Lead is a ubiquitous element in the earth's crust that has long been used by humans for a variety of purposes.
Lead poisoning, or plumbism, has an equally long history, dating back to antiquity. Today, lead poisoning is primarily an important environmental health problem for young children exposed to deteriorated lead paint and an occupational illness of adults exposed via the workplace. There is no known physiologic role for lead, and thus any lead presence in human tissue represents toxic contamination.
Lead is a silvery-gray, soft metal, with an atomic weight of 207.21 daltons and an atomic number of 82 Daltons. It has a low melting point, 621.3°F (327.4°C), and boils at 2948°F (1620°C) at atmospheric pressure.159 It occurs principally as two isotopes, 206Pb and 208Pb. Metallic lead is relatively insoluble in water and dilute acids, but dissolves in nitric, acetic, and hot, concentrated sulfuric acids. In compounds, lead assumes valence states of +2 and +4. Inorganic lead compounds may be brightly colored and vary widely in water solubility; several are used extensively as pigments in paints such as lead chromate (yellow) and lead oxide (red). Lead also forms organic compounds, of which two, tetramethyl and tetraethyl lead (TEL), were used commercially as gasoline additives.74 These are essentially insoluble in water but readily soluble in organic solvents.135 Lead complexes with ligands containing sulfur, oxygen, or nitrogen as electron donors. It thus forms stable complexes with several ligands common to biologic molecules, including −OH, −SH, and −NH2. Complexes with sulfhydryl (−SH) groups are thought to be of most toxicologic importance.
Lead's low melting point and high malleability made it one of the first metals smelted and used by humans. Ancient Egyptians and Hebrews used lead, and the Phoenicians established lead mines in Spain circa 2000 B.C. The Greeks and Romans released lead during the process of extracting silver from ore. Roman society found many uses for lead, including pipes, cooking utensils, and ceramic glazes, and a common practice was to use sapa, a grape syrup simmered down in lead vessels, as a sweetener and preservative.109 Postindustrial lead use increased dramatically, and today lead is the most widely used nonferrous metal, with global extraction on the order of 9 million tons annually.74 Lead is used widely for its waterproofing and electrical- and radiation-shielding properties. Use of both lead-based paint for house paint and leaded gasoline has been essentially eliminated by regulation in the United States since the 1980s, but is still a concern in many nations, and persistence of lead paint in older U.S. homes still constitutes an enormous environmental challenge.3
History of Lead-Related Health Effects
Dioscorides, a Greek physician in the 2nd century B.C., observed adverse cognitive effects, and Pliny cautioned the Romans of the danger of inhaled fumes from lead ...