DDT By Travis Slaysman

DDT Background DDT or dichlorodiphenyltrichloroethane is part of the organochlorine insecticide family. It’s a crystalline solid at room temperature and its tasteless and almost odorless. Chemical Formula: C14H9Cl5 Molar Mass: 354.49 g/mol Melting Point: 108.5 ⁰ C Boiling Point: 260 ⁰ C

DDT Discovery DDT was first synthesized in 1874 by German chemists. At this time no one realized any advantages of the compound. In 1939, a Swiss chemist by the name of Paul Hermann Müller discovered that DDT was an extremely effective at killing insects, in particular, mosquitoes. DDT was used commonly in World War II to help control the spread of malaria and typhus.

Paul Hermann Müller Paul Hermann Müller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods.”

Brief DDT History After World War II, DDT was made commercially available as an insecticide which subsequently led to widespread production and use of the insecticide. In 1962, an American Biologist by the name Rachel Carson wrote a book, Silent Spring, which catalogued the detrimental environmental impacts by unregulated and unquestioned spraying of DDT in the United States. As use soared the impact DDT has on the environment began to become more noticeable.

DDT Use DDT became the most common pesticide used on crops in the United States in a very short period of time. From 1950 -1980 it is estimated that 1.8 million tons of DDT was produced. The average usage of DDT until its ban in 1972 was approximately 600,000 tons/year. DDT is still being produced internationally. In 2009, 3314 tons of DDT was produced.

Experimental DDT was studied intensely while its use was still prevalent from approximately 1940 – 1975, studies since then have declined due to its ban. During the 1950’s, DDT use began to decline due to research that was coming out on the possible toxic properties of DDT and its metabolites, DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane).

Environmental Impact DDT and its metabolites have been studied for possible toxic effects in both humans and the wildlife population. Research discovered a multitude of serious impacts on different species, with the bird population seeming to be the most effected. Many believe DDT to be one of the main reasons that particular bird populations dwindled to the point they became an endangered species.

Environmental Impact DDT has been classified as acutely toxic to birds. Research has shown that DDE, a metabolite of DDT has been shown to cause thinning of bird’s eggshells. DDT is toxic to birds at doses of approximately 400 mg/kg, but doses as low as 10-15 mg/kg show a decline in their fertility as well as fewer hatchlings per clutch.

Toxicity in Aquatic Life DDT is highly acutely toxic to aquatic life as well as amphibians. Fish are not able to detect DDT in their environment, making them more susceptible to ingesting it. When ingested by fish, DDT disrupts membrane function and enzyme activity. DDT has a half life range of 2 – 16 years in a soil environment. Its half life in aquatic environments is 150 years.

Environmental Impact Predatory birds are the most susceptible to DDT because of their diet. The fish they consume contain DDT which builds up in their system as it can’t be metabolized. Bioaccumulation, which is the increased concentration of a toxin as it moves up the food chain, is one of the biggest concerns left from DDT usage. DDT’s persistence in the environment made it an ideal choice as an insecticide, but it’s also the reason why it is still a concern.

Toxicity in Humans DDT is soluble in lipids and oils, causing it to be stored in the fatty tissue of humans. When fat is broken down, usually during periods of starvation, DDT is released into the blood stream where its toxic to the liver and nervous system. Humans are usually becomes present in the body due to ingestion rather than inhalation or absorption through skin contact. DDT is classified as a B2 carcinogen, meaning it’s been shown to cause cancer is lab animals, but not in humans.

Ethical Issues DDT is an extremely potent poison to mosquitoes, which carry a multitude of diseases. From 1946 to 1950, reported cases of malaria dropped from 400,000 to almost zero. Although DDT was banned in the United States in 1972, DDT is still used where there is a great risk of malaria and other disease carried by mosquitoes.

Banning of DDT When the book Silent Spring was released, it is believed to start what many refer to as the modern environmental movement. A year after the book was released, John F. Kennedy formed a committee in order to investigate the claims made in the book. The committee had come to the conclusion that Rachel Carson’s thesis was accurate, and that persistent toxic pesticides should be phased out as soon as possible.

Banning of DDT In 1967, a group of lawyers and scientists paired up and founded the Environmental Defense Fund and began a push for a ban on the use of DDT. The EDF subsequently filed a law suit looking to specifically ban DDT. In 1971 the United States Court of Appeals requested the EPA begin the de-registration of the pesticide, and in 1972, the ban on DDT use in the United States became official.

DDT After the Ban After the United States banned DDT, other European countries followed suit. DDT’s worldwide use was further restricted by the Stockholm Convention in 2004, which has been ratified by over 170 countries. Use of DDT is only permitted for ‘vector control’ which means that its use is only for the elimination and control of disease spreading insects.

Current DDT Use Many African, South American and Asian countries still spray DDT to this day in order to control spread of disease. It is sprayed in controlled manners in relatively confined spaces, usually in homes. India and North Korea both still use DDT as means of an agricultural pesticide. Currently, approximately 3000 – 4000 tons are produced annually.

Works Cited U.S. EPA: DDT – A Brief History and Status. http://www.epa.gov/opp00001/factsheets/chemicals/ddt-brief-history-status.htm (accessed March 28, 2013) NPIC: DDT Technical Fact Sheet http://npic.orst.edu/factsheets/ddtgen.pdf (accessed March 28, 2013) NPIC: DDT General Fact Sheet. http://npic.orst.edu/factsheets/ddttech.pdf (accessed March 29, 2013) DDT.http://en.wikipedia.org/wiki/DDT#Effects_on_wildlife_and_eggshell_thinning (accessed March 29, 2013)