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Lead in children's blood samples could be tied to behavioral and emotional problems, a new study reported. According to the researchers, even low exposures of lead can be linked to these issues.

"This research focused on lower blood lead levels than most other studies and adds more evidence that there is no safe lead level," explained NIEHS (National Institute of Environmental Health Sciences) Health Scientist Administrator Kimberly Gray, Ph.D. "It is important to continue to study lead exposure in children around the world, and to fully understand short-term and long-term behavioral changes across developmental milestones. It is well-documented that lead exposure lowers the IQ of children."

For this study, the researchers took blood samples from more than 1,300 preschool aged children in China. The researchers measured the blood lead concentrations and calculated an average of 6.4 micrograms per deciliter. Previous studies had focused on higher levels of lead exposure at 10 micrograms per deciliter. The U.S. Centers for Disease Control and Prevention (CDC) considers levels above five micrograms per deciliter as above normal. The team also recorded the children's behavioral and emotional problems by assessing their levels of anxiety, depression and aggressiveness at the age of six. The children's problems were reported by teachers and parents.

The researchers found that even low lead levels were tied to an increase the behavioral and emotional problems. As the lead concentration levels increased, these problems did as well. The researchers stated that monitoring children's lead levels during doctor visits could be vital in assessing children's behaviors.

"Young children are particularly vulnerable to the toxic effects of lead, because lead can affect children's developing nerves and brains," said senior author Jianghong Liu, Ph.D., from the University of Pennsylvania School of Nursing, Philadelphia according to the press release. "The sources of lead exposure may explain why concentrations of lead are different. In China, we found that blood lead concentrations increased with age in preschool children. In the United States, however, blood lead concentrations increase with age in children up to 2-3 years old and then decline."

The study was published in the journal, JAMA Pediatrics.