Blood lead level
Blood lead level (BLL), is a measure of the amount of lead in the blood. 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. 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. 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. Measurement Measuring a person's blood lead level requires a blood sample, which may be performed with a fingerstick or a blood draw. The amount of lead found in the blood sample may be measured in micrograms of lead per deciliter of blood (μg/dL) especially in the United States; 5 μg/dL is equivalent to 0.24 μmol/L (micromolar). BLL cannot measure long-term lead exposure. An x-ray fluorescence test provides measurements from the bone because lead is predominantly stored in the human body in calcified tissues such as bones. No safe level The Centers for Disease Control and Prevention (CDC) changed its view on blood lead levels in 2012 because of "a growing body of studies concluding that blood lead levels (BLLs) lower than 10 μg/dL harm children" with "irreversible" effects, and "since no safe blood lead level in children has been identified, a blood lead 'level of concern' cannot be used to define individuals in need of intervention". The new policy is to aim to reduce average blood lead levels in US children to as low a level as possible. The CDC now publishes a "reference" blood lead level which they hope can decrease in coming years. The reference value is "based on the 97.5th percentile of the BLL distribution among children 1–5 years old in the United States". As of 2021, the value is set at 3.5 μg/dL. It is not a level deemed by the CDC as "safe". The reference level is designed to be used as a policy tool. Parents, clinicians, communities, state and federal authorities and political leaders are expected to monitor blood lead test levels, aware that children testing higher than the reference level are testing higher than 97.5% of all US children. The CDC expects action to be taken when test levels are found to exceed the