الفهرس 
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Abstract
The heightened concern for reduction of environmental pollution
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that has been occurring over the past 20 - 25 years has stimulated active
continuing research on the toxicology of heavy metals. Man has succeeded
in poisoning himself with these metals repeatedly throughout recorded
history. The heavy metals include mainly iron, copper, manganese,
cadmium, arsenic, nickel, aluminum, silver, and beryllium. These metals
differ from other toxic substance in that they are neither created nor
destroyed by humans.l’ )
Heavy metals produce their toxicity by forming complexes with
organic compounds. These modified biological molecules lose their ability
to function properly, and results in malfunction or death of the affected
cells. The most common groups involved in ligand formation are oxygen,
sulfur, and nitrogen. When metals bind to these groups they inactivate
important enzyme systems, or affect protein structure. (2,)
Chelation is the first anti-dote to heavy metal intoxication. Chelators
are the class of compounds which are used in the treatment of heavy metal
intoxication. A chelator is a flexible molecule with tow or more
electronegative groups that can form stable co-ordinate covalent bonds with
cationic metal atoms. The complexes are then excreted by the body.