Exposure to lead levels considered safe by the Centers for Disease Control and Prevention (CDC) may actually impair a child's intellectual abilities, according to a new report on the toxic substance. As part of the study, researchers from Cornell University followed 172 infants, testing their blood for lead starting at 6 months old. The group then gave the children intelligence tests at age 3 and 5. Children with lead concentrations of 10 micrograms per deciliter of blood scored seven points lower on IQ tests than those who had one microgram of lead per deciliter of blood. The study is one of the first to reveal the possible dangers that 10 micrograms of lead may have on an infant.

The CDC insists children with blood lead levels under 10 micrograms are not at risk of suffering intellectual damage and say only at 15 micrograms should health officials conduct an investigation into how the child is being exposed to lead. A spokesperson for the CDC said the agency plans to review the possible health risks of low-level lead exposure this fall.