Pesticides are substances intended to prevent, destroy, or repel pests. Although most are synthetic chemicals, some are plant derivatives, inorganic dusts, or biological agents such as bacteria or their toxins.

The term "pesticide" is usually further sub-divided into more specific terms such as fungicide (kills fungi), herbicide (kills plants), acaricide (kills mites and ticks), avicide (kills birds), insecticide (kills insects).

DDT was developed as the first of the modern insecticides early in World War II. It was initially used with great effect to combat malaria, typhus, yellow fever, dengue fever and other insect-borne human diseases. Therefore, the use of small amounts of DDT means the difference between life and death for thousands of people in the developing world today.

Europe and North America have not harboured malarial mosquitoes since the 1940s. In one of the most miraculous public health developments in history, Greece saw malaria cases drop from between one and two million cases a year to close to zero, thanks to DDT. Meanwhile, in India, malaria deaths went from nearly a million in 1945 to only a few thousand in 1960.

In what is now Sri Lanka, malaria cases went from 2,800,000 in 1948, before the introduction of DDT, down to 17 in 1964 - and then, tragically, back up to 2,500,000 by 1969, five years after DDT use was discontinued there. In South Africa malaria cases increased 10-fold in the late 90s but dropped 80% in 2000 alone in KwaZulu Natal, the one province that made extensive use of DDT. In Madagascar, malaria incidence declined more than 90% after just two annual spray cycles.

When DDT was sprayed on house walls in modest quantities every 6 months, it exerted powerful control over indoor transmission of malaria. It is an astonishing fact that the World Health Organisation (WHO) guidance for spraying houses is the same today as it was in the eradication era more than 50 years ago.

Perhaps 100 million lives have been saved because of DDT's success in eradicating malaria, yet the same interests now think of it largely as one of those nasty chemicals which need to be banned.

There has been a campaign of misinformation which led to the ban of DDT. In her 1962 book, Silent Spring, Rachel Carson chronicled DDT's poisonous effects, showing, for example, how it killed the robins that ate the earthworms that dined on the leaves of Dutch elm trees that had been sprayed with the insecticide.

The public outcry was tremendous. The book led to the establishment of the Environmental Protection Agency (EPA) in 1970 in the United States.

On June l4, l972, the EPA's first administrator, William Ruckelshaus, ignored the advice of his scientific advisors and announced a ban on virtually all domestic use of the pesticide.

This was done despite the fact that DDT had earlier been hailed as a "miracle" chemical which repelled and killed mosquitoes which carried malaria.

No DDT-related human fatalities or chronic illnesses have ever been recorded, even among the DDT-soaked workers in anti-malarial programmes or among prisoners who were fed DDT as volunteer test subjects - let alone among the 600 million to one billion who lived in repeatedly-sprayed dwellings at the height of the substance's use.

The only recorded cases of DDT poisoning were from massive accidental or suicidal ingestions, and even in these cases, it was probably the kerosene solvent rather than the DDT itself that caused illness.

Dr Norman Moore, the British scientist who first claimed that DDT might be the cause of declining eagle populations (one of the chief non-human-health arguments for eliminating the chemical), conceded that the pesticide's huge benefits might easily outweigh its purported effects on animals.

"If I were living in a hut in Africa, I would rather have a trace of DDT in my body than die of malaria," he mused. In the late 1970s, Dr Roberts, a medical zoologist, travelled to Brazil to conduct experiments in malaria control.

He built two houses and sprayed the inside of one with DDT.

Hundreds of mosquitoes entered the unsprayed house, he said.

None entered the sprayed house. Since then, Dr. Roberts has become an ardent defender of DDT. "We have got to stop pressuring countries to stop using DDT. It is immoral," he said.

To put it more succinctly, one could say "criminal" instead of "immoral" particularly in this era of multi-drug resistant malaria. It is interesting to note that when the malaria-carrying anopheles mosquito was annihilated in Europe and North America, then and only then did DDT become too toxic for the environment!

The anopheles mosquito delayed the colonisation of inland Africa. What an irony that 100 years on, the same insect is delaying the modernisation of our economies!

The only difference is that today the insect is aided along by misinformed armchair campaigners for environmental protection. They prefer to line their pockets with travel allowances as they hop from conference to conference rather than protect the lives and economies of their fellow countrymen.

Somewhere in the world (including Uganda), one child dies every 12 seconds around the clock because of malaria. Some 300 million people a year are debilitated by malaria, at immense cost to both human health and the economies of poor nations like Uganda. Based on statistics compiled in 1978, costs of chemicals for protecting a person showed malathion to be five times more expensive than DDT.

A study of DDT alternatives for malaria control in Ecuador showed that the cost of other insecticides was many times higher than the cost of $1.44 to spray one house per year with DDT.

Generally, the cost of treating one house with DDT ranges from $1.60 to $8.50, compared with $4.20 to $24 for pyrethroids. High costs and downward trends in foreign aid suggest that many countries (read Uganda) cannot afford the switch to DDT alternatives.

DDT is the most cost-effective chemical we have for the prevention of malaria. I would rather die of DDT effects (and no one has) in say 20 years' time than of multi-drug resistant malaria today.

The writer holds a PhD in Chemistry, an MSc in Health Economics and Health Policy, and a Post-graduate Certificate in Health Care management

ALLAFRICA.COM