Methodology, inference and causation - Environmental lead exposure and childhood intelligence

Kaufman's critique of the literature on the associations between lead expos ure and child intelligence raises important methodological and inferential points. We address the concerns he raises regarding measuring known and unk nown confounders, statistical modeling, reverse casuality and quality contr ol. Mismeasurement of potential confounders of the lead-IQ relationship, su ch as parenting skills, parental intelligence, maternal smoking during preg nancy, or otitis media can either strengthen or weaken the estimated associ ation between exposure and child intelligence. Despite some variability in design and measurement, a series of comprehensive prospective investigation s in varied populations, by different sets of investigators, provide consis tent replication; taken together these studies point to the conclusion that lead exposure has adverse consequences for child development, and that the deficits are likely to he small in comparison to the contribution of measu red social factors. (C) 2001 National Academy of Neuropsychology. Published by Elsevier Science Ltd.