Pesticides
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Pesticide: DDT
Dichloro-diphenyl-trichlorethane is an organochloride pesticide that was invented during World War II and used to wipe out Malaria in North America and prevent other insect born diseases. It is better known as DDT. It is formed by the reaction between Chlorolbenzene and Trichloroacetaldehyde through a form of organic synthesis. It was the first widely used pesticide and was one of the key contributors to the agricultural revolution. This was because it killed a wide range of insects without causing immediate observable harm to crops or people. However, more recently, it has been discovered as the cause for numerous environmental problems.
How DDT Works
DDT can be applied to agricultural crops to eliminate pests, wetland areas to kill aquatic insect larva, or even the walls of homes to prevent malaria-carrying mosquitoes from entering. After its application, DDT is absorbed into the bodies of the insects where it then proceeds to attack the cell membranes. The cells that are most greatly affected by DDT are the neurons in the insects. DDT is absorbed across the plasma membrane of the cells causing leaks in the membrane which allow potassium and sodium ions to escape. The concentration of sodium and potassium ions is vital because they are responsible for directing neurons when to fire, thus causing muscle contractions. So when the levels of these two ions are unstable, uncontrollable siezuring and paralysis occurs and eventually lead to the death of the insect.
Environmental Effects
Although such dramatic effects are not seen in vertebrates, the biomagnification and the persistence of DDT causes numerous other environmental issues. The most well known example of this is the calcium depletion in bald eagle eggs. This depletion makes the eggs very soft and unproductive of the embryo, which restricts the proper and full development of the bald eagle young. This caused a great drop in the overall bald eagle population which in turn lead to a nationwide ban of DDT use in June of 1972.
The reason that DDT affects the eagles and many other facets of the environment so strongly is because of the principle of biomagnification. DDT is a very persistent chemical that does not readily break down in the environment. It is also not soluble in water so once it is sprayed, it often remains for decades. Despite being non-water soluble, DDT is readily fat soluble, so after the chemical is consumed by an herbivore, it is stored in the organism’s fat cells. When that first organism is later consumed, the DDT in its fat will be consumed by the predator and incorporated into its anatomy as well. The DDT never leaves the systems of the animals it is in until it is consumed, so the levels of the chemical are amplified as you move up the food chain. In top predators the quantities become so high that numerous undesirable effects are observed.
Conclusion
Despite the discovery of the harmful effects of DDT, it is still widely used in third world countries to prevent the spread of insect borne disease. DDT is a very effective pesticide due to the fact it kills insects by upsetting their vital nervous system. Even though it is banned in the U.S. the effects of DDT are still evident here in some species of migratory birds. Because of DDT’s dangerous biomagnification’s effects, it is not safe or environmentally friendly to widely use.
Researched and written by: Stephanie Stewart, Lynn Schofield, Lense Solomon, Megan Savage and Christie Pelzer
Bibliography
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