Lead

LEAD

Lead (Pb) is a soft, corrosion-resistant gray metal that is a common environmental contaminant in air, food, paint, and water. Lead is recovered from mined sulfide ores, and has been used to fashion items such as statues and tools since at least 6500 B.C.E. The Romans used lead to fashion potable water piping. The relationship between plumbing and lead has become a permanent part of the English language—the word "plumbing" derives from the Latin word for lead, plumbum. Besides plumbing, lead has been used to manufacture items such as ceramics, cosmetics, lead batteries, leaded paint, and leaded gasoline. Common chemical species of lead used commercially include lead acetate, lead carbonate, lead chloride, and lead oxide.

Figure 1

The Agency for Toxic Substances and Disease Registry (ATSDR) estimates that more than one million workers in one hundred occupations are exposed to lead, such as in the lead-battery recycling and lead-smelting industries. Equally important, almost all persons are exposed to lead in residential settings from sources such as paint chips, food, water, cigarettes, and clothing that has been worn in lead-contaminated work environments.

Adverse health effects from lead exposure have been recognized since the time of the Romans. The National Research Council (NRC) traces society's more recent interest in lead poisoning to an 1839 publication by Tanquerel des Planches, who described lead colic in 1,207 occupationally exposed workers. It is now recognized that even low levels of lead exposure are associated with adverse health effects. The U.S. Centers for Disease Control and Prevention (CDC) has identified a lead concentration of ten micrograms per deciliter (µg/dL) of blood as the level of concern above which significant health risks occur. Acute exposure to lead compounds may cause brain damage, kidney damage, and gastrointestinal distress. Chronic exposure to lead results in effects on the blood, the central nervous system, blood pressure, the kidneys, the male reproductive system, and vitamin D metabolism. Children, particularly impoverished children living in homes with lead paint, are particularly at risk from the toxic effects of lead, and may exhibit slowed cognitive development and decreased intelligence after chronic exposure. Figure 1 identifies the health effects of lead at different blood level concentrations.

Because lead does not biodegrade, the approximately 300 million metric tons of lead produced to date remains in the environment. This suggests that humans will continue to be exposed to lead despite the phasing out of lead in consumer products such as gasoline and paint. In the early 1970s, the federal government recognized that steps had to be taken to reduce human exposure to lead, and banned residential leaded paint (1978), and phased out leaded gasoline between 1975 and 1995. The removal of lead from gasoline has proceeded more slowly in the rest of the world. In some countries leaded gasoline remains a significant source of exposure.

The CDC estimates that children's blood lead levels have declined over eighty percent since the mid-1970s. The Lead Contamination Act of 1988 authorized the CDC to initiate programs to eliminate childhood lead poisoning in the United States. The Lead Contamination Act of 1988 authorized the CDC to make grants to state and local agencies for comprehensive programs designed to screen infants and children for elevated blood lead levels, ensure referral for medical and environmental intervention for lead-poisoned infants and children, and provide education about childhood lead poisoning. Despite this impressive decrease in blood lead levels, more than one million children in the United States have blood lead levels above 10 µg/dL, and are at risk of permanent neurological impairment.

MARGARET H. WHITAKER

BRUCE A. FOWLER

(SEE ALSO: Blood Lead; Environmental Determinants of Health; Heavy Metals; Occupational Disease; Occupational Safety and Health; Regulations Affecting Housing)

BIBLIOGRAPHY

Agency for Toxic Substances and Disease Registry (ATSDR) (1993). Toxicological Profile for Lead. Washington, DC: U.S. Department of Health and Human Services.

—— (2000). Case Studies in Environmental Medicine: Lead Toxicity. Available at http://www.atsdr.cdc.gov/HEC/caselead.html.

Centers for Disease Control and Prevention (1997). "Update: Blood Lead Levels—United States 1991–1994." Morbidity and Mortality Weekly Report 46(7):141–146 and erratum in 46(26):607.

Lewis, J. (1985). "Lead Poisoning: A Historical Perspective." EPA Journal. Available at http://www.epa.gov/history/topics/perspect/lead.htm.

National Research Council, Commission on Life Sciences (1993). Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations. Available at http://stills.nap.edu/books/030904927X/html/.

President's Task Force on Environmental Health Risks and Safety Risks to Children (2000). Eliminating Childhood Lead Poisoning: A Federal Strategy Targeting Lead Paint Hazards. Available at http://www.epa.gov/children/whatwe/leadhaz.pdf.

U.S. Environmental Protection Agency (U.S. EPA) (1998). Lead in Your Home: A Parent's Reference Guide. Office of Prevention, Pesticides, and Toxic Substances. Available at http://www.epa.gov/lead/leadrev.pdf.