"One of the best tools we have against malaria is indoor residual house spraying. Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT."
The WHO called on all development agencies and governments to incorporate the use of DDT in their malaria control programmes and to issue statements on where they intended to use it and how they would manage it. WHO promoted the use of DDT for malaria control until the 1980s.
The Malaria Eradication Programme, endorsed by the WHO’s 1950 Kampala conference, made DDT the cornerstone of malaria control and brought down the rates of the disease in Asia, Latin America and southern Africa. The WHO says that, as a result, about 700 million people were no longer at risk by the end of the programme in 1969.
But most of Africa missed out and, the WHO says, "the burden of malaria that remains today, much of which is in sub-Saharan Africa and in remote rural areas of Asia and Latin America or among marginalised populations, is unacceptably high. Today malaria remains a major cause of poverty and underdevelopment and it is estimated that 3.2 billion people live at continuous risk of this disease." There are 350m cases of malaria every year and a million die, mostly children under five years old, 90% of whom live in Africa.
The WHO says use of DDT declined because of lack of government money but also because of "general disapproval" of its use for fear of its effect on human and animal health. It is one of the persistent organic pollutants that linger in the body for years and whose long-term impact is not completely understood.
But the fears, says WHO, are unjustified when it is appropriately used for indoor residual spraying only. It will not be recommended for use in forested regions of the Amazon and south-east Asia, where there are no structures to spray. There is no justification for its use in agriculture, the WHO said, and regulations will need to be in place to prevent the contamination of crops.
Barbara Dinham of the Pesticide Action Network said the issue of DDT spraying was "very emotive at the moment. There is an argument from a group of public health scientists that environmentalists are more concerned about the environment than about people dying of malaria in developing countries."
She and other groups concerned about pesticides would not block the use of DDT "until it is quite clear that alternatives are available", she said. "But there are serious chronic health implications of exposure to DDT. It is a case of acute effects versus long-term effects."
Using DDT, she said, could be "sowing the seeds of endocrine disruption and cancers, particularly breast cancer".