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Lead Poisoning

Definition

Lead poisoning occurs when a person swallows, absorbs, or inhales lead in any form. The result can be damaging to the brain, nerves, and many other parts of the body. Acute lead poisoning, which is somewhat rare, occurs when a relatively large amount of lead is taken into the body over a short period of time. Chronic lead poisoning is a common problem in children that occurs when small amounts of lead are ingested over a longer period. The Centers for Disease Control and Prevention (CDC) defines childhood lead poisoning as a whole-blood lead concentration equal to or greater than 10 micrograms/dL.

Description

Lead can damage almost every system in the human body, and it can also cause high blood pressure ( hypertension ). It is particularly harmful to the developing brain of fetuses and young children. The higher the level of lead in a child's blood and the longer this elevated level lasts, the greater the chance of ill effects. Over the long term, lead poisoning in a child can lead to learning disabilities, behavioral problems, and even mental retardation . At very high levels, lead poisoning can cause seizures, coma, and even death.

Many children with elevated blood levels are exposed to lead through peeling paint in older homes. Others are exposed through dust or soil that has been contaminated by old paint or past emissions of leaded gasoline. Since children between the ages of 12 and 36 months are apt to put things in their mouths, they are more likely than older children to take in lead. Pregnant women who come into contact with lead can pass it along to the fetus.

Over 80 percent of American homes built before 1978 have lead-based paint in them, according to the Centers for Disease Control and Prevention (CDC). The older the home, the more likely it is to contain lead paint, and the higher the concentration of lead in the paint is apt to be. Some homes also have lead in the water pipes or plumbing. Without knowing it, people may have lead in the paint, dust, or soil around their homes or in their drinking water, since lead cannot be seen, smelled, or tasted. Because lead does not break down naturally, it can continue to cause problems until it is removed.

Demographics

According to the Agency for Toxic Substances and Disease Registry, approximately one out of every six children in the United States has a high level of lead in the blood. According to the National Center for Environmental Health, there were about 200 deaths from lead poisoning in the United States between 1979 and 1998. Most of the deaths were among males (74%), African Americans (67%), adults over the age of 45 (76%), and Southerners (70%).

Causes and symptoms

Before scientists knew how harmful it could be, lead was widely used in paint, gasoline, water pipes, and many other products. In the early 2000s house paint is almost lead-free, gasoline is unleaded, and household plumbing is no longer made with lead materials. Still, remnants of the old hazards remain. Following are some sources of lead exposure:

Evidence as of 2004 suggested that lead may be harmful to children even at low levels that were once thought to be safe, and the risk of damage rises as blood levels of lead increase. The symptoms of chronic lead poisoning take time to develop, however. Children can appear healthy despite having high levels of lead in their blood. Over time, though, problems such as the following may arise:

It is also known that certain genetic factors increase the harmful effects of lead poisoning in susceptible children; however, these factors are not completely understood.

Lead poisoning is also harmful to adults, in whom it can cause high blood pressure, digestive problems, nerve disorders, memory loss, and muscle and joint pain . In addition, it can lead to difficulties during pregnancy, as well as cause reproductive problems in both men and women.

In the early 2000s, chronic exposure to lead in the environment has been found to speed up the progression of kidney disorders in people without diabetes.

Acute lead poisoning, while less common, shows up more quickly and can be fatal. Symptoms such as the following may occur:

The CDC recommends testing all children at 12 months of age and, if possible, again at 24 months. Testing should start at six months for children at risk for lead poisoning.

Diagnosis

A high level of lead in the blood can be detected with a simple blood test. In fact, testing is the only way to know for sure if children without symptoms have been exposed to lead, since they can appear healthy even as long-term damage occurs. Based on test results and a child's risk factors, the doctor will then decide whether further testing is needed and how often. In some states, more frequent testing is required by law.

Children with an increased risk of lead poisoning include those for whom the following is true:

Testing is also important for adults whose job or hobby puts them at risk for lead poisoning. This need applies to people who take part in the following activities:

Treatment

The first step in treating lead poisoning is to avoid further contact with lead. For adults, this usually means making changes at work or in hobbies. For children, it means that parents and guardians need to find and remove sources of lead in the home. In most states, the public health department can help assess the home and identify lead sources.

If the problem is lead paint, a professional with special training should remove it. Removal of lead paint is not a do-it-yourself project. Scraping or sanding lead paint creates large amounts of dust that can poison people in the home. This dust can stay around long after the work is completed. In addition, heating lead paint can release lead into the air. For these reasons, lead paint should only be removed by someone who knows how to do the job safely and has the equipment to clean up thoroughly. Occupants, especially children and pregnant women, should leave the home until the cleanup is finished.

Medical professionals should take all necessary steps to remove bullets or bullet fragments from people with gunshot injuries.

If blood levels of lead are high enough, the doctor may also prescribe chelation therapy. This refers to treatment with chemicals that bind to the lead and help the body pass it in urine at a faster rate. There are four chemical agents that may be used for this purpose, either alone or in combination. Edetate calcium disodium (EDTA calcium) and dimercaprol (BAL) are given through an intravenous line or in shots, while succimer (Chemet) and penicillamine (Cuprimine, Depen) are taken by mouth. (Although many doctors prescribe penicillamine for lead poisoning, this use of the drug has not been approved by the Food and Drug Administration.)

Changes in diet are no substitute for medical treatment. However, getting enough calcium, zinc, and protein may help reduce the amount of lead the body absorbs. Iron is also important, since people who are deficient in this nutrient absorb more lead. Garlic and thiamine, a B-complex vitamin, have been used to treat lead poisoning in animals. However, their usefulness in humans for this purpose has not as of 2004 been demonstrated. Nutritional, botanical, and homeopathic medicines can be administered once the source is removed to help correct any imbalances brought on by lead toxicity.

Prognosis

If acute lead poisoning reaches the stage of seizures and coma, there is a high risk of death. Even if the person survives, there is a good chance of permanent brain damage. The long-term effects of lower levels of lead can also be permanent and severe. However, if chronic lead poisoning is caught early, these negative effects can be limited by reducing future exposure to lead and getting proper medical treatment.

Prevention

KEY TERMS

Chelation therapy —A treatment using chelating agents, compounds that surround and bind to target substances allowing them to be excreted from the body.

Dimercaprol —A chemical agent used to remove excess lead from the body.

Edetate calcium disodium —A chemical chelating agent used to remove excess lead from the body.

Penicillamine (Cuprimine, Depen) —A drug used to treat medical problems (such as excess copper in the body and rheumatoid arthritis) and to prevent kidney stones. It is also sometimes prescribed to remove excess lead from the body.

Pica —A desire that sometimes arises in pregnancy to eat nonfood substances, such as dirt or clay.

Succimer —A chelating agent that is used to remove excess lead from the body. Sold under the trade name Chemet.

Avoid preparing or serving food in containers that have lead in their glazing. Do not consume homemade liquor that has been distilled.

Parental concerns

Lead tastes sweet. Parents living in homes built prior to 1978 should be vigilant regarding removing all flaking or peeling paint. Simply re-painting such surfaces will not resolve the problem. Parents must monitor the environments in which their children play and the objects that go into their children's mouths. Cleanliness is a must if old paint is in a child's environment. Removal (stripping paint to bare metal or bare wood) of lead is the best way to prevent lead exposure in children.

Resources

Goto, Collin S. "Heavy Metal Intoxication." In Nelson Textbook of Pediatrics , 17th ed. Edited by Richard E. Behrman, et al. Philadelphia: Saunders, 2003, pp. 2355–7.

Gupta, S. K., et al. Emergency Toxicology: Management of Common Poisons. Boca Raton, FL: CRC Press, 2003.

Klaasen, Curtis D., and John Doull. Casarett and Doull's Toxicology: The Basic Science of Poisons , 6th ed. New York: McGraw Hill, 2001.

Markowitz, Morrie. "Lead Poisoning." In Nelson Textbook of Pediatrics , 17th ed. Edited by Richard E. Behrman, et al. Philadelphia: Saunders, 2003, pp. 2358–61.

Clark, S., et al. "The influence of exterior dust and soil lead on interior dust lead levels in housing that had undergone lead-based paint hazard control." Journal of Occupational and Environmental Hygiene 1, no. 5 (2004): 273–82.

Dietert, R. R., et al. "Developmental immunotoxicology of lead." Toxicology and Applied Pharmacology 198, no. 2 (2004): 86–94.

Dorea, J. G. "Mercury and lead during breast-feeding." British Journal of Nutrition 92, no. 1 (2004): 21–40. Kwong W. T., et al. "Interactions between iron deficiency and lead poisoning: epidemiology and pathogenesis." Science of the Total Environment 330, no. 1–3 (2004): 21–37.

Sandel, M., et al. "The effects of housing interventions on child health." Pediatric Annals 33, no. 7 (2004): 474–81.

Stretesky, P. B., and M. J. Lynch. "The relationship between lead and crime." Journal of Health and Social Behavior 45, no. 2 (2004): 214–29.

American Academy of Clinical Toxicology. 777 East Park Drive, PO Box 8820, Harrisburg, PA 17105–8820. Web site: http://www.clintox.org/index.html.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211–2672. Web site: http://www.aafp.org/.

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007–1098. Web site: http://www.aap.org/default.htm.

American Association of Poison Control Centers. 3201 New Mexico Avenue NW, Washington, DC 20016. Web site: http://www.aapcc.org/.

American College of Occupational and Environmental Medicine. 55 West Seegers Road, Arlington Heights, IL 60005. Web site: http://www.acoem.org/.

"CDC Childhood Lead Poisoning Prevention Program: Spotlight on Lead." Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/nceh/lead/lead.htm and http://www.cdc.govceh/lead/factsheets/leadfcts.htm (accessed November 11, 2004).

"Lead-based Paint Hazard Control Grant Program." U.S. Department of Housing and Urban Development. Available online at http://www.hud.gov/offices/lead/ (accessed November 11, 2004).

"Lead in Paint, Dust, and Soil." U.S. Environmental Protection Agency. Available online at http://www.epa.gov/lead/ (accessed November 11, 2004).

"Lead Poisoning." National Library of Medicine. Available online at http://www.nlm.nih.gov/medlineplus/leadpoisoning.html (accessed November 11, 2004).

"Occupational Lead Poisoning." American Academy of Family Physicians. Available online at http://www.aafp.org/afp/980215ap/stauding.html (accessed November 11, 2004).

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