It’s a heavy metal. It’s linked to learning problems in school children. And every child is exposed.
Sounds like lead?
Signs are emerging that cadmium – a widespread contaminant that gets little attention from health experts and regulators – could be the new lead.
Children with higher cadmium levels are three times more likely to have learning disabilities and participate in special education, according to a new study led by Harvard University researchers.
Absorbed from the soil, cadmium is found in certain foods, particularly potatoes, grains, sunflower seeds and leafy greens, as well as tobacco. It also has been discovered in some inexpensive children’s jewelry, prompting new voluntary industry standards last fall.
Dr. Robert Wright, the study’s senior author, emphasized that the links to learning disabilities and special education were found at commonplace levels previously thought to be benign.
“One of the important points of the study is that we didn’t study a population of kids who had very high exposures. We studied a population representative of the U.S. That we found any [effect] suggests this is occurring at relatively low levels,” said Wright, an associate professor of pediatrics and environmental health at Harvard.
Scientists said the new findings are a sign that cadmium could have dangerous properties similar to lead that alter the way children’s brains develop. More research is necessary, though, to confirm and refine the potential effects on kids.
“It does certainly point to the fact that we need more attention paid to the neurotoxic effects of cadmium in children," Wright said.
Until now, the nervous system has not received much attention as a target for cadmium. Some studies of adult workers, however, have shown that high exposures can trigger neurological problems, and small, earlier studies of children found links to mental retardation and decreased IQs.
The new study is the largest to look at connections between cadmium in urine and neurological effects, and the only one that has used a national group of children.
“Collectively, the studies are very consistent. They provide fairly substantial support that cadmium is a neurotoxin,” said Dr. Bruce Lanphear, a pediatrician and epidemiologist at Simon Fraser University who was a co-author of the study.
Lanphear, one of the world’s leading experts on the effects of lead in children, added that “the pattern we’re seeing here with cadmium is very consistent with what we see with other toxicants,” including lead and mercury.
The two scientists recommended that government re-examine its standards and guidelines for cadmium in food, soil, workplaces and consumer products to consider the effects on children’s brains.
Current regulations for cadmium are based on threats to adults, and the kidneys have been considered the most sensitive organ to its toxic effects. Classified as a known human carcinogen, it is linked to lung, kidney and prostate cancer in workers.
“We’ve got a large new national study showing a threefold increase [in children’s learning disabilities and special education]. But I wouldn’t go so far to say we definitely need to lower regulatory levels. It deserves to be re-evaluated, though,” said Lanphear.
Of the 2,199 children between the ages of 6 and 15 included in the new study, 12.6 percent had a learning disability and 10.5 percent were enrolled in special education classes, according to the study, published online in Environmental Health Perspectives last month. The children were not tested for disabilities; instead it was reported by their parents on a questionnaire that is part of the National Health and Nutrition Examination Study.