Pests have plagued humanity for as long as history has been kept, leading to many diseases in the process. Many people have tried to fight these pests and diseases, but came up empty. DDT was the world’s first known pesticide and is arguably the world’s most well known. DDT was first synthesized by Othmar Ziedler in 1873.
It was not until 1939 that its true properties were unearthed by Swiss Scientist Paul Hermann Mueller, which granted him the Nobel Prize in Physiology and Medicine in 1948.
DDT was one of the many insecticides in World War II to battle insects carrying diseases such as typhus and malaria. Since its use in World War II, DDT has caused much controversy because of its implications on the environment and human health.
Impact:
After DDT’s creation in 1939, its impact was felt immensely throughout the world. Its first real use was in World War II; where areas that were going to be attacked were sprayed down to make sure no diseases would infect the allied troops. As well as spraying down the city, it was spread against walls of buildings and trenches to kill the mosquitoes that would rest on the walls to digest after feeding.
After 1945 DDT was used for a different reason, to combat diseases carried by insects and as an agricultural insecticide killing crop-eating plants. DDT was one of the main reasons that most of the world eliminated malaria as a major disease.
Malaria was a disease that was primarily carried by mosquitoes and after the malaria eradication program, which was carried out in the 1950’s using DDT, malaria was nearly eliminated from all but tropical nations. It was not as successful in tropical nations because of the continuous lifecycle of mosquitoes and the poor infrastructure in those nations.
Using DDT was never pursued in the Saharan-African area of the world because of these perceived difficulties, thus their death rate due to malaria and other diseases carried on insects has never really reduced. “The use of DDT did have a major impact for the rest of the world such as in India it reduced malaria from 75 million cases to fewer than 5 million cases in a decade.”[1] Spraying DDT on livestock and crops led to them almost doubling their yields.
DDT after being sprayed on crops and livestock is eventually concentrated to a greater extent as one moves up the food chain, with humans being at the top. The greater concentration of DDT has been linked to cancer in humans. Even though there is no conclusive evidence, DDT is still widely listed as a possible carcinogen, a cancer-causing substance.
DDT is an organochlorine which in studies has been linked to triggering different hormonal responses in animals, mostly acting as an estrogen mimic. This estrogen mimic can alter the hormonal balance in women and is linked to an increased chance of breast cancer. DDT, since it is soluble in fats, is also able to embed itself into the plasma membrane of cells in animals.
When embedding itself into these membranes, it causes the cell to leak both potassium and sodium ions. The leaking of sodium and potassium ions from neurons causes nerve impulses to fire when they aren’t supposed to, allowing the poisoned individual to die from either convulsions or paralysis.[2]
DDT has had a huge environmental impact on the world. It is highly toxic to different marine life, such as crayfish, daphnids, and sea shrimp. The most widely known environmental impact that DDT has had is on birds.
When DDT is taken in by certain types of birds, it interferes with certain reproductive enzymes. These certain reproductive enzymes lead to how much calcium is deposited in eggshells, and less calcium in their shells made them more prone to cracking.
These weaker eggshells crack when the mother bird tries to incubate them herself, thus leading to less offspring being born of that type of bird. DDT is one of the many things that were blamed for the massive decrease of bald eagles in the 1950s and 1960s.
DDT’s impact was felt greatly on the global level with it greatly reducing insect carried diseases and allowing crops to grow to their full potential, but it did not come without its human and environmental negative impacts.
Legislation:
For many years, DDT was considered the “wonder pesticide” that saved the lives of millions of people. The use of DDT was widespread until the publication of Silent Spring, by the American marine biologist, Rachel Carson, in 1962. The book, which was eventually printed in 17 countries and in 10 languages made the dangers of DDT well known.
Suspicion began to grow that DDT, by entering the food chain and eventually concentrating in higher animals, caused reproductive dysfunctions. A major dysfunction was the eggshells of some birds becoming very thin. On top of this some of the insects, which DDT was killing off developed DDT-resistant strains. The populations of these insects started to grow while their natural predators, such as wasps, were being killed by DDT.
She called pesticides such as DDT “biocides” to imply that they were killing everything living, not just pests. According to Carson, pesticides, and especially DDT, were carcinogens, which were upsetting the balance of nature.
President Kennedy also read Carson’s work and shortly after, the Life Science Panel, under the President’s Science Advisory was ordered to begin reviewing pesticide use and in 1963, the panel called for legislative measures to protect the environment from these chemicals. Eventually, in 1973 DDT was banned in the U.S except for use in extreme health emergencies.[3]
Many other nations have also banned it or placed it under strict control, but still many groups and countries continue to use malaria, largely to prevent malaria. Madagascar, Ethiopia, Eritrea, Sudan, South Africa, Namibia, Solomon Island, Papua New Guinea, Algeria, Thailand, and Myanmar (countries involved in the Malaria Control Project) still use DDT to control malaria because of its “low cost, high effectiveness, persistence, and relative safety to humans.”
Risks and Benefits:
First, the positive aspects of DDT will be discussed. DDT is a pesticide, which are agents used to destroy pests such as insects, which can cause epidemic diseases such as Malaria or Typhus. Using such a compound is beneficial to humans because by killing off the disease-carrying pests; the disease can’t be spread thus saving lives. For this reason, it was used in World War II as DDT was sprayed on the battleground to control insect typhus and malaria vectors.
As a result of this, typhus was nearly eliminated from the world. DDT was also responsible for ridding malaria from Europe and North America. And economically speaking, using DDT is cost-efficient, and highly effective.
In defense of accusations that DDT is toxic to humans, there have actually been no substantial scientific studies so far which indicate that DDT is actually toxic to humans or other primates. Even though DDT “possibly causes cancer” studies have actually not found a link between DDT and cancer in humans.
In one study, 35 workers exposed to 600 times the average DDT exposure levels over a period of 9 to 19 years. No elevated cancer risk was observed. In another study, humans voluntarily ingested 35 mg of DDT daily for about two years and were then tracked for several years afterward. No elevated risk was observed.
Why then is DDT banned? The first risk of DDT is because it concentrates in biological systems, particularly in body fat. This means that DDT, once it enters the body gets stored as fat, which leads it to be able to build up and become toxic. Also, DDT is a toxin for a range of phyla.
This is good for getting rid of unwanted pests, but also un-harmful insects and animals are also killed including wasps, which are the natural predators of many of the unwanted pests.
The third Risk of using DDT is that it bioaccumulates in the food chain reaching its greatest concentrations at the top (humans.) The higher concentrations also have proved to cause reproductive dysfunctions, such as thin eggshells in some birds. This is bad because the eggs break when birds sit on their eggs to incubate them. This in turn puts bird species in danger of under population.
Yet another risk of DDT is that it is highly toxic to aquatic life, including crayfish, daphnids, sea shrimp, and many species of fish. It may also be moderately toxic to some amphibian species. If DDT use around these aquatic creatures goes unchecked, then a great loss of aquatic populations will be suffered and a significant amount of bioaccumulation will move up in the aquatic food chain, leading to long-term exposure.
As for the risks concerning humans, DDT as states before may be stored in the body as fat and may become toxic. There are some accusations that DDT could be related to breast cancer. For example, the diminishing rates of breast cancer in Israel have paralleled a decline in environmental contamination with DDT and benzene hexachloride.
The facts are obvious. DDT does pose risks. The ultimate question stands: Do the benefits of using DDT outweigh the risks? Alternatives to DDT are often riskier or more costly. In countries where money is a prime factor, there is no alternative.
The truth is that DDT has been very successful in preventing malaria and reducing mortality. As a result, however, the lives and chains of many species of birds, bugs, and aquatic species have been put into jeopardy. These factors have to be measured out to make a decision to either permit or ban DDT.
References:
Editors of Encyclopedia Encarta Online. (1997-2005).
DDT, Encyclopedia Encarta Online. Retrieved March 31, 2006,
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http://encarta.msn.com/encyclopedia_761561463/DDT.html
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http://www.swissinfo.org/images/specials/malaria/malaria_special.jpg
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http://www.fao.org/ag/againfo/resources/documents/WAR/war/U6600B/u6600b0b.jpg
Picture Egg
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http://markc1.typepad.com/relentlesslyoptimistic/images/ddt2.jpeg
Health Journal: Vitamins. (2006, January 25).
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Editors of Encyclopedia Wikipedia Online. (1997-2005).
http://www.bodyandfitness.com/Information/Health/Research/vitamins.html
DDT, Encyclopedia Wikipedia Online. Retrieved March 30, 2006,
from Encyclopedia Wikipedia Online on the World Wide Web:
http://en.wikipedia.org/wiki/DDT
Retrieved April 1, 2006, from the World Wide Web:
http://www.chem.duke/edu/~jds/cruise_chem/pest/today.html
Carson, Rachel (1962).Silent Spring. New York,
New York: Mariner Books.
[1] http://encarta.msn.com/encyclopedia_761561463/DDT.html
[2] http://www.chem.duke.edu/~jds/cruise_chem/pest/today.html
[3] http://www.chem.duke.edu/~jds/cruise_chem/pest/today.html
