Lead poisoning
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. Lead poisoning causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems. Some of the effects are permanent. In severe cases, anemia, seizures, coma, or death may occur.
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 has set the upper limit for blood lead for adults at 10 μg/dL and for children at 3.5 μg/dL; before October 2021 the limit 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. This includes 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 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.
In 2021, 1.5 million deaths worldwide were attributed to lead exposure. It 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. Thousands of American communities may have higher lead burdens than those seen during the peak of the Flint water crisis. Those who are poor are at greater risk. Lead is believed to result in 0.6% of the world's disease burden. 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. Globally, over 15% of children are known to have blood lead levels 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. Concerns for low levels of exposure began in the 1970s, when it became understood that due to its bioaccumulative nature, there was no safe threshold for lead exposure.
Classification
Classically, "lead poisoning" or "lead intoxication" has been defined as exposure to high levels of lead, typically associated with severe health effects. 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. 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 or chronic, but the latter is much more common.
Diagnosis and treatment of lead exposure are based on blood lead level, measured in micrograms of lead per deciliter of blood. Urine lead levels may be used, 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.
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.
Lead forms a variety of compounds and exists in the environment in various forms. Features of poisoning differ depending on whether the agent is an organic compound, or an inorganic one. Organic lead poisoning is now very rare, because countries across the world have phased out the use of organic lead compounds as gasoline additives. These compounds are still used in industrial settings. Organic lead compounds, which cross the skin and respiratory tract easily, affect the central nervous system predominantly.
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. 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. Signs that occur in adults at blood lead levels exceeding 100 μg/dL include wrist drop and foot drop, and signs of encephalopathy, such as those that accompany increased pressure within the skull, delirium, coma, seizures, and headache. 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.