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DDT for pest control

In 1874, a German scientist called Othmar Zeidler produced an odourless white substance that resembled table salt. It had 14 atoms of carbon, nine of hydrogen and five of chlorine, and it was completely useless - or so Zeidler reckoned.

However, in 1939, when the Swiss scientist Paul Mueller stumbled on the same compound, he found that it killed insects with remarkable speed and efficiency. Within four years, the Merck chemical company was producing it in bulk. The Italian Government used a consignment to stem an insect-borne epidemic of typhus, and US Army personnel were issued with small tins of this miraculous new de-lousing powder.

Dichlorodiphenyltrichloroethane, called "DDT" for short, seemed destined to make the world a safer place for humanity and in 1948 Mueller was awarded a Nobel Prize. By 1962, 80 million kilogrammes of the pesticide was being used annually, and it formed the basis of a global malaria eradication campaign which, by 1967, had stamped out the disease in developed countries and dramatically reduced it in Asia and Latin America.

In the two decades after Mueller first synthesised it, DDT is thought to have prevented 500 million deaths. But by the mid-1960s, science had discovered its darker side.

Insoluble in water, DDT cannot easily be flushed out of the environment and, because it is soluble in fats, it accumulates in animals that ingest it, interfering with their reproductive systems and working its way up the food chain to the very animals that created it.

In her 1962 book, Silent Spring (subsequently published by Penguin), Rachel Carson suggested that pesticides such as DDT were upsetting the balance of nature and causing an increase in cancers. Within a decade, its use had been banned in the West and "chemicals" had become a dirty word in the public mind.

Recent years have seen a backlash, however, with many accusing the anti-pesticide lobby of a major blunder that has cost countless lives. In 2001, a United Nations conference voted for a worldwide ban on a range of persistent organic pollutants, but allowed 25 countries to continue using DDT for malaria control until alternatives are found.

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