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Demise of a ‘necessary evil’
DDT (dichlorodiphenyltrichloroethane) is one of 12 industrial chemicals to be outlawed under the United Nation’s 2001 Stockholm convention on Persistent Organic Pollutants (POPs), which formally came into force on 17th May, 2004 after ratification by 50 States. DDT, the first of the chlorinated organic insecticides was originally prepared in 1873, but it was not until 1939 that Muller of Geigy Pharmaceutical in Switzerland discovered the effectiveness of DDT as an insecticide. For this discovery, Paul Muller was awarded the Nobel Prize.
After World War-2 the use of DDT increased enormously on worldwide basis, primarily because of its effectiveness against the mosquito that spread malaria and lice that carry typhus. The world health organization (WHO) estimates that during the period of its use approximately 25 million lives were saved, DDT seemed to be an ideal insecticide is cheap and relatively of low toxicity to mammals (oral LD50 is 300 to 500mg/kg). However, the problem related to the extensive use of DDT began to appear in the late 1940’s.Many species of insects developed resistance to DDT and was also discovered to have a high toxicity towards fish. The chemical stability of DDT and its fat solubility compounded the problem. DDT is not metabolized very rapidly by animals instead it is deposited and stored in the fatty tissues. It is persistent in the soil with a “half-life” of about 75 years. Half-life is a term commonly used to describe the amount of time in the years it takes a particular chemical to break down naturally by half.
Compounding the problem, DDT had an unforeseen side-effect that appeared when many species of birds contaminated with DDT.The presence of DDT inhibited the proper formation of the egg shell, leaving the newly hatched eggs too thin and brittle to survive exposure, killing the developing chicks. The decrease in live hatching was noted by Rachel Carson, whose book “Silent Spring” lead the campaign to outlaw the insecticide. Carson also documented how the chemical caused birth defects, cancer and genetic damage in many species including humans.
DDT was banned for all use in the United States on 30th June, 1972.But despite its ban in USA it continued to be used in the rest of the world. Reportedly the ban only applied to its usage in America, not its production. At that time and until only recently, while American farmers were being denied the use of DDT, America was importing vegetables from Mexico, which still use it. While the residue o0f DDT is harmless to eat, the point is, it was inexpensive compared to the alternatives so it’s banned usage put American farmers a competitive disadvantage.
In Pakistan manufacture of DDT was started in1954 at Naushera [NWFP] and in 1964 at Kala Shah Kaku [Punjab] with production capacity of 600 and 1320 tons of DDT technical per annum respectively. According to Federal Plant Protection Department Karachi most of the production of Kala Shah Kaku and the total production of Naushera factory was utilized in the health sector for anti malaria campaign until 1977 when mosquitoes were reported to have developed resistance against DDT.So far consumption of DDT in agriculture sector was concerned, it was very low. Only 104 tons of technical material was used singly or in combination with other pesticides during 1984 Kharif season. The reason for low consumption was mainly due to some apprehension and fear on account of propaganda against DDT, which was not based on evidence. However on a summary submitted by the Production Division Government of Pakistan, the EEC in its meeting held on 22-1-1980 took the following decisions -
1. DDT and BHC need not be used for malaria eradication programme.
2. The Plant Protection Department may continue using these pesticides against cotton bollworms, locust, cutworms, termites, etc.
However in early 1990’s DDT, BHC and some other long persistent pesticides were either banned or withdrawn by MINFAL.
According to Jim Wills head of the UN Environment Programme [UNEP] there is still a role for DDT. Chemical division of UNEP estimated that about 25 countries would use DDT under exemption from the DDT pesticide, which stands banned from 17th May 2004. According to UN estimate malaria kills one African child every 30 second despite difficult choice in using a known poison to spray homes in developing countries.
In spite of the fact that DDT has been outlawed as one of a ‘’Dirty dozen “chemical from May, 2004 there are certain quarters who believe that banning of DDT is aimed at controlling global population. Their arguments are based upon the fact that according to the US Agency for International Development, Malaria cases in Srilanka plumbed from 2.8 million in 1948 to seventeen in 1963. In India death from Malaria fell from 750,000 per year to1500 a year. The reason was widespread use of DDT insecticide. Malaria rates soared when Brazil and Peru stopped using DDT in 1990’s[Peru is the same country that banned chlorinated drinking water at EPA’s suggestion, only to suffer thousands of death from cholera]. Ecuador slashed its malaria rate by extending its own DDT programme during the same period.
Reportedly, Dr. Charles Wurster, former Chief Scientist for the Environmental Defence Fund, was once asked if he thought a ban on DDT might result in the use of far more dangerous chemicals and an explosion of malaria cases in Srilanka. He replied “probably - so what? People are the cause of all the problems. We have too many of them. We need to get rid of some of them, and this is as good a way as any”. Moreover, the Malaria Foundation International, a group of more than 350 physicians and scientists, who have spent their lives fighting malaria, published an open letter in September 1999 to the U N delegates urging them not to ban DDT until an alternative is available.
Every chemical substance has desirable and undesirable effects and these have to be weighted one against the other and DDT is not exception. It is a well-known fact that DDT has been more extensively and intensively studied than any of the other chemical in the history of man by toxicologists, pharmacologists, chemists, biochemists, residue experts, regulatory agencies etc. According to the draft summary submitted by the Department of Plant Protection to the EEC on 18-12-1984 for consideration “The evidence is coming forward showing that DDT is not so persistent under hot, humid conditions and is difficult to justify not using a safe, efficient and inexpensive pesticides such as DDT when the risk -benefit balance is so weighted on the benefit side”.
In the back drop of these arguments it can be said that time has come for the environmental interest group to be put under the glare of the same public scrutiny and accountability that they demand for industry and private citizens.
The writer
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