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When it comes to safe levels of lead, how low is low enough? An important question raised by two separate studies in the New England Journal of Medicine.
Over the past 30 years the CDC has repeatedly lowered the safe limit.
Today it stands at 10-- 10 micrograms per deciliter of blood. Higher levels have been linked to behavioral problems and lower i.q. scores.
Now researchers from Cornell University have found that even at these lower levels, lead still is cause for concern.
They studied 172 children, tracking lead levels and i.q.'s from six months of age to five years. They found lead concentration, even levels below ten, had a negative impact on i.q. results, that suggests even more children may be affected by lead.
In a second study, researchers found that lead levels even just slightly higher could delay puberty.
They surveyed more than 2,000 girls between the ages of 8 and 18 and found that compared to girls with a lead concentration of one, those with a level of three had delays of 2-6 months in the time they reached certain stages of development.
This was true for African-Americans as well as Mexican-Americans, regardless of body weight or other factors that influence puberty in girls.
While a small delay in puberty may not have a big impact on health, it highlights the possibility that lead may affect other hormones.
The effects of lead appear to be long-lasting, and experts say prevention is the best strategy.
Removing lead from gasoline helped dramatically but lead exposure continues, mostly from deteriorating paint in older homes.
Children under six are most at risk because they're growing so fast and they tend to put things in their mouths.
If you live in a house or apartment built before 1978 and have young children, you can have your paint and dust checked for lead. And if you think your child is at risk, ask your doctor to run a blood test.