Exposure to very small amounts of lead before birth retards a child's mental and physical development during the first two years of life, and perhaps longer, researchers reported April 23 in the NEW ENGLAND JOURNAL OF MEDICINE. Even exposure to amounts of lead considered safe for children caused lower scores on tests of problem-solving, perception, memory, learning and coordination.
The Boston researchers studied 249 infants over a two-year period, dividing them into three groups according to their exposure to the metallic poison, lead. Lead exposure was judged from blood samples taken from umbilical cords at birth. The lowest group had less than 3 micrograms of lead per deciliter of blood (ug/dl); the next group had 3 to 10 ug/dl; and the high exposure group had 10 to 25 ug/dl. Twenty-five ug/dl is the threshold above which lead is considered unacceptably high in a child, according to criteria set by the federal Centers for Disease Control in Atlanta, GA.
Children in the low-lead exposure group consistently performed better on a series of tests aimed at measuring their overall mental and physical development, compared to the high lead exposure group.
All 249 of the children came from socially advantaged families. Thus, researchers wonder if their results don't underestimate the problem because, in an impoverished environment, the effects of lead might be amplified by factors such as poor nutrition.
The researchers point out that other studies of umbilical cord blood reveal that about 25% of all urban
newborns have more than 10 ug/dl lead in their blood.
--Peter Montague, Ph.D.
Descriptor terms: developmental disorders; lead; children; new england journal of medicine; studies; cns; central nervous system; statistics;