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Throwback Thursday: DDT's history in Canada

Why the pesticide DDT was revered after the Second World War

  • May 06, 2015
  • 480 words
  • 2 minutes
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In 1945 after the Second World War, the pesticide commonly known as DDT — which stands for dichlorodiphenyltrichloroethane — was revered as a miracle solution for the increasingly prevalent spruce budworm infestation in Ontario’s balsam forests. This was the subject of A. P. Leslie’s article entitled “DDT in Ontario’s Forests” in that year’s October issue of the Canadian Geographical Journal. Leslie described DDT as potentially the “only one hope” for immediate control of the budworm and as something that “offers the greatest reason for optimism.”

Of course, at the time, DDT was still a relatively new chemical agent and Leslie included a disclaimer explaining such — “DDT may create as much harm as it can good unless used by those in possession of full available knowledge of its characteristics.” According to Leslie, a German chemist had discovered the pesticide earlier in 1874, about 70 years prior to the publication of this article, but it was not used mainstream for agricultural and environmental management purposes until after it was purchased by a Swiss chemical house in 1937.

Since 1945, DDT has become one of the most well known pesticides for its possible side effects on humans and wildlife that come into contact with it and for its long-lasting resistance. We now have a better understanding of the chemical, but still not a complete perspective.

After mental and human health concerns arose in 1972 due to the continuing accumulation of the water-insoluble DDT in the environment, international action was taken to control its spread. The registered use of DDT was suspended in Canada in 1985 and the use of existing stocks was only permitted until the end of 1990, after which time it was banned under the Pest Control Products Act. Today, it is prohibited under the Canada–Ontario Agreement Respecting the Great Lakes Basin Ecosystem and was banned worldwide for agricultural uses at the 2001 Stockholm Convention on Persistent Organic Pollutants.

The full list of side effects is incomplete, but results from studies show varying symptoms based on the amount of DDT present, in humans and wildlife. For instance, laboratory animals given a lethal amount of DDT were shown to develop liver tumours, according to research from Oregon State University. Other studies suggest that DDT is linked to cancer in humans, but there is no conclusive evidence proving such theory.

DDT has not been blacklisted by the entire world and has been said to have saved millions of lives. The most prevalent argument in support of the pesticide was that it could be used to combat malaria in African countries by killing the mosquito populations that spread the infectious disease.

Its use remains as controversial as it was decades ago, but a new player is currently taking its spotlight: neonicotinoids, also known as the bee-killing pesticide that has been referred to as “the new DDT.”


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