Dichloro-diphenyl-trichloroethane (DDT)

• DEFINITION: Synthetic organochlorine insecticide

Dichloro-diphenyl-trichloroethane, better known as DDT, has been used extensively in agriculture and for control of insect-borne diseases worldwide. However, its persistence in the environment and ability to accumulate in the food chain have had devastating consequences for wildlife. The harmful effects of DDT became a major focus for the emerging environmental movement during the 1960s.

During the 1930s scientists began searching for organic (carbon-based) insecticides. Prior to that time, insecticides were mainly derived from toxic metals, such as arsenic and mercury. In 1939, while experimenting with chlorinated hydrocarbons, Swiss chemist Paul Hermann Müller discovered the insecticidal properties of DDT, a chemical that had first been synthesized more than half a century earlier. His findings led to the development of the first synthetic, organic insecticide, which was introduced commercially by the Swiss chemical company J. R. Geigy A.G. in 1942.

DDT was initially used to provide protection against typhus to civilians and Allied troops during World War II by killing body lice. Before that, pyrethrum powder was a common means for combating body lice; however, Japan was the chief exporter of this chrysanthemum-derived repellent, and hostilities had left the Allies with insufficient pyrethrum supplies. DDT’s key role in suppressing a typhus epidemic in Italy in 1943 led to Müller’s receiving the Nobel Prize in Physiology or Medicine in 1948.

When news of DDT’s effectiveness was released by the British government in 1944, the US Department of Agriculture (USDA) concluded that before DDT could be recommended for use by farmers, more information about its toxicity was needed. By the 1946 crop year, limited use was permitted even though evidence suggested that DDT might have some acute toxic effects on birds and that it could be stored in animal fat and excreted in milk. Commercial demand for DDT was fueled in large part by accounts of how well it had performed during wartime. The success of DDT served as an impetus for chemical companies to begin an intensive search for other organic pesticides.

Between 1940 and 1980, at least 1.8 billion kilograms (4 billion pounds) of DDT were used. More than 1,200 different formulations were developed for industrial, agricultural, and public health applications in the United States alone. Annual worldwide production peaked in 1964 at 90 million kilograms (198 million pounds).

Milestones in DDT History

YearEvent1874The first synthesis of DDT is reported.1939Paul Müller discovers DDT's insecticidal properties.1942The first commercial DDT formulations are introduced by the Swiss company J. R. Geigy.1943-1945DDT is used on civilians and military troops in Europe for the control of lice and typhus.1946The limited use of DDT on crops is permitted by the U.S. Department of Agriculture.1948Müller receives the Nobel Prize in Physiology or Medicine for the development of DDT as an insecticide. The first insects to develop resistance to DDT are observed.1950sDDT is used widely for agriculture, public health, and domestic pest control. Laboratory and field studies reveal the negative effects of DDT.1957The Clear Lake study shows the bioaccumulation of DDT in aquatic life and birds; citizens on Long Island, New York, file a suit in an attempt to halt aerial DDT spraying.1958Robert Barker publishes the results of studies that link DDT to declines in robin populations.1961Annual production levels of DDT in the United States peak at 160 million pounds.1962 Rachel Carson publishes Silent Spring, which explains the dangers of DDT to a broad audience.1963The President's Science Advisory Committee releases a report on pesticide use that becomes the keystone of the drive to ban DDT.1964The U.S. Federal Commission on Pest Control is established.1967The Environmental Defense Fund (EDF) is formed.1968Joseph Hickey and Daniel Anderson publish a report on DDT's impact on declining raptor populations.1968The Wisconsin Hearings, the first major legal challenge to the use of DDT, begin.1969Malaria is virtually eliminated in China, largely as a result of DDT use.1969 Michigan and Arizona become the first states to ban DDT use.1969The EDF files petitions with U.S. federal agencies seeking the elimination of the use of DDT.1969The use of DDT in residential areas is banned in the United States.1970The Environmental Protection Agency (EPA) is established.1972The EPA bans DDT use in the United States.Studies suggest that DDT acts as an endocrine disrupter.1993Reports in the Journal of the National Cancer Institute claim that DDT may increase the risk of breast cancer.1998International negotiations to phase out the production and use of DDT and other persistent organic pollutants begin in Montreal, Canada.2000 South Africa reintroduces the use of DDT to combat the spread of malaria by mosquitoes.2004DDT is among the chemicals covered by the Stockholm Convention on Persistent Organic Pollutants, an international treaty designed to eliminate or reduce the release of toxic, bioaccumulative chemicals.2008Twelve nations, including India and several Southern African countries, are reported to be using DDT to combat malaria.

A New Pollutant

The insecticidal properties of DDT are related to its ability to act as a nerve poison and to pass freely through insect cuticles. In addition to causing convulsions, paralysis, and death, DDT can also interfere with calcium-dependent processes. Because DDT in crystalline form is not readily absorbed through animal skin (unlike DDT mixed in solution), the compound was initially regarded as a safe alternative to metal-based insecticides.

Although effective, DDT does have undesirable characteristics. As a broad-spectrum insecticide, DDT kills a wide variety of organisms, including beneficial insects such as bees. Also, development of resistance to DDT among pest insects was observed as early as 1948. Because of its chemical composition, DDT is preferentially stored in animal fat and is therefore not readily excreted by animals that ingest it. This fat solubility and DDT’s persistence in the environment cause the pesticide to accumulate in the food chain.

The first clear evidence of the bioaccumulation of DDT came from a case study in Clear Lake, California. Between 1949 and 1957 DDT was used to control gnats on the lake. By the mid-1950s, the health of fish-eating birds in the area began to decline; several bird species, especially grebes, were dying in large numbers. Because no infectious agent was found, scientists used new analytical methods developed to measure compounds in tissues. High levels of DDT were detected in plankton, fish, and birds in and around Clear Lake. The studies also clearly showed biomagnification: Levels of pesticide residues were found to be sequentially higher at each step in the food chain, with concentrations in grebes and gulls up to 100,000 times greater than in the formulations of DDT that were sprayed.

By the mid-1950s DDT’s toxicity was becoming evident throughout the United States. DDT was used in the Midwest and New England to control the elm bark beetle, an insect that spreads the fungus that causes Dutch elm disease. Several studies between 1954 and 1958 noted sharp declines in robin populations—in some areas by as much as 70 to 90 percent. Extensive aerial spraying for gypsy moths during the 1950s from Michigan to New England coincided with significant declines in many species of songbirds and bees. Ironically, this affected populations of some of the natural predators of the intended target pests.

The DDT spraying also had a negative impact on agriculture. In addition to reduced pollination caused by the loss of bees, farmers were discovering that cows’ milk and farm produce were contaminated with pesticide residues. In the Pacific Northwest, DDT used to control the spruce budworm devastated salmon populations. Coastal spraying along the Atlantic Ocean to control the salt marsh mosquito took a heavy toll on migrating birds, marine life, and raptors.

The effect of DDT on raptor populations is well known. In 1968 an article in Science magazine by wildlife ecologists Joseph Hickey and Daniel Anderson reported that the decline in populations of birds of prey was largely caused by eggshell breakage caused by chlorinated hydrocarbons. Calcium processes were altered in birds containing high DDT levels in their fatty tissues, resulting in the production of eggs with dangerously thin shells. The young did not hatch because the eggs were crushed during incubation. The bald eagle, peregrine falcon, and osprey ended up on the brink of extinction largely as a result of widespread DDT use.

Ban on DDT

During the late 1950s the first DDT-related lawsuits were filed over losses to farmers and beekeepers and in attempts to stop further aerial spraying. The most notable case of the time was filed in 1957 by a group of citizens led by well-known ornithologist Robert Cushman Murphy in order to gain an injunction to stop the spraying of DDT over Long Island, New York. The injunction was not granted, but the case went all the way to the US Supreme Court, which declined to hear it.

Perhaps one of the most significant events leading to the ban of DDT was the publication of Rachel Carson’s book Silent Spring in 1962. The author described the negative environmental impact of pesticides such as DDT, and the subsequent public outcry led to a dramatic decline in DDT use. Production of DDT in the United States peaked in 1961, and global production began to decline around 1964. As a result of the controversy spawned by Carson’s book, the President’s Science Advisory Committee was charged with reviewing pesticide use. The committee’s report, published in 1963, called for legislative measures to safeguard the health of the land and people against pesticides. The Federal Commission on Pest Control was established in 1964, and four governmental committees studied DDT in depth between 1963 and 1969. Ultimately, these investigations led to the establishment of the Environmental Protection Agency (EPA) in 1970.

DDT was also a major impetus for the formation of associations whose missions were aimed at protecting the environment and public health. The newly formed Environmental Defense Fund (EDF) initiated a series of court hearings and lawsuits related to DDT during the late 1960s. In October, 1969, it filed petitions with the USDA and the Department of Health, Education, and Welfare seeking elimination of the use of DDT. When no effective action resulted, EDF, along with other environmental groups and individuals, took the case to court. On May 28, 1970, the US Court of Appeals for the District of Columbia rendered two major rulings on DDT in response to EDF’s litigation. In addition to leading to the eventual ban of DDT, these rulings set important environmental law precedents: They provided power to membership associations (environmental groups) and served to protect public interests.

In 1972, the EPA banned the use of DDT in the United States except in cases of pest-control emergencies (for example, to avoid outbreaks of typhus, bubonic plague, and rabies) and highly restricted the use of other chlorinated hydrocarbons. However, the ban applied only to DDT use within US borders; it still allowed American companies to produce DDT for export, which they continued to do for several years. Many other countries also banned or severely restricted DDT manufacture and use.

Persistence of DDT

Even decades after the ban on DDT in the United States and several other countries, the pesticide continues to be found in significant concentrations in marine animals and other wildlife. DDT can be detected in the tissues of almost every person on earth, especially Indigenous peoples living in the Arctic and workers from insecticide production plants and agriculture. DDT is present in human breast milk, and it can pass through the placenta from mother to fetus to impair brain development and increase the risk of birth defects.

New concerns about DDT’s toxicity arose as a result of studies published beginning during the early 1990s. Data suggest that DDT and its metabolites can act as endocrine disrupters—compounds that mimic naturally occurring hormones in animals. Evidence indicates that such compounds can decrease sperm count and fertility, affect the onset of puberty, alter male and female characteristics in wildlife, increase the risk of cancer of reproductive organs, and otherwise affect growth, development, metabolism, and reproduction.

In 2004 an international treaty restricting production and use of DDT entered into force. This treaty, the Stockholm Convention on Persistent Organic Pollutants, was intended to eliminate or reduce the release of several toxic, bioaccumulative chemicals. DDT is among the initial twelve persistent organic pollutants (POPs) specified in the treaty. Unlike most of the other POPs, DDT was still allowed to be used for disease vector control under the Stockholm Convention until other effective and affordable control methods could be developed. The convention allowed the spraying of indoor walls with DDT, notably as a weapon against malaria and other mosquito-borne tropical diseases, and many countries in Africa and Asia continued to employ DDT in this way. South Africa credited much of its success in controlling malaria in the early twenty-first century to its reintroduction of DDT use in 2000. The World Health Organization supported the indoor use of DDT in 2006 in African countries where malaria continued to be a major problem. The organization recommends that if indoor DDT spraying for mosquito control is conducted, it should be part of an integrated vector management approach—that is, one that uses insecticide-treated mosquito nets, drainage of mosquito-breeding bodies of water, and other methods to discourage overdependence on DDT and development of DDT-resistant mosquito species.

Bibliography

Carson, Rachel. Silent Spring. 50th anniversary ed., Mariner Books, 2022.

Colborn, Theo, Dianne Dumanoski, and John P. Myers. Our Stolen Future: Are We Threatening Our Fertility, Intelligence, and Survival? Penguin Random House, 1997.

“DDT - A Brief History and Status.” EPA, United States Environmental Protection Agency, 12 Mar. 2024, www.epa.gov/ingredients-used-pesticide-products/ddt-brief-history-and-status. Accessed 31 Jan. 2025.

Dunlap, Thomas R., ed. DDT, “Silent Spring,” and the Rise of Environmentalism: Classic Texts. University of Washington Press, 2008.

Glausiusz, Josie. “Can a Maligned Pesticide Save Lives?” Discover, vol. 28, no. 11, 2007, pp. 34–36.

Karasov, William H., and Carlos Martínez del Rio. Physiological Ecology: How Animals Process Energy, Nutrients, and Toxins. Princeton University Press, 2007.

Schapira, Allan. “DDT: A Polluted Debate in Malaria Control.” The Lancet, vol. 368, no. 9553, 2006, pp. 2111–2113.

World Health Organization. DDT and Its Derivatives: Environmental Aspects. Author, 1989.