About the Pesticide DDT

Most of the examples in Silent Spring illustrating the misuse of pesticides in the U.S centred on the chemical DDT. Dichloro-Diphenyl-Trichloethane (DDT for short) was first synthesized in 1874 by a German chemist, but it wasn’t until 1939 that its role as an insecticide was discovered.

 

Uses of DDT

Its effects were so apparent as an insect destroyer that it was hailed as the ultimate pesticide. It killed all insects indiscriminately and was used universally. During wartime it was used to dust hundreds of thousands of soldiers, refugees and prisoners to control mosquito spreading malaria and lice transmitting typhus.
It was used globally to spray farmlands to combat various insect pests that damaged crops. DDT was so frequently used in the farming industry during the 1950’s and 1960’s that it was nearly as common spraying DDT onto crops as it was spraying water.

 

How much DDT was used?

Silent Spring was written at the peak of DDT use in the United States. This enabled Rachel Carson to gather the necessary facts concerning the devastation the chemical caused. Birds died en mass, as did fish and other types of animals that lived around the areas where DDT was regularly sprayed.
But DDT was sprayed for many years after the book was completed. The total amount of DDT used globally from between 1950 to 1980 in agriculture was more than 40,000 tonnes each year. Since the 1940’s more than 2 million tonnes of DDT have been produced. It is estimated that more than 675,000 tonnes was applied to U.S soil before the 1972 ban (see the EPA report).

 

DDT and Malaria

DDT is still one of the most effective ways to combat the spread of malarial disease (though it is not the only way...). Malaria infects more than a quarter of a billion people globally and kills more than 1 million of them.
Approximately 5,000 tonnes of DDT is produced yearly for the control of malaria. North Korea, China and India still produce significant amounts of DDT for export and apparently production of the chemical has been on the rise for a number of years.

 

How DDT works

DDT works by disrupting the operation of neurons in insects. Its insecticidal properties are derived from its action on the sodium ion channels, where it induces them to open up causing them to activate spontaneously. This leads to uncontrolled neural activity within insects which eventually results in their death.
But certain insects can get a mutation in their sodium channel gene which makes them resistant to DDT. However, this can prevented by the careful use of the chemical when it is used as an insecticide.