An organochlorine is defined as any organic compound that contains carbon and hydrogen, and shares electron pairs from one or more chlorine atoms through covalent bonding. Several chemicals fall into this category, including organochlorine pesticides. In fact, polychlorinated biphenyls (PCBs), chlorofluorocarbons (CFCs), and dichloro-diphenyl-trichloroethane (DDT) all contain chlorinated hydrocarbons. Another chemical class known as polychlorinated dibenzodioxins (PCDDs),or dioxins, are also classified as organochlorines.
With rare exceptions, organochlorine substances do not occur naturally in isolation, but are found in biological hosts like bacteria and various marine organisms. In addition, many organochlorine compounds are components of alkaloids, flavonoids, and terpines that occur naturally in plants and animals. In fact, peas contain a chlorinated version of the hormone indole-3-acetic acid, while poisonous tree frogs native to Ecuador harbor an organochlorine alkaloid in their skin known as epibatidine. Other types of organochlorines are by-products of natural chemical reactions. Dioxins, for example, are produced under high temperatures during forest fires and at sites where lightening has struck.
Some types of organochlorines are highly toxic. In fact, organochlorine insecticides such as DDT, aldrin, and endrin, were used extensively in the 1940s in the U.S. to protect agricultural crops, but with an unfortunate environmental impact. Since many organochlorines are not water soluble, they tend to accumulate in the fatty tissue of marine and wildlife. They not only remain persistent in the environment, but are also carried considerable distances by ocean currents and atmospheric winds. This is why they are found in unspoiled regions, such as the Arctic.
The use of organochlorine pesticides in the U.S. was banned in the 1980s and 1990s by the Environmental Protection Agency. However, many are still being used in other countries today. In terms of human health, organochlorines present in the environment are suspected of causing a range of complications, including birth defects and cancer.
However, not all chlorinated hydrocarbon compounds are toxic. In fact, more than 100 serve useful purposes in medicine. For instance, the antidepressant drug sertraline (Zoloft), the antibiotic vancomycin, and the antihistamine loratadine (Claritin) all contain organochlorines. These agents are also found in a variety of foods and food products, such as certain legumes and artificial sweeteners.
Man-made organochlorines aside, many chemists and biologists maintain that naturally chlorinated compounds have very specific biological functions that are as essential for life as oxygen, nitrogen, and carbon. Of particular interest is the potential for some of these compounds in the future of medicine, especially those derived from marine life. For example, spongistatin, an organochlorine metabolite obtained from a sponge that thrives in the Indian Ocean, exhibits powerful anti-cancer properties. Researchers are hopeful that similar compounds found in blue-green alga may one day provide a cure for HIV and AIDS.
