AFRICA – The call for a total ban of DDT (dichloro-diphenyl-trichloroethane), a synthetic insecticide used in malaria-endemic countries that causes harm to the environment and human body, has sparked a debate.
Some argue that it has anti-malarial properties, while others argue that it is harmful to the environment and human health. It is prohibited in some countries, despite the fact that it is widely used in others to control mosquitoes that transmit malaria.
Professor Bontle Mbongwe, a Botswana academic and associate professor of Environmental Health and Toxicology at the University of Botswana, has now chimed in on the discussion.
In an interview with Africa Renewal, Prof Mbongwe says that any decision to ban DDT should be supported by evidence from an assessment of its risks to human health and the environment.
She warns that “accumulating evidence suggests that DDT and other pyrethroids (man-made pesticides) may have negative effects on pregnancy,” adding that “pyrethroids have also been linked to increased cases of mortality and an adverse effect on the cardiovascular system.”
She suggests conducting a thorough investigation into the levels of DDT in breastmilk.
In addition, she laments that “The health impacts from exposure to persistent organic pollutants such as DDT are more acute in developing countries, especially on women and children’s health.
“Because DDT does not degrade, it remains intact in the environment for many years; therefore, human beings and the environment are exposed to its toxic effects, some of which may affect the development of children.
“Even more concerning, DDT is transported through the environment and across boundaries through the soil, water, and especially air,” she says.
In general, the decision to use or prohibit DDT is frequently influenced by factors such as the cost-effectiveness of alternatives, their hazardous properties, and their impact on human health and the environment.
The environmentalist is one of the newest members of the Stockholm Convention on Persistent Organic Pollutants, an international environmental treaty signed in May 2004 that aims to eliminate and limit the production and use of persistent organic pollutants.
DDT is one of the Convention’s listed organic pollutants. The expert group is in charge of evaluating scientific, technical, environmental, and economic data on the production and use of DDT and other disease vector control alternatives.
Prof Mbongwe is from a malaria-prone region; she appears to prefer a limited use of DDT, which is currently only permissible under the Stockholm Convention, in controlling disease vectors, in accordance with World Health Organization recommendations and guidelines, and when safe and affordable alternatives are not available locally.
Given the difficulty of completely eliminating DDT use, this limited permission could be a first step toward limiting its widespread use.
The good news is that global DDT use for disease vector control has decreased from ten countries using it for Indoor Residual Spraying (IRS) in 2010 to five countries in 2019.
Prof Mbongwe conducted a comprehensive study of DDT in Botswana in 2000, measuring concentrations and metabolites in water, plants, invertebrates, and fish from selected lagoons in the large Okavango Delta, where DDT has been used for malaria control and treatment of African sleeping sickness for approximately 50 years.
Nonetheless, countries frequently have limited capacity for entomological surveillance, insecticide-resistance monitoring, and vector control, all of which are critical for programs that rely on IRS or Insecticide Treated Nets with limited modes of action.
International organizations such as the United Nations Environment Programme, the United Nations Industrial Development Organization, the Global Environment Facility, and the Bill and Melinda Gates Foundation are assisting countries with additional financial assistance.
In terms of technology and research, collaboration between researchers and operational program staff is encouraged in order to develop new tools for malaria vector control.
Prof Mbongwe notes that the use of insecticide-treated nets for malaria control and elimination has increased in recent years, effectively reducing reliance on DDT.
Sub-Saharan African countries are transitioning away from DDT and pyrethroids and toward more organophosphate chemicals known as neonicotinoids.
Prof Mbongwe believes that increased capacity for insecticide-resistance monitoring in some countries has resulted in better detection of DDT resistance, which has encouraged other countries to consider non-DDT insecticides for IRS.
“There is also a shift toward developing national strategies on IRM [Insecticide Resistance Management] for disease vectors. Finally, countries are taking measures to develop and implement Integrated Vector Management, and this can potentially reduce reliance on DDT and other chemical insecticides for disease vector control,” she further explains.