DDT and other Organochlorine Insecticides
Organochlorine insecticides, such as DDT, chlordane, 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.
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 (1). 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 (2)." However, concerns regarding its effect on the environment were already emerging (e.g., 3,4,5,6), though the true impact of DDT on wildlife would not be known for decades.
|Click on image to enlarge.
The tendency of DDT and other organochlorines to concentrate in the fat of humans, livestock, and wildlife contributes to its ability to adversely affect organisms (7). In particular, greater accumulation in species higher on the food chain, known as biomagnification, has resulted in severe adverse effects on many forms of wildlife, especially predatory species (1). DDT was a major reason for the declines of the bald eagle, brown pelican, and peregrine falcon in North America (1). Exposure to DDT and its metabolites (breakdown products), DDD and DDE, can cause direct mortality to individuals, or result in sublethal effects that can interfere with the ability to survive or reproduce (8). Experimental studies showed that DDE in particular was responsible for effects to reproduction such as embryo toxicity and eggshell thinning (1). DDT is also highly toxic to aquatic life, including crayfish, daphnids, sea shrimp and many species of fish (9). DDT may be moderately toxic to some amphibian species, especially in the larval stages (10).
The Service was heavily involved in studying the effects 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 that the Environmental Protection Agency (EPA) banned the use of DDT in the United States due to potential harm to human health and the environment (37 FR 13369). After 1972, DDT was only authorized for use in a public health or economic emergency (37 FR 13369).
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 and residues can still be found in most areas of the United States (11). Where residues remain high, adverse effects to wildlife can still occur. For instance, while DDE levels in the environment have fallen dramatically overall, eggshell thickness remains depressed in areas where DDE concentrations persist (e.g. 12, 13, 14).
Restrictions on the use of other organochlorines followed DDT, with the last being phased out only in 2010 (endosulfan, EPA News Release) and 2011 (dicofol, EPA Memorandum of Agreement).
US Fish and Wildlife Service Historic News Releases - DDT
Rachel Carson: A Conservation Legacy
Pest Management (IPM)
- Blus, L.J. 2003. Organochlorine Pesticides. In D.J. Hoffman, B.A. Rattner, G.A. Burton Jr, and J. Cairns Jr., eds. Handbook of Ecotoxicology, 2nd edition. Lewis Publishers, New York. p. 313- 340.
- U.S. Department of Agriculture. 1952. Insects: The Yearbook of Agriculture. United States Government Printing Office, 780 p.
- Hotchkiss, N. and R.H. Pough. 1964. Effect on forest birds of DDT used for gypsy moth control in Pennsylvania. Journal of Wildlife Management 10: 202-207.
- Dewitt, J.B., J.V. Derby, and G.F. Mangan. 1955. DDT vs. wildlife. Relationships between quantities ingested, toxic effects and tissue storage. Journal of the American Pharmaceutical Association 44: 22-24.
- Burden, E. H. W. J. 1956. A case of DDT poisoning in fish. Nature 178: 546-547.
- Barker, R.J. 1958. Notes on some ecological effects of DDT sprayed on elms. The Journal of Wildlife Management 22: 269-274.
- Ecobichon, DJ. 2001. Toxic Effects of Pesticides. In C.D. Klaasen, ed., Casarett and Doull's Toxicology: The basic science of poisons, 6th edition. McGraw-Hill, New York. p. 763-810.
- Blus, L.J. 2011. DDT, DDD, and DDE in Birds. In Environmental Contaminants in Biota: Interpreting Tissue Concentrations, 2nd edition. W.N. Beyer and J.P. Meador, eds. CRC Press, New York. p. 425-446.
- Beckvar, N. and G.R. Lotufo. 2011. DDT and other organohalogen pesticides in aquatic organisms. In Environmental Contaminants in Biota: Interpreting Tissue Concentrations, 2nd edition. W.N. Beyer and J.P. Meador, eds. CRC Press, New York. p. 47 – 101.
- Sparling D.W. 2010. Ecotoxicology of Organic Contaminants to Amphibians. In D.W. Sparling, G. Linder, C.A. Bishop, and S.K. Krest, eds. Ecotoxicology of amphibians and reptiles, 2nd edition. CRC Press, New York. p. 261-288.
- Gilliom, R.J., J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2006. The Quality of our Nation's Waters – Pesticides in the Nation's Streams and Ground Water, 1992-2001: U.S. Geological Survey Circular 1291, 172 p. http://pubs.usgs.gov/circ/2005/1291/
- Gervais, J.A., D.K. Rosenberg, D.M. Fry, L. Trulio, and K.K. Sturm. 2000. Burrowing owls and agricultural pesticides: evaluation of residues and risks for three populations in California, USA. Environmental Toxicology and Chemistry 19:337-343.
- King, K.A., B.J. Zaun, H.M. Schotborgh, and C. Hurt. 2003. DDE-induced eggshell thinning in white-faced ibis: a continuing problem in the western United States. The Southwestern Naturalist 48: 356-364.
- Burnett, L.J, K.J. Sorenson, J. Brandt, E.A. Sandhaus, D. Ciani, M. Clark, C. David, J. Theule, S. Kasielke, and R.W. Risebrough. 2013. Eggshell thinning and depressed hatching success of California condors reintroduced to central California. The Condor 115:477-491.