Ithaca, N.Y. -- Very small amounts of lead in children's blood -- well below federal standards -- are associated with reduced IQ scores, a six-year U.S. study found.

Senior author Richard Canfield, of Cornell University, in Ithaca, N.Y., compared children whose blood-lead levels were between 0 and 5 mcg/dl with children in the 5 to 10 mcg/dl range. The Centers for Disease Control and Prevention's standard is 10 micrograms per deciliter (mcg/dl) -- about 100 parts per billion.

The study, published in the journal Environmental Health Perspectives, found that even after taking into consideration family and environmental factors known to affect a child's cognitive performance, blood lead levels played a significant role in predicting nonverbal IQ scores.

"We found that the average IQ scores of children with blood-lead levels of only 5 to 10 mcg/dl were about 5 points lower than the IQ scores of children with blood-lead levels less than 5 mcg/dl," Canfield said in a statement.

"This indicates an adverse effect on children who have a blood-lead levels substantially below the CDC standard, suggesting the need for more stringent regulations -- our findings emphasize the very real dangers associated with low-level exposures, to which lead in toys can contribute."

© 2007 United Press International.