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Organochlorine Insecticides

Organochlorine insecticides are neurotoxins that have high lipophilicity, are very hydrophobic, and are chemically stable. Metabolic degradation in target and non-target organisms or environmentally by either chemical, photolytic, or microbial processes is slow. As a result, organochlorine insecticides are persistent in the environment and have a long half-life.

There are three major types of organochlorine insecticides:

  • Dichlorodiphenylethanes: Such as DDT, DDD, TDE, Methoxychlor, Rhothane, Methlochlor, Perthane, Dicofol (Kelthane).
  • Chlorinated Cyclodienes: Such as Aldrin, Dieldrin, Endrin, Heptachlor, Chlordane, Endosulfan.
  • Chlorinated Benzenes & Cyclohexanes: Such as Lindane, Toxaphene, Mirex, HCB, HCH, Chlordecone (Kepone).
Structural classification of organochlorine insecticides.

(Amdur, Mary O., John Doull, and Curtis D. Klaassen. Toxicology, 1991, p. 574)

The lethal mechanism of action of organochlorine insecticides is a persistent opening of the sodium channels in neurons, resulting in repetitive firing of action potentials. K+ permeability is also reduced, calmodulin is inhibited, and Na, K, & Ca ATPase are also inhibited. These effects slow nerve repolarization.

Structure of typical mamalian neurons. Operation of gated channels.

(Marieb, Elaine N. Human Anatomy & Physiology, 1995. p. 351)

Passive and active forces that establish and maintain the resting membrane potential.

(Marieb, Elaine N. Human Anatomy & Physiology, 1995. p. 352)

The mechanism of a graded potential.

(Marieb, Elaine N. Human Anatomy & Physiology, 1995. p. 353)

The phases of the action potential and the role of gated ion channels in those phases.

(Marieb, Elaine N. Human Anatomy & Physiology, 1995. p. 355)

A schematic diagram of an oscilloscope recording.

(Amdur, Mary O., John Doull, Curtis D. Klaassen. Toxicology, 1991, p. 577)

Diagram of axonopathies.

(Amdur, Mary O., John Doull, Curtis D. Klaassen. Toxicology, 1991, p. 418)

Proposed sites of action id cyclodiene-type organochlorine insecticides.

(Amdur, Mary O., John Doull, Curtis D. Klaassen. Toxicology, 1991, p. 577)

Potential sites of action of classes of insecticides on the axon and the terminal portions of the nerve.

(Amdur, Mary O., John Doull, Curtis D. Klaassen. Toxicology, 1991, p. 573)

Organochlorine pesticides have a high bioconcentration factor and high biomagnification in the food chain. Organochlorines can produce xenoestrogenic activity (may have significance to human breast cancer) and cause major reproductive effects on prey in upper trophic levels (ex. pelicans, falcons, eagles).

The concentrations of DDT in the brains and fat of rats.

(Smith, Roger P. A Primer of Environmental Toxicology, 1992, p. 117)

Storage of DDE in the body fat of male and female rats.

(Smith, Roger P. A Primer of Environmental Toxicology, 1992, p. 117)

A natural food web of plants, crustacae, fish and birds in a Long Island estuary.

(Smith, Roger P. A Primer of Environmental Toxicology, 1992, p. 123)

How DDT residues become concentrated as they are passed up a simple food web.

(Smith, Roger P. A Primer of Environmental Toxicology, 1992, p. 124)

Signs and symptoms of acute and chronic toxicity following exposure to organochlorine insecticides.

(Amdur, Mary O., John Doull, Curtis D. Klaassen. Toxicology, 1991, p. 575)
 

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