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A renewed role sought for DDT in malaria war

Sunday, July 21, 2002

By Wallace Chuma, Post-Gazette Staff Writer

Ever since local author Rachel Carson attacked the use of DDT 40 years ago in her book "Silent Spring," the pesticide has come to symbolize the devastation humans can cause to the environment.

But now, many health experts and activists around the world say DDT should be reintroduced to fight one of the deadliest diseases on the planet -- malaria.

The issue is especially critical in sub-Saharan Africa, a region that accounts for more than 90 percent of the world's malaria deaths. There, several countries are considering once again using the pesticide to kill the mosquitoes that carry the parasitic disease, which strikes children particularly hard.

At the time the United States banned DDT in 1972, the global crusade against malaria had achieved substantial success. But when most African nations were no longer able to use DDT, the disease rebounded and is now back to its pre-1972 levels.

According to the World Health Organization, malaria kills a child around the world every 30 seconds, and is Africa's second most deadly disease, just behind AIDS.

Malaria afflicts 300 million to 500 million people and claims 2 million to 3 million lives per year; and the United Nations estimates that it cuts Africa's economic growth by 1.3 percent yearly.

Victims of bites from carrier mosquitoes usually succumb to fevers, head and body aches and drenching sweats. For children, pregnant mothers and people with weakened immune systems, these initial symptoms are often followed by profound anemia or uncontrollable seizures, and the patients can die in a matter of hours.

DDT, which stands for dichloro-diphenyltrichloroethane, had been an effective and relatively cheap means of controlling mosquitoes. The pesticide is sprayed inside homes and on mosquito breeding sites.

While some environmental activists have raised fears that DDT can harm human beings, the objective evidence is weak. In a 2000 article in The Lancet, a respected British medical journal, English toxicologist A.G. Smith said that despite years of studies, "The effects on human beings at likely exposure levels [of DDT] seem to be very slight," and much weaker than with some other pesticides.

Nevertheless, DDT has been banned in the United States since 1972 because its excessive use in agriculture threatened the extinction of several bird species, notably the bald eagle.

Carson's key role

Carson, a Springdale Borough native, had as much to do with the ban as anyone. She and other environmentalists contended that DDT from agricultural use -- farmers in the United States used to put 80,000 tons on the fields each year -- was being washed into rivers and entering the food chain. The DDT would contaminate fish, and when they were consumed by the bald eagle and other birds of prey, the pesticide caused their eggs to become too fragile to hold their tiny embryos.

For African countries and other parts of the developing world which had long relied on the United States for DDT supplies, the ban was a severe blow. Not only were they faced with finding new suppliers, but U.S. officials waged an anti-DDT campaign through the United Nations and the U.S. Agency for International Development.

In the end, with the exception of South Africa, African nations forgot about DDT, and tried other methods of malaria control.

Since the ban, scientists have faced the challenge of coming up with an environmentally friendly yet economical substitute for DDT to control mosquito breeding.

They haven't succeeded yet.

Fours years ago, the United Nations Children's Fund, the World Health Organization and the World Bank launched the "Roll Back Malaria" campaign in a bid to prevent and control the scourge.

The campaign involves the use of mosquito nets, mosquito coils that are burned to drive away the insects and other repellents. But these methods have had limited effectiveness, especially in developing countries, where per capita income is extremely low and people often use what money they have for food, shelter and clothing rather than mosquito controls.

Because of that, DDT is being seriously considered again, mainly as a spray on the walls of homes.

Zimbabwe's acting minister of health, Dr. David Parirenyatwa, said last week: "As a country, we are already on the way to reintroducing it. Research has shown that the pesticide is effective in selective indoor spraying. More so, it is affordable."

In April, health ministry representatives from the 14 nations in the South African Development Community agreed in principle that something urgent had to be done to contain the increasing child death rate caused by malaria, and that DDT would probably be one effective tool.

'A critical situation'

"We agreed ... that the insecticides we normally use are too expensive now," Parirenyatwa said. "At the same time we are faced with a critical situation. So we will assess areas most suitable for the use of DDT to complement the fight against malaria."

Only 23 countries in the world now use DDT, and China and India are the major manufacturers of the pesticide.

And while the United States is unlikely to approve DDT again, some experts here say that policy shouldn't necessarily apply to the rest of the world.

Dr. Bernard Goldstein, an expert in environmental health and dean of the University of Pittsburgh Graduate School of Public Health, said there would be no justification for reintroducing DDT in the United States, where malaria is not a major killer. "At the same time, we should also be careful not to limit the use of DDT in other countries, especially those nations without resources."

Some environmentalists fear that if DDT is used again in developing nations, a black market would soon develop to use it as an agricultural pesticide. But Goldstein said that's a problem that authorities in those countries will have to address.

Dr. Douglas J. Perkins, an assistant professor of infectious diseases and microbiology at Pitt, said the challenge for most countries affected by malaria is a lack of resources for fighting the disease; so it is natural for them to favor the cheapest approaches.

Perkins, who is studying severe malarial anemia in western Kenya, one of the world's hot spots for malaria, acknowledged that limited use of DDT would cut the breeding cycle of mosquitoes and reduce mortality.

But he said that if that were tried, it should be accompanied by efforts to develop an effective malaria vaccine and better drug treatments.

And Ellen Dorsey, executive director of Chatham College's Rachel Carson Institute, said that if DDT were used again in Africa, its effects wouldn't necessarily be confined to that continent.

Paying for alternatives?

"We've learned in the past 40 years that environmental issues know no national boundaries. If we allow DDT in other parts of the world, the effects will still come back to the U.S.," Dorsey said.

The challenge for this nation, she said, is to take the lead in setting global standards for chemical use and providing financial support to developing countries so they can fight malaria without having to use toxic chemicals.

"We allow the chemical death rain to fall as though there were no alternative, whereas in fact there are many. In our ingenuity, we could soon discover many more, given the opportunity," she said.

One reason the malaria scourge and the debate over DDT are not major topics in the U.S. is that only a few people ever have contact with the disease.

Between 1997 and last year, there were only 22 malaria cases reported to the Allegheny County Health Department by local residents, and all of them were among people who had traveled overseas.

Health Department spokesman Guillermo Cole said none of the local people died from the disease.

But in sub-Saharan Africa, malaria immediately invokes images of death. And that is why so many officials are looking at the lives they could save in the short term by bringing back a pesticide that some thought had disappeared for good.

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