Vol. 12, No. 4, 2006 Page 7
High lead levels and prenatal exposure to tobacco markedly increase children's risk for attention deficit hyperactivity disorder (ADHD), according to a new study that confirms previous findings (see related articles, Crime Times, 1996, Vol. 2, No. 4, Page 3 and Crime Times, 2006, Vol. 12, No. 3, Page 3). ADHD, in turn, is a significant risk factor for academic and career problems, antisocial behavior, and substance abuse.
Joe Braun and colleagues analyzed data from more than 4,000 children participating in the National Health and Nutrition Examination Survey (NHANES) for 1999-2002. Of these children, 4.2% were diagnosed with ADHD and were taking stimulant medications. The researchers' analysis showed that "prenatal tobacco exposure and blood lead concentration were significant predictors of ADHD," while postnatal tobacco exposure had no detectable effect.
The researchers found that the effects of prenatal tobacco exposure were more pronounced for girls than for boys, with the risk doubling for males but more than quadrupling for females. While boys are normally at much higher risk for ADHD than girls, Braun et al. say, "When females are exposed to prenatal tobacco smoke, their risk of ADHD becomes equivalent to that of unexposed males."
The researchers also detected a significant dose-response relationship between blood lead levels and ADHD, even at low lead levels. They note, "This result is consistent with previous studies that have found cognitive deficits in children with blood lead levels below 10 micrograms per deciliter [the currently accepted safety threshold]."
Their data, the researchers say, "suggest that prenatal tobacco exposure accounts for 270,000 excess cases of ADHD and lead exposure accounts for 290,000 excess cases of ADHD in U.S. children."
"Exposures to environmental toxicants and attention deficit hyperactivity disorder in U.S. children," Joe Braun, Robert S. Kahn, Tanya Froehlich, Peggy Auinger, and Bruce P. Lanphear, Environmental Health Perspectives, online publication, September 19, 2006. Address: Bruce Lanphear, Mail Location 7035, 2800 Winslow Avenue, Cincinnati, OH 45206, bruce.lanphear@cchmc.org.