Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury.
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 the metal. 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.