Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by the presence of lead in the human body. Symptoms of lead poisoning may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, numbness and tingling in the hands and feet. Some of the effects are permanent. In severe cases, anemia, seizures, coma, or death may occur. Chronic lead poisoning occurs due to prolonged exposure.
Exposure to lead can occur through contaminated air, water, dust, food, or consumer products. Lead poisoning poses a significantly increased risk to children and pets as they are far more likely to ingest lead indirectly by chewing on toys or other objects that are coated in lead paint. Additionally, children absorb greater quantities of lead from ingested sources than adults. Exposure at work is a common cause of lead poisoning in adults, with certain occupations at particular risk. Diagnosis is typically by measurement of the blood lead level. The Centers for Disease Control and Prevention (US) has set the upper limit for blood lead for adults at 10 μg/dL (10 μg/100 g) and for children at 3.5 μg/dL; before October 2021 the limit for children was 5 μg/dL. Elevated lead may also be detected by changes in red blood cells or dense lines in the bones of children as seen on X-ray.
Lead poisoning is preventable. Prevention strategies include individual efforts such as removing lead-containing items from the home, workplace efforts such as improved ventilation and monitoring, state and national policies that ban lead in consumer products such as paint, gasoline, ammunition, wheel weights, and fishing weights, reduce allowable levels in water or soil, and provide for cleanup of contaminated soil. Workers' education could be helpful as well. The major treatments are removal of the source of lead and the use of medications that bind lead so it can be eliminated from the body, known as chelation therapy. Chelation therapy in children is recommended when blood levels are greater than 40–45 μg/dL. Medications used include dimercaprol, edetate calcium disodium, and succimer.
With chronic lead poisoning causing millions of deaths per year and brain damage in millions of children, the burden of lead poisoning on the worldwide population is immense. The World Health Organization has described chronic lead exposure and poisoning as a worldwide public health emergency, with urgent interventions needed to reduce exposure to lead and improving health systems' capicity to screen for and treat lead poisoning. In 2019, 5.5 million deaths worldwide were attributed to cardiovascular disease caused by lead poisoning. Chronic lead poisoning is a leading contributor to intellectual disability, learning disabilites, and behavioral problems in children. Lead poisoning causes an estimated 30% of intellectual disability of otherwise unknown cause. Every year, lead poisoning causes a loss of 765 million IQ points in children. The global disease burden of deaths from lead poisoning and intellectual disabilities in children was estimated at 6.0 trillion dollars during 2019 (or 7% of the worldwide gross domestic product).
Lead poisoning occurs most commonly in the developing world. An estimated 800 million children have blood lead levels over 5 μg/dL in low- and middle-income nations, though comprehensive public health data remains inadequate. Those who are poor are at greater risk. Lead is believed to result in 0.6% of the world's disease burden. Globally, over 15% of children are known to have blood lead levels (BLL) of over 10 μg/dL, at which point clinical intervention is strongly indicated.
People have been mining and using lead for thousands of years. Descriptions of lead poisoning date to at least 200 BC, while efforts to limit lead's use date back to at least the 16th century. Human exposure to lead increased significantly during the 20th century, when industrialization led to lead being used in a variety of industrial processes and household products. Public health efforts to limit exposure to lead began in the 1970s, when it became understood that due to its bioaccumulative nature, there was no safe threshold for lead exposure. Humans have 100 times more lead in their bodies as compared to humans in pre-industrialized times. However, efforts to reduce lead exposure (such as the worldwide banning of leaded gasoline) have lead to a 95% reduction in humans' lead levels since the 1970s in some countries (such as the United States).
Classification
Classically, "lead poisoning" or "lead intoxication" has been defined as exposure to high levels of lead, typically associated with severe health effects.Grant (2009) p. 785 Poisoning is a pattern of symptoms that occur with toxic effects from mid to high levels of exposure; toxicity is a wider spectrum of effects, including subclinical ones (those that do not cause symptoms). However, professionals often use "lead poisoning" and "lead toxicity" interchangeably, and official sources do not always restrict the use of "lead poisoning" to refer only to symptomatic effects of lead.
The amount of lead in the blood and tissues, as well as the time course of exposure, determine toxicity. Lead poisoning may be acute (from intense exposure of short duration) or chronic (from repeated low-level exposure over a prolonged period), but the latter is much more common.Trevor, Katzung, Masters (2007) p. 479 Diagnosis and treatment of lead exposure are based on blood lead level (the amount of lead in the blood), measured in micrograms of lead per deciliter of blood (μg/dL). Urine lead levels may be used, though less commonly.
The US Centers for Disease Control and Prevention and the World Health Organization state that a blood lead level of 10 μg/dL or above is a cause for concern; however, lead may impair development and have harmful health effects even at lower levels, and there is no known safe exposure level. Authorities such as the American Academy of Pediatrics define lead poisoning as blood lead levels higher than 10 μg/dL.
Signs and symptoms
Lead poisoning can cause a variety of symptoms and signs which vary depending on the individual and the duration of lead exposure. Symptoms are nonspecific and may be subtle, and someone with elevated lead levels may have no symptoms. Symptoms usually develop over weeks to months as lead builds up in the body during a chronic exposure, but acute symptoms from brief, intense exposures also occur. Symptoms from exposure to organic lead, which is probably more toxic than inorganic lead due to its lipid solubility, occur rapidly. Poisoning by organic lead compounds has symptoms predominantly in the central nervous system, such as insomnia, delirium, cognitive deficits, tremor, hallucinations, and convulsions.
Symptoms may be different in adults and children; the main symptoms in adults are headache, abdominal pain, memory loss, kidney failure, male reproductive problems, and weakness, pain, or tingling in the extremities.
Early symptoms of lead poisoning in adults are commonly nonspecific and include depression, loss of appetite, intermittent abdominal pain, nausea, diarrhea, constipation, and muscle pain. Other early signs in adults include malaise, fatigue, decreased libido, and problems with sleep. An unusual taste in the mouth and personality changes are also early signs.
In adults, symptoms can occur at levels above 40 μg/dL, but are more likely to occur only above 50–60 μg/dL. Symptoms begin to appear in children generally at around 60 μg/dL. However, the lead levels at which symptoms appear vary widely depending on unknown characteristics of each individual. At blood lead levels between 25 and 60 μg/dL, neuropsychiatric effects such as delayed reaction times, irritability, and difficulty concentrating, as well as slowed motor nerve conduction and headache can occur.Kosnett (2006) p.240 Anemia may appear at blood lead levels higher than 50 μg/dL. In adults, abdominal colic, involving paroxysms of pain, may appear at blood lead levels greater than 80 μg/dL.Kosnett (2005) p. 825 Signs that occur in adults at blood lead levels exceeding 100 μg/dL include wrist drop and foot drop, and signs of encephalopathy (a condition characterized by brain swelling), such as those that accompany increased pressure within the skull, delirium, coma, seizures, and headache.Henretig (2006) p. 1314 In children, signs of encephalopathy such as bizarre behavior, discoordination, and apathy occur at lead levels exceeding 70 μg/dL. For both adults and children, it is rare to be asymptomatic if blood lead levels exceed 100 μg/dL.
Acute poisoning In acute poisoning, typical neurological signs are pain, muscle weakness, numbness and tingling, and, rarely, symptoms associated with inflammation of the brain. Abdominal pain, nausea, vomiting, diarrhea, and constipation are other acute symptoms. Lead's effects on the mouth include astringency and a metallic taste. Gastrointestinal problems, such as constipation, diarrhea, poor appetite, or weight loss, are common in acute poisoning. Absorption of large amounts of lead over a short time can cause shock (insufficient fluid in the circulatory system) due to loss of water from the gastrointestinal tract. Hemolysis (the rupture of red blood cells) due to acute poisoning can cause anemia and hemoglobin in the urine. Damage to kidneys can cause changes in urination such as acquired Fanconi syndrome and decreased urine output. People who survive acute poisoning often go on to display symptoms of chronic poisoning.
Chronic poisoning Chronic lead poisoning is due to prolonged, generally low level, exposure to lead over months to years causing lead to accumulate in the body. Chronic poisoning usually presents with symptoms affecting multiple organ systems including the gastrointestinal, muscular, cardiovascular, and neurological systems. Signs of chronic exposure include cardiovascular disease (with a higher risk of heart disease and heart attack), neurological dysfunction (including intellectual disabilities in children and cognitive impairment in adults), hypertension (high blood pressure), kidney disease, pre-term births or pregnancy complications, and anti-social criminal behaviors. A "lead hue" of the skin with pallor and/or lividity is another feature. A blue line along the gum with bluish black edging to the teeth, known as a Burton line, is another indication of chronic lead poisoning.Rambousek (2008) p.177 Children with chronic poisoning may refuse to play or may have hyperkinetic or aggressive behavior disorders.
Effects on pregnancy and children
Pregnant women who have elevated blood lead levels are at greater risk of premature birth or a low birth weight. In a Canadian prospective population based cohort study, an increase in blood lead levels in pregnant women by 10 μg/L was associated with a 70% increased risk of preterm birth. In the same study, in those with low vitamin D levels, lead toxicity was associated with an even greater risk of preterm birth, a 3 times higher risk.
Children are at greater risk for lead poisoning because their smaller bodies are in a continuous state of growth and development, and their bodies therefore absorb lead from the environment at a greater rate than adults. Young children usually absorb 4 to 5 times more lead than an adult from a given source. Younger children also crawl on the floor and explore objects and fixtures with their mouths and therefore more prone to ingesting and inhaling dust that is contaminated with lead.
The classic signs and symptoms in children are loss of appetite, abdominal pain, vomiting, weight loss, constipation, anemia, kidney failure, irritability, lethargy, learning disabilities, and behavioral problems.