Lead poisoning, also called plumbism and saturnism, happens when lead enters the human body. It can cause symptoms like stomach pain, trouble passing stool, headaches, being easily upset, memory issues, trouble having children, and numbness or tingling in the hands and feet. Lead poisoning is linked to about 10% of intellectual disabilities with no known cause and can lead to behavior problems. Some effects may last forever. In serious cases, it can cause anemia, seizures, unconsciousness, or death.
People can be exposed to lead through air, water, dust, food, or products. Children and pets are at higher risk because they may chew on items coated with lead paint. Children absorb more lead from food or objects than adults. Adults often get lead poisoning from work, especially in certain jobs. Doctors usually check blood lead levels to diagnose the condition. In the United States, the limit for adults is 10 micrograms per deciliter (μg/dL) and for children is 3.5 μg/dL. Before 2021, the child limit was 5 μg/dL. High lead levels may also show up in red blood cells or through X-rays of children’s bones.
Lead poisoning can be prevented. This includes removing lead items from homes, improving workplace safety, and banning lead in products like paint, gasoline, and fishing weights. Rules to lower lead in water or soil and clean polluted areas also help. Teaching workers about lead safety is important. Treatments include removing the lead source and using medicines that help the body remove lead, called chelation therapy. This therapy is used for children with blood lead levels above 40–45 μg/dL. Medicines used include dimercaprol, edetate calcium disodium, and succimer.
In 2021, 1.5 million deaths worldwide were linked to lead exposure. It is most common in developing countries. About 800 million children in low- and middle-income nations have blood lead levels above 5 μg/dL, though data is limited. Many U.S. communities may have high lead levels worse than during the Flint water crisis. Poorer people are more likely to be affected. Lead is thought to cause 0.6% of global disease. Half of the U.S. population was exposed to harmful lead levels as children, mainly from car exhaust. Lead pollution peaked in the 1970s, causing widespread loss of thinking ability. Globally, over 15% of children have blood lead levels above 10 μg/dL, which requires medical help.
Humans have used lead for thousands of years. Records of lead poisoning date back to at least 200 BC. Rules to limit lead use began in the 16th century. Concerns about even small amounts of lead started in the 1970s, when scientists learned that lead builds up in the body over time and there is no safe level of exposure.
Classification
"Lead poisoning" or "lead intoxication" refers to exposure to high levels of lead, which can cause serious health problems. Poisoning usually means a group of symptoms that appear after exposure to moderate or high amounts of lead. Toxicity includes a broader range of effects, even those that do not cause noticeable symptoms. However, many professionals use the terms "lead poisoning" and "lead toxicity" interchangeably, and official sources do not always limit "lead poisoning" to cases with clear symptoms.
The amount of lead in the blood and body tissues, along with how long the exposure lasts, determines the level of toxicity. Lead poisoning can occur suddenly (acute) from short-term, intense exposure or over time (chronic) from repeated, low-level exposure. Chronic exposure is more common. Doctors diagnose and treat lead exposure by measuring blood lead levels, which are expressed in micrograms of lead per deciliter of blood (μg/dL). Urine lead levels may also be tested, though less often. In chronic cases, lead tends to build up first in bones and later in the kidneys. If a test called a "chelation challenge" is performed, urine measurements are often more helpful than blood measurements for skilled professionals to assess total lead exposure.
The U.S. Centers for Disease Control and Prevention and the World Health Organization say that a blood lead level of 10 μg/dL or higher is a cause for concern. However, lead can harm development and health even at lower levels, and no safe level of exposure is known. The American Academy of Pediatrics defines lead poisoning as blood lead levels above 10 μg/dL.
Lead exists in many forms and can be found in the environment in different ways. The effects of lead poisoning depend on whether the compound is organic (contains carbon) or inorganic. Organic lead poisoning is now rare because most countries have stopped using organic lead compounds in gasoline. These compounds are still used in industrial settings. Organic lead compounds can enter the body through the skin or lungs and mainly affect the central nervous system.
Signs and symptoms
Lead poisoning can cause many different symptoms, and these symptoms may vary depending on the person and how long they have been exposed to lead. Some symptoms may be hard to notice, and a person with high lead levels might not feel sick at all. Symptoms often appear slowly over weeks or months when lead builds up in the body over time, but sudden, severe symptoms can also happen after short, intense exposure. Exposure to organic lead, which is more harmful than inorganic lead because it dissolves easily in fat, causes symptoms quickly. Poisoning from organic lead mainly affects the brain and nervous system, causing problems like trouble sleeping, confusion, memory loss, shaking, hallucinations, and seizures.
Symptoms can differ between adults and children. In adults, common symptoms include headaches, stomach pain, memory loss, kidney failure, problems with male reproduction, and weakness or tingling in the arms and legs. Early signs in adults may include feeling sad, not wanting to eat, stomach pain, nausea, diarrhea, constipation, and muscle pain. Other early signs include feeling tired, trouble sleeping, and changes in taste or mood.
In adults, symptoms may appear when blood lead levels are above 40 micrograms per deciliter (μg/dL), but they are more likely to occur at levels above 50–60 μg/dL. In children, symptoms usually begin at around 60 μg/dL. However, the exact blood lead levels at which symptoms appear can vary for each person. At levels between 25 and 60 μg/dL, adults may experience slower thinking, irritability, and trouble focusing, along with headaches and slower nerve function. Anemia may occur when blood lead levels are above 50 μg/dL. In adults, severe stomach pain may happen at levels above 80 μg/dL. At levels above 100 μg/dL, adults may have trouble moving their hands or feet, brain swelling, and symptoms like confusion, seizures, or coma. In children, brain swelling symptoms like unusual behavior or lack of interest may occur at levels above 70 μg/dL. Most people with blood lead levels above 100 μg/dL will have symptoms.
In cases of sudden, severe poisoning, common signs include pain, muscle weakness, numbness, and rarely, brain inflammation. Other symptoms may include stomach pain, vomiting, diarrhea, or constipation. Lead can cause a metallic taste in the mouth. Problems like constipation, poor appetite, or weight loss are common in sudden poisoning. Large amounts of lead absorbed quickly can cause shock due to fluid loss. Sudden poisoning can also break red blood cells, leading to anemia and blood in the urine. Kidney damage may cause changes in urination or reduced urine output. People who survive sudden poisoning often later develop symptoms of long-term poisoning.
Long-term poisoning usually affects many body systems and includes three main types of symptoms: stomach problems, muscle and nerve issues, and brain-related problems. Brain and nerve symptoms often happen after intense exposure, while stomach issues develop from long-term exposure. Signs of long-term poisoning include trouble remembering, depression, nausea, stomach pain, loss of coordination, and numbness in the hands and feet. Fatigue, sleep problems, headaches, confusion, slurred speech, and anemia are also common. A pale or bluish tint to the skin and a blue line along the gum, called a Burton line, may appear. Children with long-term poisoning may avoid playing or show aggressive behavior. Vision problems, such as blurred vision, can occur due to nerve damage in the eyes.
Pregnant women with high lead levels are more likely to have premature babies or babies with low birth weight. Children are more at risk for lead poisoning because their small bodies are growing and developing. Young children absorb 4 to 5 times more lead than adults from the same source. They are also more likely to touch and swallow lead-contaminated dust on the floor.
Common signs in children include loss of appetite, stomach pain, vomiting, weight loss, constipation, anemia, kidney failure, irritability, sleepiness, learning problems, and behavioral issues. Slow development of skills like speaking and permanent intellectual disability are also common. In rare cases, high lead levels may cause white lines on fingernails.
A 2020 report by UNICEF and Pure Earth found that lead poisoning affects millions of children worldwide. The report stated that one in three children, up to 800 million globally, have blood lead levels at or above 5 μg/dL, the level at which action is typically needed.
Lead affects all body systems, especially the nervous system, but also the bones, teeth, kidneys, heart, immune system, and reproductive system. Hearing loss, tooth decay, and cataracts are linked to lead exposure. Lead exposure during pregnancy or early life can cause tooth decay. Adults and children share similar health effects from lead, though adults usually need higher lead levels to experience symptoms.
High lead levels can damage the kidneys, and even lower levels may cause harm. Lead can cause kidney disease and a condition called Fanconi syndrome, which affects kidney function. Long-term exposure at lower levels may also harm kidneys in people with existing health issues like high blood pressure or diabetes. Lead can block the removal of a waste product called urate, increasing the risk of gout.
Studies suggest lead exposure is linked to high blood pressure, heart disease, heart rhythm changes, and stroke-related deaths, though evidence is limited. People exposed to high lead levels may be more likely to have heart problems on days with high pollution.
Lead affects both male and female reproductive systems. In men, high lead levels can reduce sperm count and change sperm movement and shape. In pregnant women, high lead levels can cause miscarriage, early birth, low birth weight, and developmental problems in children. Lead can pass from the mother to the baby through the placenta.
Exposure routes
Lead is a common type of pollution found in the environment. It can come from old lead-based paint that is worn or broken down (such as peeling, chipping, cracking, or getting wet). It can also come from activities like fixing or painting buildings, which create lead dust. Other sources include industries that work with lead, like factories that process lead-acid batteries or make lead pipes. Burning certain types of paper, like joss paper, can also release lead into the air. In the United States, the largest uses of lead are in storage batteries and ammunition. Children who live near places that process lead, like smelters, often have higher levels of lead in their blood. In 2009, parents in China protested after nearly 2,000 children near zinc and manganese smelters were found to have lead poisoning. Lead can enter the body through air, dust, soil, water, or products people use. Leaded gasoline has also contributed to lead pollution. Some studies suggest a connection between leaded gasoline and crime rates. Human activity has increased lead in the air for about 2,000 years. All lead pollution in the air comes from human actions, such as mining, smelting, and using gasoline.
In adults, work-related exposure is the main cause of lead poisoning. People who work in places that make products with lead, such as radiation shields, ammunition, surgical tools, plumbing, circuit boards, jet engines, and ceramic glazes, are at risk. Other jobs that involve lead include mining, smelting, plumbing, auto mechanics, glass manufacturing, construction, battery production, firing ranges, and plastic manufacturing. Workers in welding, rubber production, printing, and metal smelting may also be exposed. Even using gun ranges can lead to exposure, whether they are indoors or outdoors. Parents who work with lead can bring lead dust home on their clothes or skin, exposing their children. Lead exposure increases the risk of health problems like high blood pressure and stroke.
Lead can enter food in several ways. If food is grown in soil with high lead levels, or if lead dust settles on crops, it can be absorbed. Animals that eat lead-contaminated food can pass lead to humans through milk or meat. In Bangladesh, lead chromate was added to turmeric to make it more yellow starting in the 1980s. This was a major source of lead poisoning until the government took action after a 2019 report. By 2021, leaded turmeric was no longer sold, and lead levels in workers dropped by about 30%. In Hong Kong, food can have up to 6 parts of lead per million in solid foods and 1 part in liquid foods.
In 2022, a study found that 23 of 28 dark chocolate brands tested had lead or cadmium. Cocoa beans near polluting factories can absorb lead from dust. The Centers for Disease Control (CDC) has guidelines that link blood lead levels to how much lead is in food. As of 2021, the CDC’s reference level for children is 3.5 micrograms of lead per deciliter of blood. For children, this means daily lead intake should not exceed 2.2 micrograms. For women of childbearing age, the limit is 8.8 micrograms per day. In California, the maximum safe daily lead intake is 15 micrograms for non-cancer risks and 0.5 micrograms for cancer risks.
Lead-based paint is a major source of lead exposure for children. In the U.S., about 38 million homes had lead-based paint as of 2000, down from 64 million in 1990. Worn lead paint creates dangerous dust and soil. Children are at risk because they crawl on floors and may eat paint chips or dust. Even small amounts of lead, like a paint chip, can contain large amounts of the metal. Removing lead paint by sanding or burning creates more dust, so it is safer to cover it with new paint.
In the past, oil painters used lead-based pigments, like lead white, for colors such as yellow or white. Some artists, like Caravaggio, may have been poisoned by lead from their paints. Lead in soil contributes to pollution in cities. It can come from old paint, gasoline, oil, tire weights, pesticides, landfills, or nearby industries like smelters. In Montevideo, Uruguay, old industrial sites caused lead exposure in the 2000s. Even though leaded gasoline is no longer used in many countries, lead in soil remains a concern for urban farming. New methods, like solar evaporation, are being studied to clean up lead-contaminated soil.
Lead can move from the air or soil into groundwater and surface water. It can also be in drinking water from lead pipes or fixtures. Acidic water increases lead leaching from pipes, so some cities add chemicals to make water less acidic. Chloramines, used to treat water, can make pipes more corrosive. In the U.S., 14–20% of lead exposure comes from drinking water.
Toxicokinetics
Toxicokinetics refers to how the body processes a toxin over time, including how it enters the body, spreads through the body, changes in the body, and leaves the body.
Exposure to lead can happen through breathing in lead dust (inhalation), swallowing it (ingestion), or sometimes through contact with the skin. Lead can enter the body through mucous membranes, such as the mouth, nose, and eyes, or through breaks in the skin. Tetraethyllead, a substance once used as a gasoline additive and still used in aviation fuel, can pass through the skin. Other forms of lead, like inorganic lead, are also absorbed through the skin. The main ways inorganic lead enters the body are through ingestion and inhalation. In adults, about 35–40% of inhaled lead dust settles in the lungs, and about 95% of that enters the bloodstream. When inorganic lead is swallowed, about 15% is absorbed, but this rate is higher in children, pregnant women, and people with low levels of calcium, zinc, or iron. Infants may absorb about 50% of ingested lead, though less is known about absorption rates in children.
The body stores lead mainly in the blood, soft tissues, and bones. Lead in the blood stays for weeks, in soft tissues for months, and in bones for years. Lead stored in bones, teeth, hair, and nails is tightly bound and not available to other parts of the body, and it is generally not considered harmful. In adults, 94% of absorbed lead is stored in bones and teeth, while children store about 70% in these areas. This difference may explain why children experience more serious health effects from lead exposure. Lead stored in bones can remain there for years or even decades and may slowly return to the bloodstream long after exposure stops. In men, lead in the blood typically stays for about 40 days, but it may stay longer in children and pregnant women because their bones are constantly changing, which can release lead back into the bloodstream. If lead exposure occurs over many years, it is removed from the body more slowly, partly because lead stored in bones is released again over time. Other tissues, such as the brain, spleen, kidneys, liver, and lungs, also store lead, though in smaller amounts than blood, bones, and teeth. Lead leaves the body very slowly, mostly through urine. Smaller amounts are also removed through feces, and tiny amounts are found in hair, nails, and sweat.
Toxicodynamics
Toxicodynamics is the study of how toxins affect the body, including the ways they cause symptoms. Lead is not needed by the body for any normal functions, and it harms the body in many ways. Lead and other heavy metals create harmful molecules that damage cell structures, such as DNA and cell membranes. Lead also disrupts DNA transcription, enzymes that help make vitamin D, and enzymes that keep cell membranes strong. Anemia can occur when the cell membranes of red blood cells become weaker due to damage. Lead affects the metabolism of bones and teeth and changes the permeability of blood vessels and the production of collagen. Lead may harm the developing immune system by causing the body to produce too many inflammatory proteins. This process may make lead exposure a risk factor for asthma in children. Lead exposure has also been linked to lower activity in immune cells like polymorphonuclear leukocytes. Lead also interferes with the normal use of calcium in cells, causing it to build up inside them.
The main reason lead is toxic is that it stops many enzymes from working by attaching to sulfhydryl groups found on those enzymes. Part of lead's harm comes from its ability to act like other metals that help with biological processes. These metals are needed for many enzyme reactions, but lead replaces them at the enzymes where they work. Lead can attach to the same enzymes as these metals, but because of its different chemical structure, it does not work properly as a cofactor, stopping the enzyme from carrying out its normal reactions. Essential metals that lead replaces include calcium, iron, and zinc.
The lead ion has a lone pair in its structure, which can change how ligands are arranged. In 2007, this was suggested to play a role in how lead affects enzymes.
A major reason lead causes health problems is that it stops an important enzyme called delta-aminolevulinic acid dehydratase (ALAD) from working properly. This enzyme is needed to make heme, a part of hemoglobin. Lead also stops another enzyme called ferrochelatase, which is involved in heme production. Ferrochelatase helps combine protoporphyrin and iron to form heme. Lead's interference with heme production leads to the creation of zinc protoporphyrin and anemia. Another effect is the buildup of heme precursors, like aminolevulinic acid, which can harm neurons. High levels of aminolevulinic acid are linked to lead poisoning, which causes symptoms similar to acute porphyria.
The brain is the body part most affected by lead exposure. Lead can pass through the cells that form the blood-brain barrier because it can replace calcium ions and be taken up by calcium-ATPase pumps. Lead poisoning harms the normal development of a child's brain and nervous system, making children more likely to suffer from lead neurotoxicity than adults. In a child's developing brain, lead interferes with the formation of synapses in the cerebral cortex, the development of neurochemicals like neurotransmitters, and the organization of ion channels. It causes the loss of myelin sheaths around neurons, reduces the number of neurons, interferes with communication between neurons, and slows the growth of neurons.
Lead ions (Pb), like magnesium ions (Mg), block NMDA receptors. This means higher levels of Pb reduce long-term potentiation (LTP) and increase long-term depression (LTD) in neurons. These changes lead to fewer NMDA receptors, creating a cycle that worsens LTD. Targeting NMDA receptors is thought to be a major reason lead harms neurons.
Diagnosis
Diagnosis involves checking for clinical signs and reviewing a person's medical history, including possible ways they might have been exposed to lead. Clinical toxicologists, doctors who specialize in poisoning, may help with diagnosis and treatment. The main way to diagnose and assess the seriousness of lead poisoning is by testing blood lead levels (BLL) through laboratory analysis.
Blood film examination can show basophilic stippling, which are small dots visible in red blood cells under a microscope. It may also show changes linked to iron-deficiency anemia, such as microcytosis (small red blood cells) and hypochromasia (pale red blood cells). This condition is sometimes called sideroblastic anemia. However, basophilic stippling can also appear in other conditions, like megaloblastic anemia caused by vitamin B12 or folate deficiencies. Unlike other types of sideroblastic anemia, no ring sideroblasts are found in bone marrow samples.
Exposure to lead can be checked by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells that increases when blood lead levels are high, but this increase happens a few weeks after exposure. Combining EP levels with blood lead levels can help determine when the exposure occurred. If blood lead levels are high but EP levels are normal, this suggests recent exposure. However, EP levels alone are not sensitive enough to detect blood lead levels below about 35 μg/dL. Because of this and because EP levels also rise in iron deficiency, this method is less commonly used for detecting lead exposure.
Blood lead levels mainly show recent or current lead exposure, not the total amount of lead in the body. Lead stored in bones can be measured noninvasively using X-ray fluorescence. This method may be the best way to measure long-term exposure and total body lead levels. However, this method is not widely used and is mainly for research. Another sign of high lead levels is the presence of radiodense lines called lead lines in the long bones of growing children, especially near the knees. These lines, caused by increased calcification from disrupted bone metabolism, become wider with longer exposure. X-rays may also show lead-containing materials, such as paint chips, in the gastrointestinal tract.
Measuring fecal lead content over several days can accurately estimate total childhood lead intake. This method helps assess the extent of oral lead exposure from food and environmental sources.
Lead poisoning has symptoms similar to other conditions and may be overlooked. Conditions that must be ruled out when diagnosing lead poisoning include carpal tunnel syndrome, Guillain–Barré syndrome, renal colic, appendicitis, encephalitis in adults, and viral gastroenteritis in children. Other conditions to consider in children include constipation, abdominal pain, iron deficiency, subdural hematoma, brain tumors, emotional or behavioral disorders, and intellectual disability.
The current acceptable blood lead level for healthy children without high environmental exposure is less than 3.5 μg/dL. For adults, it was previously less than 25 μg/dL. Before 2012, the level for children was 10 μg/dL. Workers exposed to lead in the U.S. must leave their jobs if their blood lead level exceeds 50 μg/dL for construction workers or 60 μg/dL for other workers.
In 2015, the U.S. Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC), and National Institute for Occupational Safety and Health (NIOSH) set the reference blood lead level for adults at 5 μg/dL. An elevated blood lead level (BLL) is defined as a BLL of 5 μg/dL or higher. This definition is used by the Adult Blood Lead Epidemiology and Surveillance (ABLES) program, the Council of State and Territorial Epidemiologists (CSTE), and the CDC's National Notifiable Diseases Surveillance System (NNDSS). Before 2015, an elevated BLL was defined as 10 μg/dL or higher. The average blood lead level among U.S. adults was 1.2 μg/dL in 2009–2010.
Blood lead levels in poisoning victims have varied. In children exposed to lead paint in older homes, levels ranged from 30 to 80 μg/dL. In people working with pottery glazes, levels ranged from 77 to 104 μg/dL. In individuals who consumed contaminated herbal medicines, levels ranged from 90 to 137 μg/dL. In indoor shooting range instructors, levels ranged from 109 to 139 μg/dL. The highest recorded levels were 330 μg/dL in people who drank fruit juices from glazed earthenware containers.
Prevention
Prevention for lead poisoning can be divided into three types: primary, secondary, and tertiary prevention.
Primary prevention tries to stop lead poisoning before it happens by dealing with the main causes. This can be done by removing sources of lead (such as by governments, companies, or individuals) or by teaching people about lead exposure, where it comes from, and how it harms health. This helps prevent lead poisoning from occurring in the first place.
One effective way to reduce lead in water is to replace lead pipes. Lead service lines are a major source of lead in drinking water. Replacing these pipes has been shown to greatly lower lead levels in water. When replacing lead pipes as a primary prevention method, it is important to replace all of the lead pipes instead of only part of them. Replacing only part of the pipe can move or loosen lead in the remaining sections, which may increase lead levels in water.
Teaching workers about lead and how to reduce their exposure, especially if their blood or urine lead levels are high, can help prevent lead poisoning in workplaces.
Other primary prevention steps for individuals include washing children’s hands more often, giving them more calcium and iron in their diet, stopping them from putting their hands in their mouths, vacuuming regularly, and removing items that contain lead, such as blinds or jewelry, from the home. In homes with lead pipes or plumbing that uses lead solder, these can be replaced. Cheaper but less permanent methods include running water in the morning to flush out the most contaminated water or changing the water’s chemistry to prevent damage to pipes. Lead testing kits are available for home use, but they must be used correctly. Kits approved by the U.S. Environmental Protection Agency (EPA) have an accuracy rating of at least 95%. Some professional companies warn that using do-it-yourself kits may create health risks if users do not understand their limits. Hot water often has more lead than cold water, so only cold water should be used for drinking, cooking, or making baby formula. Most lead in household water comes from plumbing inside the home, not from the local water supply, so using cold water can help avoid lead exposure. Dust control and household education do not seem to lower children’s blood lead levels effectively.
At the national and local levels, prevention measures include banning lead use where it is not needed and strengthening rules that limit lead in soil, water, air, dust, and products. For example, a 1978 U.S. law limited the amount of lead in paint used for homes, furniture, and toys to 0.06% or less. In 2008, the U.S. EPA reduced the allowed lead level in air to 0.15 micrograms per cubic meter, giving states five years to meet this standard. The European Union’s Restriction of Hazardous Substances Directive limits lead in electronics and electrical equipment. Some areas have programs to reduce lead when it is found in high amounts, such as in drinking water. In extreme cases, entire towns near former lead mines have been bought out by the government and relocated, as happened in Picher, Oklahoma, in 2009. Removing lead from airplane fuel would prevent about 450 tons of lead from being released into the environment each year.
Secondary prevention looks for early signs of lead exposure in people and takes action to stop the problem from getting worse and causing long-term health issues. Screening can be an important method for people at high risk, such as those living near industries that use lead. The United States Preventive Services Task Force (USPSTF) said in 2019 that general screening for people without symptoms, including children and pregnant women, is unclear in its benefits. However, the American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) recommend checking for risk factors and testing people who have them.
Tertiary prevention focuses on treating lead poisoning, reducing symptoms, and improving the quality of life for people already affected. These treatment methods are discussed in the next section.
Treatment
The main treatments for lead poisoning include removing the person from the source of lead and, for those with very high blood lead levels or symptoms of poisoning, using chelation therapy. Treating deficiencies in iron, calcium, and zinc is also important because these deficiencies can increase how much lead the body absorbs. If lead-containing materials are found in the digestive system (as shown by X-rays), methods like whole bowel irrigation, cathartics, endoscopy, or surgery may be used to remove the lead and prevent further harm. Lead-containing bullets or shrapnel near fluid-filled areas may also need to be surgically removed to avoid further exposure. If lead encephalopathy is present, anticonvulsants may be used to control seizures, and treatments like corticosteroids or mannitol may help reduce brain swelling. For organic lead poisoning, the lead compound must be removed from the skin, further exposure must be prevented, seizures must be treated, and chelation therapy may be used for those with high blood lead levels.
Before modern chelating agents were available, doctors sometimes gave iodide salts, a practice popularized by Louis Melsens and others in the 19th and early 20th centuries.
A chelating agent is a substance that can bind to metal ions, such as lead, forming a harmless compound that is excreted in urine. These agents are used to treat lead poisoning and include edetate disodium calcium (CaNa₂EDTA), dimercaprol (BAL), which are injected, and succimer and D-penicillamine, which are taken orally. Chelation therapy is used for severe cases of lead poisoning, encephalopathy, and when blood lead levels are above 25 μg/dL. While chelation is widely supported for those with symptoms, its use in people without symptoms but with high blood lead levels is debated. Chelation therapy is less effective for long-term exposure to low levels of lead. Therapy usually stops when symptoms improve or blood lead levels return to normal. In cases of long-term exposure, blood lead levels may rise again after stopping chelation because lead stored in bones can be released into the blood; repeated treatments may be needed.
People receiving dimercaprol should be checked for peanut allergies because the medicine contains peanut oil. Calcium EDTA is effective if given four hours after dimercaprol. Administering dimercaprol, DMSA (succimer), or DMPS before calcium EDTA helps prevent lead from moving back to the central nervous system. Using dimercaprol alone might cause lead to move to the brain and testes. A side effect of calcium EDTA is kidney damage. Succimer is preferred for mild to moderate cases, such as when children have blood lead levels above 25 μg/dL. The most common side effect of succimer is stomach discomfort. It is important to note that chelation therapy reduces blood lead levels but may not prevent long-term cognitive issues caused by lead in tissues. This could be because the treatment does not remove enough lead from tissues or cannot reverse existing damage. Chelating agents may also lower levels of necessary nutrients like zinc, and oral chelating agents can increase lead absorption through the intestine.
Chelation challenge, also called provocation testing, is used to determine if the body has a high amount of heavy metals, including lead, that can be removed. This test involves collecting urine before and after giving a single dose of a chelating agent to move heavy metals into the urine. The urine is then tested for heavy metal levels to estimate the body’s total burden. This method mainly measures lead in soft tissues, though its ability to reflect long-term exposure or lead stored in bones is debated. While the test has been used to decide if chelation therapy is needed or to diagnose heavy metal exposure, some evidence suggests it may not be reliable because blood levels after chelation are not always comparable to standard diagnostic ranges. A single chelating dose could also move heavy metals to sensitive areas like the brain.
Epidemiology
Lead has been used for many years, and its effects are found around the world. Everyone has some amount of lead in their blood, though levels vary. In the 1950s, the use of leaded gasoline caused a sharp increase in lead pollution in the air. Lead is a major environmental health issue because it affects a large number of people and causes serious health problems. Globally, lead exposure is linked to about 0.2% of all deaths and 0.6% of years lost due to illness or disability. However, efforts to prevent lead exposure receive very little funding compared to other health issues, such as HIV. For every year of healthy life affected by lead, only about $0.31 is spent on prevention, which is about 600 times less than the funding for HIV.
Since the 1970s, regulations in developed countries have reduced lead exposure, but many developing countries still allow lead in products. As of June 2022, only 45% of countries had laws to control lead in paint. Regions like the Middle East, North Africa, and Sub-Saharan Africa are more likely to lack such laws. While leaded gasoline has been banned in many developed countries, exposure in developing countries has increased nearly three times. In areas where leaded gasoline is still used, it is the main source of lead exposure. In addition, the use of pesticides in developing countries adds to the risk of lead poisoning. Poor children in these regions are especially vulnerable. In North America, 7% of children have blood lead levels above 10 μg/dL, while in Central and South America, the rate is 33–34%. One-fifth of the world’s disease burden from lead poisoning occurs in the Western Pacific, and another fifth occurs in Southeast Asia.
In developed countries, people with less education who live in poor areas are most at risk for high lead levels. In the United States, the groups most at risk include the poor, city residents, and immigrants. In the U.S., African-American children and those living in older homes are also more likely to have high blood lead levels. Many low-income people live in older homes with lead paint, which can chip and create lead dust.
Risk factors for high lead exposure include alcohol use and smoking, possibly because tobacco leaves can absorb lead from pesticides. Adults with certain conditions, such as low calcium or iron levels, old age, or diseases affecting the brain or kidneys, may be more likely to suffer from lead toxicity. Some studies suggest males are more vulnerable to lead-related brain damage, while others suggest females are.
In adults, blood lead levels increase with age, and men generally have higher levels than women. Children are more sensitive to lead than adults. They may breathe in more lead because they breathe faster and often put objects in their mouths. Children aged one to three often have the highest blood lead levels, possibly because they begin walking and exploring their environment. Blood lead levels usually peak at 18–24 months. In many countries, including the U.S., household paint and dust are the main sources of lead exposure in children.
- Map showing average blood lead levels (BLLs) in Chinese adults from 1980–2018.
- Trend of BLLs in Chinese adults in different regions from 1980–2018. BLLs decreased in all regions except South China.
Mass lead poisoning can occur. In 2009, 15,000 people were planned to be relocated from Jiyuan, China, after 1,000 children near a lead smelter were found to have high blood lead levels. The project cost about 1 billion yuan ($150 million), with 70% paid by the local government and the smelter company, and the rest by residents. The government shut down 32 of 35 lead plants in the area, affecting people from 10 villages.
In 2010, a lead poisoning epidemic in Zamfara State, Nigeria, caused at least 400 children to die.
Neurological damage from lead exposure is more severe in males, showing that lead toxicity affects men and women differently.
Prognosis
The effects of lead depend on how much and how long a person is exposed. Lead can harm the kidneys and blood, but these effects often improve once exposure stops. However, lead can cause lasting damage to the brain, especially in children. Many health, thinking, and behavior problems caused by lead poisoning in children may continue into adulthood.
Lead encephalopathy is a serious medical condition that causes permanent brain damage in about 70 to 80 percent of children who have it, even with treatment. When lead affects the brain, the risk of death is about 25 percent. Of those who survive, about 40 percent may have lasting brain problems, such as cerebral palsy, if symptoms were already present when treatment began.
Long-term exposure to lead can shorten life and cause health problems. People with high blood lead levels are more likely to die from causes like cancer, stroke, heart disease, and other health issues. Lead is considered a possible cause of cancer based on studies in animals. Research also shows that mental decline and mental health issues as people age may be linked to lead exposure. The total amount of lead a person is exposed to over many years may affect health more than recent exposure. Some problems, like high blood pressure, only become serious risks after long-term exposure (more than one year). Lead’s effects on the brain are often worse and last longer in children from low-income families compared to those with more financial resources. This does not mean wealth can prevent lead from causing long-term mental health issues.
Violence
Lead poisoning in children is connected to changes in how the brain works, which can lead to lower intelligence and more impulsive or aggressive behavior. These effects from childhood lead exposure are linked to crimes of passion, such as aggravated assault when individuals become young adults. More lead exposure in children was connected to higher rates of aggravated assault 22 years later. For example, the highest use of leaded gasoline in the late 1970s matches with the highest rates of aggravated assault in the late 1990s in cities across the United States.
History
Lead poisoning was one of the first known and most studied health risks linked to jobs. Lead is one of the earliest metals to be melted and used. It was first mined in Anatolia around 6500 BC. Its heavy weight, ease of shaping, and ability to resist rust made it useful.
In the 2nd century BC, the Greek scientist Nicander described stomach pain and muscle weakness in people with lead poisoning. In the 1st century AD, the Greek doctor Dioscorides wrote that lead can weaken the mind.
Lead was widely used in Roman water systems from about 500 BC to 300 AD. Vitruvius, an engineer who worked with Julius Caesar, wrote that water from clay pipes was healthier than water from lead pipes. He said lead could make water harmful by creating a substance called white lead, which is bad for the body. Gout, a common illness among wealthy Romans, may have been caused by lead or by eating and drinking from lead containers. A substance called sugar of lead was used to sweeten wine, and the gout caused by this was called "saturnine" gout. Some scientists think lead poisoning may have helped cause the fall of the Roman Empire, but this idea is not widely accepted.
Recent research suggests that lead in Roman water likely came from the lead pipes themselves, not from other sources. People sometimes damaged the pipes to get more water, which increased lead exposure. Romans also consumed lead through foods like defrutum, carenum, and sapa, which were made by boiling fruit in lead cookware. These items were used in cooking and cosmetics. Lead cookware was popular but not the most common type of cookware. There is no clear information about how often these foods were used.
In 1983, scientist Jerome Nriagu wrote a major paper suggesting that lead poisoning caused the collapse of the Roman Empire. Another scientist, Clair Patterson, supported this idea, but many others disagreed. A scientist named John Scarborough criticized Nriagu’s work for having many errors and unreliable sources. Today, lead is not seen as the main cause of Rome’s fall, but lead pipes in the Roman water system were a serious public health problem. Studies of ancient water show that tap water in Rome had 100 times more lead than natural spring water.
A study from 2025 found that lead pollution was highest during the Pax Romana, a time of peace and prosperity, which supports the idea that lead pollution may have contributed to the empire’s decline.
After the Roman Empire, medical writings about lead poisoning were not common until the end of the Middle Ages. In 1656, the German doctor Samuel Stockhausen identified lead dust and fumes as the cause of illnesses called "morbi metallici," which affected miners, metalworkers, and others exposed to lead.
The artist Caravaggio may have died from lead poisoning. High lead levels were found in bones from a grave believed to be his. Paints used at the time contained lead salts. Caravaggio was known for violent behavior, a symptom linked to lead poisoning.
In 17th-century Germany, the doctor Eberhard Gockel found that lead-contaminated wine caused an outbreak of stomach pain. He noticed that monks who drank wine got sick, while those who did not stay healthy. He traced the cause to sugar of lead, which was made by mixing lead with vinegar. As a result, a duke banned the use of lead in wine.
In the 18th century, lead poisoning was common because of the widespread drinking of rum. Rum was made using stills with lead parts called "worms." This caused many deaths among slaves and sailors in the West Indies. Lead poisoning from rum was also reported in Boston. Benjamin Franklin suspected lead was a danger in 1786. In the same period, people in Devon, England, who drank cider made in lead-lined presses experienced stomach pain called "Devonshire colic." Lead was illegally added to cheap wine as a sweetener. The composer Beethoven, who drank a lot of wine, had high lead levels in his hair, possibly from this. Lead poisoning may have contributed to his hearing loss and death, though the exact cause of his death is still unknown.
During the 19th century, the Industrial Revolution made lead poisoning more common in workplaces. The use of lead paint in homes increased children’s exposure to lead. Before this, most lead exposure was from jobs. In the UK, laws to protect pottery workers from lead were passed in 1864 and 1899. A researcher named William James Furnival worked to remove lead from ceramics and published a book in 1904. In the US, Alice Hamilton studied lead poisoning in workers and helped start the field of occupational safety. In 1897, Australia recognized that lead paint caused poisoning in children. France, Belgium, and Austria banned lead in interior paints in 1909. The League of Nations followed in 1922. The US did not ban lead in house paint until 1971, and it was fully banned in 1978.
In the 20th century, lead use increased worldwide. Lead was added to gasoline in the 1920s to improve engine performance. Lead from car exhaust still remains in soil and buildings today. In the 1940s, an artist named Carol Janeway studied lead poisoning from using lead glazes in tile art. She suggested other artists, like Vally Wieselthier and Dora Carrington, might also be at risk. Blood lead levels have dropped since the 1980s, when leaded gasoline was phased out. Countries that banned lead in food can solder and gasoline have seen the biggest drops in lead levels.
Today, most people have much higher lead levels than people in pre-industrial times. Because of reduced lead use in products and workplaces, serious lead poisoning is rare in most countries. However, low-level exposure to lead still occurs.
Other species
Humans are not the only living things affected by lead; plants and animals also experience lead toxicity, though the effects vary by species. Animals often show similar symptoms to humans after lead exposure, such as stomach pain, nerve problems, and changes in behavior, like increased aggression. Much of what scientists know about how lead affects the human body comes from studying animals. Animals are used to test treatments, such as medicines that help remove lead from the body, and to learn how lead moves through the body.
Farm animals like cows and horses, as well as pets, can also be harmed by lead. Pets may be exposed to lead in the same ways as humans, such as through old paint, window blinds, or toys. If a pet dog has lead poisoning, it may mean children in the same home are also at risk for high lead levels.
Lead is a major cause of poisoning in waterfowl, such as ducks. When hunters use lead shot, the spent pellets can be eaten by birds, leading to poisoning. Predators that eat these birds are also at risk. Lead shot-related bird deaths were first recorded in the United States in the 1880s. By 1919, scientists confirmed that lead shot was the cause of these deaths. Many countries, including the United States in 1991 and Canada in 1997, have banned using lead shot for hunting waterfowl. Other dangers to wildlife include lead paint, soil from lead mines, and lead weights used in fishing lines. Some countries have banned certain fishing gear containing lead.
The critically endangered California condor has also suffered from lead poisoning. These birds eat the remains of animals that have been shot but not collected, including pieces of lead bullets. In areas near the Grand Canyon, eating lead shot is the most common cause of death in condors. To protect them, hunting with lead bullets has been banned in regions where condors live. Conservation efforts also include regularly testing condors’ blood for lead levels and treating poisoned birds.
Ancient human ancestors, such as early hominins, were exposed to lead in caves where lead naturally accumulated. Homo sapiens, the species that survived, may have had a genetic change that helped their brains handle lead better, which could have supported the development of language.