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Lead
January 2006

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• What is lead?
• What are the forms of lead?
• What are the common uses of lead?
• What are the routes of exposure for lead?
• Who are the populations most at risk and how are they usually exposed?
• What are the possible toxic effects of lead?
• How can I reduce the risk of exposure to lead?
• What are the safety guidelines for lead exposure?
• What are the most important or common mediating factors?
• Is there a test to see if my child or I have been exposed to lead?
• Future Research Needs
• For more information

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What is lead?

Lead is a heavy, bluish-gray metal that has a low melting point. It occurs naturally in the Earth's crust, but it is not a particularly abundant element. It is rarely found naturally as a metal, but rather in its divalent (2+) oxidative state in ore deposits widely distributed throughout the world. The most important lead containing ores are galena (PbS), anglesite (PbSO₄), and cerussite (PbCO₃). Natural lead is a mixture of four stable isotopes: ²⁰⁸Pb (51%–53%), ²⁰⁶Pb (23.5%–27%), ²⁰⁷Pb (20.5%–23%), and ²⁰⁴Pb (1.35%–1.5%).

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What are the forms of lead?

• Metallic lead
• Inorganic lead and lead compounds (or lead salts)
• Organic lead (containing carbon)

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What are the common uses of lead?

The largest use for lead is in storage batteries in cars and other vehicles. Lead may be used as a pure metal, alloyed with other metals, or as chemical compounds.

Lead used by industry comes from mined ores ("primary") or from recycled scrap metal or batteries ("secondary"). However, most lead today is obtained from recovery of recycled scrap, mostly lead-acid batteries.

Human activities, such as lead mining and smelting operations and manufacturing and use of lead products (e.g., leaded gasoline, lead-based paint), have resulted in the contamination of many industrial and residential areas with lead.

Form	Uses
Metallic lead Lead and lead compounds (or lead salts), such as lead acetate lead chloride lead nitrate lead oxide lead phosphate lead acetate lead sulfate lead sulfide	Certain uses of lead, such as leaded gasoline, lead-based paints for domestic use, lead-based solder in food cans and water pipes, lead sinkers, and ammunition, have been reduced or banned to minimize lead’s harmful effects on people and animals. Cosmetics and hair dye - Some hair dyes and some non-Western cosmetics, such as kohl and surma, contain lead. Fishing equipment - Most fishing weights and sinkers are made from lead. Folk remedies - Many non-Western folk remedies used to treat diarrhea or other ailments may contain substantial amounts of lead. Examples of these include alarcon, ghasard, alkohl, greta, azarcon, liga, bali goli, pay-loo-ah, coral, and rueda. Glazing - Applied to some ceramicware can contain lead. Lead based paint - Although the sale of residential lead-based paint was banned in the United States in 1978, it remains a major source of lead exposure for young children residing in older houses. Lead batteries - Production of lead-acid batteries is the major use of lead. Lead-based solder - Has been banned for use in water distribution systems, but many buildings and homes contain lead pipes or lead-based solder. Lead-based solder also is used for electrical circuitry applications. Lead-shot and ammunition - It is the second highest production use of lead. Other uses of lead include the production of lead alloys, soldering materials, shielding for x-ray machines, and manufacturing of corrosion- and acid-resistant materials used in the building industry.
Organic tetraethyl lead tetramethyl lead	The use of lead in gasoline was phased out in the 1980s, and has been banned since January 1, 1996. The use of lead in gasoline has contributed to its dispersion throughout the environment. During the combustion of gasoline containing these alkyllead compounds, significant amounts of inorganic lead can be released to the surrounding areas. Current Uses Gasoline for off-road vehicles, farm equipment, and airplanes Past Uses Gasoline additives (to increase octane rating)

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What are the routes of exposure for lead?

People are most likely to be exposed to lead by consuming contaminated food and drinking water. Exposure can also occur by inadvertently ingesting contaminated soil, dust, or lead-based paint.

Form	Routes of Exposure
Metallic lead Lead and lead compounds (or lead salts), such as lead acetate lead chloride lead nitrate lead oxide lead phosphate lead subacetate lead sulfate lead sulfide	Ingestion is the primary source of exposure to the general population. Lead paint is a major source of environmental exposure for children who ingest flaking paint, paint chips, and weathered powdered paint (mostly from deteriorated housing units in urban areas). Lead paint can also contribute to soil/dust lead which can be inadvertently ingested via hand-to-mouth activity of young children. Lead can leach into drinking water from lead-based solder used in water pipes. Lead can leach into foods or liquids stored in ceramic containers made with lead glazing. Engaging in hobbies such as casting ammunition, making fishing weights, and stained glass can result in exposure to lead. Exposure by inhalation can result during activities such as soldering with lead solder or sanding or sandblasting lead-based paint.
Organic tetraethyl lead tetramethyl lead	Inhalation Dermal studies in animals have shown that organic lead is well absorbed through the skin

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Who are the populations most at risk and how are they usually exposed?

People living near hazardous waste sites, lead smelters or refineries, battery recycling or crushing centers, or other industrial lead sources may be exposed to lead and chemicals that contain lead. Workers in occupations that have sources of lead exposure (e.g., plumbers, miners, mechanics, and lead smelter or refinery workers).

Certain hobbies, folk remedies, home activities, and car repairs (e.g., radiator repair) can contribute to lead exposure. Smoking cigarettes or breathing second-hand smoke increases exposure because tobacco smoke contains small amounts of lead.

Pregnant women, the developing fetuses, and young children are particularly vulnerable to the effects of lead. Young children are more likely to play in dirt and to place their hands and other objects in their mouths, thereby increasing the opportunity for exposure via ingestion of lead-contaminated soil and dust.

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What are the possible toxic effects of lead?

The most sensitive targets for lead toxicity are the developing nervous system, the hematological and cardiovascular systems, and the kidney. However, because of lead’s many modes of action in biological systems, lead could potentially affect any system or organs in the body. The effects are the same whether it is breathed or swallowed.

Blood Lead Concentrations Corresponding to Adverse Health Effects
Life Stage	Effect	Blood lead (µg/dL)
Children	Depressed ALAD* activity	<5
	Neurodevelopmental effects	<10
	Sexual maturation	<10
	Depressed vitamin D	>15
	Elevated EP**	>15
	Depressed NCV***	>30
	Depressed hemoglobin	>40
	Colic	>60
Adults	Depressed GFR****	<10
	Elevated blood pressure	<10
	Elevated EP (females)	>20
	Enzymuria/proteinuria	>30
	Peripheral neuropathy	>40
	Neurobehavioral effects	>40
	Altered thyroid hormone	>40
	Reduced fertility	>40
	Depressed hemoglobin	>50
Elderly adults	Depressed ALAD*	<5
	Neurobehavioral effects	>4

*aminolevulinic acid dehydratase (ALAD) **erythrocyte porphyrin (EP) ***nerve conduction velocity (NCV) ****glomerular filtration rate (GFR) Source: ATSDR Toxicological Profile for Lead (Draft for Public Comment), 2005.

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How can I reduce the risk of exposure to lead?

• Do not allow children to chew or mouth surfaces that may have been painted with lead-based paint (homes built before 1978).
• If you have a water lead problem, the U.S. Environmental Protection Agency (EPA) recommends that you flush your cold water pipes if they have not been used in over 6 hours by running water until it is cold (5 seconds to 2 minutes) before drinking or cooking with it.
• Avoid some types of paints and pigments that contain lead and are used as make-up or hair coloring; keep these kinds of products away from children.
• Hire a professional contractor, who is required to follow certain health safety requirements for remediation or renovation involving lead-based paint, (www.epa.gov/lead/pubs/leadinfo.htm#remodeling).
• Wash children's hands and faces often to remove lead dusts and soil, and regularly clean the house of dust and tracked in soil.

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What are the safety guidelines for lead exposure?

Air	National Institute for Occupational Safety and Health (NIOSH) Recommended exposure limit (REL) time-weighted average (TWA) - 0.05 mg/m3 Immediately dangerous to life or health (IDLH) - 100 mg/m3 Occupational Safety and Health Administration (OSHA) Air - workplace 50 µg/m3 Action level - 40 µg/100 g of whole blood The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold limit values (TLV)/(TWA) - 0.05 mg/m3 TLV/TWA guideline for lead arsenate - 150 µg/m3 TLV/TWA guideline for other forms of lead - 50 µg lead/m3 U.S. Environmental Protection Agency (EPA) National Primary and Secondary Ambient Air Quality Standards - 1.5 µg/m3 World Health Organization (WHO) Air quality guidelines -- 0.5 µg/m3
Water	EPA Maximum contaminant level (MCL) - action level 0.015 mg/L Action level for public supplies - 15 µg/L WHO Drinking Water Quality Guidelines - 0.01 mg/L
Blood	Centers for Disease Control and Prevention (CDC) Level of concern for children - 10 µg/dL OSHA Cause for written notification and medical exam - 40 µg/dL Cause for medical removal from exposure - 50 µg/dL ACGIH Advisory; biological exposure index - 30 µg/dL
Food	Food and Drug Administration (FDA) Bottled drinking water - 0.005 mg/L
Other	ACGIH Biological exposure indices (lead in blood) - 30 µg/100 mL Consumer Product Safety Commission Paint - 600 ppm FDA Ceramicware (µg/mL leaching solution) - 0.5-3.0 µg/mL

µg/m3: micrograms per cubic meter µg/dL: micrograms per deciliter µg/L: micrograms per liter g: gram

mg/L: milligrams per liter mL: milliliter ppm: parts per million

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What are the most important or common mediating factors?

Factors that determine the severity of the health effects from lead exposure include

• Dose
• Age of the person exposed
  • the developing nervous system is the most sensitive system to the effects of lead
  • the efficiency of lead absorption from the gastrointestinal tract is greater in children than in adults
• Life stages of women (childbirth, lactating, menopause)
• Occupational exposures
• Duration of exposure
• Health and lifestyle of the person exposed
• Nutritional status of the person exposed
  • a diet adequate in calcium and iron may decrease lead absorption

The toxic effects of lead exposure may be worse in individuals with inherited genetic diseases or gene polymorphisms such as thalassemia, individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, and carriers of certain gene polymorphic forms (e.g., ALAD and vitamin D receptor). Research continues about this topic.

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Is there a test to see if my child or I have been exposed to lead?

Blood	The screening test of choice is blood lead levels. Blood tests are commonly used to screen children for lead poisoning. Analysis of lead in whole blood is the most common and accurate method of assessing lead exposure. Exposure to lead also can be evaluated by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells known to increase when the amount of lead in the blood is high. However, the EP level is not sensitive enough to identify children with elevated blood lead levels below about 25 micrograms per deciliter (µg/dL).
Bone and Teeth	X-ray fluorescence techniques have been used to determine lead concentration in bones and teeth. It is not widely available and is used mostly in research. Lead partitions to bone over a lifetime of exposure; therefore, bone lead measurements may be a better indicator of cumulative exposure than blood lead.
Urine	Measurements of urinary lead levels have been used to assess lead exposure. The measurement of lead excreted in urine following chelation with calcium disodium EDTA (EDTA provocation) has been used to detect elevated body burden of lead in adults and children.
Hair and Nails	These are not reliable for testing due to errors external contamination. They are relatively poor predictors of blood lead, particularly at low concentrations.

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Future Research Needs

To close current gaps in the scientific database on the health effects of lead, a long–term research program is needed that might include the following:

• Further short-term studies or studies in vitro designed to clarify mechanisms of action for the various toxicities might be useful.
• Studies identifying exposures during different developmental periods can help identify critical periods of vulnerability for immunocompetence, development of sex organs, or neurobehavioral parameters.
• Chronic-duration exposure studies in animals would expand information on the toxicity of lead. Special studies that examine biochemical and morphological effects of lead may provide new information on mechanisms of action of lead, particularly for the effects of greatest concern such as neurobehavioral changes in children.
• Development of new and more sensitive tests of specific neuropsychological functions.
• Further investigation of links between lead and amyotrophic lateral sclerosis, essential tremor, schizophrenia, and Parkinson’s disease.
• Epidemiological studies designed in a manner that permits more rigorous assessments of effect modification.
• Studies about the long-term consequences of lead-related neurobehavioral deficits detected in infants and children and the manifestation of chronic neurobehavioral problems in adolescence and adulthood.
• Further characterization of bone lead concentration as a biomarker of exposure for various effect end points (e.g., blood pressure and renal effects).
• Studies of the potential prevalence of elevated bone lead stores in women of reproductive age and the associated risk that this poses to fetal development by mobilization of maternal bone stores during pregnancy.
• Further clarification of the role of some genetic polymorphisms.
• Evaluation of cohorts from prospective studies into adulthood for potential late-appearing effects including cancer.

For more information

• Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological Profile for Lead

  http://www.atsdr.cdc.gov/toxprofiles/tp13.html

• ATSDR ToxFAQs™ for Lead

  http://www.atsdr.cdc.gov/tfacts13.html

• ATSDR Case Studies in Environmental Medicine Lead Toxicity

  http://www.atsdr.cdc.gov/csem/lead/

• ATSDR Interaction Profile for Chemical Mixtures for Arsenic, Cadmium, Chromium, and Lead

  http://www.atsdr.cdc.gov/interactionprofiles/ip04.html

• ATSDR Interaction Profile for Chemical Mixtures for Lead, Manganese, Zinc, and Copper

  http://www.atsdr.cdc.gov/interactionprofiles/ip06.html

• ATSDR Interaction Profile for Chemical Mixtures for Chlorpyrifos, Lead, Mercury, and Methylmercury

  http://www.atsdr.cdc.gov/interactionprofiles/ip11.html

• Centers for Disease Control and Prevention Lead Web Page

  http://www.cdc.gov/lead/

• U.S. Environmental Protection Agency Lead Web Page

  http://www.epa.gov/lead/

• U.S. Department of Labor, Occupational Safety & Health Administration

  http://www.osha.gov/SLTC/lead/

For more information, contact:

Agency for Toxic Substances and Disease Registry
Division of Toxicology and Environmental Medicine
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Phone: 1-800-CDC-INFO (800-232-4636)
TTY 888-232-6348

FAX: (770)-488-4178
Email: CDCINFO@cdc.gov

This page was updated on 01/04/2008