Dartmouth Toxic Metal Research

The facts on lead

What is lead?

Lead is an element, one of the basic chemical building blocks found in nature. A bluish-white metal, lead occurs naturally in harmless trace amounts in soil, rocks and water. A few centuries of mining and smelting changed this natural distribution so that toxic amounts of lead are now clustered near current and former lead plants and mines.

In nature, lead is usually associated with other metals such as sulfur, zinc, silver, copper and sometimes gold. In various combinations, these elements form minerals such as pyrite, sphalerite, quartz and barite.

What are the uses of lead?

Soft, malleable, and easy to work with, lead melts with modest heating, it resists corrosion, and it lasts a long time. Those features have made it ideal for fashioning everything from bullets and guns to pipes and fishing sinkers. In pure form, lead atoms are relatively large and can pack tightly together, which makes the metal a good radiation shield, since radiation particles cannot pass through. Though lead has long been valued for its versatility, the US government has banned it from many commercial products because of its toxic properties.

As an additive to combustion fuels, lead quiets pinging motors and boosts engine performance. Until 1986, gasoline in the United States contained lead, and leaded gasoline is still common in some parts of the world. Lead has also been widely used as the basic pigment in paint. Lead-based house paints were used extensively in the United States until 1977, when the Consumer Product Safety Commission limited lead in most paints to a trace - .06 percent by dry weight. Many old houses have never been rid of it and it continues to pose a potential hazard, especially to children who ingest flakes or dust from deteriorating lead-based paint.

For hundreds of years, people used lead to make ordinary household objects, including utensils, crystal and ceramics. Food cans, soda cans and household plumbing joints were soldered with lead through the mid-1980s and into the 1990s. Though these practices have been discontinued in the U.S., many imported cans, glazed ceramics, and pottery may still contain lead. Vinyl mini-blinds imported from China, Taiwan, Mexico, and Indonesia, sometimes contain lead, as do certain brands of playground equipment, hair dyes, and dishware. The best way to find out if your belongings have lead in them is to call the manufacturer. Most list 1-800 numbers on their packages.

Although the United States is moving toward lead-free alternatives, lead shot, lead bullets and lead fishing sinkers are still in common use. These products have caused widespread lead contamination in lakes, streams, and other bodies of water, and the metal is working its way through the food web. This is directly harmful to animals – for example, lead contamination has brought the California condor to the brink of extinction – but also serves as a conduit of exposure for humans who eat fish and other contaminated animals.

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Who is at risk of harm from lead poisoning?

Today people in the United States have far less lead in their bodies than they did several decades ago. The sharp drop in blood lead levels coincided with federal legislation imposing severe restrictions on the use of lead in commercial products. Nevertheless, lead poisoning remains the most common environmental health problem affecting children in the United States.

An estimated half a million American children under the age of six have at least 10 micrograms of lead in every deciliter of their blood. This level is high enough to adversely affect their intelligence, behavior and development, according to the Centers for Disease Control and Prevention. While these blood levels warrant immediate medical attention, recent research has linked adverse effects with much lower levels. Repeated exposure to smaller amounts of lead may be just as fatal for young children as higher short-term exposures, particularly since the symptoms of small doses may go unnoticed and untreated.

Young children are particularly vulnerable to lead poisoning because of their tendency to put chips of peeling paint into their mouths, or to suck on fingers contaminated with lead-laced dust. Studies show that children absorb lead into their bodies at a higher rate than adults. Just as children naturally absorb more nutrients from their diets, they absorb more toxicants that a mature body would flush away. For example, if they swallow an identical amount of lead an adult may absorb 20 percent into his bloodstream; a child may absorb up to 70 percent. In addition, children’s bodies are smaller, so the same blood lead level represents a much larger proportion of lead relative to a child’s body weight. All of these factors put young, developing systems at particular risk for neurobehavioral, kidney, and blood disorders.

Those at the highest risk for lead poisoning are children who live in urban neighborhoods where old houses are in poor repair. Often families in these neighborhoods have low income levels, so malnutrition, inadequate health care, and substandard housing may put this group at particular risk. Of the young children in the United States (between 1 and 5 years old) who have dangerously high levels of lead in their blood, 80 percent are Medicaid enrollees, according to estimates by the National Health and Nutrition Examination Survey (1991-1994). Because they disproportionately populate low-income areas, minority children are the most likely victims of lead poisoning in this group. Low-income children are also the least likely to be screened. No group is invulnerable to lead poisoning, however. Many cases of lead poisoning occur in affluent children who live in a recently renovated pre-1978 house where proper precautions were not taken to contain lead hazards. Screening is recommended for all young children who spend time in housing built before 1978.

Nearly all of the factors that make small children susceptible to lead poisoning are exacerbated in the case of fetuses. A pregnant woman who might show no signs of lead exposure can pass on dangerous levels of lead to her fetus. Even previous lead exposures present a risk since lead - along with calcium - may be released from a mother’s bones into her bloodstream as a result of the calcium stress that comes with pregnancy and nursing. Neurological disorders are of particular concern since a developing fetus has no blood-brain barrier.

Many adults and older children also harbor dangerous levels of the metal in their bodies. Adults often develop lead poisoning as a direct result of the jobs they do. More than 70 percent of work-related lead poisonings occur in construction workers, according to a report in 2000 by the Massachusetts Department of Public Health. House painters and those who are licensed to remove leaded paint from old structures had the highest levels of lead in their blood, the report found. Yet, workers in the lead smelting, refining, and manufacturing industries experience the highest and most prolonged occupational exposures to lead (ATSDR 1999). Also at risk are those in brass/bronze factories, rubber products and plastics industries, steel welding/cutting operations, battery manufacturing plants, bridge maintenance and repair workers, waste incinerator workers, and those who still solder electrical and other metal parts with lead.

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What is the most common way to be exposed to lead?

The source of greatest concern is old housing - specifically houses once painted with products containing lead as a pigment. The chips and dust from peeling or cracking leaded paint remain highly toxic. Sanding, scraping or heating painted doors, windows, stairs or fences can release leaded dust into the air, where children and adults may breathe it in. Even vacuuming, sweeping, or walking can circulate the dust, which eventually gathers on the floor where it is accessible to infants and toddlers engaging in hand-to-mouth activity. Lead-based dust from deteriorating paint can also be present in the soil around old homes.

A 1999 report in the Journal of the American Medical Association (JAMA), "Reducing Blood Levels: Benefits and Strategies," estimated that 11 percent of homes built in the United States before 1980 have soil-lead concentrations exceeding 1000 parts per million (ppm), or one part per thousand. To put that into perspective, the Environmental Protection Agency estimates that play areas with bare soil concentrations greater than 400 ppm are hazardous to young children. The JAMA report goes on to say that lead concentrations in the soil of some urban communities may be as high as levels in communities contaminated by smelting and mining. The U.S. Department of Housing and Urban Development calculates that 38 million dwellings built before 1978 contain at least some lead-based paint. Many of those dwellings are in New England.

A second major source of lead exposure comes from soil contaminated by lead residues from leaded gasoline and industrial processes. For many years, lead smelters, battery plants, and automobiles released dangerous doses of lead-infused emissions into the air and soil. Traces of lead from these sources remain in the soil, particularly in urban areas.

Though the use of lead has been curtailed in many household products, the metal can still end up in food and water, mostly from residual sources. Food may be prepared with leaded utensils or stored in leaded pots and ceramics. Drinking water may be transported through old pipes soldered with lead.

What are the symptoms of lead poisoning?

Unfortunately, there are no smoking-gun symptoms specific to lead poisoning. In most cases, people are exposed to relatively low levels of lead over long periods of time, so symptoms accumulate slowly, in a manner that makes them hard to connect to the source of the problem. To make matters worse, effects can differ for each victim, varying with age, gender and nutritional status. Even healthy-seeming children may have elevated levels of lead in their blood. When symptoms do arise, they can mimic other conditions common among the low-income children most at risk for lead poisoning (malnutrition, anemia, colic, etc.).

The signs of ongoing lead exposure commonly surface as generalized impairments such as lowered IQ, impaired speech and hearing, hyperactivity, decreased verbal activity and decreased learning and memory abilities. These conditions can arise from blood levels lower than 10 micrograms per deciliter. Typical symptoms of high doses (35-50 micrograms per deciliter) in children and 40-60 micrograms per deciliter in adults) include fatigue, lethargy, abdominal discomfort, irritability, headache, vomiting, constipation, tremor and weight loss. By the time a body has accumulated up to 100 micrograms per deciliter (70 micrograms per deciliter for children), the affects can include severe abdominal cramping, paralysis, seizures, coma and eventually death.

These are general guidelines, however. Individuals vary enormously in how their bodies respond to lead poisoning. Some develop severe reactions at relatively mild doses. Others develop an assortment of these at the same time. The risk for developing each type of symptom is highly dependent upon the person’s age.

In children, lead poisoning has been linked to behavior problems, neurological disorders, learning difficulties, slowed growth, poor hearing, low IQ scores and mental retardation. A 2001 study by physicians at the Children’s Hospital Medical Center in Cincinnati, Ohio, found an average decline of 5.7 points in children’s IQ scores for every additional 10 micrograms per deciliter of lead in the bloodstream. A 2003 study showed that cognitive defects can also arise in children whose blood levels are below the government guideline 10 micrograms per deciliter.

In adults, lead poisoning can look like gout or arthritis, among other disorders. Symptoms may include numb joints, difficulty moving, feelings of heaviness, sleeplessness, intestinal distress, or constipation. Reproductive problems, memory impairments, concentration problems, and high blood pressure can also occur. Lead poisoning may harm pregnancies, having an association with congenital abnormalities, premature births, low birth weights, miscarriages and stillbirths.

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How does lead harm living things?

The human body does not metabolize lead, but rather absorbs it directly into the bloodstream. If lead gets into an adult body through the skin or digestive tract, the amount of lead absorbed into the blood is generally about 20 percent of the amount ingested. If inhaled into the lungs, where exhaling is the only method of excreting waste, a body can absorb up to 100 percent into the bloodstream.

Once absorbed into the body, lead may be present for weeks to months before being excreted as waste. A small fraction remains in the body indefinitely, mostly in the bones and teeth. This stored lead may stay put, but it can also be released back into the bloodstream during times of stress (pregnancy, illness, etc), in effect repeating the lead exposure.

Once lead gets into the bloodstream, it circulates through body with red blood cells and plasma. It is the small amount of lead in blood plasma that gets transferred into soft (brain, liver) and mineralizing (bone, teeth) tissues. And it is this small amount which appears to do the damage associated with lead poisoning.

Lead finds a home in bones and teeth because the body treats this mineral much as it would calcium. In fact, some molecules in our bodies incorporate lead as easily as they incorporate calcium. Replacing calcium with lead results in a calcium deficiency for the body, possibly leading to osteoporosis. The main danger, however, lies in the possibility of later lead release.

The consequences of lead contamination in soft tissues can be severe because lead interferes with enzymes that help the brain and other cells work. Its primary affects are on the peripheral and central nervous system, kidney function, blood cells, and the metabolism of Vitamin D and calcium. But lead can also cause hypertension, reproductive toxicity, and developmental effects.

In children, high-level lead contamination of the nervous system can cause encephalopathy, a degenerative disease of the brain associated with hyperirritability, loss of muscle control, convulsions, stupor, and coma or death. At lower levels, lead’s interference with this system can cause Attention Deficit and Hyperactivity Disorder, hearing impairment, impaired balance and peripheral nerve function, and learning disabilities. Adults are not at risk for developmental disorders, but encephalopathy and/or impaired motor control and nerve function can result from extremely high blood lead levels. These conditions result from lead poisoning-associated brain swellings and lesions on the brain called cerebellar calcifications.

Acute, high doses of lead appear to have reversible affects on the kidneys. Lead at these doses impairs the ability of the kidneys to filter wastes from the bloodstream and control blood levels of certain chemicals leading to symptoms such as increased levels of sugar, phosphates, and amino acids in the urine. Chronic exposures, however, can stress the kidneys to the point of irreversible damage. Interstitial nephritis is a permanent condition associated with chronic lead poisoning that usually ends in kidney failure.

Lead interferes with the body’s ability to make hemoglobin, the filling for red blood cells. It does this by inhibiting two processes necessary to make heme, the part of hemoglobin that feeds oxygen to cells. There are several types of anemia associated with diminishing amounts of hemoglobin. Depending on the ingestion levels and time span over which lead is absorbed, the resultant anemia can cause fatigue, dizziness, weakness, irritability, pallor, rapid heartbeat, and shortness of breath. There are also neural, kidney, hormonal and liver functions that depend on the same processes as those used to make heme.

Cardiovascular diseases can have many causes and risk factors. Lead exposure may contribute to the onset and development of the disease, though there is little hard evidence to suggest the role it plays. Several studies show elevations of blood pressure in those who have been exposed to lead. The cumulative estimate for rise in systolic blood pressure lies around 1-2mm with each doubling of blood lead, or a 1-2 percent variance in blood pressure. Additionally, cardiovascular diseases seem to be exacerbated by kidney diseases (and vice versa) in a way that makes the two conditions difficult to link separately to lead poisonings. While reducing lead exposure may curb the effects on a patient’s kidneys, it may not save them from developing cardiovascular problems. One study found that adults who had been exposed to lead as children had a significantly higher risk of hypertension 50 years later.

Who should be screened for lead poisoning?

The Centers for Disease Control (CDC) identified children enrolled in the Medicaid program as a high-risk group for lead poisoning. They now recommend universal screening of blood lead levels for all Medicaid enrolled children at ages 1 and 2 years. They hope that children exposed to low lead levels during their first year can be prevented from accumulating dangerous levels by the age of two.
In addition to Medicaid enrolled children, the CDC recommends that states adopt plans for screening all children from high-risk areas. Universal screening is considered critical if more than 27 percent of the houses in an area were built before 1950 or if more than 12 percent of children in a community have elevated blood lead levels. In addition, states are recommended to use a targeted approach to screen children in low-risk areas who live in older housing.

Ultimately, it is up to the states to identify and monitor high-risk areas and administer the necessary screens. According to a 1999 report by the General Accounting Office, only 20 percent of children eligible for Medicaid had received blood tests for lead exposure. While these tests are mandatory for all Medicaid eligible children (below the age of 7) and covered by the federal Medicaid program, this report found that states are simply not performing the appropriate tests.

For non-Medicaid children, tracking lead levels requires state cooperation. The results of these tests may not get to the federal monitoring agencies since local instead of federal governments must pay for monitoring these children. The CDC's National Health and Nutrition Examination Survey (NHANES) keeps track of nationwide lead levels through data provided by states to the CDC. Yet, only 28 states reported to the CDC for their latest report, NHANES 1999.

You can find out about lead screening in your state by calling the local department of health or by talking to your doctor.

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Can lead poisoning be treated?

The first step is to get tested. If you expect you or your family are being exposed, tell your doctor who order tests and interpret the results of those tests in the context of a patient’s symptoms and risk factors.

In most cases of mild lead exposure, removing the source is the best treatment. Paint from walls, older kitchen appliances, and children’s toys are good places to start looking for lead contamination. In particular, children should be discouraged from putting foreign objects into the mouth. Once the lead source has been removed, blood levels often drop back to normal. In most cases, there will be no noticeable long-term effects. Iron and calcium supplements are generally recommended to prevent malnutrition since lead poisonings can exacerbate these conditions (and vice versa).

The United States Centers for Disease Control (CDC) set standards in 2002 for taking medical and municipal action according to the blood lead levels of those exposed. At a BLL of 10-19 micrograms per deciliter (µg/dL), the recommended action is to schedule diagnostic testing to monitor exposure levels and provide counseling on avoiding the major exposure pathways — for instance, by mopping floors or repainting. Dietary counseling is also recommended.

Aggressive environmental intervention by governmental agencies (investigation of child's residence, lead hazard reduction, etc.) becomes a requirement at individual exposure levels of 20-44 micrograms per deciliter. Medical treatment up to this point usually involves neuro-developmental monitoring and lab work to determine iron status. In some cases, the child may be prescribed calcium and iron supplements to treat the malnutrition typically caused by lead poisoning (calcium deficiency can cause lead stored in the bones to be released into the bloodstream).

Once the blood lead level reaches 45-69 micrograms per deciliter, the CDC recommends chelation therapy to chemically remove lead from the bloodstream. Chelating drugs bind to metals in the bloodstream escorting them out of the body via urine and bile. Because these drugs can have harmful side effects, such as releasing lead stored in bones, they are generally prescribed only for those who have very high blood lead levels. At a blood lead level of 70 micrograms per deciliter, lead poisoning is considered a medical emergency necessitating all actions listed above.

How do we know if we have a lead problem in our home or neighborhood?

The first thing to do is assess your risks:

- Do you live in an old building, built before 1978?

- Do you live in the Northeast?

- Is your neighborhood urban and/or economically poor?

- Is your building or neighborhood in a state of disrepair?

- Is paint chipping off of walls, windowsills or counters?

If you answered yes to one or more of these questions, you should consider testing your home for lead. Test kits are commercially available and simple to use. The cost is approximately $30.

Professional assessments are more reliable, but costs may be prohibitive for many people.

Under Title X, section1018, the United States Environmental Protection Agency (EPA) and the Department of Housing and Urban Development (HUD) published joint regulations in1996 requiring landowners of properties built before 1978 to inform renters and buyers about any known sources of lead on the property and/or any records pertaining to lead contaminant tests.

Your local health department or water supplier can provide information on testing your water for lead. In water, the metal cannot be seen, tasted, smelled, or boiled away. If you think your water might be contaminated, use the cold-water tap for drinking and cooking (hot water is more likely to leach lead particles from solder or pipe metal). Let water run through the faucet for 15 to 30 seconds before using it to dispose of water that has been standing in pipes.

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What should we do if we think we have lead in our home?

There are blood tests to assess your family’s exposure to lead. These tests are simple, quick, and relatively inexpensive. Most health plans cover lead tests. The tests are free to children enrolled in Medicaid and other state health programs.

If you suspect your home has high levels of lead the Department of Housing and Urban Development’s Office of Lead Hazard Control offers these tips:

- Have your physician test your children for lead exposure, even if they seem healthy.

- Wash children's hands, bottles, pacifiers and toys often.

- Make sure children eat healthy, low-fat foods, high in iron and calcium.

- Contact your state health department to learn how to get professional risk assessments, paint inspections, and soil inspections in your area. The EPA web site www.epa.gov/lead can help provide contact information.

- Regularly clean floors, windowsills and other surfaces.

- Wipe off shoes before entering the house.

- Talk to your landlord about fixing surfaces with peeling or chipping paint.

- Take precautions to avoid exposure to lead dust when remodeling or renovating (call 1-800-424-LEAD for guidelines).

- Don’t use a belt-sander, propane torch, dry scraper, or dry sandpaper on painted surfaces that may contain lead.

- Don't try to remove lead-based paint yourself.

Efforts to remove leaded paint often end up spreading the metal around, raising the risk of lead poisoning. Simply painting over lead-based paint helps but does not solve the problem. Renovations can remove lead, but must be done by specially trained, certified lead-abatement contractors. For help finding a lead abatement firm in your area and for information about financial aid for lead abatement, go to the EPA website: www.epa.gov/lead or call 1-888-LEADLIST for a list of lead service providers.

If you work with lead, shower and change your clothes before coming home. Wash your work clothes separately from the rest of the family’s laundry.

What are the government standards and guidelines on lead?

The federal government sets regulatory standards to protect people from lead hazards. On January 5, 2001, the United States Environmental Protection Agency set new standards. Lead is now considered a hazard if there are greater than 40 micrograms of lead in dust per square foot on floors; 250 micrograms of lead in dust per square foot on interior window sills; and 400 parts per million (ppm) of lead in bare soil in children's play areas or 1200 ppm average for bare soil in the rest of the yard. Additionally, the action level for public drinking supplies is 15 micrograms of lead per liter of water.

Several other federal agencies have stated guidelines for acceptable lead levels that range from non-enforceable industry advice to legal regulations.

Who monitors lead in the environment?

In the United States, the federal government controls lead use and monitors exposure. Most state and city health agencies also have lead programs. The US Department of Health and Human Services (HHS) Center for Disease Control (CDC) provides information about exposure and health effects through its Agency for Toxic Substances and Disease Registry.

The EPA’s Office of Pollution Prevention and Toxics controls industrial sources of lead pollution. The Office of Air and Radiation establishes standards for industrial lead emissions and sets standards for ambient air quality. The Office of Indoor Air Quality works to improve the quality of air indoors, which includes reducing lead-based paint hazards in the home. The Office of Solid Waste and Emergency Response manages lead standards in solid and hazardous waste. The same office oversees the cleanup of lead contamination at Superfund sites. The Office of Water sets standards for lead in drinking water, industrial run-off, and lakes, rivers, and streams.

Where can I get more information about lead poisoning?

The National Lead Information Center is a good source. Call 1-800-LEAD-FYI to learn how to protect children from lead poisoning. For other information on lead hazards, call the center's clearinghouse at 1-800-424-LEAD. For the hearing impaired, call, TDD 1-800-526-5456 (FAX: 202-659-1192, Internet: EHC@CAIS.COM).

You can also call the EPA's Safe Drinking Water Hotline at 1-800-426-4791 for information about lead in drinking water, or contact your local state or city Department of Health for detailed information about lead and lead programs in your area.

The Consumer Product Safety Commission Hotline is another resource. To request information on lead in consumer products, or to report an unsafe consumer product or a product-related injury call 1-800-638-2772. (Internet: info@cpsc.gov). For the hearing impaired, call TDD 1-800-638-8270.

Or visit the

U.S. Environmental Protection Agency’s website on lead

Other helpful links:

ATSDR Case studies in environmental medicine

CDC Childhood Lead Poisoning Prevention Program

NHDHHS Childhood Lead Poisoning Prevention Program