Blood lead level

Blood lead level (BLL), is a measure of lead in the blood. It is often 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).

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". It is currently 5 μg/dL. According to the CDC, in 2012, "approximately 450,000 children in the United States have BLLs higher than this reference value". There were more than 24 million US children under the age of 6 in 2014. If 2.5% are assumed to have blood lead levels higher than the reference amount, then there were approximately 600,000 US children with elevated blood lead levels in 2014. It is not a level deemed by the CDC as "safe". No level of lead in the blood of children is currently thought to be 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 reference. As blood lead levels slowly decline in response to such action, the reference will also decline. CDC will recalculate a new reference every four years.

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. Today, BLL measurements from remote human populations have 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. The National Academies evaluated this issue in 1991 and confirmed that the blood lead level of the average person in the US was 300 - 500 times higher than that of preindustrial humans.

Lead is toxic and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglobin synthesis, anemia, acute central nervous system disorders, and possibly death.

...
Wikipedia