The internet is a wonderful place to get lost. In arguments. It is also a wonderful resource for complex issues such as those surrounding The DDT Debate. The case for DDT as a vector control boils down to four arguments, which appear below.
Dichloro-diphenyl-trichloroethane (in short, DDT) is a synthetic chemical that is particularly good at killing insects. A vector is an organism that spreads diseases from host to host without harm to itself, like the mosquito does. Following extensive research on the environmental impact of the extensive use of DDT in the 1940s-1950s, DDT was banned in North America and Europe in the 1970s. Thereafter, most other countries also stopped using the pesticide.
The PRO-DDT argument is five-fold: 1) it is effective in repelling and/or killing mosquitoes and thus in reducing the risk of malaria infection, 2) it is relatively cheap and thus affordable for developing countries, 3) it is safe for human health if used responsibly, and 4) it is pro-poor.
Effectiveness: Supporters say that DDT lasts twice as long as other pesticides and that its repellent effect delays the process by which the mosquitoes develop resistance to the pesticide. Studies of previous DDT usages in developing countries show that malaria rates reduced tremendously when DDT was employed and soared again when it was stopped.
In her influential New York Times article Tina Rosenberg argues that “A malaria-eradication campaign with DDT began nearly worldwide in the 1950’s. When it started, India was losing 800,000 people every year to malaria. By the late 1960’s, deaths in India were approaching zero. In Sri Lanka, … 2.8 million cases of malaria per year fell to 17.” Furthermore, Rosenberg writes, “The move away from DDT in the 60’s and 70’s led to a resurgence of malaria in various countries — Sri Lanka, Madagascar, Swaziland, South Africa and Belize, to cite a few; those countries that then returned to DDT saw their epidemics controlled. In Mexico in the 1980’s, malaria cases rose and fell with the quantity of DDT sprayed.”
Cost: Apparently, DDT costs less than other pesticides. The patent on DDT has expired and Rosenberg writes that it is mainly produced in India and China. It is therefore more affordable for Ministries of Health in countries like Uganda.
Health Risks: Supporters claim that the amount of DDT needed for vector-control is tiny compared to those used in agriculture before it was banned. Donald Roberts, professor at the Uniformed Services University of the Health Sciences in Bethesda, Md, USA, told Rosenberg the “the quantities used for house spraying are so small that Guyana, to take one example, could protect every single citizen of its malarious zones with the same amount of DDT once used to spray 1,000 acres of cotton.”
The World Health Organisation, WHO, has recently reversed its position on DDT. It now allows DDT for indoor spraying, stating that “DDT presents no health risk when used properly.” Usaid, which partly sponsors the DDT campaign in Apac, takes the same stand: “If used correctly for this purpose [that is, residual indoor spraying], [DDT] poses no known risk to human health. Malaria, on the other hand, kills more than 1 million people each year.”
Research has linked DDT to cancers and other diseases, but the DDT supporters dismiss these as ‘inconclusive.’ States the WHO: “Extensive research and testing has since demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans”. (In the forth-coming blog post against DDT, you will see that not all scientists agree.)
Pro-poor: Malaria disproportionately affects poor people, with almost 60 percent of malaria cases occurring among the poorest 20 percent of the world’s population, according to the WHO. Compared to insecticide-treaded bed nets which are paid for by individual users, the cost of a DDT campaign is borne by governments and their donors, rather than ‘the poor’ themselves. Another argument is that malaria impedes economic growth. The WHO found that malaria alone shrinks the economy in countries where it is most endemic by 20 percent over 15 years.
The DDT supporters claim that the anti-DDT position is contributing to the death of millions of adults and children to malaria, by removing the possibility of effectively killing mosquitoes. In the words of Rosenberg: “Once we discovered it was harming the ecosystem, we made even its safe use impossible for far poorer and sicker nations.”