(04-30) 16:10 PDT BALTIMORE (AP) -- Children exposed to lead at
levels now considered safe scored substantially lower on
intelligence tests, according to researchers who suggest one in
every 30 children in the United States suffers harmful effects from
Children with a lead concentration of less than 10 micrograms per
deciliter of blood scored an average of 11.1 points lower on the
Stanford-Binet IQ test than the mean of children with a lead
concentration of 1 microgram or less, the researchers found. The
mean is the intermediate value between the lowest and highest
``There is no safe level of blood lead,'' said Dr. Bruce
Lanphear, lead author of the lead study presented Monday at the
Pediatric Academic Societies annual meeting.
Lanphear said newborns have lead in their blood because of its
presence in their mothers, but children are most commonly exposed to
lead by inhaling lead-paint dust or eating paint flakes. Lead-based
paint was widely used in homes throughout the 1950s and 1960s until
it was banned in 1978.
At high levels, lead can cause kidney damage, seizures, coma and
Before 1970, scientists believed lead poisoning took effect at 60
micrograms per deciliter. But the toxicity standard has been lowered
over the years to the point where a concentration of 10 micrograms
or less now is considered safe.
The researchers said their work suggests that lead is a potent
toxin at levels previously thought to be harmless.
Experts predicted the study would prompt federal regulators to
lower the acceptable blood-lead standard.
``This is a wonderful study that has very serious implications
for public health in the United States and the rest of the world,''
said Dr. Daniel Courey, a pediatrics and developmental behavior
professor at Columbus Children's Hospital in Columbus, Ohio.
Lanphear's team tracked 276 children in Rochester, N.Y., from
ages 6 months to 5 years, measuring blood lead levels every six
months and administering the IQ test at age 5.
The study also found an average 5.5-point decline in IQ for every
additional 10-microgram increase in blood-lead concentration, said
Lanphear, a physician at Children's Hospital Medical Center in
The study adjusted for other predictors of lowered IQ such as the
mother's IQ, tobacco exposure and intellectual environment in the
home, Lanphear said.
Lanphear's findings confirm what those who work with ``lead
kids'' already know, said Ruth Ann Norton, executive director of the
Baltimore-based Coalition to End Childhood Lead Poisoning.
``There are kids who are disruptive, then there are 'lead kids'
-- very disruptive, very low levels of concentration,'' Norton said.
Besides affecting reading and reasoning abilities, lead also is
linked to hearing loss, speech delay, balance difficulties and
violent tendencies, Norton said.
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