• Lead is a heavy metal
• It exists in four isotopic forms and is classified as a metal.
• Chemically, its low melting point and ability to form stable
compounds has made it useful for hundreds of products.
• Clinically, it is purely a toxicant; no organism has an
essential function that is lead dependent.
• Medical knowledge pertaining to its toxicity has existed for
more than 2,000 years.
• Its commercial attractiveness has resulted in the
processing of millions of tons of lead ore. The
result is widespread dissemination of lead in the
• Clinically the blood lead level (BLL) is the gold
standard for determining health effects. An ideal
BLL is 0.
• BLL up to 10 μg/dL has been acceptable.
• In a major survey, the National Health and
Nutrition Examination Survey II, conducted on a
representative sample of the U.S. population
between 1976 and 1980, showed greater than
85% of preschool-aged children had elevated
BLLs; 98% of African-American preschoolers had
• Over the next 15 yr, government regulations
resulted in the significant reduction of three main
contributors to lead exposure:
(1) the elimination of the use of tetraethyl leaded
(2) the banning of lead-containing solder to seal
food and beverage containing cans
(3) the application of a federal rule that limited the
amount of lead allowed in paint intended for
household use to less than 0.07% by weight.
• Continued surveillance by the CDC has shown
that the prevalence of elevated BLLs has declined
markedly and is now below 10% of preschoolers.
SOURCES OF EXPOSURE
• Lead poisoning may occur in utero because lead readily
crosses the placenta from maternal blood.
• The source of maternal blood lead - redistribution from
endogenous stores, her skeleton, environmental exposure.
• Products that contain lead - batteries, cabl...