Respond to this Article March 2003

Better Living Through Chemistry

DDT could save millions of Africans from dying of malaria--if only environmentalists would let it.

By Alexander Gourevitch

By most measures, Uganda is one of the success stories of African development. Under President Yoweri Museveni, a former guerrilla and darling of the international donor community, Uganda has achieved GDP growth of 6 percent per year, gradually expanding political freedoms, and a measure of peace. In a continent beset by poverty and political disorder, Uganda has slowly become a model for how to get things right. Even the AIDS epidemic, which infected an estimated 20 percent of Uganda's population a decade ago, seems to be under control.

But a more old-fashioned plague has come back to haunt Uganda: malaria. The mosquito-borne illness costs Uganda more than $347 million a year. Today, up to 40 percent of the country's outpatient care goes to people thus infected. Total infections are so numerous that the government doesn't even try to track them, but last year, 80,000 people died of the disease, half of them children under the age of five.

So last December, at a convention of regional health ministers held in Kampala, Jim Muhwezi, an army officer and member of parliament who today serves as Uganda's minister of health, announced the launch of a new campaign against the epidemic, using Dichloro-diphenyl-trichloroethane, or DDT. To Muhwezi, DDT--a pesticide widely proscribed in Europe and banned in the United States since 1972--was a cheap, effective weapon against malaria for a poor country with minimal public health resources. And in South Africa, the recent reintroduction of DDT spraying had reduced malaria rates by 75 percent over two years. "Instead of sitting back and watching our people die of malaria and lose in economic terms," he proclaimed, "an all-out war against the disease must be waged."

But Muhwezi encountered opposition almost immediately. After his announcement, Andrew Sisson, a USAID official attending the Kampala convention, told one session that in the United States DDT had been found to "cause environmental problems," according to Muhwezi. A member of Uganda's parliament warned Muhwezi that Europe and the United States might ban imports of Uganda's fish and agricultural exports, a fear shared by local environmentalists, according to the Nairobi East African, Kenya's leading daily. Since USAID prefers to fund bednets as a solution to Uganda's mosquito problem, Muhwezi is unsure if he'll be able to obtain international assistance to fund a DDT-based malarial eradication project. "We hope they'll come along. But if they don't, we'll do it alone."

Until recently, one might have considered Uganda's to be a tragic but unavoidable tradeoff--deprive many of an uncontaminated natural environment, or save few from malaria. In much of the world, after all, the popular conception of DDT is of a dangerous and toxic chemical that pollutes water and poisons the food chain; in the United States, DDT is remembered as the pesticide that helped put bald eagles on the endangered species list. But a growing body of scientific evidence suggests that the popular conception is wrong. Older studies on the effects of DDT have been called into question, and newer ones militate against the notion that DDT is inherently dangerous. For the kind of use Muhwezi has in mind, in fact, DDT may not be dangerous at all.

The stakes are high. Uganda is but one of many African countries suffering from malaria epidemics. Africa already accounts for 90 percent of the 2 million deaths and 300 million infections around the world each year, and it costs the continent 1.3 percent in annual growth per year, according to the economist Jeffrey Sachs. Mosquitoes are increasingly resistant to the main insecticide put into use to replace DDT; and the parasite that causes the disease has, in recent years, become increasingly resistant to the cheapest and most common medical treatment, a drug called chloroquine. Yet most international aid agencies, development agencies, and lending institutions have moved away from funding spraying projects in general, and DDT use specifically. Without assistance, African governments cannot afford spraying programs, leaving them bereft of a safe, effective, and cheap defense. Which means that aid agencies and governments opposed to DDT use may end up costing Africa millions of needless deaths.

Bad Medicine?

DDT first came to the United States after the late 1930s, when Dr. Paul Muller, a chemist with the Swiss firm J.R. Geigy, found that minuscule amounts of DDT killed just about every insect he could find. Slow to break down, a single application of DDT remained toxic for up to a year, which made spraying programs much easier to administer, especially in remote locations. It was cheap to produce, easy to ship, and did not require the extensive safety gear of other insecticides. And remarkably, even when mosquitoes developed resistance to the toxicity of DDT, it still acted as a repellent and irritant, driving nocturnal mosquitoes out of homes before they had a chance to bite. (This mechanism was discovered later--originally, it was just toxicity and safety that attracted people to DDT. )

Impressed, the U.S. military deployed DDT in 1942 to fight a third front against diseases like malaria, dengue, and typhus, which until then had seriously impaired U.S. fighting forces, especially in Italy and the Pacific Theater. Army personnel sprayed soldiers, dusted beachheads, and even deloused concentration camp survivors with DDT. After the war, DDT came into use for commercial and public health purposes. Farmers used DDT to protect cash crops like cotton, corn, and apples from a wide variety of agricultural pests. Around the same time, the U.S. government launched an ambitious DDT-centered malaria eradication project which by the early '60s had virtually eliminated malaria from Southern Europe, the Caribbean, and parts of East and South Asia. (In India, for example, annual deaths went from 800,000 to zero.) At the time, DDT was thought to be such an effective and useful substance that in 1948, Muller received a Nobel Prize in medicine. "To only a few chemicals does man owe as great a debt as to DDT," declared the National Academy of Sciences in a report in 1970. "In little more than two decades, DDT has prevented 500 million human deaths, due to malaria."

But by then, the tide had begun to turn against DDT. During the 1960s, reports began to emerge of increasing resistance to the drug among insects, probably sparked by its widespread use in agriculture. At the same time, case-detection followed by medical treatment began to emerge as the new model for malaria control. (By 1979, the World Health Organization had formally endorsed this approach over that of preemptive insecticide spraying.) Most important, however, was the publication of Rachel Carson's book Silent Spring in 1962.

Carson's book was a lyrical broadside against synthetic chemicals in general, but against DDT in particular. She noted that as DDT seeped into the ground and ran off into streams, worms and fish stored it in their fatty tissues. Over time, songbirds like the robin and other prized avians, including bald eagles and peregrine falcons, ingested enough contaminated prey that they died of DDT poisoning. If they didn't die outright, Carson warned, studies also showed that DDT prevented reproduction by thinning eggshells. Carson also trumpeted studies of rats which suggested DDT was a liver carcinogen, and gathered anecdotal evidence of harm in human beings, like a farmer whose bone marrow wasted away after repeatedly inhaling a mixture of DDT and benzene hexachloride he used to spray his fields.

Silent Spring practically launched the modern environmental movement. The Environmental Defense Fund cut its teeth in national politics raising public alarm over--and bringing lawsuits against--DDT use, which in turn pushed the recently created Environmental Protection Agency to hold a series of hearings on DDT. The critics were so successful that, although the administrative judge presiding over the hearings concluded that "DDT is not a carcinogenic hazard to man ... DDT is not a mutagenic or teratogenic hazard to man," the EPA banned it anyway in 1972. (Chemical companies, of course, were more than happy to supply the less practical, more expensive alternatives.) The U.S. ban was a turning point; soon after, anti-DDT sentiment went global. Environmental organizations campaigned against its use abroad, wealthy countries began to restrict funding for DDT projects, and the World Health Organization shifted away from promoting it for public health uses. By 2000, a group of environmental activists, led by the World Wildlife Fund, was promoting a U.N. "persistent organic pollutants" treaty known as the Stockholm Convention, which would have banned DDT worldwide for all uses. Only at the last minute was an exemption added for public health use.

Reconsidering a Rogue Agent

But over the years, mainstream scientific opinion has absolved DDT of many of its supposed sins. Indeed, the Stockholm Convention partially backfired because it brought to light a slew of studies and literature reviews which contradicted the conventional wisdom on DDT. Like nearly any chemical, DDT is harmful in high enough doses. But when it comes to the kinds of uses once permitted in the United States and abroad, there's simply no solid scientific evidence that exposure to DDT causes cancer or is otherwise harmful to human beings.

Not a single study linking DDT exposure to human toxicity has ever been replicated. In 1993, Mary Wolff, an associate professor at Mount Sinai Medical Center, published a small study linking DDT exposure to breast cancer. But numerous follow-up studies with human subjects--including one large five-study review comparing 1,400 women with breast cancer to an equivalent number of controls--found no evidence for the link. David Hunter, an epidemiologist at Harvard University who ran one of the follow-up studies, says of the breast cancer connection, "the studies have really put that idea to rest." Similarly, various studies have contradicted initial concerns that DDT might cause myeloma, hepatic cancer, or non-Hodgkins lymphoma.

Other reports over the years postulating human toxicity in DDT exposure turned out to be cases of correlation without causation. In its heyday, for instance, DDT was mixed with a variety of dangerous chemicals, sometimes petroleum derivatives. In every anecdote of death or human harm by DDT that Carson related, the chemical had been dissolved in some other, highly toxic, substance, such as fuel oil, petroleum distillate, benzene hexachloride, or methylated naphthalenes. Such "mixtures with other chemicals or solvents," a 2000 review article in the medical journal The Lancet noted, were responsible for many of the reported deaths from DDT and for other problems like dermatitis. But even these dangers do not extend to public health use, where DDT is dissolved in water and sprayed as a thin film.

That's not to say that DDT is harmless. Matthew Longnecker studied American women who had lived during the period of high DDT use and suggested that high levels of DDT in the bloodstream of pregnant women might cause pre-term delivery and low birthweight, for instance. But public health use doses--two grams per square meter of wall sprayed indoors at most every six months--aren't likely to produce those concentrations. Since DDT is not absorbed through the skin, spraying DDT in houses is unlikely to expose pregnant women--or anyone else--to amounts great enough to pose a danger. And scant evidence suggests DDT gets into the environment in significant amounts when sprayed indoors. According to a WHO report in 2000, "The targeted application of insecticides to indoor walls ... greatly reduces dispersion of the chemicals into the environment. For this reason, the environmental risks from such targeted measures [are] considered minimal."

Agricultural use, on the other hand, is very different, amounting to literally tons of the chemical sprayed outdoors every few weeks. But almost nobody who supports using DDT to combat malaria wants to see it come back into use as an agricultural pesticide. The ideal pesticide is one that will stay on the crop but break down and virtually disappear by the time of harvest. DDT, on the other hand, is persistent and takes a long time to break down--which is why it tends to accumulate in the environment over time. "Even though there's no evidence right now that it's harmful to human beings, there's no sense in taking the risk of using it when other pesticides, better-suited for agricultural use, are available," says Donald Roberts, an expert on tropical health at the Uniformed Services University of the Health Sciences in Bethesda, Md. DDT is also so cheap that, when it was legal, farmers often used it well in excess of the officially prescribed amounts.

Yet environmental activists resist distinguishing between the agricultural and public health uses of DDT. Richard Liroff, a spokesman for the World Wildlife Fund, says, "We hang most of our argument" against DDT spraying on studies like Longnecker's. But the clear benefits of DDT use would seem to outweigh the potential dangers. Malaria, after all, also causes low birthweight in newborns (and mental retardation in infants). And while DDT may prove to have as-yet-unknown side effects, malaria has a well-known, direct effect: It kills millions of people a year.

Environmental Mea Culpa

But although prevailing scientific opinion favors the use of DDT in anti-malarial campaigns, international aid agencies still take their cues from environmental groups. Roll Back Malaria (RBM), a WHO-sponsored consortium of aid agencies, international institutions, and NGOs, has a 40-page action plan for reducing countries' reliance on DDT, with the goal of eventually eliminating its use for public health purposes. And the international donors who fund most anti-malaria campaigns usually follow RBM's technical guidelines. "Bottom line is, [RBM] favors the ultimate elimination of DDT from the malaria toolbox," says Dr. John Paul Clark, a former RBM adviser with expertise in DDT, although he concedes that "there are a number of countries that are not economically or epidemiologically ready to make that switch at this time."

While few organizations have a de jure ban on DDT projects, very few have actually put money behind them. No international aid agency will fund DDT use. The World Bank is currently funding a malaria control project in Eritrea on the condition that the country not use DDT. The recently formed Global Environmental Facility has donated money to projects in both Africa and South America, likewise with the intent of weaning recipient nations off DDT. In an emailed statement, USAID's malaria team informed me that its "activities are focused to reduce reliance on the pesticide DDT." They are "emphasizing prevention, medical intervention, and mosquito nets dipped in pyrethroid." Richard Tren, head of a group called Africa Fighting Malaria, says that the international aid agencies of Sweden, the United Kingdom, Norway, Japan, and Germany have all told him they would not fund DDT projects, nor will UNICEF. And lacking the resources to develop domestic programs on their own, most African countries bend to the requirements of these international funders. (South Africa is one of the few African countries wealthy enough to fund its own program.)

Those alternatives that aid agencies will fund are either less effective, more expensive, harder to administer, or inadequate on their own. "Eco-friendly" approaches like mosquito repellent trees or mosquito-larvae-eating fish have been tried in East Africa, where the malaria epidemic is particularly bad, but with little success. The pesticide pyrethroid was originally developed as a biodegradable DDT alternative, but mosquito resistance throughout Africa is rendering it increasingly useless. Other substitute pesticides, like carbamates and organophosphates, have turned out to be no more safe or effective than DDT, and most lack DDT's ability to repel mosquitoes even after they build up resistance to it. DDT is at least four times less expensive than the cheapest alternative--even though it is only still produced by one factory in India--and requires less frequent spraying. Both are significant advantages in poor African countries with minimal infrastructure, where every dollar not spent bringing malaria under control can be used for other public health priorities, such as supplying clean water. "DDT is long-acting, the alternatives are not," says Donald Roberts. "DDT is cheap, the alternatives are not. End of story."

Amir Attaran, a former WHO expert on malaria, once supported funding alternative pesticides, but South Africa's experience changed his mind. "If South Africa can't get by without DDT, it's pretty much as if to say that nobody can," says Attaran. "They really tried to phase this stuff out, and had the budget to afford the alternatives ... They tried and failed." (South Africa had switched from DDT to pyrethroid in the mid-1990s, but switched back in 2000 when the mosquitoes became resistant to the pyrethroid, causing malaria cases to skyrocket). There has also been a move to use insecticide treated bednets, particularly in East Africa, but few believe that bednets alone can address the problem. "All large-scale programs that have been successful have been based on insecticide control," notes Brian Sharp, Director of the Malaria Research Program for South Africa's Medical Research Council and director of their spraying program. "I don't believe we should discriminate against [bednets or DDT] ... One has to practice integrated vector control ... [But] DDT is an important tool in this fight."

It is difficult to get a clear answer from aid agencies why they won't fund DDT. They may be hesitant because they receive contradictory guidance: National DDT bans conflict with WHO guidelines saying it's safe and effective, which in turn conflict with Roll Back Malaria's blueprint for phasing out DDT. Nobody seems to want to stick his or her neck out to clarify things. Most importantly, already-underfunded Western aid agencies are concerned about a backlash if they did fund DDT, since doing so might well provoke the lingering fear of DDT among the citizens of wealthier countries. Several experts told me that they are specifically afraid of tangling with the environmental lobby. When Attaran circulated a letter two years ago protesting a total ban on DDT, the head of Roll Back Malaria excoriated him for undermining RBM's relations with environmental groups. Attaran, formerly a lawyer for the Sierra Club, thinks the environmentalists should correct the misperceptions they have perpetuated. They should do what "the pharmaceutical [companies] did on access to AIDS medicine in Africa. They did a mea culpa. The environmentalists need to do the same thing."

"It Shouldn't Be This Hard"

That's not to say that all anti-malaria aid dollars should go to DDT. It makes sense to balance between funding available measures and investing in new ones. Presently, however, too little money goes to DDT at a time when few effective tools are available. Local conditions will determine the best course of action; in some places, DDT may be less effective than others, and funding should be adequate and open enough for countries to experiment with what's right for them. Brian Sharp, for instance, argues that money could go to a rotational spraying program, under which DDT would be rotated with other insecticides to prevent the development of resistance among mosquitoes and extending the effectiveness of non-DDT alternatives. Yet opposition to DDT has undercut even that compromise.

An environmentalist mea culpa would be a start, but in the United States, at least, nothing short of congressional hearings or an executive order from the Bush administration is likely to spur USAID to change its ways. The most direct approach would be a reconsideration of the EPA ban on DDT, with an explicit mandate to use some of the foreign aid budget for DDT spraying should countries ask for it. USAID's current goals for Uganda are for at least 60 percent of the country's population to have access to drugs and bednets; Jim Muhwezi, for one, would like USAID to set its goals higher. But it's not easy to get them to listen, especially with poor African countries trying to curry favor with aid agencies. Indeed, neighboring Tanzania has stayed away from DDT because, among other things, it is too "controversial," according to Alex Mwita, the program manager for Tanzania's National Malaria Control Programme. "You have to remove the myths that people have in their minds that it is not a good chemical." It shouldn't be this hard. African governments know what they need to do to control malaria--they just need the money. Like Mwita, Brian Sharp says he's waiting for the West to get over its "misguided opposition to DDT." So is Africa.

Alexander Gourevitch is an American Prospect writing fellow.


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