Braun et al. (2006) published the dose-response curve in Environmental Health Perspectives. NHANES quintile analysis confirms it. Lead in the top blood-lead quintile is associated with a 4.1x increase in ADHD prevalence over the bottom quintile.
NHANES blood-lead in 4-15-year-olds, segmented into quintiles, correlated with parent-reported ADHD diagnosis. The relationship is monotonic and dose-responsive. There is no apparent safe lower bound. The bottom quintile still shows elevated risk versus the cleanest 5% of children.
The historical framing was "below the action level is safe." The data does not support that. Every increment of blood lead adds to the ADHD risk on a smooth curve.
It tells you what is circulating today. It does not tell you what is in the bones, and it does not tell you the average over the past year.
Find the source. Remove the dose. The blood result follows in 1-2 months.
All three compete with lead at the gut absorption step. A well-fed kid absorbs less of the dose that does land in their mouth.
