Lead Sources and Health

Plumbum, Pb, or lead, the 82nd element, is usually found in the Earth's crust as lead sulphide or galena and in the atmosphere as lead sulphate or lead carbonate. Lead is malleable, has a low melting point, and therefore has many uses. Lead poisoning may be the oldest industrial disease because humans have used lead for over 8,500 years. There are many sources of lead exposure, and most humans have elevated lead levels or lead stores. Lead poisoning was first described in 250 B.C.E. from a case of leadinduced anemia and colic. Despite this report, it was used to sweeten wine (lead acetate) that was known to cause gout and colic and to make skin ointments and kitchen utensils.

Lead is an almost ubiquitous pollutant. A 2006 New York City study found lead levels in household dust exceeded both the Housing and Urban Development and Environmental Protection Agency indoor levels by three- to 18-fold. Environmental exposure can include lead-based paint, soil, and dust in the vicinity of lead-use industries, ceramic glazes, vehicle exhaust, and plumbing leachate. Industrial sources of lead include metal alloy foundries, glass manufacturers (high-quality crystal glass contains lead), typesetters and printers, roofing manufacturers, mining and smelters, battery manufacturers and recyclers, paint strippers, electronic product manufacturers, furniture refinishers, and demolition companies.

Common activities that may have lead exposure include pottery glazing, stained-glass making, oil painting, target shooting and hunting, lead soldering, painted-furniture stripping, and fishing using lead-weighted lines. Lead is also found in some Ayurvedic, south Asian, and traditional Chinese medicines; cosmetics (e.g., eyeliner); hair dyes; and children's toys. Lead-based paints for the home, children's toys, and household furniture were banned in the United States in 1978, but many countries still manufacture and use leadbased paints. Lead can also be found in foods grown in regions exposed to sources of lead through surface and irrigation water and dust and air pollution from various automotive and industrial sources.

Lead can be absorbed in the gut from water or pica (ingestion of dirt, paint, or particles that contain lead). It binds to red blood cells, preventing the formation of hemoglobin for carrying iron, and becomes distributed throughout the body into soft tissues, bones, teeth, and fat cells. It accumulates over a lifetime, with 95 percent residing in the bones, but is [Page 252]released very slowly. In the nervous system, it can cause paralysis of motor nerves (e.g., painless wrist drop) and lower cognitive function. It can also cause acute abdominal pain, kidney damage, high blood pressure, and reproductive failure. It may also cause irritability; insomnia; metallic taste; lethargy or hyperactivity; headache; and even seizure, coma, and death.

Children under the age of six are especially and permanently susceptible to any level of lead ingested. One hypothesis is that 65 to 90 percent of violent crimes are committed by individuals with elevated preschool lead levels. The average person has 100 parts per billion of lead in his or her blood, a level considered to be much higher than that in ancient times. Virtually everyone is exposed to lead; for example, leaded gasoline was phased out in most but not all countries in 2007, lead solder and brass fittings occur in many water pipes, and dust from diverse industrial sources places lead in the atmosphere.

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