The UnAustralian

Monday, February 02, 2004
Putting Myths to Bed

Published in today's Australian is a letter which should (but won't, there is always another mule in the wings) put to rest the nonsense on ddt recently peddled by Christopher Pearson.

CHRISTOPHER Pearson (Inquirer, 24-25/1) blames "the environmental lobby . . . with direct responsibility for millions of needless deaths, mostly of children in the Third World, from malaria". The argument is that Rachel Carson's book Silent Spring falsely accused the insecticide DDT of dangers to both human health and the environment, that this accusation led to the banning of DDT in mosquito control programs in areas where malaria is endemic (mostly the tropics), and as a direct result of this ban, millions of people died.

This argument is arrant nonsense, recycled from an article in Quadrant, in turn recycled from a number of unscientific and unsubstantiated websites. As professionals and teachers in the field of parasite disease control, we are only too well aware of how such rubbish can be transmuted from cyberspace junk to popular folklore. Your readers should be aware of the facts:

The manufacture and use of DDT was banned in the US in 1972, on the advice of the US Environmental Protection Agency. The use of DDT has since been banned in most other developed nations, but it is not banned for public health use in most areas of the world where malaria is endemic. Indeed, DDT was recently exempted from a proposed worldwide ban on organophosphate chemicals.

DDT usage for malaria control involves spraying the walls and backs of furniture, so as to kill and repel adult mosquitoes that may carry the malaria parasite. Other chemicals are available for this purpose, but DDT is cheap and persistent and is often a very effective indoor insecticide which is still used in many parts of the world.

DDT is not used for outdoor mosquito control, partly because scientific studies have demonstrated toxicity to wildlife, but mainly because its persistence in the environment rapidly leads to the development of resistance to the insecticide in mosquito populations. There are now much more effective and acceptable insecticides, such as Bacillus thuringiensis, to kill larval mosquitoes outdoors.

Reductions in the use of DDT did occur in a number of developing nations after the US ban in 1972. This reflected concerns over environmental consequences of DDT, but was also a result of many other factors. One of the important factors in declining use of DDT was decreasing effectiveness and greater costs because of the development of resistance in mosquitoes. Resistance was largely caused by the indiscriminate, widespread use of DDT to control agricultural pests in the tropics. This problem, in fact, was anticipated by Carson: "No responsible person contends that insect-borne disease should be ignored . . . The question that has now urgently presented itself is whether it is wise or responsible to attack the problem by methods that are rapidly making it worse."

Malaria is a major, ongoing disease problem in much of the developing world. Increases in the incidence of the disease have occurred for complex reasons. Reduced insecticide usage is one, but others include the resistance to treatment in both the parasite and the mosquito vectors, changes in land use that have provided new mosquito habitat, and the movement of people into new, high-risk areas.

Most nations where malaria is a problem, and most health professionals working in the field of malaria control, support the targeted use of DDT, as part of the tool kit for malaria control. Most also agree that more cost-effective, less environmentally persistent alternatives are needed. There are some effective alternative chemicals for the control of adult mosquitoes, but preventing their further development is lack of invest ment by industry, because malaria is largely a disease of the poor.

Malaria is responsible for enormous suffering and death. The facts are readily available in the scientific literature. To blame a reduction in DDT usage for the death of 10-30 million people from malaria is not just simple-minded, it is demonstrably wrong. To blame a mythical, monolithic entity called the environmental lobby for the total reduction in DDT usage is not just paranoid, it is also demonstrably wrong. Your article is not only poor journalism, it is an insult to the people who work for the control of parasitic diseases that afflict developing nations.

Dr Alan Lymbery
Professor Andrew Thompson
Parasitology Unit
Division of Health Sciences
Murdoch University

| 5:04 PM