Allowable limit for blood lead – why does it keep changing

A recent article suggests the CDC limit for blood lead may be lowered again. The logic for this is to base the limit on the 97.5th percentile of NHANES data, and to revisit the limit every 4 years. An article in Pediatrics has the details. Basically, the 97.5th percentile for blood lead has been decreasing – it was around 7 in 2000. And in the Pediatrics article it is stated that: “No safe blood lead concentration in children has been identified.” Nor has human physiology changed!

It’s hard to understand the logic behind the limit. If a child had a blood lead of 6 in 2011, the child was ok according to the CDC standard, but not ok in 2013. Similarly, a blood lead of 4 in 2016 was ok but not in 2017?

Here is a summary of lead standards in the USA through time.

1960s 60ug/dL
1978   30ug/dL
1985   25ug/dL
1991   10 ug/dL
2012    5 ug/dL
2017?   3.48 ug/dL

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