Lead (symbol Pb, atomic number 82) is a soft, dense, bluish-gray metal that melts at the relatively low temperature of 328°C (662°F). It has many beneficial uses in compounds as well as in its metallic form, but is toxic at almost any level in the body. Mentioned in the Bible, lead was one of the first known metals. Its toxicity was also recognized long ago; Greek physicians made the first clinical description of lead poisoning in the first century B.C.E., and lead is arguably the earliest known industrial pollutant.

Lead taken internally in any of its forms is highly toxic. At higher body levels, the symptoms of lead poisoning are anemia, weakness, constipation, colic, palsy, and often a paralysis of the wrists and ankles. At low levels, there may be no symptoms. Young children are especially at risk from lead, even at levels once thought safe. Low-level...