DDT, Target of Global Ban, Finds Defenders in Experts on Malaria
The New York Times August 29, 1999
Sunday, Late Edition
BYLINE: By SHERYL GAY STOLBERG
DATELINE: WASHINGTON, Aug. 28
It has been 27 years since the United States banned the pesticide DDT, and the payoff is undeniable. The peregrine falcon, once pushed to the brink of extinction, came off the endangered species list this month, and the bald eagle may soon follow. Brown pelicans are flourishing in Florida. On the shores of Long Island, the ospreys are back.
Now the United Nations is drafting a treaty that may lead to a worldwide ban on DDT. But the negotiations, set to resume in Geneva next month, are drawing opposition from an unlikely quarter: public health professionals, who say DDT is necessary to stop the spread of malaria, a disease that kills as many as 2.7 million people each year, mostly children in undeveloped countries.
"A child dies of malaria every 12 seconds," said Dyann F. Wirth, a malaria expert at the Harvard School of Public Health and president of the American Society of Tropical Medicine and Hygiene. "That could go up dramatically if we lose this important control tool."
Dr. Wirth is among more than 370 medical researchers in 57 countries who are urging that the treaty allow DDT to be sprayed in small quantities on the interior walls of homes, where it acts as a repellent to the disease-carrying insects. The scientists argue that if the pesticide, which is cheap and effective, must be eliminated, it should be phased out gradually, and only if Western countries conduct research on the more expensive alternatives and help pay for them.
Some type of public health exception is likely, said Jim Willis, director of chemicals for the United Nations Environmental Program, which is sponsoring the talks. But the specifics are engendering intense acrimony between the public health experts and environmentalists, and have created some friction in the Federal Government, as it tries to formulate its policy for the negotiations.
"This poses an unusual dilemma," said a State Department official involved in the talks. "Usually the dynamic is protection versus economics. There, it is very easy for one side to paint the other as the black hat. But here there is a peculiar tradeoff between health and the environment."
Most countries no longer use DDT for agricultural purposes (or do not admit to it if they do), but experts estimate that 23 nations still use it for malaria control. The biggest users are China and India. Mexico has pledged to stop spraying DDT by 2007. And the World Bank has lent India $200 million to help devise alternatives to DDT.
The DDT dilemma stems from a United Nations plan to eliminate, or greatly reduce, the use of 12 toxic chemicals classified as persistent organic pollutants. The group -- "the dirty dozen" to environmentalists -- consists of eight pesticides, including DDT, as well as chemical byproducts and industrial chemicals. All accumulate in the food chain and can travel thousands of miles through air, water and bird migration, causing lasting contamination.
In her 1962 book "Silent Spring," Rachel Carson, a marine biologist, chronicled DDT's poisonous effects, showing, for example, how it killed the robins that ate the earthworms that dined on the leaves of Dutch elm trees that had been sprayed with the insecticide. The public outcry was tremendous; the book led to the establishment of the Environmental Protection Agency in 1970 and the United States ban on DDT in 1972.
The treaty negotiations on the group of pollutants began in 1998 and are scheduled to conclude by the end of next year. The Geneva meeting, which runs from Sept. 6 to 11, is the third of five scheduled sessions, but the first to examine each chemical in detail. Mr. Willis of the United Nations predicted "a rather thorough discussion of the DDT issue."
Among advocacy groups hoping to influence the talks, that discussion is already under way, and it is fraught with competing studies and statistics. Experts are arguing about everything from whether DDT is harmful to human health (the evidence is inconclusive) to whether the recent rise in malaria rates in Mexico results from cutbacks in spraying, or from last year's hurricanes, which provided fertile breeding grounds for mosquitoes. (The answer is probably both.)
"Positions have hardened," said Dr. Gerald T. Keusch, director of the Fogarty International Center, the branch of the National Institutes of Health devoted to promoting scientific research overseas. "In the heat it has not been possible to step back and look at the light."
On one side is the nonprofit World Wildlife Fund and Physicians for Social Responsibility, a doctors' group concerned with environmental health. They argue that even small amounts of DDT sprayed inside homes are harmful to the environment and cite studies suggesting that the pesticide turns up in the breast milk of nursing mothers and has other "subtle effects on human health."
Taking its cue from Mexico, the wildlife fund is pressing for a ban on DDT by 2007. But the idea of a specific date is extremely contentious, and the State Department official said the United States would not ask for on
On the other side are two scientists' groups, the tropical medicine society, and the Malaria Foundation International, a nonprofit organization dedicated to promoting research. Several months ago, at the behest, curiously enough, of a Vancouver environmental lawyer and cell biologist, Amir Attaran, the foundation posted a letter about the negotiations on its Web site, arguing that "setting a firm deadline to ban DDT places an unethical burden on the world's poorest countries."
As of Thursday, 371 scientists, including 3 Nobel laureates, had signed. As the group's founder, Dr. Mary Galinski, a molecular biologist at Emory University in Atlanta, explained: "We don't want a knee-jerk reaction to ban DDT."
The debate is occurring as malaria is making a deadly comeback, re-emerging in regions where it was once under control and killing many more people than it did decades ago, at least partly because of a reduction in DDT use. The World Health Organization estimates that there are 300 million to 500 million new cases of the disease each year, and last year started a project called Roll Back Malaria to combat it.
There are drugs to treat malaria, but some patients cannot afford them and drug resistance is an increasing problem. So the best means of prevention is to keep mosquitoes from biting people. At least one expert, Dr. Donald R. Roberts of the Uniformed Services University of the Health Sciences in Bethesda, Md., argues that "DDT is the best insecticide we have today for controlling malaria."
In the late 1970's, Dr. Roberts, a medical zoologist, traveled to Brazil to conduct experiments in malaria control. He built two houses and sprayed the inside of one with DDT. Hundreds of mosquitoes entered the unsprayed house, he said. None entered the sprayed house. Since then, Dr. Roberts has become an ardent defender of DDT. "We have got to stop pressuring countries to stop using DDT," he said. "It is immoral."
Others, including Dr. Galinski, say they have no problem eliminating the pesticide, so long as alternatives are in place. But that is a frightening thought to Dr. Wen Kilama, a Tanzanian entomologist who in June presided over an expert panel, convened by the World Health Organization, to debate the future of the pesticide in malaria prevention.
Because mosquitoes develop resistance to pesticides, Dr. Kilama says that getting rid of DDT would be a mistake. "The mosquitoes are very complex and one should not rely on one measure alone, particularly one type of insecticide," he said in a telephone interview last week. "It's like when you fight, you have a pocketful of arrows and now you have only one arrow left."
Tanzania no longer uses DDT; the country cannot afford it, Dr. Kilama said. But with the economy improving, he added, "I can see a lot of hope coming up" that Government-sponsored spraying might resume. In the meantime, some Tanzanians sleep under nets soaked in pyrethroids, another chemical. But the nets cost $4 to $5 apiece, too high a sum for many villagers, and Dr. Kilama said they work only by "mass effect," which means entire neighborhoods must use them.
Further south, in Botswana, health officials have also abandoned DDT, but for a different reason. Only three countries -- China, India and Mexico -- still manufacture the pesticide, and Thandie Phindela, a malaria control officer in Botswana's Ministry of Health, said the country could not get a reliable supply this year. "The environmentalists are trying to put pressure on the use of DDT," she said. "We had to resort to pyrethroids."
But pyrethroids are more expensive. According to Kathleen Walker, an entomologist with the E.P.A., the cost of treating one house with DDT ranges from $1.60 to $8.50, compared with $4.20 to $24 for pyrethroids. In the end, she said, some countries may have to abandon house spraying altogether and begin research on other, cheaper alternatives.
That is the World Wildlife Fund's view: its contaminants expert, Richard Liroff, urges "more creative thinking about moving away from DDT." He points to an experiment in India, where gambusia -- a larvae-eating fish -- were deposited in bodies of water where mosquitoes breed. But Dr. Kilama, of Tanzania, said such steps are not practical in a country where a hippopotamus footprint after a heavy rain can create an instant breeding ground.
As the debate continues, the World Health Organization is drafting its own plan to help countries cut back on DDT. But the organization has no idea how much the effort will cost; the price tag will vary from nation to nation. As to who will pay, said Jenny Pronczuk, a chemical safety expert, "Well, that's a problem."
Read open letter to treaty delegates and sign.
Read current list of signatures.
Copyright © 1999-2003
Malaria Foundation International
All Rights Reserved