 Blood
Lead Levels Below "Acceptable" Value Linked With IQ Deficits, According To New
Study
Bruce Lanphear, MD, MPH
Children's Hospital Medical Center , Cincinnati
Contact: Jim Feuer, ph
0011
513-636-4420
Lead is toxic at concentrations in the blood that were previously thought
to be harmless, accord-ing to a new study by a physician at Children's Hospital Medical
Center of Cincinnati.
The study, to be presented at 1 p.m. April 30 at the Pediatric Academic Societies
annual meeting, shows that IQ declines as blood lead rises in children who have a blood
lead concentration lower than 10 micrograms per deciliter, the level currently considered
acceptable. The lowest blood lead concentration associated with adverse effects has not
yet been defined.
"This indicates that millions more children in the United States than previously
thought endure the detrimental effects of lead exposure," says Bruce Lanphear, M.D.,
M.P.H., a physician in Cincinnati Children's division of General and Community Pediatrics
and the study's main author.
Dr. Lanphear and his research colleagues studied 276 6-month-old children born in five
hospitals in Rochester, NY. They measured blood lead at 6, 12, 18, 24, 26, 48 and 60
months of age. A standard IQ test (Stanford-Binet IV) was administered when the children
reached 60 months. The researchers found an inverse relation of blood lead concentrations
and IQ.
"Not only is there an adverse affect below currently acceptable levels, but the
decline in IQ for each microgram per deciliter increase in blood lead is greater at lower
levels," says Dr. Lanphear. "Among all children studied, there was on average a
5.5 point reduction in IQ for every 10 micrograms per deciliter increase in blood lead.
But for children who had blood lead less than 10 micrograms per deciliter, there was an
11.1 point reduction in IQ for the initial 10 microgram per deciliter increase in blood
lead."
Before 1970, lead poisoning was defined by a blood lead greater than 60 micrograms per
deciliter. Since then, levels considered acceptable declined several times, before
reaching the current 10 micrograms per deciliter standard. Under this definition of lead
toxicity, one in every 30 children in the United States is adversely affected by lead
exposure, including lowered intelligence, behavioral problems and diminished school
performance.
"Despite the dramatic decline over the last two decades in the prevalence of
children who have blood lead concentrations above 10 micrograms per deciliter, these data
underscore the increasing importance of prevention as the consequences of lower blood lead
concentrations are recognized," says Dr. Lanphear. "The results of our study
argue for a reduction in blood lead levels considered acceptable to half of what they are
now, or even lower. They also argue for a policy shift toward primary prevention - the
elimination of residential lead hazards before children are unduly exposed."
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