The evidence linking lead and tobacco exposure to developmental problems in children has been mounting for decades, and a new study has added another: a stronger link between these toxins and ADHD.
Prenatal exposure to either cigarettes or high lead levels more than doubles a child’s chances of developing ADHD, according to the study, led by researchers at the University of Cincinnati and published Monday in Pediatrics.
The cumulative effect is more devastating: Unborn babies exposed to both lead and tobacco were eight times more likely to develop ADHD, which affects between 2 and 5 percent of kids and is marked by restlessness, inability to focus and impulsive behavior.
“Neither of those are new ideas, and saying that lead and smoking aren’t good for developing kids probably won’t shock anybody,” says Dr. Karin Vander Ploeg Booth, a developmental and behavioral pediatrician at the University of Chicago Medical Center. “But this study confirms in a much stronger way that [ADHD] is about more than just genes.”
The majority of ADHD cases have long been thought to be largely inherited. Otherstudies have found that a person with ADHD has a 20 to 30 percent chance of having a child, sibling or parent with the disease.
But studies like this one strengthen the role of environmental factors, which Dr. Mark Stein, a University of Illinois at Chicago psychiatrist, says is good news for prevention.
“There’s a huge cost to ADHD, not just in treatment but in terms of the stress it puts on families and lost educational opportunities and social opportunities,” says Stein, who heads the ADHD clinic at the University of Illinois at Chicago. “If we can reduce that 10 to 20 percent by just modifying environmental factors, that’s encouraging.”
Though anti-smoking campaigns and lead abatement programs have cut risk in recent decades, they haven’t eliminated it. More than 16 percent of women admitted to smoking while pregnant in a 2008 federal study, a number that has declined only slightly in the past decade.
Lead poisoning continues to be a problem in cities, especially in low-income communities or those with older housing. (Lead-based paint was banned in 1977.) Gov. Pat Quinn in July signed a $5 million grant program to help homeowners reduce lead paint.