Lead poisoning can cause a variety of symptoms and signs which vary depending on the individual and the duration of lead exposure.[14][15] Symptoms are nonspecific and may be subtle, and someone with elevated lead levels may have no symptoms.[16] 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.[17] Symptoms from exposure to organic lead, which is probably more toxic than inorganic lead due to its lipid solubility, occur rapidly.[18] Poisoning by organic lead compounds has symptoms predominantly in the central nervous system, such as insomnia, delirium, cognitive deficits, tremor, hallucinations, and convulsions.[13]
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.[19]
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.[20] Other early signs in adults include malaise, fatigue, decreased libido, and problems with sleep.[14] An unusual taste in the mouth and personality changes are also early signs.[21]
In adults, symptoms can occur at levels above 40 μg/dL, but are more likely to occur only above 50–60 μg/dL.[14] Symptoms begin to appear in children generally at around 60 μg/dL.[22] However, the lead levels at which symptoms appear vary widely depending on unknown characteristics of each individual.[23] 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.[24] Anemia may appear at blood lead levels higher than 50 μg/dL.[20] In adults, Abdominal colic, involving paroxysms of pain, may appear at blood lead levels greater than 80 μg/dL.[15] 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.[25] In children, signs of encephalopathy such as bizarre behavior, discoordination, and apathy occur at lead levels exceeding 70 μg/dL.[25] For both adults and children, it is rare to be asymptomatic if blood lead levels exceed 100 μg/dL.[15]
