DDT: A useful poison

Dec 14th 2000
JOHANNESBURG
From The Economist

ON DECEMBER 10th, a small victory for common sense was won in Johannesburg. Delegates from 120 countries, who were trying to draft a United Nations treaty to ban "persistent organic pollutants", agreed to exempt DDT if it is being used for malaria control.

For rich people, malaria is not much of a problem. The Anopheles mosquito, which spreads the disease, was eradicated from Europe and North America half a century ago, largely through the use of pesticides such as DDT. Having employed the stuff to such great effect, however, rich countries then banned it because of its environmental consequences (it accumulates in animals that eat insects, slowly poisoning them).

That is fair enough. But with a convert's zeal, many rich countries have tried to impose their decision on the poor world, where about 300m people suffer from malaria every year, and more than a million die. Sick people find it hard to work, so the disease helps to keep poor countries poor. Jeffrey Sachs, a development economist at Harvard University, estimates that sub-Saharan Africa would be almost a third richer today had the disease been eradicated in 1965.

The most cost-effective way of fighting malaria is to spray the insides of houses with DDT. This either kills the mosquitoes, or drives them away. The recommended alternatives, pyrethroids, are four times as expensive as DDT and also less effective.

The widespread use of DDT in the 1950s and 1960s all but eliminated malaria in several developing countries and saved an estimated 500m lives by 1970. Since then, the use of the stuff has shrunk. Of the roughly 100 countries where malaria is endemic, only 23 now employ DDT to fight the disease. And that is frequently the fault of aid donors who help to finance the battle against malaria.

In the early 1990s, for example, the United States Agency for International Development stopped the governments of Bolivia and Belize from using DDT. In Madagascar, the United Nations Development Programme tried to persuade the government to replace DDT with Propoxur, a less effective pesticide. To its credit, Madagascar refused. In Mozambique, both NORAD, the Norwegian development agency, and SIDA, its Swedish counterpart, said that they could not support the use of DDT, as it was banned in their own countries. That the problems of a desperately poor malarial country in Africa might be somewhat different from those of wealthy, non-malarial Scandinavia seems not to have occurred to them.

Mozambique's DDT-spraying operation, disrupted by civil war in the 1980s, was duly squashed before it could get going again after peace returned in the 1990s. Samuel Mabunda, the head of the country's malaria-control programme, concedes that the evidence now suggests that DDT-spraying would be cheap and effective, but says that the government has no definite plans to start spraying again.

When DDT-spraying stops, the number of malaria cases frequently explodes. South Africa stopped spraying in 1996. Its caseload subsequently rose by 150%. It recently started spraying again, and the disease is retreating. In Mozambique, infection rates are 20-40 times higher than in neighbouring Swaziland, which never stopped using DDT.

Environmentalists argue that DDT-spraying causes harm to humans, but no replicated, peer-reviewed study has ever demonstrated this. Nor is it likely that the tiny quantities used in house-spraying have any serious effect on the environment. Amir Attaran, another Harvard academic, estimates that the volume of DDT used to protect the entire high-risk population of Guyana for a year is equivalent to what a farmer might spray on to a single field of cotton.

The treaty drafted in Johannesburg, which is due to be signed in May, is a welcome antidote to this nonsense. But it is still far from ideal. That is because countries that use DDT for malaria control must record and report how much they use, how they use it and where they get it from.

This may not sound onerous, but in places such as Mozambique, where the annual budget for fighting malaria is less than 30 cents a person, any additional bureaucracy could prove to be a big drain on resources. Concern for the environment is generally an admirable thing. Obsession, at the cost of human lives, is of more questionable value.