Lead and PCBs as risk factors for attention deficit/hyperactivity disorder.
OBJECTIVE
Attention deficit/hyperactivity disorder (ADHD) is the most frequently diagnosed neurobehavioral disorder of childhood, yet its etiology is not well understood. In this review we present evidence that environmental chemicals, particularly polychlorinated biphenyls (PCBs) and lead, are associated with deficits in many neurobehavioral functions that are also impaired in ADHD.


METHODS
Human and animal studies of developmental PCB or lead exposures that assessed specific functional domains shown to be impaired in ADHD children were identified via searches of PubMed using "lead" or "PCB exposure" in combination with key words, including "attention," "working memory," "response inhibition," "executive function," "cognitive function," "behavior," and "ADHD."


RESULTS
Children and laboratory animals exposed to lead or PCBs show deficits in many aspects of attention and executive function that have been shown to be impaired in children diagnosed with ADHD, including tests of working memory, response inhibition, vigilance, and alertness. Studies conducted to date suggest that lead may reduce both attention and response inhibition, whereas PCBs may impair response inhibition to a greater degree than attention. Low-level lead exposure has been associated with a clinical diagnosis of ADHD in several recent studies. Similar studies of PCBs have not been conducted.


CONCLUSIONS
We speculate that exposures to environmental contaminants, including lead and PCBs, may increase the prevalence of ADHD.
Eubig
Paul A
PA
Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA. eubig@illinois.edu
Aguiar
Andréa
A
Schantz
Susan L
SL
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000139:chemically induced* / Q000453:epidemiology* / Q000209:etiology; D002648:Child; D004781:Environmental Exposure / Q000706:statistics & numerical data; D004785:Environmental Pollutants / Q000009:adverse effects* / Q000097:blood; D004787:Environmental Pollution / Q000706:statistics & numerical data; D006801:Humans; D007854:Lead / Q000009:adverse effects* / Q000097:blood; D011078:Polychlorinated Biphenyls / Q000009:adverse effects* / Q000097:blood; D012307:Risk Factors
D004785:Environmental Pollutants; D007854:Lead; D011078:Polychlorinated Biphenyls