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| Lead poisoning | |
|---|---|
| Other names | Plumbism, colica pictorum, saturnism, Devon colic, painter's colic |
 | |
| An X-ray demonstrating the characteristic finding of lead poisoning in humans—dense metaphyseal lines | |
| Specialty | Toxicology |
| Symptoms | Intellectual disability, abdominal pain, constipation, headaches, irritability, memory problems, inability to have children, tingling in the hands and feet[1][2] |
| Complications | Anemia, seizures, coma[1][2] |
| Causes | Exposure to lead via contaminated air, water, dust, food, consumer products[2] |
| Risk factors | Young age, pica[2] |
| Diagnostic method | Blood lead level[2] |
| Differential diagnosis | Iron deficiency anemia, malabsorption, ADHD, anxiety disorder, polyneuropathy[3] |
| Prevention | Removing lead from the home, improved monitoring and education in the workplace, laws that ban lead in products[2][4][5][6] |
| Treatment | Chelation therapy[4] |
| Medication | Dimercaprol, edetate calcium disodium, succimer[7] |
| Deaths | 540,000 (2016)[2] |
Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body.[2] Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, and tingling in the hands and feet.[1] It causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems.[2] Some of the effects are permanent.[2] In severe cases, anemia, seizures, coma, or death may occur.[1][2]
Exposure to lead can occur by contaminated air, water, dust, food, or consumer products.[2] Lead poisoning poses a significantly increased risk to children as they are far more likely to ingest lead indirectly by chewing on toys or other objects that are coated in lead paint.[2] 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.[7] Diagnosis is typically by measurement of the blood lead level.[2] 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,[8] previously before October 2021 5 μg/dL[9][10] 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.[4]
Lead poisoning is preventable.[2] This includes individual efforts such as removing lead-containing items from the home,[5] workplace efforts such as improved ventilation and monitoring,[6] state and national policies that ban lead in 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.[2][4] Workers' education could be helpful as well.[11] 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.[4] Chelation therapy in children is recommended when blood levels are greater than 40–45 μg/dL.[4][12] Medications used include dimercaprol, edetate calcium disodium, and succimer.[7]
In 2013, lead is believed to have resulted in 853,000 deaths worldwide.[2] It occurs most commonly in the developing world.[2] There also are numerous cases in the developed world, with there being thousands of American communities with higher lead burdens than seen during the peak of the Flint water crisis.[13] Those who are poor are at greater risk.[2] Lead is believed to result in 0.6% of the world's disease burden.[5] According to a study, half of the US population has been exposed to substantially detrimental lead levels in early childhood – mainly from car exhaust, from which lead pollution peaked in the 1970s and caused widespread loss in cognitive ability.[14][15][globalize]
People have been mining and using lead for thousands of years.[4] Descriptions of lead poisoning date to at least 2000 BC,[4] while efforts to limit lead's use date back to at least the 16th century.[5] Concerns for low levels of exposure began in the 1970s with there being no safe threshold for lead exposure.[2][4][16]
Classification
Classically, "lead poisoning" or "lead intoxication" has been defined as exposure to high levels of lead typically associated with severe health effects.[17] 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).[18] 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.[18]
The amount of lead in the blood and tissues, as well as the time course of exposure, determine toxicity.[19] Lead poisoning may be acute (from intense exposure of short duration) or chronic (from repeat low-level exposure over a prolonged period), but the latter is much more common.[20] 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 as well, though less commonly. In cases of chronic exposure, lead often sequesters in the highest concentrations first in the bones, then in the kidneys. If a provider is performing a provocative excretion test, or "chelation challenge", a measurement obtained from urine rather than blood is likely to provide a more accurate representation of total lead burden to a skilled interpreter.[21]
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.[22][23] Authorities such as the American Academy of Pediatrics define lead poisoning as blood lead levels higher than 10 μg/dL.[24]
Lead forms a variety of compounds and exists in the environment in various forms.[25] Features of poisoning differ depending on whether the agent is an organic compound (one that contains carbon), or an inorganic one.[26] Organic lead poisoning is now very rare, because countries across the world have phased out the use of organic lead compounds as gasoline additives, but such compounds are still used in industrial settings.[26] Organic lead compounds, which cross the skin and respiratory tract easily, affect the central nervous system predominantly.[26]
Signs and symptoms
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Lead poisoning can cause a variety of symptoms and signs which vary depending on the individual and the duration of lead exposure.[27][28] Symptoms are nonspecific and may be subtle, and someone with elevated lead levels may have no symptoms.[29] 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.[30] Symptoms from exposure to organic lead, which is probably more toxic than inorganic lead due to its lipid solubility, occur rapidly.[31] Poisoning by organic lead compounds has symptoms predominantly in the central nervous system, such as insomnia, delirium, cognitive deficits, tremor, hallucinations, and convulsions.[26]
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.[32]
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.[33] Other early signs in adults include malaise, fatigue, decreased libido, and problems with sleep.[27] An unusual taste in the mouth and personality changes are also early signs.[34][35]
In adults, symptoms can occur at levels above 40 μg/dL, but are more likely to occur only above 50–60 μg/dL.[27] Symptoms begin to appear in children generally at around 60 μg/dL.[5] However, the lead levels at which symptoms appear vary widely depending on unknown characteristics of each individual.[36] 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.[37] Anemia may appear at blood lead levels higher than 50 μg/dL.[33] In adults, abdominal colic, involving paroxysms of pain, may appear at blood lead levels greater than 80 μg/dL.[28] 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.[38] In children, signs of encephalopathy such as bizarre behavior, discoordination, and apathy occur at lead levels exceeding 70 μg/dL.[38] For both adults and children, it is rare to be asymptomatic if blood lead levels exceed 100 μg/dL.[28]
Acute poisoning
In acute poisoning, typical neurological signs are pain, muscle weakness, numbness and tingling, and, rarely, symptoms associated with inflammation of the brain.[32] Abdominal pain, nausea, vomiting, diarrhea, and constipation are other acute symptoms.[39] Lead's effects on the mouth include astringency and a metallic taste.[39] 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.[39] Hemolysis (the rupture of red blood cells) due to acute poisoning can cause anemia and hemoglobin in the urine.[39] Damage to kidneys can cause changes in urination such as acquired fanconi syndrome and decreased urine output.[39] People who survive acute poisoning often go on to display symptoms of chronic poisoning.[39]
Chronic poisoning
Chronic poisoning usually presents with symptoms affecting multiple systems,[26] but is associated with three main types of symptoms: gastrointestinal, neuromuscular, and neurological.[32] Central nervous system and neuromuscular symptoms usually result from intense exposure, while gastrointestinal symptoms usually result from exposure over longer periods.[39] Signs of chronic exposure include loss of short-term memory or concentration, depression, nausea, abdominal pain, loss of coordination, and numbness and tingling in the extremities.[34][unreliable medical source?] Fatigue, problems with sleep, headaches, stupor, slurred speech, and anemia are also found in chronic lead poisoning.[32] A "lead hue" of the skin with pallor and/or lividity is another feature.[40][41] 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.[42] Children with chronic poisoning may refuse to play or may have hyperkinetic or aggressive behavior disorders.[32] Visual disturbance may present with gradually progressing blurred vision as a result of central scotoma, caused by toxic optic neuritis.[43]
Effects on children
A pregnant woman who has elevated blood lead levels is at greater risk of a premature birth or with a low birth weight.[44] Children are more at risk for lead poisoning because their smaller bodies are in a continuous state of growth and development.[45] Young children are much more vulnerable to lead poisoning, as they absorb 4 to 5 times more lead than an adult from a given source.[46] Furthermore, children, especially as they are learning to crawl and walk, are constantly on the floor and therefore more prone to ingesting and inhaling dust that is contaminated with lead.[47]
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.[48] Slow development of normal childhood behaviors, such as talking and use of words, and permanent intellectual disability are both commonly seen. Although less common, it is possible for fingernails to develop leukonychia striata if exposed to abnormally high lead concentrations.[49]
On July 30, 2020, a report by UNICEF and Pure Earth revealed that lead poisoning is affecting children on a "massive and previously unknown scale". According to the report, one in three children, up to 800 million globally, have blood lead levels at, or above, 5 micrograms per decilitre (μg/dL), the amount at which action is required.[50][51]
By organ system
Lead affects every one of the body's organ systems, especially the nervous system, but also the bones and teeth, the kidneys, and the cardiovascular, immune, and reproductive systems.[52] Hearing loss and tooth decay have been linked to lead exposure,[53] as have cataracts.[54] Intrauterine and neonatal lead exposure promote tooth decay.[55][56][57][58][59][60][61] Aside from the developmental effects unique to young children, the health effects experienced by adults are similar to those in children, although the thresholds are generally higher.[62]
Kidneys
Kidney damage occurs with exposure to high levels of lead, and evidence suggests that lower levels can damage kidneys as well.[63] The toxic effect of lead causes nephropathy and may cause Fanconi syndrome, in which the proximal tubular function of the kidney is impaired.[64] Long-term exposure at levels lower than those that cause lead nephropathy have also been reported as nephrotoxic in patients from developed countries that had chronic kidney disease or were at risk because of hypertension or diabetes mellitus.[65] Lead poisoning inhibits excretion of the waste product urate and causes a predisposition for gout, in which urate builds up.[66][67][68] This condition is known as saturnine gout.
Cardiovascular system
Evidence suggests lead exposure is associated with high blood pressure, and studies have also found connections between lead exposure and coronary heart disease, heart rate variability, and death from stroke, but this evidence is more limited.[69] People who have been exposed to higher concentrations of lead may be at a higher risk for cardiac autonomic dysfunction on days when ozone and fine particles are higher.[70]
Reproductive system
Lead affects both the male and female reproductive systems. In men, when blood lead levels exceed 40 μg/dL, sperm count is reduced and changes occur in volume of sperm, their motility, and their morphology.[71] A pregnant woman's elevated blood lead level can lead to miscarriage, prematurity, low birth weight, and problems with development during childhood.[72] Lead is able to pass through the placenta and into breast milk, and blood lead levels in mothers and infants are usually similar.[30] A fetus may be poisoned in utero if lead from the mother's bones is subsequently mobilized by the changes in metabolism due to pregnancy; increased calcium intake in pregnancy may help mitigate this phenomenon.[73]
Nervous system
Lead affects the peripheral nervous system (especially motor nerves) and the central nervous system.[30] Peripheral nervous system effects are more prominent in adults and central nervous system effects are more prominent in children.[36] Lead causes the axons of nerve cells to degenerate and lose their myelin coats.[30]
Lead exposure in young children has been linked to learning disabilities,[75] and children with blood lead concentrations greater than 10 μg/dL are in danger of developmental disabilities.[39] Increased blood lead level in children has been correlated with decreases in intelligence, nonverbal reasoning, short-term memory, attention, reading and arithmetic ability, fine motor skills, emotional regulation, and social engagement.[72]
The effect of lead on children's cognitive abilities takes place at very low levels.[53][72][76] There is apparently no lower threshold to the dose-response relationship (unlike other heavy metals such as mercury).[77] Reduced academic performance has been associated with lead exposure even at blood lead levels lower than 5 μg/dL.[78][79] Blood lead levels below 10 μg/dL have been reported to be associated with lower IQ and behavior problems such as aggression, in proportion with blood lead levels.[18] Between the blood lead levels of 5 and 35 μg/dL, an IQ decrease of 2–4 points for each μg/dL increase is reported in children.[39] However, studies that show associations between low-level lead exposure and health effects in children may be affected by confounding and overestimate the effects of low-level lead exposure.[80]
High blood lead levels in adults are also associated with decreases in cognitive performance and with psychiatric symptoms such as depression and anxiety.[81] It was found in a large group of current and former inorganic lead workers in Korea that blood lead levels in the range of 20–50 μg/dL were correlated with neuro-cognitive defects.[82] Increases in blood lead levels from about 50 to about 100 μg/dL in adults have been found to be associated with persistent, and possibly permanent, impairment of central nervous system function.[63]
Lead exposure in children is also correlated with neuropsychiatric disorders such as attention deficit hyperactivity disorder and anti-social behaviour.[76] Elevated lead levels in children are correlated with higher scores on aggression and delinquency measures.[5] A correlation has also been found between prenatal and early childhood lead exposure and violent crime in adulthood.[72] Countries with the highest air lead levels have also been found to have the highest murder rates, after adjusting for confounding factors.[5] A May 2000 study by economic consultant Rick Nevin theorizes that lead exposure explains 65% to 90% of the variation in violent crime rates in the US.[83][84] A 2007 paper by the same author claims to show a strong association between preschool blood lead and subsequent crime rate trends over several decades across nine countries.[85][86] Lead exposure in childhood appears to increase school suspensions and juvenile detention among boys.[87] It is believed that the US ban on lead paint in buildings in the late 1970s, as well as the phaseout of leaded gasoline in the 1970s and 1980s, partially helped contribute to the decline of violent crime in the United States since the early 1990s.[86]
Exposure routes
| Part of a series on |
| Pollution |
|---|
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Lead is a common environmental pollutant.[24] Causes of environmental contamination include lead-based paint that is deteriorating (e.g. peeling, chipping, chalking, cracking, damp or damage), renovation, repair or painting activities (disturbing or demolishing painted surfaces generate toxic lead dust ),[88] industrial use of lead, such as found in facilities that process lead-acid batteries or produce lead wire or pipes, metal recycling and foundries,[89] and burning of joss paper.[90][91][92] Storage batteries and ammunition are made with the largest amounts of lead consumed in the economy each year, in the US as of 2013.[93] Children living near facilities that process lead, such as lead smelters, have been found to have unusually high blood lead levels.[94] In August 2009, parents rioted in China after lead poisoning was found in nearly 2000 children living near zinc and manganese smelters.[95] Lead exposure can occur from contact with lead in air, household dust, soil, water, and commercial products.[22] Leaded gasoline has also been linked to increases in lead pollution.[96][97] Some research has suggested a link between leaded gasoline and crime rates.[98][99] Man-made lead pollution has been elevated in the air for the past 2000 years.[100][101][102] Lead pollution in the air is entirely due to human activity (mining and smelting, as well as in gasoline).
Occupational exposure
In adults, occupational exposure is the main cause of lead poisoning.[5] People can be exposed when working in facilities that produce a variety of lead-containing products; these include radiation shields, ammunition, certain surgical equipment, developing dental X-ray films prior to digital X-rays (each film packet had a lead liner to prevent the radiation from going through), fetal monitors, plumbing, circuit boards, jet engines, and ceramic glazes.[34][unreliable medical source?][104] In addition, lead miners and smelters, plumbers and fitters, auto mechanics, glass manufacturers, construction workers, battery manufacturers and recyclers, firing range workers, and plastic manufacturers are at risk for lead exposure.[94] Other occupations that present lead exposure risks include welding, manufacture of rubber, printing, zinc and copper smelting, processing of ore, combustion of solid waste, and production of paints and pigments.[105] Lead exposure can also occur with intense use of gun ranges, regardless of whether these ranges are indoor or out.[106] Parents who are exposed to lead in the workplace can bring lead dust home on clothes or skin and expose their children.[105] Occupational exposure to lead increases the risk of cardiovascular disease, in particular: stroke, and high blood pressure.[107]
Food
Lead may be found in food when food is grown in soil that is high in lead, airborne lead contaminates the crops, animals eat lead in their diet, or lead enters the food either from what it was stored or cooked in.[108] Ingestion of lead paint and batteries is also a route of exposure for livestock, which can subsequently affect humans.[109] Milk produced by contaminated cattle can be diluted to a lower lead concentration and sold for consumption.[110]
In Bangladesh, lead chromate has been added to turmeric to make it more yellow.[111] This is believed to have started in the 1980s.[111] It was believed to have been one of the main sources of high lead levels in the country.[112] Following a 2019 report identifying adulterated turmeric as the main cause of lead poisoning in Bangladesh, the government began a rapid crackdown and public service campaign on it. By 2021, leaded turmeric had vanished from the Bangladeshi market, and blood lead levels in workers at turmeric mills had dropped by a median of 30%.[113][114]
In Hong Kong, the maximum allowed lead parts per million is 6 in solid foods and 1 in liquid foods.[115]
In December 2022, 28 dark chocolate brands were tested by Consumer Reports, which found that 23 of them contained cadmium, lead or both.[116] When cocoa beans are set outside near polluting industrial plants, they can be contaminated by dust containing lead.[117]
Cannabis
In 2007, a mass poisoning due to adulterated marijuana was uncovered in Leipzig, Germany, where 29 young adults were hospitalized with lead poisoning for several months after having smoked marijuana that had been tainted with small lead particles. One hypothesis from the police was that lead, with its high specific gravity, was used to increase the weight of street marijuana sold by the gram, thereby maximizing the dealers' profits. The researchers estimated that the profit per kilogram increased by as much as $1,500 with the lead added. It is common for drugs to be cut with less-expensive substances to increase the profits of dealers or distributors (e.g., cocaine is routinely adulterated with sugars, talcum powder, magnesium salts, and even other drugs). It is thought that the adverse reactions to many of these drugs are a result of poor manufacturing rather than face-value overdoses.[118][119]
Besides adulteration, cannabis plants have an inherent ability to absorb heavy metals from the soil. This makes them useful for remediating contaminated sites. But this may also make cannabis dangerous for consumers who ingest it. Some cannabis strains have been bred specifically to remove pollutants from soil, air or water, a method known as phytoremediation.[120]
In 2022, around 40% of cannabis products sold at unlicensed storefronts in New York City were found to contain heavy metals (e.g., lead, nickel), pesticides, and bacteria.[121]
Paint
Some lead compounds are colorful and are used widely in paints,[122][123] and lead paint is a major route of lead exposure in children.[124] A study conducted in 1998–2000 found that 38 million housing units in the US had lead-based paint, down from a 1990 estimate of 64 million.[125] Deteriorating lead paint can produce dangerous lead levels in household dust and soil.[126] Deteriorating lead paint and lead-containing household dust are the main causes of chronic lead poisoning.[32] The lead breaks down into the dust and since children are more prone to crawling on the floor, it is easily ingested.[125] Many young children display pica, eating things that are not food. Even a small amount of a lead-containing product such as a paint chip or a sip of glaze can contain tens or hundreds of milligrams of lead.[127] Eating chips of lead paint presents a particular hazard to children, generally producing more severe poisoning than occurs from dust.[128] Because removing lead paint from dwellings, e.g. by sanding or torching, creates lead-containing dust and fumes, it is generally safer to seal the lead paint under new paint (excepting moveable windows and doors, which create paint dust when operated).[129] Alternatively, special precautions must be taken if the lead paint is to be removed.[129]
In oil painting, it was once common for colours such as yellow or white to be made with lead carbonate. Lead white oil colour was the main white of oil painters until superseded by compounds containing zinc or titanium in the mid-20th century. It is speculated that the painter Caravaggio and possibly Francisco Goya and Vincent Van Gogh had lead poisoning due to overexposure or carelessness when handling this colour.[130]
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