| Abstrakt: |
This section explores the toxic properties of lead. Since lead is never found naturally in its metallic state, this is evidence that the earliest civilizations had learned to smelt lead from its ore, galena, to produce the metal. The commercial importance of lead is based on its relative abundance, ease of casting, high density, low melting point, low strength, ease of fabrication, acid resistance, electrochemical reaction with sulfuric acid, and chemical stability. The three primary sources of lead exposure in the U.S. are: lead-based paint found in older homes, lead in urban soil and dust, and lead in drinking water. The importance of leaded gasoline as an environmental source of lead exposure is highlighted by the National Health and Nutrition Examination Survey data, which demonstrated that as lead consumption in gasoline declined from 1976 to 1980, the mean blood lead level of the U.S. population dropped markedly. Lead has no physiological role in the human body or, for that matter, in any biological process; there is no such thing as a normal blood lead level. In erythrocytes, anemia is a clinical manifestation of lead poisoning. The anemia is produced by two mechanisms--impairment of heme biosynthesis and accelerated destruction of erythrocytes. |
