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Study Links Cadmium Exposure to Learning Disabilities in Kids

Does Exposure to This Heavy Metal Cause Learning Delays?
WebMD Health News
Reviewed by Laura J. Martin, MD

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Jan. 27, 2012 -- Children with high levels of the heavy metal cadmium in their urine may be more likely to have learning disabilities and/or need special education, a new study shows.

Cadmium occurs naturally in some soils. Children are most likely to be exposed to it through food such as grains and root vegetables, as well as through tobacco smoke. Some children’s toys and jewelry have also been found to contain cadmium. 

Cadmium exposure can damage the kidney and lungs and has been linked to cancer. Studies on whether or not it affects learning and behavior among children have had mixed results.

In the new study of close to 2,200 children ages 6 to 15, those who had the highest levels of cadmium in their urine were more likely to have learning disabilities or need special education, compared to children with the lowest levels of this metal in their urine. The findings are based on parents' reports of their children's learning issues.

The new findings appear in Environmental Health Perspective.

But just because your child was exposed to cadmium does not mean he or she will develop a learning disability, says researcher Robert Wright, MD. He is a professor of pediatrics at Harvard Medical School in Boston. "It doesn’t mean that if they get exposed to cadmium, something terrible will happen, but there were more learning disabilities and special education seen in kids who were exposed to cadmium than those who weren’t," he says.

No Cadmium/ADHD Risk Seen

So what can concerned parents do to limit exposure to cadmium? This can be easier said than done, Wright says: “It is a little hard to figure out cadmium in food because it comes from soil, so it is based on where it is grown.”

It's easier to avoid tobacco smoke. 

As far as children’s toys, “there is no added value to having cadmium in children’s products, and this is evidence that is a dangerous practice. We need tighter regulations,” he says.

Cadmium levels were not linked to risk of attention deficit hyperactivity disorder (ADHD) in the new study.

“This suggests that cadmium seems to affect [mental] issues such as learning disabilities and the need for special education, but not behavior,” Wright says. ADHD is more of a behavioral disorder. It is marked by hyperactivity, trouble concentrating, and impulsivity.

More Study of Cadmium Risks Needed

Jerome Paulson, MD, says the new study adds to the evidence suggesting that cadmium may be dangerous to children. He is co-director of Mid-Atlantic Center for Children's Health and the Environment, and the medical director for national and global affairs of the Children’s Health Advocacy Institute at the Children’s National Medical Center in Washington, D.C.

“There are conflicting results in the literature as to whether or not cadmium exposure has a neurocognitive impact on children, and this relatively large study does seem to indicate an association,” he says. That said, the researchers relied on parents’ reports of the children’s issues, which may not be 100% accurate.

Helen Binns, MD, MPH, says parents can only control the controllables. Cadmium does not seem to be one of them right now. She is a professor of pediatrics and preventive medicine at Northwestern University Feinberg School of Medicine and director of the Lead Evaluation Clinic and the Nutrition Evaluation Clinic at Children’s Memorial Hospital in Chicago.

“We don’t yet know where the exposures are coming from,” she says. “We need more research related to what it is doing and where it is coming from.”

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