Malaria continues to be controlled in at least 23 countries of the world by DDT residual spraying. In this technique, a small quantity (2 g/m2) of DDT is applied to the interior walls and ceiling of dwellings and serves to (i) repel, (ii) irriate and (iii) kill parasite-bearing mosquitoes for a period of 6-12 months. Both parasite inoculation rates and the mean survival time of mosquitoes are consequently reduced, greatly slowing disease transmissibility. These dynamics were observed positively in numerous national malaria eradication programs in the 1950s and 1960s; and they are today observed negatively in South America, where a tremendous resurgence of malaria is coincident with a reduction of DDT house spray rates.
Nevertheless, a treaty now being negotiated by UNEP and over 110 countries aims to “reduce and/or eliminate…the emissions and discharges” of DDT. This would make DDT unavailable or unaffordable for house spraying, where there are no equally cost-effective alternative pesticides for developing countries to rely on. Although environmental and health concerns are cited in justification, indoor DDT spraying has little environmental impact; and the adverse health associations contended by environmentalists, such as cancer or endocrine disruption, have in no instance been observed and confirmed by later epidemiological studies. Policymakers therefore plainly face a risk-benefit analysis where the putative risks are speculative or based on animal toxicology, while the benefits are tangible and observable in large human populations.
Learning Objectives: The session will help listeners understand a current debate between environmentalists and public health experts over a proposed treaty to ban DDT, where that substance is still very useful for malaria control
Keywords: International Public Health, Environmental Health Hazards
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.