Blood lead level

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Blood lead level (BLL), is a measure of the amount of lead in the blood.^[1][2] Lead is a toxic heavy metal and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglobin synthesis as well as anemia, acute central nervous system disorders, and possibly death.^[3]

Pre-industrial human BLL measurements are estimated to have been 0.016 μg/dL, and this level increased markedly in the aftermath of the industrial revolution. At the end of the late 20th century, BLL measurements from remote human populations ranged from 0.8 to 3.2 μg/dL. Children in populations adjacent to industrial centers in developing countries often have average BLL measurements above 25 μg/dL. In the United States, the average blood level for children aged 1–5 years fell from 15.2 μg/dL in 1976–1980 to 0.83 μg/dL in 2011–2016, a change largely attributed to phasing out leaded gasoline.^[4]

No level of lead in the blood of children is currently thought to be safe, but in 2021, the US Centers for Disease Control and Prevention (CDC) identified 3.5 μg/dL as the blood lead level of concern in children which should prompt further medical investigation. Approximately 2.5% of American children have at least this much lead in their blood.^[5]