60-Second Science

Even Low Lead Levels Lower IQ

Kids with lead levels within the high end of currently acceptable standards have lower IQ scores than kids with even lower levels. Cynthia Graber reports.

Toy companies and parents reacted quickly this year when some toys made in China were found to contain lead.  Because lead is known to affect kids’ cognitive development.  In 1991, the Centers for Disease Control set a federal standard of 10 micrograms of lead per deciliter of blood.  So the eight percent of US kids five and younger who have lead levels between 5 and 10 micrograms are considered safe.  But recent Cornell University research in the journal Environmental Health Perspectives supports a stricter standard.   

The research team had previously followed kids from birth through age five. The current study looked again at the children at age six.  The kids were divided into two groups: one with blood lead levels between 0 and 5, and the other with 5 to 10—again, currently considered okay. Turned out that those in the 5-10 group had IQ scores about five points lower than those with the lowest lead levels.  Scientists say this could affect educational performance later in life.  They recommend reconsidering federal standards for lead in consumer products and reevaluating the acceptable blood lead levels in children.

—Cynthia Graber 

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