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NATURE

Opinions vary on fate of DDT

peregrine falcon
Since the U.S. ban on DDT, the peregrine falcon population has rebounded.  

September 8, 1999
Web posted at: 1:05 PM EDT (1705 GMT)

ENN



Negotiations on an international treaty to regulate persistent organic pollutants, known as POPs, resume this week in Geneva, and the use of DDT to control malaria in developing countries will certainly be a hot topic on the agenda.

The World Wildlife Fund, Physicians for Social Responsibility and Malaria Foundation International all have varying positions on the fate of DDT as method of malaria control, and each hopes that their research and opinions will catch the attention of the delegates at the conference.

DDT has been used since the 1940s in Africa and elsewhere to check the spread of malaria, and works by repelling or killing the mosquitoes that carry the virus. Often it is sprayed on the interior walls of homes, which is where engorged mosquitoes appear to land most.

Malaria kills up to 2.7 million people a year and almost all fatalities are either children or pregnant women. While DDT has been banned in many countries, 23 countries still use the chemical for agricultural purposes and disease control.

WWF, Physicians for Social Responsibility and the Malaria Foundation all generally agree that DDT is harmful to the environment and ought to be phased out of use at some point, and that western developed countries need to help monetarily and otherwise with the transition. However, they have different ideas about how these phase-outs should be handled.

WWF advocates that DDT be phased out and banned from use by the year 2007. "Such a deadline is an important tool for motivating donor behavior. Without it, it is much more likely that the recent history of under-funding of work on malaria will continue into the future," said WWF. The 'donors' referred to here are western countries that WWF feels must help fund the transition.

WWF's call for a specific deadline to ban the use of DDT is "profoundly unethical," said Dr. Amir Attaran of the Malaria Project, a lobbying group for the Malaria Foundation. Attaran authored an "open letter" to diplomats negotiating the POP treaty that defends the use of DDT and calls on the delegates to reject the call for a ban. This letter was written on behalf of and circulated by the Malaria Foundation, and over 370 scientists and doctors have signed it so far. It has been sent to the treaty delegates representing developing countries.

In the letter, Attaran writes, "In our view, setting a deadline for the elimination of DDT — whether that deadline is in 2007 or some other date — unacceptably endangers health in countries with malaria." The Malaria Foundation believes that the elimination of DDT as a weapon against malaria should only take place after "western countries research and successfully implement effective, affordable alternatives to replace DDT," states the letter.

Physicians for Social Responsibility says its goals are an improvement of malaria control and the phase out of DDT, both at the same time. "We believe that this is possible," said Sharon Newsome, director of the Environment and Health Program for the physician group.

To achieve this, plans to phase out the use of DDT ought to be up to the 23 individual countries that still use it, with the emphasis at the treaty discussions centering on how to help these countries fund their programs to move away from DDT, said Newsome. Physicians for Social Responsibility does not specify a date by which the phase out should happen.

To help countries build programs for phasing out DDT, Physicians for Social Responsibility has published the Modern Malaria Control Handbook, which contains medical and scientific information on all aspects of malaria control. The book outlines 150 studies that demonstrate how it is possible to control malaria without the use of DDT, and "emphasizes an integrated public health approach," said Newsome, which would include case detection and treatment, vector habitat elimination and control, and community education and action. "There is no question that a well-designed program does not have to rely on DDT," she said.

One malaria control technique that both the physicians and WWF support as an alternative to DDT is the impregnation of bednets with synthetic pyrethroids. These chemicals are not as toxic as DDT and are thought to break down in the environment more readily.

In a WWF study in Africa, researchers tested the effectiveness of repelling or killing mosquitoes using bednets impregnated with synthetic pyrethroids versus ones that were not. The results showed that there was a substantial decline in malaria cases where the impregnated bednets were used, said Richard Liroff of WWF.

The Physicians for Social Responsibility believe that pyrethroids can take the place of DDT in an integrated public health approach. The system they advocate would include the identification and treatment of malaria, habitat elimination, community education and controlling the disease using bednets impregnated with pyrethroids.

Attaran considers pyrethroids to be a possible alternative and thinks that they can be effective in some places, but doubts the chemicals' ability to work everywhere. He also pointed out that pyrethroids are much more expensive than DDT and that this is a critical issue for poor developing countries. Not only do they cost more, pyrethroids require more applications that DDT, which adds to the overall price tag.

Liroff of the WWF agrees that pyrethroids are more expensive than DDT, but he believes that recent studies focusing on the application the pesticide indicate it will be possible to find ways to lower the cost.

WWF's parent organization, Worldwide Fund for Nature released a study Tuesday showing that there are alternatives to DDT that would be less harmful to the environment and human health, and just as cheap. The study was conducted in six areas in Africa, India, the Philippines, South America and Mexico and focused on variety of alternative techniques.

These include pesticide-impregnated bednets to reduce the need for indoor spraying, odor-baited cloth targets to attract and kill mosquitoes, lower-risk pesticides used in rotation to avoid the development of resistance, introduction of natural predators and sterile insects, and widespread elimination of mosquito breeding grounds.

One sticking point between the different organizations has to do with whether or not a ban of DDT has even been called for. WWF has made clear that they feel there should be a ban by 2007. But, said Newsone, "Negotiators have never, ever said that they were going to ban DDT."

"This is totally false," said Attaran. To back up this claim, Attaran looks at the process by which the diplomats are negotiating. At the last treaty meeting, the representatives were split up into working groups, which would then return to the plenary session with their results.

A certain working group was asked to divide through consensus the various POPs into two lists — chemicals that ought to be banned, and those whose use should be restricted. DDT was not placed on either list, and because the group could not reach consensus over the fate of DDT, Attaran feels it is implicit that some country in that group is definitely thinking about banning the substance.

Attaran also points out that the treaty process has not gotten very far, and that none of the representatives have really stated their opinion publicly about anything yet. It is because of this that the open letter was written, to let the diplomats who have not stated their position on DDT have an opportunity to read the letter, ponder the information it presents and use it to help them come to a conclusion about the fate of DDT.

Though effective at controlling malaria, DDT does not break down in the environment and is known to bio-accumulate in fish, wildlife and people. Studies have also shown that DDT, like all POPs, can travel thousands of miles from where it was used through air, water and bird migration, causing persistent contamination.

The chemical is thought to pose a considerable health hazard to animals, with recent research linking it to altered sex ratios in gull populations, the thinning of eggshells for birds of prey and the suppression of the immune system in dolphins and harbor seals.

Although its influence on human health is unclear, DDT has shown up in samples of breast milk all over the world, even where the chemical is not used. Scientists are concerned about its effect on the brain development of fetuses and of children who are exposed to this milk. One recent study shows a relationship between DDT and reduced lactation in new mothers in certain areas of Mexico, Africa and the United States.

The research is not conclusive and study of the pesticide still continues.

Copyright 1999, Environmental News Network, All Rights Reserved



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RELATED SITES:
Physicians for Social Responsibility
Malaria Foundation International
World Wildlife Fund: WWF's efforts to phase out DDT
Malaria Foundation International Cover Letter
Indoor Usage of DDT for Malaria Control
United Nations Environmental Programme
WWF study shows effective anti-malarial alternatives to DDT
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