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DDT, Malaria and Africa

This has been a heated controversy for some time, and it is not cooling down anytime soon. As many know, the use of DDT to control insects in agriculture has been highly restricted since the 1960's, due in no small part to Rachel Carson's Silent Spring, which connected DDT to cancer of the liver in humans and damage to bird reproduction. The successful restriction of DDT heralded the birth of the environmental movement in the United States as a political force, which means that any attempt to relax the restrictions is bound to spark a fierce ideological battle.

Now bring in Africa and the contemporary use of DDT in control of malaria. More than a million people die each year from malaria, mostly children under the age of 5, and 90% of the cases occur in sub-Saharan Africa. In the light of this public health catastrophe, observers over the years have argued that the benefits of using of DDT in small quantities for indoor spraying of walls and ceilings far outweigh the risks. Some have gone further, claiming that the restrictions on DDT have directly lead to millions of avoidable deaths, and thus crazy environmentalists (for some, read: eco-imperialists) have the blood of Africans on their hands. Worse still, the argument goes, while developed nations successfully eliminated malaria by using DDT in the 1940's and 1950's, those same nations now support a restriction on the use of DDT in poorer countries where where malaria is endemic, access to treatment is often limited, and economies are seriously impacted by the disease.

Two weeks ago, the World Health Organization officially announced its support of the use of DDT in indoor spraying, not only in epidemic areas (that was the old policy) but also 'in areas of constant and high malaria transmission, including throughout Africa.' The change in policy has strong backing from USAID and some US government officials, most notably Republican Senator Tom Coburn, who is quoted as saying:

“Finally, with WHO’s unambiguous leadership on the issue, we can put to rest the junk science and myths that have provided aid and comfort to the real enemy – mosquitoes – which threaten the lives of more than 300 million children each year.”

Republicans talking about health policy issues being resolved by a reference to scientific scholarship, of course, is heavy on irony, and naive to boot. The announcement by the WHO is hardly likely to put the DDT issue to rest in the short-term. While many (also in developing countries) have warmly welcomed the new policy, others remain flatly unconvinced. At the recent Intergovernmental Forum on Chemical Safety conference in Budapest, some delegates staged a protest over the new DDT policy, citing concerns about the potential effects of indoor spraying on reproductive health, neurological effects, effect on breast milk and increased risk of breast cancer, not to mention the possibility of resistance of mosquitoes to DDT. Inevitably, some raised the suspicion that dropping restrictions on DDT was ultimately driven by the financial interests of chemical industries in the US, rather than a concern for public health in Africa. A recent review article in the Lancet (2005) makes the usual song and dance, i.e. more research is needed:

Although DDT is generally not toxic to human beings and was banned mainly for ecological reasons, subsequent research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning, abrogating the benefit of reducing infant mortality from malaria. ... DDT might be useful in controlling malaria, but the evidence of its adverse effects on human health needs appropriate research on whether it achieves a favourable balance of risk versus benefit.

At the moment, how the risks relate to the benefits of using DDT in Africa still seem to be somewhat in the eye of the beholder. But given that the use of DDT in spraying is one of the few affordable and effective preventative interventions against malaria, and that hundreds of thousands die of the disease each year, the burden of proof would seem to fall on those who focus on the risks.
-Stuart Rennie