VI. Neurotoxicity of the Cyclodiene and Hexachlorocyclohexane Derivatives ... ...... ...................... .... . 122 A. Signs and Symptoms of Poisoning ............................. 123
given period of time which resulted in death. . Toxicity values taken from Hayes. 20 lindane, aldrin, dieldrin, endrin, and chlordane (Table 1) between 1939 and 1945 had immediate consequences. These chemicals were used in massive amounts during World War ll for the control of mosquito-borne diseases such as malaria, dengue fever, and filariasis. Metcalf! has summarized the critical role that the CHis have played both in world health and in world food production. Their impact has been truly remarkable. It has been estimated that by 1953, DDT alone had saved approximately 50 million lives and averted 1 billion cases of human disease. 2 DDT has been suggested to be the single most important factor in the world population explosion between 1950 and 1970.1 The CHis, prior to 1970, were the standard agents used in insect control. They were registered for use on over 300 agricultural commodities and were universally employed to control such pests as the codling moth, pink bollworm, gypsy moth, and the spruce budwonn. In retrospect, it is
The hazards inherent in the large scale use of the CHis began to emerge during the same period. Hayes3 published a review article in 1959 focusing upon the pharmacology and toxicology of DDT which contains 685 references, most dealing with some aspect of acute or chronic toxicity to man, domestic animals, or wildlife. The environmental impact of massive CHI application was presented publicly and dramatically in 1962 by Carson4 in Silent Spring. More careful and balanced assessments soon became available. M At present, strict controls exist upon the use of CHis in most countries to limit their adverse impact on the environment. This use limitation followed logically from their implied hazards. CHis tend to persist unchanged in the environment for long periods of time, tend to accumulate in soils, and may be translocated from their point of application into rivers, lakes, and oceans. Because of their persistence and high lipid-solubility, they enter into all organisms and tend to accumulate along various food chains in all ecosystems. This accumulation can lead to undesirable kills of many invertebrates, who are particularly sensitive to their toxic actions. The ingestion of CHI-containing organisms by various predators results in high body burdens of the CHis and their metabolites in the predator. This mechanism has been implicated in certain widescale loss of fish and birds.7"12• Problems such as these have led to severe restrictions in the use of the more persistent CHis. In addition to the already apparent impact of the CHis, there are real concerns remaining about the consequences of the continuous presence of pesticide residues in man and domestic animals. There is concern, too, that continued exposure may result in oncogenic, mutagenic, and teratogenic effects which might not become apparent until many years of chronic exposure have occurred. These latter concerns are not restricted to the CHis and apply universally to any chemical substance. However, the long persistence of CHis in the environment and in the tissues of animals and man makes their removal very difficult if and when unacceptable toxicity should occur.