Nearly half a million cases of attention-deficit hyperactivity disorder among U.S. children are related to exposures to lead or their mothers' smoking while pregnant, a nationwide study suggests. The two environmental hazards might account for more than a quarter of drug-treated ADHD cases.
The finding bolsters earlier research that linked smoke exposure to ADHD and provides the best evidence yet that lead, a brain-damaging metal, might also contribute to the common behavioral disorder.
Published online on Sept. 19 for an upcoming Environmental Health Perspectives, the study analyzed data on 4,704 children who were 4 to 15 years old when they participated in a recent nationwide survey of health and nutrition.
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