Environmental Contaminants Program Home Page, U.S. Fish and Wildlife Service

Featured Topics:

US Fish and Wildlife Service Historic News Releases - DDT

Common Myths About Rachel Carson and DDT

For more information on Rachel Carson's accomplishments:

The U.S. Department of State's Bureau of International Information Programs has developed a wonder web site and document (1.8 MB pdf) entitled "Rachel Carson: Pen Against Poison."

GOT A QUESTION?
USFWS Customer Service Center
1-800-344-WILD

Division of Environmental Quality
4401 North Fairfax Drive, Suite 322
Arlington, Virginia 22203
703-358-2148

GOT A QUESTION?
USFWS Customer Service Center
1-800-344-WILD

U.S. Fish & Wildlife Service home page

Back

Chlorinated Hydrocarbons (Organochlorines) - DDT

Chlorinated hydrocarbon insecticides, such as chlordane, DDT, toxaphene, aldrin and dieldrin were the main family of insecticides used following their introduction after World War II. Many of these chemicals originated from attempts to develop agents of chemical warfare, but were found to be lethal to insects. (3)

DDT (Dichloro-Diphenyl-Trichloroethane) is a man-made chemical widely used to control insects on agricultural crops and insects that carry diseases like malaria and typhus. The value of DDT as an insecticide was first discovered in 1939 and the discoverer won the Nobel Prize(3). In the 1952 edition of the U.S. Department of Agriculture's book "Insects: The Yearbook of Agriculture," the agency hailed it as one or our safest all-around insecticides based on its "cost, ease of handling, safety to humans, effectiveness in destroying the pest, and safety to wildlife." It was not until decades later that the true impact of DDT on wildlife was known.

Image that shows how DDT moves thru the food web.

Click on image to enlarge.

Problems associated with DDT, as well as many chlorinated hydrocarbons, involved their tendency to concentrate in the fat of humans, livestock, aquatic foodchains, and wildlife. This latter phenomena, called bioaccumulation, has had, and continues to have, severe adverse effects on many forms of wildlife.

Many predatory birds were heavily impacted by DDT. DDT was a major reason for the decline of the bald eagle in North America in the 1950s and 1960s as well as the brown pelican and the peregrine falcon. DDT and its metabolites (breakdown products), DDD and DDE, are toxic to embryos and disrupt calcium absorption,**** thereby impairing eggshell quality. Studies in the 1960s and 1970s failed to find a mechanism for the hypothesized thinning. However, more recent studies in the 1990s and 2000s have laid the blame at the feet of DDE. Some studies have shown that although DDE levels have fallen dramatically, eggshell thickness remains 10–12 percent thinner than before DDT was first used. In addition, DDT, DDE and other chlorinated hydrocarbons, can affect the parents behavior during incubation and can result in death of unhatched embryos and eagle chicks.

DDT is also highly toxic to aquatic life, including crayfish, daphnids, sea shrimp and many species of fish. DDT may be moderately toxic to some amphibian species, especially in the larval stages.

The Service was heavily involved in studying the affects of DDT on fish and wildlife, a process which began shortly after the chemical came into use as a pesticide (see US Fish and Wildlife Service Historic News Releases - DDT.) By 1945, the Service determined that DDT is "Capable of Considerable Damage to Wildlife, Beneficial Insects, and Indirectly to Crops" (see News Release of August 22, 1945 [pdf file]).

The Service continued to conduct studies on, and to voice its concern over, the effects of DDT on fish and wildlife for more than 25 years. It was not until 1972, and then because of the potential harm to human health, that the Environmental Protection Agency (EPA) banned the use of DDT in the United States barring a public health or economic emergency. Restrictions that control the use of aldrin and dieldrin were imposed in the United States in 1974.

Since implementation of these restrictions, residues of the pesticides have significantly decreased in many regions where they were formerly used. However, DDT, DDD and DDE persist in the environment for a very long time. DDT, DDD and DDE residues can still be found in most areas of the United States.

Other chlorinated hydrocarbon insecticides still being used in the US include dicofol and endosulfan. Methoxychlor was another chlorinated hydrocarbon permitted for use in the United States. However, in 2004, the EPA determined that methoxychlor was not eligible for reregistration .

US Fish and Wildlife Service Historic News Releases - DDT

**** The death of unhatched embryos and disruption calcium absorption represent areas where the endocrine disrupting portion is shown through calcitonin, a hormone which aids in regulating Calcium deposition in the eggshell from the shell glands of the uterus of birds and reptiles.

Common Myths About Rachel Carson and DDT:

1. DDT Has Been Banned in United States.

Only the GENERAL use of the pesticide has been banned in the United States. The EPA’s order did not affect public health and quarantine uses, or exports of DDT. In addition, the EPA maintains the ability to allow any Federal or State agency to use DDT if emergency conditions exist, including economic emergencies.

2. DDT was Banned Because it was Harmful to Wildlife.

Concerns about impacts to wildlife were not the only justification for the general ban on DDT. According to the EPA, the Agency banned the use of DDT because the widely-used pesticide was found to be "...accumulating in the food chain, posing a risk to public health and the environment.”(1)

This general use ban came after three years of intensive governmental inquiries into the uses of DDT. As a result of this examination, EPA determined that “the continued massive use of DDT posed unacceptable risks to the environment and potential harm to human health.” (2)

For more information on DDT and human health please visit the:
Agency for Toxic Substances and Disease Registry - ToxFAQs™ for DDT, DDE, and DDD

3. Rachel Carson Called for the Elimination of All Pesticides.

“It is not my contention that chemical insecticides must never be used. I do contend that we have poisonous and biologically potent chemicals indiscriminately into the hands of person largely or wholly ignorant of their potentials for harm.” (3)

Carson encouraged the responsible use of pesticide with an awareness of the chemicals' impact on all living things, not the all-out banning of pesticides. In fact, in the context of malaria control, she argued that DDT users should "spray as little as you possibly can" rather than "spray to the limit of your capacity." (3)

In Audubon magazine she wrote, "We do not ask that all chemicals be abandoned. We ask moderation. We ask the use of other methods less harmful to our environment" (4). Countering claims that she was advocating a back-to-nature philosophy, she said, "We must have insect control. I do not favor turning nature over to insects. I favor the sparing, selective and intelligent use of chemicals. It is the indiscriminate, blanket spraying that I oppose" (5).

This approach of controlling pests today underlies Integrated Pest Management (IPM), which integrates a number of useful strategies — cultural, mechanical or physical, biological, and chemical — into an ecologically sound and economically viable program. This management technique is used extensively in managing the Service's National Wildlife Refuges.