Study Says Kids In Danger Even At Low Levels of LeadAug 12, 2003 | San Jose Mercury News
Such has repeatedly been the case with children's exposure to lead, a substance known since 1923 to damage the brain.
Years ago, doctors worried only about what is called frank lead poisoning -- blood levels of 60 micrograms or higher. Since 1943, it has been known that the brains of children exposed to these high levels never recover from the damage.
Then, more careful studies of children living in lead-contaminated environments showed that blood levels from 40 to 60 micrograms also took a significant toll on the developing brain, lowering IQ scores and causing language and attention problems, as well as behavior disturbances.
Repeatedly over 30 years, follow-up studies of lead-exposed children have demonstrated IQ reductions and other memory and learning disturbances associated with successively lower blood lead levels.
Those findings prompted long-delayed federal action, bans on lead-based paint, lead in gasoline and lead solder used to seal food cans.
Later findings also led to a reduction in the ``level of concern'' for blood lead levels in infants and young children, the point where efforts should be made to identify the source and reduce exposure. That level today, set by the Centers for Disease Control and Prevention, is 10 micrograms a deciliter.
If a child tests below that, parents are told that there is no cause for concern.
Now, however, findings published in April in the New England Journal of Medicine strongly suggest not only that any amount of lead is harmful to a child's brain but also that greater damage seems to occur at levels below 10 micrograms than above that.
In other words, there is no threshold for lead's effects on the brain, and just small amounts seem to have relatively large effects.
If a blood level of, say, 15 micrograms can shave two points off a child's IQ, then a level of five micrograms might reduce IQ by five points or more.
The new study, headed by Dr. Richard L. Canfield, a developmental psychologist in the division of nutritional sciences at Cornell University, followed 172 children from relatively poor families in Rochester, N.Y., whose blood lead levels were repeatedly measured from age 6 months to 5 years.
In 101 children, blood levels never exceeded 10 micrograms.
Although levels from 10 to 20 micrograms were associated with a two-point IQ loss, a lifetime average level below 10 micrograms was linked to a decline of 7 IQ points.
So what do a few lost IQ points mean? Well, they could make the difference between average and below average intelligence requiring remedial education or it could mean a potential genius is just very bright. This could mean that more than 90 percent of American children, all with lead levels below 10 micrograms, are being harmed by lead.
Furthermore, these effects are permanent.
Perhaps more important from a societal view are the links between lead exposure in childhood and later delinquent and criminal behavior. In a study of 300 students in the Pittsburgh region, teenage boys with elevated lead levels were more likely to have committed anti-social acts like bullying, vandalism, arson and shoplifting.
While sources of lead encountered by American children have declined greatly, they have not been eliminated. One-quarter of American homes with children younger than 6 contain lead-based paint. Children can be exposed to lead-containing dust when windows are opened and closed, when old paint on walls, ceilings, radiators or floors chips or is sanded or scraped off, or when old bathroom tiles are demolished.
Renovations of older houses, especially by do-it-yourselfers, can leave lead-contaminated residues in the air and on surfaces handled by babies and toddlers. The best way to contain lead-painted surfaces is to seal them with several fresh coats of non-leaded paint or have a certified lead-abatement service remove the old paint.
In addition, Canfield said, parents should be sure that babies and toddlers are periodically tested for lead and not be satisfied with an ``OK'' result. Find out the number.
If his own children had a reading of five or more micrograms, Canfield said, he would want to find the source of their exposure and eliminate it.