THE STORY OF DDT is a tale of two worlds. The miracle pesticide of the 1930s was banned by developed nations decades ago as a health and environmental hazard. Malaria is virtually nonexistent in the West.
But it is still the cheapest, most effective weapon against malaria in developing countries, where each yearsome 2.5 million people die from, and 500 million are infected by, the mosquito-transmitted disease.
That division is sharply drawn in negotiations on a United Nations treaty that would ban DDT worldwide. The international accord aims to phase out a dozen toxic chemicals known as persistent organic pollutants (industrial compounds such as dioxin and PCBs and various pesticides) that can accumulate in the food chain, travel long distances and persist in the environment for decades.
The goal of the treaty is desirable. Many of these harmful chemicals now have less toxic substitutes. But that effort must be tempered to recognize the misery that could be multiplied by a ban on DDT. (The United States outlawed the substance 27 years ago, primarily on evidence that it endangered survival of bald eagles and other meat-eating birds, though the chemical was also suspected to be in human breast milk).
There is no effective vaccine against malaria, drugs to treat it are not widely available and the disease's resistance to the drugs that exist is rising. Alternatives such as pyrethroid chemicals are more expensive and not as potent. Draining mosquito breeding pools is highly problematic.
Much of the malaria infection today can be traced to a lack of DDT: Some poor countries cannot afford to buy it from remaining manufacturers in India, China and Mexico; other countries can't get reliable supplies from these chemical makers.
Spraying interior walls of houses with DDT to eliminate the malaria-carrying anopheles mosquito is still recognized as the most effective control in the Third World. Malaria has become more widespread in recent years, in part because of the phase-out of DDT manufacturing.
Finding safe, widely available alternatives to the poison is essential. Researchers in Africa are looking at native plants and fungus that can repel mosquitoes or kill their larvae. Industrial nations recently committed to expanded research, searching for both cure and preventive. Bill Gates is giving billions of dollars to develop a malaria vaccine. India got $200 million from the World Bank to find alternatives to DDT.
But for now, DDT is too important to poor countries to warrant a world ban.