Neurotoxin
Neurotoxins are a special class of metabolic poisons that attack nerve cells. Disruption of the nervous system as a result of exposure to neurotoxins is usually quick and destructive. Neurotoxins are categorized according to the nature of their impact on the nervous system. Anesthetics (ether, chloroform, halothane), chlorinated hydrocarbons (DDT, Dieldrin, Aldrin), and heavy metals (lead, mercury) disrupt the ion transport across cell membranes essential for nerve action. Common pesticides, including carbamates such as Sevin, Zeneb and Maneb and the organophosphates such as Malathion and Parathion, inhibit acetylcholinesterase, an enzyme that regulates nerve signal transmission between nerve cells and the organs and tissues they innervate.
Environmental exposure to neurotoxins can occur through a variety of mechanisms. These include improper use, improper storage or disposal, occupational use, and accidental spills during distribution or application. Since the identification and ramifications of all neurotoxins are not fully known, there is risk of exposure associated with this lack of knowledge.
Cell damage associated with the introduction of neurotoxins occurs through direct contact with the chemical or a loss of oxygen to the cell. This results in damage to cellular components, especially in those required for the synthesis of protein and other cell components.
The symptoms associated with pesticide poisoning include eye and skin irritation, miosis, blurred vision, headache, anorexia, nausea, vomiting, increased sweating, increased salivation, diarrhea, abdominal pain, slight bradycardia, ataxia, muscle weakness and twitching, and generalized weakness of respiratory muscles. Symptoms associated with poisoning of the central nervous system include giddiness, anxiety, insomnia, drowsiness, difficulty concentrating, poor recall, confusion, slurred speech, convulsions, coma with the absence of reflexes, depression of respiratory and circulatory centers, and fall in blood pressure.
The link between environmental neurotoxin exposure and neuromuscular and brain dysfunction has recently been identified. Physiological symptoms of Alzheimer's disease, amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), and lathyrism have been identified in populations exposed to substances containing known neurotoxins. For example studies have shown that heroin addicts who used synthetic heroin contaminated with methylphenyltetrahydropyridine developed a condition which manifests symptoms identical to those associated with Parkinson disease. On the island of Guam, the natives who incorporate the seeds of the false sago plant (Cycas circinalis) into their diet develop a condition very similar to ALS. The development of this condition has been associated with the specific nonprotein amino acid, B methylamino-1-alanine, present in the seeds.
Resources
Books
Aldrich, T., and J. Griffith. Environmental Epidemiology. New York: Van Nostrand Reinhold, 1993.
Periodicals
Griffith, J., R.C. Duncan, and J. Konefal. "Pesticide Poisonings Reported By Florida Citrus Field Workers." Environmental Science and Health 6 (1985): 701–27.
Other
Agency for Toxic Substances and Disease Registry, Annual Report 1989 and 1990. Atlanta, GA: U.S. Department of Health and Human Services.
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