Chlorinated Hydrocarbons

In addition to making very useful polymers, rubbers, plastics, solvents, and cleaners, chlorinated hydrocarbons also are potent pesticide substances. Perhaps the best known chlorinated hydrocarbon insecticide is DichloroDiphenylTrichloroethane, or DDT. First synthesized in the 1800s, the insecticidal properties of DDT were not discovered until 1939. Paul Muller, while working for the Swiss company Geigy, first uncovered the effectiveness of DDT against insects. After demonstrations of its effectiveness and relative safety to humans was established, the use of DDT exploded around the globe in the war against disease-carrying and agricultural insect pests.

The first major use of DDT was during World War II to control lice infestation in Allied troops. Its success led to the large-scale use of DDT to control the blood-sucking insects spreading yellow fever, malaria, typhus, and plague. Its initial use met with exceptional results. For example, by the 1960s, malaria cases in India fell from tens of millions of infections, to fewer than 200,000. Fatal cases of malaria in India dropped from near one million, to just two thousand per year.

However, the success of DDT application in the fight against insect transmitted disease led to massive misuse of the chemical. Widespread overuse quickly led to the development of resistant insects, upon which the poison had no effect. At the same time, evidence was accumulating that toxic levels of DDT were accumulating in the fatty tissues of animals higher on the food chain, including fish, mammals, birds, and humans. Like other chlorinated hydrocarbons, the persistence of DDT in the environment allows for biological magnification in nature, a process where minute quantities in run-off water is concentrated into toxic levels as it travels upward in the food chain. Because of its harmful effects on vertebrates as well as insects, its creation of resistant insect species, its environmental persistence, and its biological magnification, the use of DDT has been banned in many countries despite its general effectiveness.

Apart from DDT, there are other chlorinated hydrocarbon pesticides that have been developed. These include Chlordane, Aldrin, Mirex, and Toxaphene. Because other, less persistent, insecticide alternatives have been developed, the use of chlorinated hydrocarbon insecticides in general has fallen by the wayside in most places.