by replicated scientific inquiry,” and they quote World Health Organization documents that “have consistently and accurately characterized DDT-sprayed houses as the most cost effective and safe approach to malaria control.”

In the second Lancet article, titled “How Toxic Is DDT?” A.G. Smith of Leicester University, United Kingdom, states DDT is safer than many other chemical insecticides. Even in DDT-sprayers and occupants of DDT-sprayed households, Smith notes, “associated toxicity has not been found.” His conclusion: “[T]he effects [of DDT] on human beings at likely exposure levels seem to be very slight.”

The debate

From its first use during World War II, DDT was (and still is) the most effective and least expensive insecticide ever known. After the war, DDT stopped the incipient epidemic of typhus, spread by lice. Subsequently, it was used–and overused–as an agricultural pesticide, with millions of tons applied to American and European farmlands, again with remarkable success in eradicating insects responsible for crop damage.

DDT’s overuse may also have led to environmental effects on certain wildlife, especially birds. The scientific controversy about the extent of this toxicity remains, and many doubt whether there was any actual damage at all. But two facts are especially important.

  • Whatever effects on the environment there may have been resulted from intensive over-utilization of DDT in agriculture, not from malaria control.
  • The theoretical environmental benefits of banning DDT were not, and are not, worth the very real, deadly toll in human life and suffering.

Some have also accused DDT of being a risk to human health. But this substance has been heavily used for more than 50 years worldwide, and there have been no valid reports of adverse human health effects. Some rodent studies purported to show evidence of liver damage, but there is no real threat to human health from DDT.

In Africa especially, as well as in Asia and Latin America, DDT remains the most effective means of reducing the deadly toll of insect-borne diseases–mainly malaria, but also sleeping sickness and yellow fever. Malaria alone afflicts approximately 200 million people worldwide; more than 2 million die each year. During the years when DDT was routinely used as a household insecticide and insect repellant, the epidemics were largely held in check, dramatically reducing the toll of disease and death.

Ironically, a group of diplomats representing malaria-free Western countries, the United Nations Environmental Programme, is meeting to push through a worldwide ban on DDT as one chemical in the “persistent organic pesticide” category. The only group that stands to gain from this perverse ban are the pesticide manufacturers, whose more expensive–and less effective–products will be used in DDT’s place.

Hundreds of doctors and public health experts, including three Nobel Prize winners, recently petitioned the United Nations not to ban DDT for house spraying in malarious regions. As The Lancet editorial puts it, “Whose health is being protected? The answer seems to be that the health of people in poorer countries is being put at a very real risk to protect the citizens of wealthier countries from a theoretical risk.”

Dr. Gilbert L. Ross is medical director of the American Council on Science and Health in New York.