A famous Horace quote reads: “Nothing is an unmixed blessing”. This underlines the dual nature of human innovations ~ how they can solve our problems but also create new ones which lead to disasters. Yogi Berra aptly said: “The future isn’t what it used to be.” This aphorism was used by Sir Arthur C Clarke, and later by Apple Computer co founder Steve Jobs as a preface to their optimistic extrapolations about the future of technology.

It also holds good appropriately in case of an well-known synthetic organic chemical named Dich Lo ro diphenyl trichloroethane (in short, DDT). This pleasant smelling white powder was initially hailed as savior of humanity but finally it has been blamed as a destroyer. Till the chance synthesis of urea, an organic compound, in the laboratory by Friedrich Wohler in 1828, scientists firmly believed that organic compounds are synthesized only in living bodies of animals and plants under the influence of their unique living force or vital forces. J J Berzelius coined the term “organic compounds” for products derived from living beings.

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In 1828, Wohler unexpectedly got urea, an organic compound, in the laboratory while he attempted to prepare ammonium cyanate from cyanic acid and ammonia, all inorganic compounds. After achieving success in synthesizing an organic compound like urea in the laboratory out of inorganic compounds, he was so overwhelmed that he wrote a letter to Berzelius stating that “I must tell you that I can prepare urea in the laboratory without requiring a kidney of an animal, either man or dog.” Encouraged by the achievement of Wohler in synthesizing urea in a laboratory, Othmar Zeidler, an American student, who was working on his doctorate under the supervision of legendary chemist Adolf van Baeyer, successfully prepared DDT in 1874.

This white, tasteless, water insoluble, fat soluble, crystalline chemical attracted no attention until the Swiss chemist Dr. Paul Hermann Muller (also known as Pa uly Mueller) revealed its insect icidal property. The organic synthetic chemical has changed the world dramatically and completed its 150th birth anniversary in 2024. Dr. Pauly Mueller began his career as a research chemist for the dye division of J R Geigy (one of Switzerland’s reputed chemical manufacturers) in Basel in May 1925; and successfully, produced synthetic tanning agents.

Actually he was keenly interested in the study of plants including their protections. He even once said that his love for plants led him to choose botany as a minor subject at university. So, when, in 1935, Geigy began research on moth-and plant-protection age – nts, Muller actively involved himself. In 1937, he patented a technique for synthesizing novel rhodanide ~ and cyanate ~ based compounds which showed bactericide and insecticide activity. He also developed the product Gram in one, a seed disinfectant which was safer than the mercury based disinfectants at the time. But, for all intents and purposes, Muller was especially int – erested in developing insecticide as he was motivated by as many as five contemporary inadequacies in controlling insects:

(1) Available insecticides ~ both natural and synthetic ~ were not only ineffective but also expensive. The only products that were both effective and inexpensive were arsenic compounds which were poisonous to human beings and other mammals.

(2) The only available and widely used natural insecticide ~ pyrethrum ~ obtained from chrysanthemum flowers, was then widely used to control body lice (carrier of typhus), mosquitoes (carriers of malaria), and agricultural pests. But there remained a wide gap between supply and demand of the natural insecticide.

(3) The most extensive and lethal form of typhus epidemic prevailed in Russia.

(4) Malaria was a major health crisis, with an estimated 100 million cases globally and one million deaths in India alo – ne, and a devastating epidemic in Sri Lanka.

(5) There was a major food shortage in Switzerland which necessitated a better way to save food crops from insect infestations. However, during the course of his research work, Muller noticed that insects absorbed chemicals differently than mammals.

This observation led him to search for contact insecticide having quick and powerful toxicity upon the largest possible number of insect pests without causing any appreciable harm to plants and warm blooded animals. Muller contemplated insecticides which would be chemically stable and could be synthesized cheaply. He pursued his mission for four years. He studied all available data of insecticides and conducted experiments. In spite of 349 failures, he continued his research tenaciously and started his 350th experiment with an indomitable spirit. Ultimately, he achieved glorious and historical success by discovering all the traits of an ideal insecticide in DDT. Actually, Othmar Zeidler, the Viennese pharmacologist who first synthesized DDT in 1874, had not investigated its insecticidal properties.

In 1939, Muller established the astonishing effectiveness of DDT against Colorado potato beetle, and a wide range of pests, including mosquito, lice, fleas, and sandfly, which respectively spread malaria, typhus, the plague and various tropical diseases. It was indeed an epoch-making achievement in the service of humanity. After just nine years, Paul Muller was awarded the prestigious Nobel Prize in Physiology and Medicine in 1948 for his discovery of the high efficiency of DDT as a contact poison against several arthropods. The miraculous DDT, together with synthetic fertilisers, hybrid seeds and improved farming practices, brought about the Green Revolution.

In 1955, the World Health Organisation (WHO) started the Global Malaria Eradication Programme which was a crusade against malaria with financial support from many countries and used DDT as the mainstay of control. Before commencement of the programme there were around 1.8 billion malaria cases in the world; by 1967, there was a 40 per cent reduction. In some countries, the results were phenomenal; for example, in 1947 Greece had approximately two million cases, while in 1972, astonishingly, the number was merely seven.

After DDT was introduced in Sri Lanka, the number of malaria cases fell from 2.8 million in 1946 to just 110 in 1961. In India, in 1953 there were 75 million cases, and by 1968, it had come down to nearly 300,000 cases. DDT used in indoor residual spraying (IRS) seemed highly effective. The residual coating prevents malaria transmission as a spatial repellent or contact irritant or by killing mosquitoes and preventing or interrupting transmission. DDT, the persistent and pleasant smelling greasy white powder, was considered most valuable and unmatched by any other chemicals owing to some important characteristics. Winston Churchill hailed DDT as the “Miraculous powder.”

DDT was identified as a potent insecticide in 1939 and was heavily used during World War II; after the war, it became the global insecticide of choice in households, for agriculture, and for public health vector-control projects. However, the indiscriminate use of DDT has resulted in environmental pollution. Because it is persistent and fat soluble, DDT and also its breakdown products accumulate in adipose tissues of living beings and also get biomagnified (increasing accumulation and concentration of the persistent toxin at each trophic level) in the food chain ultimately threatening well-being. A well-known example of the harmful effects of DDT bio-magnification is the significant decline in the population of predatory birds such as golden and bald eagles, hawks, white pelicans, and falcons due to egg shell thinning.

Researchers found the presence of DDT in mothers’ breast milk at a concentration five times greater than the maximum permitted level in cow’s milk. DDT residues were also detected in bodies of fish, birds, bees and harmless insects. The spraying of DDT also destroyed useful and harmful insects, disturbing the natural balance between them. The devastating impacts of the uses of DDT have been described vividly by an American biologist and environmental activist, Rachel Carson in her seminal book Silent Spring in 1962. A touching paragraph of the book reads: “There is a strange stillness. The birds, for example, where had they gone? Many spoke of them, puzzled and disturbed. The feeding stations in the backyard are deserted. The few birds seen anywhere were moribund; they tremble violently and could not fly. It was spring without natural voices.

On mornings that had once throbbed with the dawn chorus of robins, catbirds, doves, jays, wrens, and scores of other bird voices, there is now no sound; only silence lay over the fields and woods and marsh.” The publication of Silent Spring opened our eyes to the dark aspects of DDT. The most important legacy of Silent Spring was public awareness that nature was vulnerable to human intervention. After this, DDT became a subject of concern, controversy and debate worldwide. The then US President John F. Kennedy ordered a review of the detrimental effects of DDT. But it was in 1972 that DDT was banned in the USA, except for use in extreme cases. Many other countries also banned DDT or placed it under str – ict control.

In 2001, the Stockholm Conference on 12 persistent organic pollutants (POPs), including DDT, resolved to give health-related exemption to DDT and its phased removal from public use. A worldwide ban on agricultural use of DDT has also been formalised. In 2006, WHO reversed its stance on DDT and recommended using indoor residual spraying. However, a final decision is yet to emerge. DDT is banned for agricultural use in India, but its production and use are restricted for public health purposes. India has obtained an exemption from the Stockholm Convention for the use of DDT in vector control. Hindustan Insecticides Ltd. (HILL) is the sole global manufacturer of DDT. As the risk of out break or resurgence of fatal diseases like malaria still exists, a complete ban on DDT is not feasible.

Few dangers associated with it can be avoided through training on judicious application of DDT. Indeed, DDT’s legacy is complex, often seen both as a “saviour” and as a “silent killer”. The debate over DDT continues with some arguing that its benefits in disease control outweigh the risks, while others emphasize the long–term environmental and health consequences. Despite phasing out of DDT, its persistence and its potential impact on human health, particularly in future generations, remain a concern. Since the publication of Silent Spring, Green Chemistry has emerged as a new discipline in chemical science. The future of DDT use is about transitioning to a more sustainable and environmentally responsible approach to vector control acknowledging its continuing role in malaria control in malaria prone zones.

(The writer is a retired IAS officer)