Explain the Development and impact of DDT and discuss the Case for its Continued Use
In 1874 a German chemist, Othmar Zeidler first produced DDT, but it was not until 1939 that its usefulness became known. It was then that a Swiss chemist called Paul Muller discovered that DDT was useful as an insecticide. Muller won the Nobel Prize for medicine and physiology for his work with DDT.
Before the Second World War few effective insecticides were known, and this became a worry to political leaders who realised that the new wartime conditions meant that people would live closer together, in air raid shelters, for example. DDT was initially used for killing the clothes moth, and also for lice, and it became known as a ‘wonder substance’ because it was far more effective than previous treatments, and it did not appear to damage mans health. The effectiveness of DDT became apparent when it became possible to compare the health of allied soldiers with that of German soldiers after the war.
After the Second World War DDT was developed for use as a pesticide, and farmers found that great benefits could be had from its use against such pests as the Colorado beetle, the gypsy moth and other insects. It was used to kill the mosquito that carries malaria, and the World Health Organisation has claimed that 25 million lives have been saved by its use. It was felt that DDT was indeed a wonder substance, and by the time of its banning in the United States in 1973 more than one billion kilograms of the chemical had been used in America.
There were dangers in the indiscriminate use of DDT however, and these were highlighted in Rachel Carson’s book, ‘Silent Spring’. In her book, Carson suggests that the reason why the dangers of DDT were overlooked is that DDT was used in a safe form, as a dusting powder to treat body lice, during World War 2. It is only when DDT is dissolved in oil that it becomes dangerous. When DDT was used as a crop spray, insects developed an immunity to it and doses had to be increased. Worse still, DDT got into the food chain, and built up in the fatty tissue of birds and animals. It takes eight years for an animals metabolism to break down half of the DDT in its body. And in the meantime, the animal continues to take in more DDT.
In America during the 1950’s it was perceived that the beetle that carries Dutch elm disease was a problem. High doses of DDT were sprayed onto Elm trees with the result that although Dutch elm disease was held in check, birds, including the American Robin were killed. It was found that the birds had become poisoned through the cumulative effect of eating poisoned earthworms. Problems were also found in relation to the peregrine falcon. Bird counts showed that the numbers of falcons in the United States had declined dramatically in the period after the Second World War. Examination of the problem discovered that the high levels of DDT inside the birds was causing them to lay eggs with very thin shells that cracked when the falcons tried to incubate them.
Today, according to the World Health Organisation, 22 countries around the world, including two of the biggest, Mexico and India, still rely on DDT to control malaria outbreaks. The chemical is sprayed on the walls of buildings, which is where mosquitoes tend to rest after they have been feeding. According to a United States Centers for Disease and Prevention publication ‘Emerging Infectious Diseases’ 1.1 million kilogrammes of DDT was used to spray housing in North, Central and South America during 1993. Although the World Health Organisation recognises the dangers in the use of DDT, particularly in Agriculture, in 1997 it called for the use of DDT to be reduced, not stopped. It is felt that the dangers of the use of DDT outweigh the benefits to be gained in terms of the numbers of lives saved, and figures produced in the CDC article show that this might be the case. The ‘Emerging Infectious Diseases’ article, written by several North American professors, ends by claiming that DDT is still needed for malaria control.
Talks aimed at regulating the use of persistent organic pollutants including DDT started under the auspices of the World Health Organisation in Geneva in Sept 1999. Several groups took part in the discussions including the World Wide Fund for Nature, and an organisation called Physicians for Social Responsibility. There was no doubt that in an ideal world DDT use should be ended, but the groups took different views on how this should happen. WWF said that DDT use should be banned from 2007 claiming that there are safer and more effective ways of dealing with malaria. WWF claims that DDT is linked to health problems such as cancer and reproductive problems in animals and humans. WWF also say that the effects of DDT can travel reach thousands of miles. Black-footed albatrosses living on Midway island, three thousand miles away from America, have been found to have high levels of DDT according to WWF research. WWF also says that high levels of DDT are linked with eggshell thinning in birds of prey. Physicians for Social Responsibility took the view that DDT use should be phased out concurrently with increased use of other methods of malaria control, but this should be left up to individual countries to manage. Physicians for Social Responsibility claims that there are many different ways of dealing with malaria, some of which are cost effective when compared to the use of DDT, and they have published a hand book detailing these methods. Physicians for Social Responsibility claims that DDT has shown up in every sample of breast milk that has been tested, including samples from the Arctic and South Africa, but in their web site they do not say on what basis this claim is made.
Another group, the Malaria Project thinks that it is wrong to ban DDT, that it is environmentalism gone too far. They also claim that the issue of banning DDT is one of poor countries set against rich countries. In the United States it was found that DDT became less and less effective, and that country was able to switch to other types of mosquito control because they could afford to do so. The Malaria Project believes that poor countries are not able to do this.
DDT is believed to be produced in India and China, and it could be argued that those countries governments have a need to keep those plants open in order to project jobs, especially as a company controlled by the Indian government owns the Indian plant. According to Greenpeace DDT is also manufactured in Italy, Spain and the United Kingdom.
DDT, according to Physicians for Social Responsibility, is now accumulating in the colder areas of the world, away from the mosquito prone tropics. It could be argued the rich countries are seeking the banning of DDT because their perception is that the West is taking all the risks in DDT use, but are not reaping any of the benefits. The question the world has to face is will the west be prepared to help developing countries to move away from the use of DDT, even though that may mean that the west has to finance this activity itself.
http://www.eb.com (the Encyclopedia Britannica web site)
Carson, Rachel (1962) Silent Spring London, Hamish Hamilton
Mellanby, Kenneth (1967) Pesticides and Pollution Fontana