DDT
Overview
 
DDT is one of the most well-known synthetic insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s. It is a chemical with a long, unique, and controversial history.

First synthesized in 1874, DDT's insecticidal properties were not discovered until 1939, and it was used with great success in the second half of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 to control malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

 and typhus
Typhus
Epidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters...

 among civilians and troops. The Swiss chemist Paul Hermann Müller
Paul Hermann Müller
Paul Hermann Müller also known as Pauly Mueller was a Swiss chemist and Nobel laureate. In 1948 he received the Nobel Prize in Physiology or Medicine for his 1939 discovery of insecticidal qualities and use of DDT in the control of vector diseases such as malaria and yellow fever.Müller was born...

 was awarded the Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...

 in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods." After the war, DDT was made available for use as an agricultural insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

, and soon its production and use skyrocketed.

In 1962, Silent Spring
Silent Spring
Silent Spring is a book written by Rachel Carson and published by Houghton Mifflin on 27 September 1962. The book is widely credited with helping launch the environmental movement....

by American biologist Rachel Carson
Rachel Carson
Rachel Louise Carson was an American marine biologist and conservationist whose writings are credited with advancing the global environmental movement....

 was published.
Encyclopedia
DDT is one of the most well-known synthetic insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s. It is a chemical with a long, unique, and controversial history.

First synthesized in 1874, DDT's insecticidal properties were not discovered until 1939, and it was used with great success in the second half of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 to control malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

 and typhus
Typhus
Epidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters...

 among civilians and troops. The Swiss chemist Paul Hermann Müller
Paul Hermann Müller
Paul Hermann Müller also known as Pauly Mueller was a Swiss chemist and Nobel laureate. In 1948 he received the Nobel Prize in Physiology or Medicine for his 1939 discovery of insecticidal qualities and use of DDT in the control of vector diseases such as malaria and yellow fever.Müller was born...

 was awarded the Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...

 in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods." After the war, DDT was made available for use as an agricultural insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

, and soon its production and use skyrocketed.

In 1962, Silent Spring
Silent Spring
Silent Spring is a book written by Rachel Carson and published by Houghton Mifflin on 27 September 1962. The book is widely credited with helping launch the environmental movement....

by American biologist Rachel Carson
Rachel Carson
Rachel Louise Carson was an American marine biologist and conservationist whose writings are credited with advancing the global environmental movement....

 was published. The book catalogued the environmental impacts of the indiscriminate spraying of DDT in the US and questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health. The book suggested that DDT and other pesticides may cause cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 and that their agricultural use was a threat to wildlife, particularly birds. Its publication was one of the signature events in the birth of the environmental movement
Environmentalism
Environmentalism is a broad philosophy, ideology and social movement regarding concerns for environmental conservation and improvement of the health of the environment, particularly as the measure for this health seeks to incorporate the concerns of non-human elements...

, and resulted in a large public outcry that eventually led to DDT being banned in the US in 1972. DDT was subsequently banned for agricultural use worldwide under the Stockholm Convention
Stockholm Convention
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...

, but its limited use in disease vector control
Vector control
Vector control is any method to limit or eradicate the mammals, birds, insects or other arthropods which transmit disease pathogens. The most frequent type of vector control is mosquito control using a variety of strategies.-Methods of Control:...

 continues to this day and remains controversial.

Along with the passage of the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

, the US ban on DDT is cited by scientists as a major factor in the comeback of the bald eagle
Bald Eagle
The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...

, the national bird of the United States, from near-extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 in the contiguous US.

Properties and chemistry

DDT is an organochlorine, similar in structure to the insecticide methoxychlor
Methoxychlor
Methoxychlor is a synthetic organochlorine used as an insecticide.-Usage:Methoxychlor is used to protect crops, ornamentals, livestock, and pets against fleas, mosquitoes, cockroaches, and other insects...

 and hithe acaricide dicofol
Dicofol
Dicofol is an organochlorine pesticide that is chemically related to DDT. Dicofol is a miticide that is very effective against red spider mite....

. It is a highly hydrophobic, colorless, crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

line solid with a weak, chemical odor
Odor
An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

. It is nearly insoluble in water but has a good solubility in most organic
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

s, fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

s, and oils. DDT does not occur naturally, but is produced by the reaction of chloral  with chlorobenzene
Chlorobenzene
Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals.-Uses:...

  in the presence of sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

, which acts as a catalyst. Trade names that DDT has been marketed under include Anofex (Geigy Chemical Corp.), Cezarex, Chlorophenothane, Clofenotane, Dicophane, Dinocide, Gesarol (Syngenta Crop.), Guesapon, Guesarol, Gyron (Ciba-Geigy Corp. - now Novertis), Ixodex, Neocid (Reckitt & Colman, Ltd), Neocidol (Ciba-Geigy Corp. - now Novartis), and Zerdane.

Isomers and related compounds

Commercial DDT is a mixture of several closely–related compounds. The major component (77%) is the p
Arene substitution patterns
Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon.- Ortho, meta, and para substitution :...

,p' isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...

 which is pictured at the top of this article. The o,p' isomer (pictured to the right) is also present in significant amounts (15%). Dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene is a chemical compound formed by the loss of hydrogen chloride from DDT, of which it is one of the more common breakdown products. DDE is fat soluble which tends to build up in the fat of animals. Due to its stability in fat, DDE is rarely excreted from the body,...

 (DDE) and dichlorodiphenyldichloroethane
Dichlorodiphenyldichloroethane
Dichlorodiphenyldichloroethane is an organochlorine insecticide that is slightly irritating to the skin. DDD is a metabolite of DDT. DDD is colorless and crystalline; it is closely related chemically and is similar in properties to DDT, but it is considered to be less toxic to animals than is DDT...

 (DDD) make up the balance. DDE and DDD are also the major metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...

s and breakdown products in the environment. The term "total DDT" is often used to refer to the sum of all DDT related compounds (p,p'-DDT, o,p'-DDT, DDE, and DDD) in a sample.

Production and use statistics

From 1950 to 1980, DDT was extensively used in agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

—more than 40,000 tonnes were used each year worldwide—and it has been estimated that a total of 1.8 million tonnes have been produced globally since the 1940s. In the U.S., where it was manufactured by Ciba, Montrose Chemical Company
Montrose Chemical Corporation of California
After World War II, Montrose Chemical Corporation of California, 20201 S. Normandie Ave., Unincorporated LA County, California began producing Dichloro-Diphenyl-Trichloroethane , the new “wonder pesticide.” Their waste disposal system funneled the plant’s processed waste into the county sewer...

, Pennwalt and Velsicol Chemical Corporation
Velsicol Chemical Corporation
Genovique Specialties Corporation was a Rosemont, Illinois based chemical company founded in 1931 that specializes in plasticizers....

, production peaked in 1963 at 82,000 tonnes per year. More than 600,000 tonnes (1.35 billion lbs) were applied in the U.S. before the 1972 ban. Usage peaked in 1959 at about 36,000 tonnes.

In 2009, 3314 tonnes were produced for the control of malaria and visceral leishmaniasis
Visceral leishmaniasis
Visceral leishmaniasis , also known as kala-azar, black fever, and Dumdum fever, is the most severe form of leishmaniasis. Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus. This disease is the second-largest parasitic killer in the world , responsible for an...

. India is the only country still manufacturing DDT, with China having ceased production in 2007. India is the largest consumer.

Mechanism of insecticide action

In insects it opens sodium ion channels in neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s, causing them to fire spontaneously, which leads to spasms and eventual death. Insects with certain mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

s in their sodium channel gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 are resistant to DDT and other similar insecticides. DDT resistance is also conferred by up-regulation of genes expressing cytochrome P450 in some insect species.

In humans, however, it may affect health through genotoxicity or endocrine disruption
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...

. See Effects on human health.

History

First synthesized in 1874 by Othmar Zeidler
Othmar Zeidler
Othmar Zeidler was an Austrian chemist credited with the first synthesis of DDT.He was a son of the Viennese pharmacist Franz Zeidler. Othmar's brother, Franz Zeidler Jr. , also became a chemist and would collaborate with him on several projects...

, DDT's insecticidal properties were not discovered until 1939 by the Swiss
Swiss (people)
The Swiss are citizens or natives of Switzerland. The demonym derives from the toponym of Schwyz and has been in widespread use to refer to the Old Swiss Confederacy since the 16th century....

 scientist Paul Hermann Müller
Paul Hermann Müller
Paul Hermann Müller also known as Pauly Mueller was a Swiss chemist and Nobel laureate. In 1948 he received the Nobel Prize in Physiology or Medicine for his 1939 discovery of insecticidal qualities and use of DDT in the control of vector diseases such as malaria and yellow fever.Müller was born...

, who was awarded the 1948 Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

 in Physiology and Medicine for his efforts.

Use in the 1940s and 1950s

DDT is the best-known of several chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

-containing pesticides used in the 1940s and 1950s. With pyrethrum
Pyrethrum
Pyrethrum refers to several Old World plants of the genus Chrysanthemum which are cultivated as ornamentals for their showy flower heads. Pyrethrum is also the name of a natural insecticide made from the dried flower heads of C. cinerariifolium and C...

 in short supply, DDT was used extensively during World War II by the Allies
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 to control the insect vectors of typhus
Typhus
Epidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters...

 — nearly eliminating the disease in many parts of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. In the South Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, it was sprayed aerially for malaria and dengue fever control with spectacular effects. While DDT's chemical and insecticidal properties were important factors in these victories, advances in application equipment coupled with a high degree of organization and sufficient manpower were also crucial to the success of these programs. In 1945, it was made available to farmers as an agricultural insecticide, and it played a minor role in the final elimination of malaria in Europe and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. By the time DDT was introduced in the U.S., the disease had already been brought under control by a variety of other means. One CDC physician involved in the United States' DDT spraying campaign said of the effort that "we kicked a dying dog."

In 1955, the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 commenced a program to eradicate malaria worldwide, relying largely on DDT. The program was initially highly successful, eliminating the disease in "Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

, much of the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

, the Balkans
Balkans
The Balkans is a geopolitical and cultural region of southeastern Europe...

, parts of northern Africa, the northern region of Australia, and a large swath of the South Pacific" and dramatically reducing mortality in Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

 and India. However widespread agricultural use led to resistant insect populations. In many areas, early victories partially or completely reversed, and in some cases rates of transmission even increased. The program was successful in eliminating malaria only in areas with "high socio-economic status, well-organized healthcare systems, and relatively less intensive or seasonal malaria transmission".

DDT was less effective in tropical regions due to the continuous life cycle of mosquitoes and poor infrastructure. It was not applied at all in sub-Saharan Africa
Sub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...

 due to these perceived difficulties. Mortality rates in that area never declined to the same dramatic extent, and now constitute the bulk of malarial deaths worldwide, especially following the disease's resurgence as a result of resistance to drug treatments and the spread of the deadly malarial variant caused by Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...

. The goal of eradication was abandoned in 1969, and attention was focused on controlling and treating the disease. Spraying programs (especially using DDT) were curtailed due to concerns over safety and environmental effects, as well as problems in administrative, managerial and financial implementation, but mostly because mosquitoes were developing resistance to DDT. Efforts shifted from spraying to the use of bednets
Mosquito net
A mosquito net offers protection against mosquitos, flies, and other insects, and thus against diseases such as malaria, dengue fever, yellow fever, and various forms of encephalitis, including the West Nile virus, if used properly and especially if treated with an insecticide, which can double...

 impregnated with insecticides and other interventions.

Silent Spring and the U.S. ban

As early as the 1940s, scientists in the U.S. had begun expressing concern over possible hazards associated with DDT, and in the 1950s the government began tightening some of the regulations governing its use. However, these early events received little attention, and it was not until 1957, when the New York Times reported an unsuccessful struggle to restrict DDT use in Nassau County, New York
Nassau County, New York
Nassau County is a suburban county on Long Island, east of New York City in the U.S. state of New York, within the New York Metropolitan Area. As of the 2010 census, the population was 1,339,532...

, that the issue came to the attention of the popular naturalist-author, Rachel Carson
Rachel Carson
Rachel Louise Carson was an American marine biologist and conservationist whose writings are credited with advancing the global environmental movement....

. William Shawn
William Shawn
William Shawn was an American magazine editor who edited The New Yorker from 1952 until 1987.-Education and Early Life:...

, editor of The New Yorker
The New Yorker
The New Yorker is an American magazine of reportage, commentary, criticism, essays, fiction, satire, cartoons and poetry published by Condé Nast...

, urged her to write a piece on the subject, which developed into her famous book Silent Spring
Silent Spring
Silent Spring is a book written by Rachel Carson and published by Houghton Mifflin on 27 September 1962. The book is widely credited with helping launch the environmental movement....

, published in 1962. The book argued that pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s, including DDT, were poisoning both wildlife and the environment and were also endangering human health.

Silent Spring was a best seller, and public reaction to it launched the modern environmental movement
Environmentalism
Environmentalism is a broad philosophy, ideology and social movement regarding concerns for environmental conservation and improvement of the health of the environment, particularly as the measure for this health seeks to incorporate the concerns of non-human elements...

 in the United States. The year after it appeared, President Kennedy
John F. Kennedy
John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the 35th President of the United States, serving from 1961 until his assassination in 1963....

 ordered his Science Advisory Committee to investigate Carson's claims. The report the committee issued "add[ed] up to a fairly thorough-going vindication of Rachel Carson’s Silent Spring thesis," in the words of the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

, and recommended a phaseout of "persistent toxic pesticides". DDT became a prime target of the growing anti-chemical and anti-pesticide movements, and in 1967 a group of scientists and lawyers founded the Environmental Defense Fund
Environmental Defense
Environmental Defense Fund or EDF is a United States–based nonprofit environmental advocacy group. The group is known for its work on issues including global warming, ecosystem restoration, oceans, and human health...

 (EDF) with the specific goal of winning a ban on DDT. Victor Yannacone
Victor Yannacone
Victor Yannacone is a controversial, pioneering environmental attorney, who played leading roles in successful campaigns to ban DDT in the U.S. and expose the effects of Agent Orange on Vietnam vets.-DDT:...

, Charles Wurster, Art Cooley and others associated with inception of EDF had all witnessed bird kills or declines in bird populations and suspected that DDT was the cause. In their campaign against the chemical, EDF petitioned the government for a ban and filed a series of lawsuits. Around this time, toxicologist David Peakall
David Peakall
David Beaumont Peakall was an internationally recognised toxicologist. His research into the effects of DDE and DDT on eggshells contributed to the ban on DDT in the US. He proved that the chemicals caused thinning of eggshells, leading to a reduction in the population of various bird species...

 was measuring DDE
Dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene is a chemical compound formed by the loss of hydrogen chloride from DDT, of which it is one of the more common breakdown products. DDE is fat soluble which tends to build up in the fat of animals. Due to its stability in fat, DDE is rarely excreted from the body,...

 levels in the eggs of peregrine falcons and California condor
California Condor
The California Condor is a New World vulture, the largest North American land bird. Currently, this condor inhabits only the Grand Canyon area, Zion National Park, and coastal mountains of central and southern California and northern Baja California...

s and finding that increased levels corresponded with thinner shells.

In response to an EDF suit, the U.S. District Court of Appeals in 1971 ordered the EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 to begin the de-registration procedure for DDT. After an initial six-month review process, William Ruckelshaus
William Ruckelshaus
William Doyle Ruckelshaus is an American attorney and, several times, U.S. government official. He served as the first head of the Environmental Protection Agency in 1970, was subsequently acting Director of the Federal Bureau of Investigation, and then Deputy Attorney General of the United States...

, the Agency's first Administrator
Administrator of the Environmental Protection Agency
The Administrator of the Environmental Protection Agency is the head of the United States federal government's Environmental Protection Agency, and is thus responsible for enforcing the nation's Clean Air and Clean Water Acts, as well as numerous other environmental statutes. The Administrator is...

 rejected an immediate suspension of DDT's registration, citing studies from the EPA's internal staff stating that DDT was not an imminent danger to human health and wildlife. However, the findings of these staff members were criticized, as they were performed mostly by economic entomologists inherited from the United States Department of Agriculture
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

, whom many environmentalists felt were biased towards agribusiness and tended to minimize concerns about human health and wildlife. The decision not to ban thus created public controversy.

The EPA then held seven months of hearings in 1971–1972, with scientists giving evidence both for and against the use of DDT. In the summer of 1972, Ruckelshaus announced the cancellation of most uses of DDT—an exemption allowed for public health uses under some conditions. Immediately after the cancellation was announced, both EDF and the DDT manufacturers filed suit against the EPA, with the industry seeking to overturn the ban, and EDF seeking a comprehensive ban. The cases were consolidated, and in 1973 the U.S. Court of Appeals for the District of Columbia ruled that the EPA had acted properly in banning DDT.

The U.S. DDT ban took place amidst a growing public mistrust of industry, with the Surgeon General
Surgeon General of the United States
The Surgeon General of the United States is the operational head of the Public Health Service Commissioned Corps and thus the leading spokesperson on matters of public health in the federal government...

 issuing a report on smoking
Smoking
Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...

 in 1964, the Cuyahoga River
Cuyahoga River
The Cuyahoga River is located in Northeast Ohio in the United States. Outside of Ohio, the river is most famous for being "the river that caught fire", helping to spur the environmental movement in the late 1960s...

 catching fire in 1969, the fiasco surrounding the use of diethylstilbestrol
Diethylstilbestrol
Diethylstilbestrol is a synthetic nonsteroidal estrogen that was first synthesized in 1938. Human exposure to DES occurred through diverse sources, such as dietary ingestion from supplemented cattle feed and medical treatment for certain conditions, including breast and prostate cancers...

 (DES), and the well-publicized decline in the bald eagle
Bald Eagle
The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...

 population.

Some uses of DDT continued under the public health exemption. For example, in June 1979, the California Department of Health Services was permitted to use DDT to suppress flea vectors of bubonic plague
Bubonic plague
Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death...

. DDT also continued to be produced in the US for foreign markets until as late as 1985, when over 300 tonnes were exported.

Restrictions on usage

In the 1970s and 1980s, agricultural use was banned in most developed countries, beginning with Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

 in 1968 then in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 in 1970, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and the United States in 1972, but not in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 until 1984. Vector control use has not been banned, but it has been largely replaced by less persistent alternative insecticides.

The Stockholm Convention
Stockholm Convention
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...

, which took effect in 2004, outlawed several persistent organic pollutant
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...

s, and restricted DDT use to vector control
Vector control
Vector control is any method to limit or eradicate the mammals, birds, insects or other arthropods which transmit disease pathogens. The most frequent type of vector control is mosquito control using a variety of strategies.-Methods of Control:...

. The Convention has been ratified by more than 170 countries and is endorsed by most environmental groups. Recognizing that total elimination in many malaria-prone countries is currently unfeasible because there are few affordable or effective alternatives, public health use is exempt from the ban pending acceptable alternatives. Malaria Foundation International states, "The outcome of the treaty is arguably better than the status quo going into the negotiations...For the first time, there is now an insecticide which is restricted to vector control only, meaning that the selection of resistant mosquitoes will be slower than before."

Despite the worldwide ban, agricultural use continues in India North Korea, and possibly elsewhere.

Today, about 3-4,000 tonnes each year are produced for vector control
Vector control
Vector control is any method to limit or eradicate the mammals, birds, insects or other arthropods which transmit disease pathogens. The most frequent type of vector control is mosquito control using a variety of strategies.-Methods of Control:...

. DDT is applied to the inside walls of homes to kill or repel mosquitoes. This intervention, called indoor residual spraying
Indoor residual spraying
Indoor residual spraying or IRS is the process of spraying the inside of dwellings with an insecticide to kill mosquitoes that spread malaria. A dilute solution of insecticide is sprayed on the inside walls of certain types of dwellings—those with walls made from porous materials such as mud or...

 (IRS), greatly reduces environmental damage. It also reduces the incidence of DDT resistance. For comparison, treating 40 hectares (98.8 acre) of cotton during a typical U.S. growing season requires the same amount of chemical as roughly 1,700 homes.

Environmental impact

DDT is a persistent organic pollutant
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...

 that is extremely hydrophobic and strongly absorbed by soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. Depending on conditions, its soil half life can range from 22 days to 30 years. Routes of loss and degradation include runoff, volatilization, photolysis and aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and anaerobic
Anaerobic digestion
Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is used for industrial or domestic purposes to manage waste and/or to release energy....

 biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

. When applied to aquatic ecosystem
Aquatic ecosystem
An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems....

s it is quickly absorbed by organisms and by soil or it evaporates, leaving little DDT dissolved in the water itself. Its breakdown products and metabolites, DDE and DDD, are also highly persistent and have similar chemical and physical properties. DDT and its breakdown products are transported from warmer regions of the world to the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 by the phenomenon of global distillation
Global distillation
Global distillation or the grasshopper effect is the geochemical process by which certain chemicals, most notably persistent organic pollutants , are transported from warmer to colder regions of the Earth, particularly the Poles and mountain tops...

, where they then accumulate in the region's food web
Food web
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

.

Because of its lipophilic
Lipophilic
Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...

 properties, DDT has a high potential to bioaccumulate, especially in predatory birds. DDT, DDE, and DDD magnify
Biomagnification
Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance that occurs in a food chain as a consequence of:* Persistence...

 through the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

, with apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...

s such as raptor birds concentrating more chemicals than other animals in the same environment. They are very lipophilic and are stored mainly in body fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

. DDT and DDE are very resistant to metabolism; in humans, their half-lives are 6 and up to 10 years, respectively. In the United States, these chemicals were detected in almost all human blood samples tested by the Centers for Disease Control in 2005, though their levels have sharply declined since most uses were banned in the US. Estimated dietary intake has also declined, although FDA food tests commonly detect it.

Marine macroalgae (seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

) help reduce
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

 soil toxicity by up to 80% within six weeks.

Effects on wildlife and eggshell thinning

DDT is toxic to a wide range of animals in addition to insects, including marine animals such as crayfish
Crayfish
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...

, daphnids
Daphnia
Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style...

, sea shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

 and many species of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

. It is less toxic to mammals, but may be moderately toxic to some amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

 species, especially in the larval
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...

 stage. Most famously, it is a reproductive toxicant for certain birds species, and it is a major reason for the decline of the bald eagle
Bald Eagle
The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...

, brown pelican
Brown Pelican
The Brown Pelican is the smallest of the eight species of pelican, although it is a large bird in nearly every other regard. It is in length, weighs from and has a wingspan from .-Range and habits:...

 peregrine falcon
Peregrine Falcon
The Peregrine Falcon , also known as the Peregrine, and historically as the Duck Hawk in North America, is a widespread bird of prey in the family Falconidae. A large, crow-sized falcon, it has a blue-gray back, barred white underparts, and a black head and "moustache"...

, and osprey
Osprey
The Osprey , sometimes known as the sea hawk or fish eagle, is a diurnal, fish-eating bird of prey. It is a large raptor, reaching more than in length and across the wings...

. Birds of prey, waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....

, and song birds
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...

 are more susceptible to eggshell
Eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.- Insect eggs :Insects and other arthropods lay a variety of styles and shapes of eggs. Some have gelatinous or skin-like coverings, others have hard eggshells. Softer shells are mostly protein....

 thinning than chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

s and related species
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...

, and DDE appears to be more potent than DDT. Even in 2010, more than forty years after the U.S. ban, California condor
California Condor
The California Condor is a New World vulture, the largest North American land bird. Currently, this condor inhabits only the Grand Canyon area, Zion National Park, and coastal mountains of central and southern California and northern Baja California...

s which feed on sea lions at Big Sur
Big Sur
Big Sur is a sparsely populated region of the Central Coast of California where the Santa Lucia Mountains rise abruptly from the Pacific Ocean. The name "Big Sur" is derived from the original Spanish-language "el sur grande", meaning "the big south", or from "el país grande del sur", "the big...

 which in turn feed in the Palos Verdes Shelf area of the Montrose Chemical Superfund
Superfund
Superfund is the common name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 , a United States federal law designed to clean up sites contaminated with hazardous substances...

 site seemed to be having continued thin-shell problems. Scientists with the Ventana Wildlife Society
Ventana Wildlife Society
Ventana Wildlife Society is a 5013 non-profit organization founded in 1977 by a group of private citizens to restore endangered species native to central California. VWS has five full-time staff biologists, together with seasonal interns, monitoring, tracking and researching endangered species,...

 and others are intensifying studies and remediations of the condors' problems.

The biological thinning mechanism is not entirely known, but there is strong evidence that p,p'-DDE inhibits calcium ATPase
Calcium ATPase
Calcium ATPase is a form of P-ATPase that transfers calcium after a muscle has contracted. The calcium ATPase are:*Plasma membrane Ca2+ ATPase *Sarcoplasmic reticulum Ca2+ ATPase - Plasma membrane Ca2+ ATPase :...

 in the membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

 of the shell gland and reduces the transport of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 from blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 into the eggshell gland. This results in a dose-dependent thickness reduction. There is also evidence that o,p'-DDT disrupts female reproductive tract development, impairing eggshell quality later. Multiple mechanisms may be at work, or different mechanisms may operate in different species. Some studies show that although DDE levels have fallen dramatically, eggshell thickness remains 10–12 percent thinner than before DDT was first used.

Effects on human health

Potential mechanisms of action on humans are genotoxicity and endocrine disruption. DDT may be directly genotoxic, but may also induce enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s to produce other genotoxic intermediates and DNA adduct
DNA adduct
In molecular genetics, a DNA adduct is a piece of DNA covalently bonded to a chemical. This process could be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as biomarkers of exposure and as such are themselves measured to reflect quantitatively,...

s. It is an endocrine disruptor; The DDT metabolite DDE
Dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene is a chemical compound formed by the loss of hydrogen chloride from DDT, of which it is one of the more common breakdown products. DDE is fat soluble which tends to build up in the fat of animals. Due to its stability in fat, DDE is rarely excreted from the body,...

 acts as an antiandrogen
Antiandrogen
Antiandrogens, or androgen antagonists, first discovered in the 1960s, prevent androgens from expressing their biological effects on responsive tissues. Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting...

 (but not as an estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...

). p,p'-DDT, DDT's main component, has little or no androgenic or estrogenic activity. Minor component o,p'-DDT has weak estrogenic activity.

Acute toxicity

DDT is classified as "moderately toxic" by the United States National Toxicology Program
National Toxicology Program
The National Toxicology Program is an inter-agency program run by the United States Department of Health and Human Services to coordinate, evaluate, and report on toxicology within public agencies....

 (NTP) and "moderately hazardous" by the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 (WHO), based on the rat oral of 113 mg/kg. DDT has on rare occasions been administered orally as a treatment for barbiturate
Barbiturate
Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

 poisoning.

Diabetes

DDT and DDE have been linked to diabetes. A number of studies from the US, Canada, and Sweden have found that the prevalence of the disease in a population increases with serum DDT or DDE levels.

Developmental toxicity

DDT and DDE, like other organochlorines, have been shown to have xenoestrogenic
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...

 activity, meaning they are chemically similar enough to estrogens to trigger hormonal responses in animals. This endocrine disrupting
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...

 activity has been observed in mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

 and rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

 toxicological studies, and available epidemiological evidence indicates that these effects may be occurring in humans as a result of DDT exposure. The US Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 states that DDT exposure damages the reproductive system and reduces reproductive success. These effects may cause developmental and reproductive toxicity:
  • A review article in The Lancet
    The Lancet
    The Lancet is a weekly peer-reviewed general medical journal. It is one of the world's best known, oldest, and most respected general medical journals...

    states, "research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning ... toxicological evidence shows endocrine-disrupting
    Endocrine disruptor
    Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...

     properties; human data also indicate possible disruption in semen quality, menstruation, gestational length, and duration of lactation."
  • Human epidemiological studies suggest that exposure is a risk factor for premature birth and low birth weight, and may harm a mother's ability to breast feed
    Lactation
    Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...

    . Some 21st century researchers argue that these effects may increase infant deaths, offsetting any anti-malarial benefits. A 2008 study, however, failed to confirm the association between exposure and difficulty breastfeeding.
  • Several recent studies demonstrate a link between in utero exposure to DDT or DDE and developmental neurotoxicity in humans. For example, a 2006 University of California, Berkeley
    University of California, Berkeley
    The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

     study suggests that children exposed while in the womb have a greater chance of development problems, and other studies have found that even low levels of DDT or DDE in umbilical cord
    Umbilical cord
    In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...

     serum at birth are associated with decreased attention at infancy and decreased cognitive skills at 4 years of age. Similarly, Mexican researchers have linked first trimester DDE exposure to retarded psychomotor development
    Psychomotor retardation
    Psychomotor retardation involves a slowing-down of thought and a reduction of physical movements in an individual. Psychomotor retardation can cause a visible slowing of physical and emotional reactions, including speech and affect...

    .
  • Other studies document decreases in semen quality among men with high exposures (generally from IRS).
  • Studies generally find that high blood DDT or DDE levels do not increase time to pregnancy (TTP.) There is some evidence that the daughters of highly exposed women may have more difficulty getting pregnant (i.e. increased TTP).
  • DDT is associated with early pregnancy loss, a type of miscarriage
    Miscarriage
    Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...

    . A prospective cohort study of Chinese textile
    Textile
    A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...

     workers found "a positive, monotonic, exposure-response association between preconception serum total DDT and the risk of subsequent early pregnancy losses." The median serum DDE level of study group was lower than that typically observed in women living in homes sprayed with DDT.
  • A Japanese study of congenital hypothyroidism
    Congenital hypothyroidism
    Congenital hypothyroidism is a condition of thyroid hormone deficiency present at birth. Approximately 1 in 4000 newborn infants has a severe deficiency of thyroid function, while even more have mild or partial degrees. If untreated for several months after birth, severe congenital hypothyroidism...

     concluded that in utero DDT exposure may affect thyroid
    Thyroid
    The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

     hormone
    Hormone
    A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

     levels and "play an important role in the incidence and/or causation of cretinism
    Cretinism
    Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones usually due to maternal hypothyroidism.-Etymology and use of cretin:...

    ." Other studies have also found the DDT or DDE interfere with proper thyroid function.

Other

Occupational exposure in agriculture and malaria control has been linked to neurological problems (i.e. Parkinsons) and asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

.

Carcinogenicity

DDT is suspected to cause cancer
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

. The NTP classifies it as "reasonably anticipated to be a carcinogen," the International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 classifies it as a "possible" human carcinogen, and the EPA classifies DDT, DDE, and DDD as class B2 "probable" carcinogens. These evaluations are based mainly on the results of animal studies.

There is evidence from epidemiological studies (i.e. studies in human populations) that indicates that DDT causes cancers of the liver
Liver cancer
Liver tumors or hepatic tumors are tumors or growths on or in the liver . Several distinct types of tumors can develop in the liver because the liver is made up of various cell types. These growths can be benign or malignant...

, pancreas
Pancreatic cancer
Pancreatic cancer refers to a malignant neoplasm of the pancreas. The most common type of pancreatic cancer, accounting for 95% of these tumors is adenocarcinoma, which arises within the exocrine component of the pancreas. A minority arises from the islet cells and is classified as a...

 and breast
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

. There is mixed evidence that it contributes to leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

, lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

 and testicular cancer
Testicular cancer
Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system.In the United States, between 7,500 and 8,000 diagnoses of testicular cancer are made each year. In the UK, approximately 2,000 men are diagnosed each year. Over his lifetime, a man's risk of...

. Other epidemiological studies suggest that DDT/DDE does not cause multiple myeloma
Multiple myeloma
Multiple myeloma , also known as plasma cell myeloma or Kahler's disease , is a cancer of plasma cells, a type of white blood cell normally responsible for the production of antibodies...

, or cancers of the prostate
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

, endometrium
Endometrial cancer
Endometrial cancer refers to several types of malignancies that arise from the endometrium, or lining, of the uterus. Endometrial cancers are the most common gynecologic cancers in the United States, with over 35,000 women diagnosed each year. The incidence is on a slow rise secondary to the...

, rectum
Colorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....

, lung
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

, bladder
Bladder cancer
Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...

, or stomach
Stomach cancer
Gastric cancer, commonly referred to as stomach cancer, can develop in any part of the stomach and may spread throughout the stomach and to other organs; particularly the esophagus, lungs, lymph nodes, and the liver...

.

Breast cancer

The question of whether DDT or DDE are risk factors of breast cancer
Risk factors of breast cancer
Risk factors of breast cancer may be divided into preventable and non preventable. Their study belongs in the field of epidemiology. Breast cancer, like other forms of cancer, is considered to result from multiple environmental and hereditary risk factors....

 has been repeatedly studied. While individual studies conflict, the most recent reviews of all the evidence conclude that pre-puberty exposure increases the risk of subsequent breast cancer. Until recently, almost all studies measured DDT or DDE blood levels at the time of breast cancer diagnosis or after. This study design has been criticized, since the levels at diagnosis do not necessarily correspond to levels when the cancer started. Taken as a whole such studies "do not support the hypothesis that exposure to DDT is an important risk factor for breast cancer." The studies of this design have been extensively reviewed.

In contrast, a study published in 2007 strongly associated early exposure (the p,p'- isomer) and breast cancer later in life. Unlike previous studies, this prospective cohort study
Prospective cohort study
A prospective cohort study is a cohort study that follows over time a group of similar individuals who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome...

 collected blood samples from young mothers in the 1960s while DDT was still in use, and their breast cancer status was then monitored over the years. In addition to suggesting that the p,p'- isomer is the more significant risk factor, the study also suggests that the timing of exposure is critical. For the subset of women born more than 14 years before agricultural use, there was no association between DDT and breast cancer. However, for younger women—exposed earlier in life—the third who were exposed most to p,p'-DDT had a fivefold increase in breast cancer incidence over the least exposed third, after correcting for the protective effect of o,p'-DDT. These results are supported by animal studies.

Use against malaria

Malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

 remains a major public health challenge in many countries. 2008 WHO estimates were 243 million cases, and 863,000 deaths. About 89% of these deaths occur in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, and mostly to children under the age of 5. DDT is one of many tools that public health officials use to fight the disease. Its use in this context has been called everything from a "miracle weapon [that is] like Kryptonite
Kryptonite
Kryptonite is a fictional material from the Superman mythos —the ore form of a radioactive element from Superman's home planet of Krypton. It is famous for being the ultimate physical weakness of Superman, and the word kryptonite has since become synonymous with an Achilles' heel —the one weakness...

 to the mosquitoes," to "toxic colonialism."

Before DDT, eliminating mosquito breeding grounds by drainage or poisoning with Paris green
Paris Green
Paris Green is an inorganic compound more precisely known as copper acetoarsenite. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks...

 or pyrethrum
Pyrethrum
Pyrethrum refers to several Old World plants of the genus Chrysanthemum which are cultivated as ornamentals for their showy flower heads. Pyrethrum is also the name of a natural insecticide made from the dried flower heads of C. cinerariifolium and C...

 was sometimes successful in fighting malaria. In parts of the world with rising living standards, the elimination of malaria was often a collateral benefit of the introduction of window screens and improved sanitation. Today, a variety of usually simultaneous interventions is the norm. These include antimalarial drugs to prevent or treat infection; improvements in public health infrastructure to quickly diagnose, sequester, and treat infected individuals; bednets
Mosquito net
A mosquito net offers protection against mosquitos, flies, and other insects, and thus against diseases such as malaria, dengue fever, yellow fever, and various forms of encephalitis, including the West Nile virus, if used properly and especially if treated with an insecticide, which can double...

 and other methods intended to keep mosquitoes from biting humans; and vector control
Vector control
Vector control is any method to limit or eradicate the mammals, birds, insects or other arthropods which transmit disease pathogens. The most frequent type of vector control is mosquito control using a variety of strategies.-Methods of Control:...

 strategies such as larvaciding with insecticides, ecological controls such as draining mosquito breeding grounds or introducing fish to eat larvae, and indoor residual spraying
Indoor residual spraying
Indoor residual spraying or IRS is the process of spraying the inside of dwellings with an insecticide to kill mosquitoes that spread malaria. A dilute solution of insecticide is sprayed on the inside walls of certain types of dwellings—those with walls made from porous materials such as mud or...

 with insecticides, possibly including DDT. IRS involves the treatment of all interior walls and ceilings with insecticides, and is particularly effective against mosquitoes, since many species rest on an indoor wall before or after feeding. DDT is one of 12 WHO–approved IRS insecticides. How much of a role DDT should play in this mix of strategies is still controversial.

WHO's anti-malaria campaign of the 1950s and 1960s relied heavily on DDT and the results were promising, though temporary. Experts tie the resurgence of malaria to multiple factors, including poor leadership, management and funding of malaria control programs; poverty; civil unrest; and increased irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

. The evolution of resistance to first-generation drugs (e.g. chloroquine
Chloroquine
Chloroquine is a 4-aminoquinoline drug used in the treatment or prevention of malaria.-History:Chloroquine , N'--N,N-diethyl-pentane-1,4-diamine, was discovered in 1934 by Hans Andersag and co-workers at the Bayer laboratories who named it "Resochin". It was ignored for a decade because it was...

) and to insecticides exacerbated the situation. Resistance was largely fueled by often unrestricted agricultural use. Resistance and the harm both to humans and the environment led many governments to restrict or curtail the use of DDT in vector control as well as agriculture.

Once the mainstay of anti-malaria campaigns, as of 2008 only 12 countries used DDT, including India and some southern African states, though the number is expected to rise.

Effectiveness of DDT against malaria

When it was first introduced in World War II, DDT was very effective in reducing malaria morbidity and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...

. The WHO's anti-malaria campaign, which consisted mostly of spraying DDT, was initially very successful as well. For example, in Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

, the program reduced cases from about 3 million per year before spraying to just 29 in 1964. Thereafter the program was halted to save money and malaria rebounded to 600,000 cases in 1968 and the first quarter of 1969. The country resumed DDT vector control but the mosquitoes had acquired resistance in the interim, presumably because of continued agricultural use. The program switched to malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...

, which though more expensive proved effective.

Today, DDT remains on the WHO's list of insecticides recommended for IRS. Since the appointment of Arata Kochi
Arata Kochi
is a Japanese physician and public health expert, who is the former director of the World Health Organization's malaria program. He had previously been director of WHO's tuberculosis programs for ten years. While at WHO, Dr...

 as head of its anti-malaria division, WHO's policy has shifted from recommending IRS only in areas of seasonal or episodic transmission of malaria, to also advocating it in areas of continuous, intense transmission. The WHO has reaffirmed its commitment to eventually phasing out DDT, aiming "to achieve a 30% cut in the application of DDT world-wide by 2014 and its total phase-out by the early 2020s if not sooner" while simultaneously combating malaria. The WHO plans to implement alternatives to DDT to achieve this goal.

South Africa is one country that continues to use DDT under WHO guidelines. In 1996, the country switched to alternative insecticides and malaria incidence increased dramatically. Returning to DDT and introducing new drugs brought malaria back under control. According to DDT advocate Donald Roberts, malaria cases increased in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 after countries in that continent stopped using DDT. Research data shows a significantly strong negative relationship between DDT residual house sprayings and malaria rates. In a research from 1993 to 1995, Ecuador increased its use of DDT and resulted in a 61% reduction in malaria rates, while each of the other countries that gradually decreased its DDT use had large increase in malaria rates.

Mosquito resistance

Resistance has greatly reduced DDT's effectiveness. WHO guidelines require that absence of resistance must be confirmed before using the chemical. Resistance is largely due to agricultural use, in much greater quantities than required for disease prevention. According to one study that attempted to quantify the lives saved by banning agricultural use and thereby slowing the spread of resistance, "it can be estimated that at current rates each kilo of insecticide added to the environment will generate 105 new cases of malaria."

Resistance was noted early in spray campaigns. Paul Russell, a former head of the Allied
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 Anti-Malaria campaign, observed in 1956 that "resistance has appeared after six or seven years." DDT has lost much of its effectiveness in Sri Lanka, Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

, Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

 and Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

, and it has largely been replaced by organophosphate
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...

 or carbamate
Carbamate
Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...

 insecticides, e.g. malathion or bendiocarb
Bendiocarb
Bendiocarb is an acutely toxic carbamate insecticide used in public health and agriculture and is effective against a wide range of nuisance and disease vector insects...

.

In many parts of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, DDT has also largely lost its effectiveness. Agricultural uses were banned in 1989, and its anti-malarial use has been declining. Urban use has halted completely. Nevertheless, DDT is still manufactured and used, and one study had concluded that "DDT is still a viable insecticide in indoor residual spraying owing to its effectivity in well supervised spray operation and high excito-repellency factor."

Studies of malaria-vector mosquitoes in KwaZulu-Natal Province, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 found susceptibility to 4% DDT (the WHO susceptibility standard), in 63% of the samples, compared to the average of 86.5% in the same species caught in the open. The authors concluded that "Finding DDT resistance in the vector An. arabiensis, close to the area where we previously reported pyrethroid-resistance in the vector An. funestus Giles, indicates an urgent need to develop a strategy of insecticide resistance management for the malaria control programmes of southern Africa."

DDT can still be effective against resistant mosquitoes, and the avoidance of DDT-sprayed walls by mosquitoes is an additional benefit of the chemical. For example, a 2007 study reported that resistant mosquitoes avoided treated huts. The researchers argued that DDT was the best pesticide for use in IRS (even though it did not afford the most protection from mosquitoes out of the three test chemicals) because the others pesticides worked primarily by killing or irritating mosquitoes—encouraging the development of resistance to these agents. Others argue that the avoidance behavior slows the eradication of the disease. Unlike other insecticides such as pyrethroids, DDT requires long exposure to accumulate a lethal dose; however its irritant property shortens contact periods. "For these reasons, when comparisons have been made, better malaria control has generally been achieved with pyrethroids than with DDT." In India, with its outdoor sleeping habits and frequent night duties, "the excito-repellent effect of DDT, often reported useful in other countries, actually promotes outdoor transmission."

Residents' concerns

For IRS to be effective, at least 80% of homes and barns in an area must be sprayed. Lower coverage rates can jeopardize program effectiveness. Many residents resist DDT spraying, objecting to the lingering smell, stains on walls, and may exacerbate problems with other insect pests. Pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...

 insecticides (e.g. deltamethrin
Deltamethrin
Deltamethrin is a pyrethroid ester insecticide.-Usage:Deltamethrin products are among the most popular and widely used insecticides in the world and have become very popular with pest control operators and individuals in the United States in the past five years. This material is a member of one of...

 and lambda-cyhalothrin) can overcome some of these issues, increasing participation.

Human exposure

People living in areas where DDT is used for IRS have high levels of the chemical and its breakdown products in their bodies. Compared to contemporaries living where DDT is not used, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

ns living in sprayed homes have levels that are several orders of magnitude greater. Breast milk
Breast milk
Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...

 in regions where DDT is used against malaria greatly exceeds the allowable standards for breast-feeding infants. These levels are associated with neurological abnormalities in babies.

Most studies of DDT's human health effects have been conducted in developed countries where DDT is not used and exposure is relatively low. Many experts urge that alternatives be used instead of IRS. Epidemiologist Brenda Eskenazi argues, "We know DDT can save lives by repelling and killing disease-spreading mosquitoes. But evidence suggests that people living in areas where DDT is used are exposed to very high levels of the pesticide. The only published studies on health effects conducted in these populations have shown profound effects on male fertility. Clearly, more research is needed on the health of populations where indoor residual spraying is occurring, but in the meantime, DDT should really be the last resort against malaria rather than the first line of defense."

Illegal diversion to agriculture is also a concern, as it is almost impossible to prevent, and its subsequent use on crops is uncontrolled. For example, DDT use is widespread in Indian agriculture, particularly mango
Mango
The mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...

 production, and is reportedly used by librarians to protect books. Other examples include Ethiopia, where DDT intended for malaria control is reportedly being used in coffee production, and Ghana where it is used for fishing." The residues in crops at levels unacceptable for export have been an important factor in recent bans in several tropical countries. Adding to this problem is a lack of skilled personnel and supervision.

Criticism of restrictions on DDT use

Critics claim that restricting DDT in vector control have caused unnecessary deaths due to malaria. Estimates range from hundreds of thousands, to millions. Robert Gwadz of the National Institutes of Health
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...

 said in 2007, "The ban on DDT may have killed 20 million children." These arguments have been dismissed as "outrageous" by former WHO scientist Socrates Litsios. May Berenbaum, University of Illinois entomologist, says, "to blame environmentalists who oppose DDT for more deaths than Hitler is worse than irresponsible." Investigative journalist Adam Sarvana and others characterize this notion as a "myth" promoted principally by Roger Bate
Roger Bate
Roger Bate is an economist who has held a variety of positions in free market, libertarian, and conservative think tanks and lobby groups promoting anti-regulatory, pro-business causes. His current work focuses on counterfeit and substandard medicines, particularly those in the developing world. ...

 of the pro-DDT advocacy group Africa Fighting Malaria
Africa Fighting Malaria
Africa Fighting Malaria is an NGO based in Washington DC and South Africa which states it "seeks to educate people about the scourge of Malaria and the political economy of malaria control"...

 (AFM).

Criticisms of a DDT "ban" often specifically reference the 1972 US ban (with the erroneous implication that this constituted a worldwide ban and prohibited use of DDT in vector control). Reference is often made to Rachel Carson
Rachel Carson
Rachel Louise Carson was an American marine biologist and conservationist whose writings are credited with advancing the global environmental movement....

's Silent Spring even though she never pushed for a ban on DDT. John Quiggin
John Quiggin
John Quiggin is an Australian economist and professor at the University of Queensland. Quiggin studied at the Australian National University, obtaining bachelor's degrees in Arts and Economics in 1978 and 1980 respectively, and completing a master's degree in Economics in 1984. Quiggin was awarded...

 and Tim Lambert wrote, "the most striking feature of the claim against Carson is the ease with which it can be refuted." Carson actually devoted a page of her book to considering the relationship between DDT and malaria, warning of the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 of DDT resistance in mosquitoes and concluding:

It is more sensible in some cases to take a small amount of damage in preference to having none for a time but paying for it in the long run by losing the very means of fighting [is the advice given in Holland by Dr Briejer in his capacity as director of the Plant Protection Service]. Practical advice should be "Spray as little as you possibly can" rather than "Spray to the limit of your capacity."

It has also been alleged that donor governments and agencies have refused to fund DDT spraying, or made aid contingent upon not using DDT. According to a report in the British Medical Journal, use of DDT in Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 "was stopped several decades ago, because 80% of the country's health budget came from donor funds, and donors refused to allow the use of DDT." Roger Bate asserts, "many countries have been coming under pressure from international health and environment agencies to give up DDT or face losing aid grants: Belize and Bolivia are on record admitting they gave in to pressure on this issue from [USAID]."

The United States Agency for International Development
United States Agency for International Development
The United States Agency for International Development is the United States federal government agency primarily responsible for administering civilian foreign aid. President John F. Kennedy created USAID in 1961 by executive order to implement development assistance programs in the areas...

 (USAID) has been the focus of much criticism. While the agency is currently funding the use of DDT in some African countries, in the past it did not. When John Stossel
John Stossel
John F. Stossel is an American consumer reporter, investigative journalist, author and libertarian columnist. In October 2009 Stossel left his long time home on ABC News to join the Fox Business Channel and Fox News Channel, both owned and operated by News Corp...

 accused USAID of not funding DDT because it wasn't "politically correct," Anne Peterson, the agency's assistant administrator for global health, replied that "I believe that the strategies we are using are as effective as spraying with DDT ... So, politically correct or not, I am very confident that what we are doing is the right strategy." USAID's Kent R. Hill states that the agency has been misrepresented: "USAID strongly supports spraying as a preventative measure for malaria and will support the use of DDT when it is scientifically sound and warranted." The Agency's website states that "USAID has never had a 'policy' as such either 'for' or 'against' DDT for IRS. The real change in the past two years [2006/07] has been a new interest and emphasis on the use of IRS in general—with DDT or any other insecticide—as an effective malaria prevention strategy in tropical Africa." The website further explains that in many cases alternative malaria control measures were judged to be more cost-effective that DDT spraying, and so were funded instead.

Other insecticides

Advocates of increased use of DDT in IRS claim that alternative insecticides are more expensive, more toxic, or not as effective. As discussed above, susceptibility of mosquitoes to DDT varies geographically. The same is true for alternative insecticides, so its relative effectiveness varies. Toxicity and cost-effectiveness comparisons lack data. Relative insecticide costs vary by location and ease of access, the habits of the local mosquitoes, the degrees of resistance exhibited by the mosquitoes, and the habits and compliance of the population, among other factors. The choice of insecticide has little impact on the total cost of a round of spraying, since product costs are only a fraction of campaign costs. IRS coverage needs to be maintained throughout the malaria season, making DDT's relatively long life an important cost savings.

Organophosphate
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...

 and carbamate
Carbamate
Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...

  insecticides, e.g. malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...

 and bendiocarb
Bendiocarb
Bendiocarb is an acutely toxic carbamate insecticide used in public health and agriculture and is effective against a wide range of nuisance and disease vector insects...

, respectively, are more expensive than DDT per kilogram and are applied at roughly the same dosage. Pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...

s such as deltamethrin
Deltamethrin
Deltamethrin is a pyrethroid ester insecticide.-Usage:Deltamethrin products are among the most popular and widely used insecticides in the world and have become very popular with pest control operators and individuals in the United States in the past five years. This material is a member of one of...

 are also more expensive than DDT, but are applied more sparingly (0.02-0.3 g/m2 vs 1-2 g/m2), so the net cost per house is about the same over 6 months.

Non-chemical vector control

Before DDT, malaria was successfully eradicated or curtailed in several tropical areas by removing or poisoning mosquito breeding grounds and larva habitats, for example by filling or applying oil to standing water. These methods have seen little application in Africa for more than half a century.

The relative effectiveness of IRS (with DDT or alternative insecticides) versus other malaria control techniques (e.g. bednets or prompt access to anti-malarial drugs) varies greatly and is highly dependent on local conditions.

A WHO study released in January 2008 found that mass distribution of insecticide-treated mosquito nets and artemisinin
Artemisinin
Artemisinin , also known as Qinghaosu , and its derivatives are a group of drugs that possess the most rapid action of all current drugs against falciparum malaria. Treatments containing an artemisinin derivative are now standard treatment worldwide for falciparum malaria...

–based drugs cut malaria deaths in half in Rwanda and Ethiopia, countries with high malaria burdens. IRS with DDT did not play an important role in mortality reduction in these countries.

Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 has enjoyed declining malaria cases and a 97% mortaility reduction after switching in 1991 from a poorly funded DDT-based campaign to a program based on prompt treatment, bednets, and pyrethroid group insecticides.

In Mexico, effective and affordable chemical and non-chemical strategies against malaria have been so successful that the Mexican DDT manufacturing plant ceased production due to lack of demand.

While the increased numbers of malaria victims since DDT usage collapsed document its value, many other factors contributed to the rise in cases.

A review of fourteen studies on the subject in sub-Saharan Africa, covering insecticide-treated nets, residual spraying, chemoprophylaxis for children, chemoprophylaxis or intermittent treatment for pregnant women, a hypothetical vaccine, and changing front–line drug treatment, found decision making limited by the gross lack of information on the costs and effects of many interventions, the very small number of cost-effectiveness analyses available, the lack of evidence on the costs and effects of packages of measures, and the problems in generalizing or comparing studies that relate to specific settings and use different methodologies and outcome measures. The two cost-effectiveness estimates of DDT residual spraying examined were not found to provide an accurate estimate of the cost-effectiveness of DDT spraying; furthermore, the resulting estimates may not be good predictors of cost-effectiveness in current programs.

However, a study in Thailand found the cost per malaria case prevented of DDT spraying ($1.87 US) to be 21% greater than the cost per case prevented of lambda-cyhalothrin–treated nets ($1.54 US), at very least casting some doubt on the unexamined assumption that DDT was the most cost-effective measure to use in all cases. The director of Mexico's malaria control program finds similar results, declaring that it is 25% cheaper for Mexico to spray a house with synthetic pyrethroids than with DDT. However, another study in South Africa found generally lower costs for DDT spraying than for impregnated nets.

A more comprehensive approach to measuring cost-effectiveness or efficacy of malarial control would not only measure the cost in dollars of the project, as well as the number of people saved, but would also consider ecological damage and negative aspects of insecticide use on human health. One preliminary study regarding the effect of DDT found that it is likely the detriment to human health approaches or exceeds the beneficial reductions in malarial cases, except perhaps in malarial epidemic situations. It is similar to the earlier mentioned study regarding estimated theoretical infant mortality caused by DDT and subject to the criticism also mentioned earlier.

A study in the Solomon Islands
Solomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...

 found that "although impregnated bed nets cannot entirely replace DDT spraying without substantial increase in incidence, their use permits reduced DDT spraying."

A comparison of four successful programs against malaria in Brazil, India, Eritrea, and Vietnam does not endorse any single strategy but instead states, "Common success factors included conducive country conditions, a targeted technical approach using a package of effective tools, data-driven decision-making, active leadership at all levels of government, involvement of communities, decentralized implementation and control of finances, skilled technical and managerial capacity at national and sub-national levels, hands-on technical and programmatic support from partner agencies, and sufficient and flexible financing."

DDT resistant mosquitoes have generally proved susceptible to pyrethroids. Thus far, pyrethroid resistance in Anopheles has not been a major problem.

See also

  • DDT in Australia
    DDT in Australia
    -DDT:Dichloro-Diphenyl-Trichloroethane) was a widely used synthetic pesticide before its used was banned in many countries. It is a persistent organic pollutant with a half life of 2-15 years.-History:...

  • DDT in New Zealand
    DDT in New Zealand
    The use of DDT in New Zealand was banned in 1989 due to negative environmental impacts.-DDT:DDT is an organochlorine insecticide that does not occur naturally. It is a persistent organic pollutant with a half life of 2-15 years...

  • DDT in the United States
    DDT in the United States
    The use of DDT in the United States is banned, except for a limited exemption for public health uses. The ban is due in a large part to Rachael Carson's book Silent Spring.-Initial concerns about DDT:...

  • Joseph Jacobs (scientist)
    Joseph Jacobs (scientist)
    Dr Joseph Jacobs was one of the scientists responsible for creating DDT.Belying the oft-repeated claim that DDT is highly dangerous to human beings, he told Joseph Farah of "falling into a vat of DDT and emerging unscathed with no after-effects."...

  • Mickey Slim
    Mickey Slim
    The Mickey Slim was a drink that had short-lived popularity in the United States in the 1940s and 1950s. According to the The Dedalus Book of Absinthe by Phil Baker, it was made by combining gin with a pinch of DDT , an insecticide that would later be banned in most countries; consumers of this...

    , a short-lived cocktail that combined gin
    Gin
    Gin is a spirit which derives its predominant flavour from juniper berries . Although several different styles of gin have existed since its origins, it is broadly differentiated into two basic legal categories...

     with a pinch of DDT.
  • Operation Cat Drop
    Operation Cat Drop
    Operation Cat Drop is the name commonly given to an account, of uncertain veracity, about the delivery, by the United Kingdom's Royal Air Force, of cats to a remote village in Sarawak, Borneo. The cats were delivered in crates, dropped by parachute, as part of a broader program of supplying cats to...


External links

Toxicity

Politics and DDT

Malaria and DDT
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