- What is lead poisoning
- Causes of Lead poisoning
- Who is at Risk of Lead Poisoning ?
- Complications of lead poisoning
- Prevention of lead poisoning
- Lead poisoning signs and symptoms in children
- Symptoms of lead poisoning in adults
- Diagnosis of lead poisoning
- Lead poisoning treatment
What is lead poisoning
Lead poisoning occurs when lead builds up in your body, often over months or years. Even small amounts of lead can cause serious health problems. Children younger than 6 years are especially vulnerable to lead poisoning, which can severely affect mental and physical development. At very high levels, lead poisoning can be fatal.
- Poisoning with lead is more harmful for children, whose brains and other organs are still developing. Adults tend to recover from lead ingestion better than children. Children who may be at risk should be screened as soon as possible.
- Lead interferes with the absorption of iron. Children with raised blood lead concentrations should be tested for iron deficiency.
Lead (Pb) is a metal that occurs naturally in the earth’s crust – natural levels of lead in soil range between 50 and 400 parts per million 1). Lead can be found in all parts of our environment. Much of it comes from human activities such as mining and manufacturing. Lead and lead compounds have been used in a wide variety of products found in and around our homes, including paint (older houses may still have lead paint), ceramics, pipes and plumbing materials, solders, gasoline, batteries, ammunition, and cosmetics.
Lead exists in three forms: metallic lead, inorganic lead and lead compounds (or lead salts), and organic lead (containing carbon). Lead in the environment rarely occurs in its elemental state, but rather in its +2 oxidation state (Pb2+) in various ores throughout the earth 2).
Since 1980, federal and state regulatory standards have helped to reduce the amount of lead in air, drinking water, soil, consumer products, food, and occupational settings. Despite the ban on using lead in paints or as a gasoline additive in the United States, human exposure to lead continues as lead does not degrade in the environment, remaining strongly absorbed to soil.
- Much of this lead is of microscopic size, invisible to the naked eye.
You could be exposed to lead by:
- Eating food or drinking water that contains lead. Water pipes in older homes may contain lead.
- Working in a job where lead is used. Adults who work with batteries, do home renovations or work in auto repair shops also might be exposed to lead.
- Using lead in a hobby, such as making stained glass or lead-glazed pottery
- Using folk remedies such as herbs or foods that contain lead.
How does lead get into the body?
Lead can get into your body in two ways — through breathing it in or by eating it. For example, lead can enter the body through eating or inhaling paint dust or chips. The soil around your home can pick up lead from sources such as exterior paint. Lead can also enter your drinking water through your plumbing.
Breathing contaminated air, drinking water, eating food, or swallowing or touching dirt that contains lead can cause many health problems. Lead can affect almost every organ and system in your body. In adults, lead can increase blood pressure and cause infertility, nerve disorders, and muscle and joint pain. It can also make you irritable and affect your ability to concentrate and remember.
More often than not, children with elevated blood lead levels are exposed to lead in their own home. Lead-based paint and lead-contaminated dust in older buildings are the most common sources of lead poisoning in children.
Lead is especially dangerous for children. A child who swallows large amounts of lead may develop anemia, severe stomachache, muscle weakness, and brain damage. Even at low levels, lead can affect a child’s mental and physical growth.
How much lead is harmful?
No amount of lead is safe. Eliminating all lead exposure in our environment is our best course of action.
New findings from the National Institute of Environmental Health Sciences 3), as well as the National Toxicology Program 4) have found many adverse health effects in both children and adults at blood lead levels below 10 micrograms per deciliter (μg/dL) and for some below 5 μg/dL.
These findings add to the body of evidence that have led the Centers for Disease Control and Prevention 5) in 2012 to now advise that any child with more than 5 micrograms per deciliter (5 μg/dL) of lead in their blood to be considered at risk and that public health actions should be initiated.
Who is at the greatest risk for exposure?
Children under the age of 6 years old are at an increased risk for lead exposure, due to their rapid rate of growth and their tendency to place toys and other objects in their mouths that could contain lead or leaded dust. This is particularly true of children living below the poverty line in older housing.
Causes of Lead poisoning
Lead is a metal that occurs naturally in the earth’s crust, but human activity — mining, burning fossil fuels and manufacturing — has caused it to become more widespread. Lead was also once used in paint and gasoline and is still used in batteries, solder, pipes, pottery, roofing materials and some cosmetics.
Lead in paint
Lead-based paints for homes, children’s toys and household furniture have been banned in the United States since 1978. But lead-based paint is still on walls and woodwork in many older homes and apartments. Most lead poisoning in children results from eating chips of deteriorating lead-based paint.
Water pipes and imported canned goods
Lead pipes, brass plumbing fixtures and copper pipes soldered with lead can release lead particles into tap water. Lead solder in food cans, banned in the United States, is still used in some countries.
Herbal and Folk remedies
- Ayurvedic medicine (traditional medicine from India and Tibet)
- Azarcon (bright orange powder thought to be medicinal)
- Ba-Baw-San (Chinese herbal medicine used for colic)
- Bint Al Zahab (Iranian powder mixed with honey and butter for colic)
- Bint Dahab (Saudi Arabian yellow powder used as a home remedy)
- Bokhoor (Kuwaiti fumes from wood and lead used to calm infants)
- Ghasard (brown powder to aid in digestion)
- Greta (Mexican yellow powder to treat gastrointestinal distress)
- Jin Bu Huan (Chinese herbal medicinal pain reliever)
- Pay-loo-ah (Vietnamese red powder to treat fever or rash)
- Po Ying Tan (Chinese herbal medicine)
- Santrinj (Saudi Arabian red powder used for teething)
- Saudi traditional medicine (orange powder for teething)
- Surma (Indian black powder used for teething)
- Tibetan herbal vitamin (used for brain health)
Other sources of lead exposure
Lead sometimes can also be found in:
- Soil. Lead particles from leaded gasoline or paint settle on soil and can last years. Lead-contaminated soil is still a major problem around highways and in some urban settings. Some soil close to walls of older houses contains lead.
- Household dust. Household dust can contain lead from lead paint chips or from contaminated soil brought in from outside.
- Pottery. Glazes found on some ceramics, china and porcelain can contain lead that can leach into food served or stored in the pottery.
- Toys. Lead is sometimes found in toys and other products produced abroad.
- Imported cosmetics:
- Eye cosmetics from Pakistan
- Kohl (a type of eyeliner from India, the Middle East, and Africa)
- Surma (powder applied to the eyes, from India)
- Tiro, an eye cosmetic from Nigeria, has been linked to lead poisoning.
- Imported candy
- Herbal or folk remedies. Lead poisoning has been linked to greta and azarcon, traditional Hispanic medicines, as well as some from India, China and other countries.
- Mexican candy. Tamarind, an ingredient used in some candies made in Mexico, might contain lead.
- Lead bullets. Time spent at firing ranges can lead to exposure.
- Occupations. People are exposed to lead and can bring it home on their clothes when they work in auto repair, mining, pipe fitting, battery manufacturing, battery reclamation, painting, construction and certain other fields.
- Ceramics workers
- Construction workers
- Furniture refinishers
- Radiator repair workers
- Imported jewelry
- Imported toys
- Paint chips from lead-based paint
- Pottery and ceramics
- Soil contaminated with lead
- Tea kettles
- Vinyl mini blinds
Factors that may increase your risk of lead poisoning include:
- Age. Infants and young children are more likely to be exposed to lead than are older children. They might chew paint that flakes off walls and woodwork, and their hands can be contaminated with lead dust. Young children also absorb lead more easily, and it’s more harmful for them than it is for adults and older children.
- Living in an older home. Although the use of lead-based paints has been banned since the 1970s, older homes and buildings often retain remnants of this paint. People renovating an older home are at even higher risk.
- Certain hobbies. Making stained glass and some jewelry requires the use of lead solder. Refinishing old furniture might put you in contact with layers of lead paint.
- Living in developing countries. Developing countries often have less strict rules regarding exposure to lead than do developed countries. American families who adopt a child from another country might want to have the child’s blood tested for lead poisoning. Immigrant and refugee children also should be tested.
Lead can harm an unborn child, so pregnant women or women likely to become pregnant should be especially careful to avoid exposure to lead.
Who is at Risk of Lead Poisoning ?
Lead poisoning in children
The prevalence and severity of childhood lead poisoning have been greatly reduced since the removal of lead from paint and gasoline in the 1970s. Despite these efforts, approximately 500,000 U.S. children younger than five years have elevated blood lead levels 6). Race and ethnicity have been linked to higher rates of lead poisoning, with non-Hispanic blacks and Mexican Americans being at higher risk than non-Hispanic whites 7). Children from households below the federal poverty level are also more likely to have elevated blood lead levels, independent of housing age 8). Others at risk include those whose home is located in a zip code with a high prevalence of lead poisoning, or areas identified by state or local guidelines 9). Finally, risk can be identified through a short personal risk questionnaire (see Table 1) 10).
Lead is particularly dangerous to children because their growing bodies absorb more lead than adults do and their brains and nervous systems are more sensitive to the damaging effects of lead. Babies and young children can also be more highly exposed to lead because they often put their hands and other objects that can have lead from dust or soil on them into their mouths. Children may also be exposed to lead by eating and drinking food or water containing lead or from dishes or glasses that contain lead, inhaling lead dust from lead-based paint or lead-contaminated soil or from playing with toys with lead paint.
Exposure to lead can have a wide range of effects on a child’s development and behavior. Blood lead levels less than 10 micrograms per deciliter (μg/dL) are associated with increased behavioral effects, delayed puberty, and decreases in hearing, cognitive performance, and postnatal growth or height. Some of these health effects are found even at low blood lead levels less than 5 μg/dL, including lower IQ scores, decreased academic achievement, and increases in both behavioral problems and attention-related behaviors. There is a wide range of lead-associated behavioral effects in the area of attention. Attention deficit hyperactivity disorder (ADHD) is one example on the more severe end of the spectrum.
Table 1. Lead Poisoning Screening Criteria
Screen children who meet any of the following criteria:
All Medicaid-enrolled or -eligible children at one and two years of age
All children who are identified as high risk based on results of a personal risk questionnaire (if one of the following questions is answered “Yes” or “Don’t know”):
Does your child live in or regularly visit a house that was built before 1950 (this could apply to a home day care center or the home of a babysitter or relative)?
Does your child live in or regularly visit a house built before 1978 with recent or ongoing renovations or remodeling (i.e., within the past six months)?
Does your child have a sibling or playmate who has or has had lead poisoning?
All refugees, recent immigrants, and international adoptees on arrival in the United States; repeat screening three to six months later for children six months to six years of age
All children who are identified to be at increased risk by the CDC’s state or local screening recommendations (i.e., high-risk zip codes)
In the absence of recommendations from the CDC, screen all children at one and two years of age, and screen children 36 to 72 months of age who have not been previously screened
CDC = Centers for Disease Control and Prevention.
Initial Screening for Children
Most children with elevated blood lead levels are asymptomatic; therefore, the decision for routine screening should not be based on signs or symptoms of lead poisoning. The CDC and the American Academy of Pediatrics recommend targeted screening of all Medicaid-enrolled and -eligible children, as well as those who were born outside of the United States (see Table 1) 12). This is a change from the universal screening used before 1997 because most children with elevated blood lead levels have since been identified by a national survey as Medicaid-enrolled or -eligible 13). The Advisory Committee on Childhood Lead Poisoning Prevention recommends that all children enrolled in Medicaid be screened for elevated blood lead levels at 12 and 24 months of age or at 36 to 72 months of age if they have not previously been screened 14).
This recommendation also applies to all children deemed to be at risk (as described above), and screening at one year of age should be performed regardless of health insurance status in these children 15). Screening of blood lead levels should be repeated at two years of age even if the level at one year is not elevated, because a low blood concentration in a one-year-old child does not preclude elevation later 16). Foreign-born children should be screened as soon as they arrive in the United States, because studies have shown a high prevalence of elevated blood lead levels in immigrants, refugees, and international adoptees 17).
The number needed to screen depends on the prevalence of elevated blood lead levels. Because the prevalence varies by location, an overall number needed to screen cannot be calculated. Physicians should refer to the CDC Web site 18) for state- and county-specific prevalence data and screening policies to guide screening decisions for children who are not eligible for Medicaid 19).
Adults, Including Pregnant Women
Adults may be exposed to lead by eating and drinking food or water containing lead or from dishes or glasses that contain lead. They may also breath lead dust by spending time in areas where lead-based paint is deteriorating, and during renovation or repair work that disturbs painted surfaces in older homes and buildings. Working in a job or engaging in hobbies where lead is used, such as making stained glass, can increase exposure as can certain folk remedies containing lead. A pregnant woman’s exposure to lead from these sources is of particular concern because it can result in exposure to her developing baby.
Many longitudinal studies have provided evidence that cumulative lead dose causes cognitive dysfunction or decline 20). The neurotoxic effects of lead in workers can be induced at blood lead levels below 18 µg/dL, somewhat higher than the critical level of lead neurotoxicity in children (5 µg/dL) 21).
In 2015, the National Institute of Occupational Safety and Health designated 5 µg/dL as an elevated blood lead level in adults. The U.S. Department of Health and Human Services recommends that blood lead levels among all adults be reduced to less than 10 µg/dL. The U.S. Occupational Safety and Health Administration Lead Standards require workers to be removed from lead exposure when blood lead levels are greater than or equal to 50 µg/dL (construction industry) or greater than or equal to 60 µg/dL in general industry, and allow workers to return to work when their blood lead level is less than 40 µg/dL. Removal may also be recommended if the person is symptomatic at any level below 70 µg/dL.
The Occupational Safety and Health Administration (OSHA) has developed rules for monitoring for lead in the workplace. OSHA requires that employee blood monitoring programs be triggered by the results found in an initial air monitoring program. If a worker has an initial blood lead test result of more than 40 µg/dL, for example, testing should be done every two months until two consecutive lead tests show a blood lead level below 40 µg/dL. Higher levels call for closer monitoring.
Because lead will pass through the blood to an unborn child, pregnant women need to limit their exposure to lead to maintain a low blood level and as close to zero as possible to protect the developing fetus.
Any lead level greater than 70 µg/dL, whether in a child or an adult, should be considered a medical emergency.
Complications of lead poisoning
Exposure to even low levels of lead can cause damage over time, especially in children. The greatest risk is to brain development, where irreversible damage can occur. Higher levels can damage the kidneys and nervous system in both children and adults. Very high lead levels may cause seizures, unconsciousness and death.
Some of the health effects associated with lead exposure
The 2012 National Toxicological Program literature-based monograph 22) on health effects of low-level lead provides this information on health effects:
|Blood Lead Level||Health Effects|
|Blood lead levels below 5µg/dL||Children: Decreased academic achievement, decreased IQ, and decreases in specific cognitive measures, increased incidence of attention-related behaviors and problem behaviors|
Adults: Decreased kidney function, maternal blood lead associated with reduced fetal growth
|Blood lead levels below 10µg/dL||Children: Delayed puberty, reduced postnatal growth, decreased IQ and decreased hearing|
Adults: Increased blood pressure, increased risk of hypertension, and increased incidence of essential tremor
Prevention of lead poisoning
Simple measures can help protect you and your family from lead poisoning:
- Wash hands and toys. To help reduce hand-to-mouth transfer of contaminated dust or soil, wash your children’s hands after outdoor play, before eating and at bedtime. Wash their toys regularly.
- Clean dusty surfaces. Clean your floors with a wet mop and wipe furniture, windowsills and other dusty surfaces with a damp cloth.
- Remove shoes before entering the house. This will help keep lead-based soil outside.
- Run cold water. If you have older plumbing containing lead pipes or fittings, run your cold water for at least a minute before using. Don’t use hot tap water to make baby formula or for cooking.
- Prevent children from playing on soil. Provide them with a sandbox that’s covered when not in use. Plant grass or cover bare soil with mulch.
- Eat a healthy diet. Regular meals and good nutrition might help lower lead absorption. Children especially need enough calcium, vitamin C and iron in their diets to help keep lead from being absorbed.
- Keep your home well-maintained. If your home has lead-based paint, check regularly for peeling paint and fix problems promptly. Try not to sand, which generates dust particles that contain lead.
Lead poisoning signs and symptoms in children
There are no signs and symptoms specific to lead poisoning, making identification based solely on patient history and physical examination difficult. Symptoms that do occur are vague and commonly encountered. These can include gastrointestinal issues (e.g., abdominal pain, constipation, nausea, vomiting), decreased growth in height, delayed sexual maturation, increased dental caries, and impaired neurologic development (e.g., behavioral changes, mental impairment, seizures, coma), hyperactivity; deficits in fine motor function, hand-eye coordination, and reaction time; and lowered performance on intelligence tests 23), 24).
In the United States, today at least 4 million households have children living in them that are being exposed to high levels of lead. There are approximately half a million U.S. children ages 1-5 with blood lead levels above 5 micrograms per deciliter (µg/dL), the reference level at which CDC recommends public health actions be initiated 25).
Primary preventive strategies such as eliminating lead as an additive from paint and gasoline have resulted in lower blood lead levels among U.S. children.
Lead poisoning symptoms in children
Signs and symptoms of lead poisoning in children include:
- Muscle and joint weakness or pain
- Excessive tiredness or lethargy
- Developmental delay
- Learning difficulties
- Behavioral problems or irritability
- Difficulty concentrating
- Loss of appetite
- Metallic taste in the mouth
- Weight loss
- Sluggishness and fatigue
- Abdominal pain, nausea or vomiting
- Hearing loss
- Eating things, such as paint chips, that aren’t food (pica)
These symptoms may or may not be present, and of course each of them can also be caused by many other common illnesses. But in cases where some of these symptoms are present for a long time, no other cause has been found, and there may have been some exposure to lead, then tests for test poisoning should be considered.
Lead poisoning symptoms in newborns
Babies exposed to lead before birth might:
- Be born prematurely
- Have lower birth weight
- Have slowed growth
Symptoms of lead poisoning in adults
Initially, lead poisoning can be hard to detect — even people who seem healthy can have high blood levels of lead. Signs and symptoms usually don’t appear until dangerous amounts have accumulated.
Lead poisoning symptoms in adults
Although children are primarily at risk, lead poisoning is also dangerous for adults. Signs and symptoms in adults might include:
- High blood pressure 26)
- Joint and muscle pain
- Difficulties with memory or concentration
- Nerve disorders
- Abdominal pain
- Mood disorders
- Reduced sperm count and abnormal sperm
- Miscarriage, stillbirth or premature birth in pregnant women
- Cardiovascular effects, increased blood pressure and incidence of hypertension
- Decreased kidney function 27)
- Reproductive problems (in both men and women)
Lead exposure has been linked to a number of health effects in adults. As a general rule, the more lead you have in your body, the more likely it is you’ll have health problems. High blood lead levels greater than 15 μg/dL are associated with cardiovascular effects, nerve disorders, decreased kidney function, and fertility problems, including delayed conception and adverse effects on sperm and semen, such as lower sperm counts and motility.
Blood lead levels below 10 μg/dL are associated with decreased kidney function and increases in blood pressure, hypertension, and incidence of essential tremor, a degenerative disorder of the central nervous system whose most recognizable feature is a tremor of the arms or hands during voluntary movements, such as eating and writing. There is also evidence showing that adults who have low levels of exposure to lead less than 5 μg/dL may have decreased kidney function. Pregnant women need to be particularly careful around lead. Maternal blood lead levels less than 5 μg/dL are associated with reduced fetal growth. Because the effects of lead are different for everyone, more research needs to be done to fully understand the health effects.
A 2004 study, supported by the National Institute of Environmental Health Sciences, also showed that lifetime lead exposure may increase the risk of developing cataracts, a clouding of the eye lens resulting in partial loss of vision, which can be common in older people 28).
Most adults with elevated blood lead levels are exposed to lead at work. Those in occupations related to mining, ironwork or welding, construction, renovation and remodeling activities, smelters, firing ranges, the manufacture and disposal of car batteries, automobile radiator repair, metal shop work, and the manufacture of pottery or stained glass are particularly at risk for lead exposure.
Extreme lead exposure can cause a variety of neurologic disorders, such as lack of muscular co-ordination, convulsions, and coma. As lead affects several enzymatic processes responsible for heme synthesis, the hematologic system is also a highly sensitive target for lead toxicity. Lead has long been recognized as a developmental neurotoxicant that can interfere with the developing brain, resulting in functional impairment. Thus, lead exposure continues to be a major public health problem, particularly in urban centers in the US and in developing nations.
Lead can accumulate in our bodies over time, where it is stored in bones along with calcium. During pregnancy, lead is released from bones as maternal calcium and is used to help form the bones of the fetus. This is particularly true if a woman does not have enough dietary calcium. Lead can also cross the placental barrier exposing the fetus the lead. This can result in serious effects to the mother and her developing fetus, including:
- Reduced growth of the fetus
- Premature birth
Lead can also be transmitted through breast milk.
Diagnosis of lead poisoning
Your child’s doctor may recommend your child be tested for lead levels during routine check-ups.
The American Academy of Pediatricians recommends that doctors and parents follow the recommendations of their state or local health department. Some areas, such as those with older homes, have a higher lead exposure risk, so more frequent testing might be recommended for children who live in those areas.
If your area doesn’t have specific lead testing recommendations, the American Academy of Pediatrics recommends your child be tested for lead levels at ages 1 and 2. Doctors might also suggest lead screening for older children who haven’t been tested.
Venous sampling is the best method for assessing the level of lead in the blood because it limits cutaneous contamination; a carefully collected finger-stick sample is an acceptable alternative 29). If finger-stick screening is used, any elevated blood lead level should be confirmed by a venous sample 30). Lead levels in the blood are measured in micrograms per deciliter (μg/dL). Laboratories that perform blood lead testing are required to meet federal proficiency standards with an error range of ± 4 μg per dL (0.19 μmol per L) or ± 10 percent, whichever is greater 31). As a result, a blood lead level of 8 μg per dL (0.39 μmol per L) could be reported as any value ranging from 4 to 12 μg per dL (0.19 to 0.58 μmol per L) and remain within the range of the proficiency standards.
There is no safe blood level of lead. The Centers for Disease Control and Prevention (CDC) currently designates a blood lead level of 10 μg per dL (0.48 μmol per L) or higher as abnormal and requiring follow-up and intervention 32). However, a level of 5 μg/dL is used to indicate a possibly unsafe level for children. Children whose blood tests at those levels should be tested periodically. Even blood lead levels lower than 10 μg per dL can affect cognitive development 33), 34). For physicians, identifying children at high risk; eliminating exposure to known sources of lead; and ensuring adequate nutrition, including preventing and correcting iron deficiency, are key strategies in the care of all children.
A child whose levels become too high — generally 45 mcg/dL or higher — should be treated.
Table 2. Summary of Recommendations for Children with Confirmed (Venous) Elevated Blood Lead Levels
|Intervention||Blood lead level (μg per dL [μmol per L])|
|10 to 14 (0.48 to 0.68)||15 to 19 (0.72 to 0.92)||20 to 44 (0.97 to 2.13)||45 to 69 (2.17 to 3.33)||> 70 (3.38)|
Actions and interventions
Repeat measurement of blood lead levels in three months If repeat levels are still in this range or higher, proceed to actions and interventions for 20 to 44 μg per dL If repeat levels are less than 15 μg per dL, perform education only at this time
Complete history and physical examination Laboratory testing (hemoglobin, hematocrit, iron status) Abdominal radiography (if particulate ingestion is suspected) with bowel decontamination (if indicated) Environmental investigation Lead hazard reduction
Chelation therapy All actions and interventions as indicated for 20 to 44 μg per dL
Hospitalize immediately and begin chelation therapy All actions and interventions as indicated for 45 to 69 μg per dL
Initial follow-up blood lead monitoring (first two to four tests after first high level)
One to three months
Two weeks to one month
As soon as possible
As soon as possible
Late follow-up blood lead monitoring (after levels begin to decline)
Six to nine months
Three to six months
Lead poisoning treatment
The first step in treating lead poisoning is to remove the source of the contamination. If you can’t remove lead from your environment, you might be able to reduce the likelihood that it will cause problems.
For instance, sometimes it’s better to seal in rather than remove old lead paint. Your local health department can recommend ways to identify and reduce lead in your home and community.
For children and adults with relatively low lead levels, simply avoiding exposure to lead might be enough to reduce blood lead levels.
For children with a blood lead level of less than 10 μg per dL, providing basic nutritional and environmental education to parents may be of benefit, although the true effectiveness is unknown 36). Identifying and treating iron deficiency are important in decreasing a child’s vulnerability to lead (see Iron Supplementation). The ultimate goal is to maintain the child’s blood lead level as low as possible because of evidence that levels of less than 10 μg per dL still pose a risk of damage to the child’s neurologic development as mentioned previously 37).
If a child’s blood lead level is measured as greater than 20 μg per dL (0.97 μmol per L) once, or greater than 15 μg per dL (0.72 μmol per L) twice, environmental investigation, including a home inspection, should be conducted 38). Children with levels below 45 μg per dL who are treated with chelation do not demonstrate measurable differences in neurologic, behavioral, and cognitive developmental outcomes 39). In addition, succimer chelation may actually be harmful in these children. The Treatment of Lead-Exposed Children trial demonstrated a decrease in the rate of growth in height between children treated with succimer and those who received placebo 40). Thus, chelation is not recommended for this group of children.
As in the group with high levels of blood lead, children with moderate levels should have confirmatory venous sampling and abdominal radiography to identify lead-containing particles. Additional laboratory testing includes hemoglobin, hematocrit, and iron studies. Table 2 outlines education and follow-up measures.
Chelation therapy is recommended by the CDC for blood lead levels of 45 μg per dL (2.17 μmol per L) or greater 41), 42). The CDC recommends consulting an expert such as a toxicologist before starting chelation therapy 43). A complete blood count; reticulocyte count; urinalysis; and testing of electrolytes, blood urea nitrogen, creatinine, and liver function should be performed and any iron deficiency should be identified 44), 45). Abdominal radiography can identify any materials containing lead that remain in the gut 46). Enemas such as mineral oil, poly-electrolyte solutions, milk and molasses, and hypertonic phosphate can then be used to eliminate these sources of additional lead absorption 47).
Chelation therapy is usually done with succimer (Chemet), but dimercaprol (Bal in oil) can also be used. Succimer is preferred because it can be administered orally and is better tolerated. Children treated with chelating agents should be monitored closely during and after treatment 48). Although succimer lowered blood lead about 25% in the short term, it did not improve IQ or other test scores. This reinforces the need for prevention. Treatment after the fact does not undo the damage caused by lead. Children must be protected from being exposed at all. Further information on dosing, side effects, and monitoring can be found in resources such as The Harriet Lane Handbook 49) or a pharmacopeia 50), 51). Additionally, an environmental investigation to identify and remediate the source of the lead should be performed in collaboration with the local health department 52). Remediation measures include removing the child from the source of lead, correcting the source of lead by home renovation or cleaning, and avoiding any sources of lead such as contaminated soil or products.
Children with levels higher than 70 μg per dL (3.38 μmol per L) should be hospitalized immediately for treatment under direct medical supervision 53).
Treating higher levels
For more-severe cases, your doctor might recommend:
- Chelation therapy. In this treatment, a medication given by mouth binds with the lead so that it’s excreted in urine. Chelation therapy might be recommended for children with a blood level of 45 mcg/dL or greater and adults with high blood levels of lead or symptoms of lead poisoning.
- EDTA chelation therapy. Doctors treat adults with lead levels greater than 45 mcg/dL of blood and children who can’t tolerate the drug used in conventional chelation therapy most commonly with a chemical called calcium disodium ethylenediaminetetraacetic acid (EDTA). EDTA is given by injection.
Chelation agents for lead
The majority of chelating agents bind to heavy metals in extracellular fluid and cannot cross the cellular membrane 54). Because they cause essential metal loss and may cause adverse drug effects such as hepatotoxicity or nephrotoxicity, while there are benefits to their use in cases of acute poisoning, they are not recommended for cases of chronic poisoning 55). Due to the risk caused by the adverse side effects of the medicine and the redistribution of lead, chelation therapy is generally not recommended in cases where blood lead levels are below 45 μg/dL in adults 56). Additionally, as rebounding commonly occurs after chelation therapy, blood lead levels should be measured before and after the treatment.
The drugs used as chelating agents for lead include dimercaptosuccinic acid (DMSA), dimercaptopropane sulfonate (DMPS), dimercaprol (British Anti-Lewisite, BAL), penicillamine, and CaNa2EDTA (Table 1).
An analogue of dimercaprol, dimercaptosuccinic acid (DMSA) is a dithiol compound which contains two sulfhydryl (–SH) groups. Dimercaptosuccinic acid (DMSA) has a large therapeutic window, and is the least toxic dithiol compound 57). While chelation therapy can result in a reduction in essential metals, DMSA has been found to not cause a reduction in essential metals such as zinc, iron, calcium, and magnesium 58). DMSA is the most efficient and safe chelating agent for lead exposure, so the chelators being used the most are DMSA recently 59).
Dimercaptopropane sulfonate (DMPS) is another analogue of dimercaprol. Less effective than CaNa2EDTA or DMSA, dimercaptopropane sulfonate (DMPS) is not commonly used in lead chelation therapy 60). Dimercaptopropane sulfonate (DMPS) is mainly used in cases of arsenic or mercury poisoning.
The drawbacks of CaNa2EDTA are that it contributes to a greater loss in essential minerals compared to DMSA or DMPS and that it redistributes lead to the brain 61). Generally, one gram of EDTA is mixed with 250 mL of a 5 % dextrose solution, gradually settling over one or two hours, and treatment is administered over a five day period. During the treatment period, the patient should be hydrated intravenously, and tests should be conducted daily on kidney function, electrolyte levels, and urine.
Penicillamine was the first chelating agent used in the treatment of lead poisoning. It reaches its greatest capacity one to four hours after oral administration. Food, antioxidants, and iron supplements can reduce absorption of penicillamine. In the past, the daily dose used was 500–1000 mg, but recent findings show that using a lower dosage had equivalent lead removal effects while reducing adverse side effects 62). Due to the narrow therapeutic window and harsh side effects of dimercaprol (British Anti-Lewisite, BAL), it is rarely used these days.
In general, chelation therapy is recommended for children only in cases where blood lead levels are 45 μg/dL or greater. In cases where blood lead levels are 45–69 μg/dL, chelation therapy can be attempted with DMSA. McKay 63) tried chelation therapy on children with blood lead levels of 20–44 μg/dL. While the blood lead levels of the children who received chelation therapy decreased temporarily compared with the control group, when a follow-up study was conducted three years later, the blood lead levels of the therapy group had risen again, and no significant difference was observed in cognitive or behavioral function nor in blood lead levels between the therapy group and the control group.
While removing the source of lead exposure is most important for reducing the health impact of lead and similar harmful heavy metals, naturally occurring essential minerals (calcium, magnesium, selenium, etc.) and other related nutrient replacement therapies can be useful in decreasing the absorption of harmful heavy metals or promoting their excretion. New strategies in heavy metal chelation therapy include the use of structurally different chelating agents (combination therapy such as DMSA and EDTA) and the co-administration of antioxidants such as DMSA and taurine 64).
Table 1. Overview of chelation drugs
|Chemical name (common names, abbreviations)||Dose||Adverse effects||Elements chelated|
|2,3-bis(sulfanyl)butanedioic acid (Dimercaptosuccinic acid; DMSA; Succimer)||10 mg/kg (or 350 mg/m2) per 8 h for 5 days, then 10 mg/kg per 12 h for 14 days (a total of 19 days), POa.||Gastrointestinal disturbances, mild increase in serum transaminase||Lead, arsenic, mercury, cadmium, silver, tin, copper|
|Sodium 2,3-bis(sulfanyl)propane-1-sulfonate (Dimercaptopropanesulfonate; DMPS; Dimaval)||Adult: 5 mg/kg per 6–8 h, PO, IMb, IVc, or SQd.||Low back (kidney) pain, gastrointestinal disturbances, skin rash, fatigue, hypersensitivity reactions||Mercury, arsenic, lead, cadmium, tin, silver, copper, selenium, zinc, magnesium|
|Children: 5-day course of 200 or 400 mg/m2/day|
|2-[2-[bis(carboxymethyl)amino]ethyl-(carboxymethyl)amino]acetic acid (Ethylenediaminetetraacetic acid; EDTA; CaNa2EDTA)||1000–1500 mg/m2/day (1–2 g/24 h for a 70-kg adult) as an IV infusion for 5 days||Renal toxicity||Lead, cadmium, zinc|
|(2S)-2-amino-3-methyl-3-sulfanylbutanoic acid (3-Sulfanyl-D-valine; Penicillamine; D- Penicillamine)||10 mg/kg/day for 7 days with a possibility of a prolonged treatment during 2 to 3 weeks, PO.||Interstitial nephritis, hypersensitivity reactions, gastrointestinal disturbances, leukopenia and thrombocytopenia||Copper, arsenic, zinc, mercury, lead|
|2,3-bis(sulfanyl)propan-1-ol (Dimercaprol; British Anti-Lewisite; BAL)||50–75 mg/m2 per 4 h for 5 days, deep IM.||Allergy, gastrointestinal symptoms, tachycardia, fever, elevation of liver function tests||Arsenic, gold, mercury, lead (BAL in combination with CaNa2EDTA)|
a PO = oral ingestion
b IM = intramuscular injection
c IV = intravenous injection
d SQ = subcutaneous injection[Source 65) ]
Several studies published within the past 10 years found an association between low iron levels and elevated blood lead levels in infants and children 66), 67). Recent studies suggest that iron therapy may lower blood lead levels in both anemic and non-anemic children 68), 69). Findings of these studies support the theory that a lack of iron may increase a child’s susceptibility to lead poisoning 70), 71). However, other studies have found that iron supplementation did not decrease lead levels in children without iron deficiency 72). The CDC currently recommends testing all children with elevated blood lead levels for iron deficiency and correcting the deficiency 73). Based on current evidence, the CDC does not recommend placing all at-risk children on an iron supplementation regimen but does generally recommend an iron-rich diet for all children 74).
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