Tighter lead limits needed, US study suggests
Date: 22-Apr-03
Country: USA
Author: Gene Emery
In a report published in the New England Journal of Medicine, the researchers said children with far less lead in their blood than allowed by current guidelines had impaired intelligence levels, and much of the damage seems to occur at very low levels of lead exposure.
"These findings suggest that more U.S. children may be adversely affected by environmental lead than previously estimated," the researchers, led by Richard Canfield of Cornell University in Ithaca, New York, wrote in their report.
"We also found that the amount of impairment attributed to lead was most pronounced at lower levels," a statement added.
The current recommended limit for lead exposure is 10 micrograms of lead per deciliter of blood.
But the Canfield team calculated that as blood levels increased from one to 10, a child's IQ fell by an average of 7.4 points, a far more precipitous decline than the researchers had seen with higher lead levels.
"It implies that there is no safety margin at existing exposures," Walter Rogan of the National Institute of Environmental Health Sciences and James Ware of the Harvard School of Public Health wrote in a commentary.
The team said the new findings "imply that the job may not be finished even when all children have blood lead concentrations below 10 micrograms per deciliter."
Most of children's' exposure to lead comes from deteriorating lead paint in older homes, and the Centers for Disease Control and Prevention in Atlanta say nearly half a million children in the United States have blood lead concentrations higher than 10 micrograms per deciliter.
As evidence has accumulated about the harmful effects of lead, the acceptable amount has decreased from 60 in the 1960s to 30 in the late 1970s, and 10 since the early 1990s.
After lead was banned from gasoline, average lead levels among U.S. children fell from 15 micrograms of lead per deciliter of blood in 1978 to 2 in 1999.
