The World Health Organization (WHO) has made occasional positive noises about the use of DDT for indoor residual spraying to combat the malaria vector in the recent past (see, for example, the 2005 publication "Frequently Asked Questions on DDT for Disease Vector Control" [pdf]), but it became news on Friday -- even characterized as a "U-turn" -- when Dr. Arata Kochi, WHO's colorful Director of the Global Malaria Programme encouraged policymakers to increase the use of the much-maligned pesticide. The announcement was covered by major news organizations, including the New York Times and Washington Post.Although this is a very positive development, the "thumbs up to DDT" message is missing a few of the devilish details. First of all, the conclusion that DDT is OK is based on a reasonable weighing of the short- and long-term costs and benefits, given the current state of the world, where other preventive measures are only modestly effective. It is not, as stated by Senator Tom Coburn (R-Oklahoma) in hailing the WHO announcement, a triumph over "junk science and myths," which suggests that those who have been concerned about the environmental and health threats of the pesticide have made it their business to falsify evidence.And the WHO itself rightly notes in a 12-page paper backing the announcement (not yet on-line) that an aggressive push for DDT use makes sense under a specific set of circumstances:
When it is indicated and can be implemented effectively, IRS [indoor residual spraying] with DDT or other recommended insecticides should be a central part of national malaria control strategies, in order to reduce malaria morbidity and mortality and accelerate progress towards global and national malaria targets. However, there are important considerations that must be taken into account when considering whether to introduce or scale up IRS. In particular, there must be sufficient capacity to deliver the intervention effectively, prevent unauthorized and un-recommended use of public health pesticides, and manage insecticide resistance. Looking to the future, intensified research efforts are needed, for example to develop new, long-acting insecticides and improved application technologies.
Those are important qualifications, and we can only hope that those who are getting the signal that it's the right time to spray are also reading the fine print, and making corresponding improvements in training and supervising those who are applying DDT, and investments in research so that we have even better choices in the future.
CGD blog posts reflect the views of the authors, drawing on prior research and experience in their areas of expertise.
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