A risk analysis model with an ecological perspective on DDT and malaria control in South Africa

The Stockholm Convention on Persistent Organic Pollutants granted a controversial exemption for some countries to continue using DDT. DDT has a history of use in malaria control, but widespread concern about health risks led to declining use. A science-based policy analysis of existing published literature was conducted to consider DDT toxicology and malaria risk in South Africa to generate data for a model that tests DDT risks and benefits in relation to infant mortality. This study investigated one aspect of DDT toxicology and risk analysis, and in the process, provided an insight into the effects of scrutinising risks and benefits more carefully than by means of aggregated data. When comparing infant mortality risk from malaria with infant mortality from DDT the results suggested that the net benefit of DDT application relies on certain assumptions associated with the toxicity of DDT. When the analytical model was run based on the best estimates available of the impact of DDT on infant mortality, the costs of DDT application outweighed the potential benefits in areas of low endemicity. According to this analytical method the only situation where DDT for malaria control had a clear net benefit in relation to infant mortality was when the malaria mortality rate was very high (e.g. the equivalent of a malarial epidemic). Our assessment concluded that the net benefits of DDT indoor residual spraying for malaria control are at best marginal and recommends consideration of less toxic, cost effective alternatives such as insecticidal nets.