Developmental psychologist Gina Muckle of Laval University in Quebec says mercury and lead exposures have a stronger effect on Attention Deficit Hyperactivity Disorder (ADHD) symptoms than do mothers who smoked during pregnancy.
In fact, children exposed to higher levels of mercury or lead are three to five times more likely to be identified by their teachers with ADHD-associated problems than are other children.
A recently published study surveyed teachers of 279 Inuit children, ages 8-14, in Nunavik, Arctic Quebec. Muckle, senior author of the study, says the findings are significant because they show for the first time that mercury’s effects on children aren’t subtle; they’re noticeable in the classroom.
Though the study examined Arctic children, the results are likely universal. “At similar levels of exposure without regard of the source of exposure, the effect should be similar,” Muckle said. Down in the “lower 48s,” the US Centers for Disease Control and Prevention report one out of every ten children in the US has been diagnosed with ADHD.
Beluga whale meat and fish consumed by Inuit mothers were the sources of their children’s exposure to mercury. Lead exposure came from food the children ate that contained lead shot from hunting.
Further analysis revealed that mercury was linked to attention deficits and lead associated with hyperactivity. The explanation for the difference may be because of the timing of exposures: in the womb for mercury and during childhood for lead.
Harvard School of Public Health epidemiologist Joe Braun said the findings “suggest the brain may be sensitive to different environmental chemicals at different times in development.”
US children are more likely to be exposed to lead from contaminated soil and lead paint and exposed to mercury from contaminants belched from smoke stacks.
In a Public Radio International interview on Living on Earth, host Steve Curwood asked Muckle what the primary sources of lead and mercury throughout North America were. Muckle said, “Mercury travels between countries through air currents—it’s reached the Arctic as well, and mercury emissions are the primary source of human exposure.
“Mercury emissions are primarily due to coal combustion for production of electricity in Canada. It’s probably about the same as it was in the United States. China was identified as the largest source of mercury deposition. They are responsible for about 45 percent of the entire mercury deposition in Canada.”
Sources: ScientificAmerican.com September 20, 2012 Environmental Health News September 21, 2012 Transcript of Living on Earth broadcast, September 22, 2012 Study published in Environmental Health Perspective, September 2012