DDT has been pesticide non grata in environmental circles ever since Rachel Carson wrote Silent Spring, a landmark 1962 book linking agricultural pesticides to ecological devastation. Now it appears that, with the support of the U.N. and most major industrialized nations, environmentalists are nearing their long-standing goal of instituting a worldwide DDT ban. But some tropical disease experts are warning that the proposed ban could reward First World environmental righteousness at the expense of the Third World, where DDT is used to combat malaria.
At the urging of environmental groups such as the World Wildlife Fund (WWF), the United Nations Environmental Program has initiated discussions of a ban on DDT and 11 other chemicals known as "persistent organic pollutants." More than 100 countries are participating in the talks, and a final decision on the ban is expected by next year. Supporters of the initiative note that DDT builds up in the food chain, can kill fish and other nonmammals following prolonged contact, is a suspected human carcinogen, and can travel great distances through the atmosphere -- DDT used in Latin America has turned up in Canada (hence the push for a global ban).
But DDT's effectiveness in controlling mosquito populations and mosquito-borne illnesses makes it an important public health tool in the Third World. Malaria kills an average of 2,800 African children every day and 2.7 million people worldwide each year. (By comparison, there has never been a documented human death caused by DDT exposure.)
"Even a tiny loss in the efficiency of...malaria control programs...would result in a tremendous number of additional deaths from the disease," wrote Dr. Amir Attaran, head of the Washington, D.C.-based Malaria Project, in a draft letter he is circulating among malaria specialists. "The relevant question is not whether DDT use has some risks (it does), but whether the risks outweigh the...public health benefits of malaria control (they do not)."
Although it is not clear how many countries use DDT to control malaria -- few will admit to using the chemical -- international pressure has led many to stop, sometimes with disastrous results. According to Don Roberts, a malaria specialist for the Defense Department who has studied World Health Organization data on malaria, Belize used DDT to virtually eliminate malaria by 1970, but stopped its spraying programs in 1992. By 1994, around 18,000 of the country's 200,000 people had contracted the disease. Spraying soon resumed, and the country's caseload for 1998 fell to about 2,000.
To be sure, using DDT as an agricultural pesticide is not safe -- it releases enormous quantities into the atmosphere and is already illegal in most countries. But very little DDT is needed for malaria control: The amount used to spray 1.6 square miles of cotton for a single growing season could treat every home that needs it in Guyana, a nation of 700,000, says Roberts.
Environmentalists argue that DDT is not essential to malaria control. "Many countries have moved away from using DDT and found alternatives," says Rich Liroff, co-manager of the DDT program at WWF. A 1998 WWF report suggests using bed nets and alternative pesticides, as well as eliminating pools of water where mosquitoes breed.
But effective alternatives tend to be far more expensive. Roberts has found that in one Latin American country -- he preferred not to name it so as not to expose its DDT use -- it costs $22 a year to treat a house with the widely used DDT alternative deltamethrin, and only $4.64 to treat the same house with DDT.
Malaria experts say they don't oppose a DDT ban, as long as effective alternatives are in place that won't bankrupt Third World public health systems. One way to guarantee that, they say, is for First World governments to subsidize DDT alternatives. So far, no such offers are on the table.