DDT Attracts Unwarranted Criticism

Jasson Urbach | 24 Aug 2023
Health Policy Unit
Imagine a medicine that has saved tens of millions of lives consistently for decades. Imagine that it is still being used highly successfully - yet, many people wish to see it taken out of use because they fear it may cause harm. They base their fears on some research studies - studies which are weak, un-replicated, often contradictory and do not amount to any kind of solid scientific evidence of harm. Most rational people would conclude that such a life-saving medicine should be used as long as the evidence is that its benefits outweigh its costs.

Such a scenario is playing out right now. Public perception and the media response is to condemn this 'medicine' and the reason they do so is because it is not actually a medicine - but an insecticide. Why, when the word 'medicine' is replaced with 'insecticide', is all rationality, fairness and balance is discarded and it becomes acceptable, even celebrated, to be biased, irrational and unreasonable - even when the very poorest members of society will pay dearly?

Following closely in the footsteps of Carte Blanche, the investigative journalism show, Special Assignment, recently ran a story entitled "Collateral Damage". The focus was, once again, on the insecticide used for malaria control, commonly known as DDT. Like the Carte Blanche exposé, the Special Assignment story was based on research conducted by Professor Riana Bornman and her colleagues from the University of Pretoria and published in the British Journal of Urology International (BJUI). The paper claims that DDT used in malaria control in the Venda area of Limpopo, is a cause of urogenital birth defects, such as un-descended testes, among boys born in sprayed houses.

My colleagues and several other senior South African scientists involved in malaria control in SA were alarmed by this research because of the overwhelming evidence that DDT has saved countless lives over many years and has successfully been used to control malaria in SA since the 1940's, with no adverse effects on humans. On closer inspection of their research we found many shortcomings, including statistical manipulations in order to achieve a desired outcome. The BJUI published our concerns and despite being given ample opportunity by the BJUI to respond to our queries, Prof. Bornman and her colleagues have declined to do so.

DDT is one of, if not, the most studied insecticide in the history of mankind. Also highlighted in the Special Assignment programme was the Pine River Statement: Human Health Consequences of DDT Use. Anyone who reads the Pine River Statement carefully cannot but conclude that it offers no evidence that would satisfy the most basic epidemiologic criteria to prove case and effect, to show that DDT is harmful to human health. This does not, however, stop the authors from saying that it 'may pose a risk for human populations'. This is hardly a definitive statement. In fact, despite a plethora of studies undertaken at great cost, there is still no conclusive evidence that DDT causes any harm to human health when used for public health purposes.

DDT was first widely used during World War II in both the European and Pacific theatres of war to control lice-spread typhus and other insect-borne diseases. The first major applications of DDT against malaria took place after WWII, with remarkable outcomes and resulted in millions of people being protected from the deadly bites of malaria carrying mosquitoes.

During the height of its production, over 40,000 tonnes were used worldwide between the 1940s and the 1970's - a period of about 30 years. In the US, production peaked in 1963 at 82,000 tonnes and the US Environmental Protection Agency (EPA) estimated more than 600,000 tonnes were applied in the US before production there was banned in 1972, due to the unfounded fears that DDT may be harmful to humans and/or the environment. Over this period millions of people came into direct contact with the insecticide and it has now been almost 40 years since the halt in production in the US.

During the 40 years since the US stopped production environmental scientists have conducted thousands of investigations at huge financial cost and published a great number of papers. In spite of all these expenditures and research efforts, with their advanced health systems, researchers in the US and in other developed countries which also used vast amounts of DDT, still cannot identify any true harm caused by almost 30 years of heavy DDT exposure.

What causes particular concern with the Bornman research is that the incidence of urogenital birth defects in the control population in Venda with no DDT exposure was 10.2 per cent, statistically equivalent to the 11 per cent in the study population. This fact is simply papered over and seemingly ignored in the sensationalist media coverage. One of the conditions measured by the researchers, hypospadias, where the opening of the penis is not at the tip, reported on both the Carte Blanche and Special Assignment shows, was actually higher in the unexposed population than in the DDT exposed population.

The only defence the poor have against malaria is the careful use of insecticides. The only proven and consistent method of preventing insect-borne diseases, unless you have a vaccine, is to kill or repel the carrier ("vector"), such as the mosquito. The risks posed by malaria far outweigh any risks posed by the safe and effective insecticides used in malaria control. To report otherwise is not only misleading, but severely undermines malaria control and harms some of the most vulnerable people in our society.