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'Acceptable' Lead Levels Linked to Lower IQ Scores in Kids

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April 30, 2001 -- Many efforts have been made to remove lead from the environment, but lead poisoning continues to be a problem in children. A disturbing new study presented today at the Pediatric Academic Societies' Annual Meeting suggests even "safe" levels of lead in the blood are dangerous enough to severely damage IQ scores in developing children.

Long recognized as a serious public health threat, lead can damage the brain and nervous system, and even a low level of lead exposure can cause learning disabilities, hearing loss, speech, language, and behavior problems, and other serious health effects in children. Lead has also been associated with dental caries.

Lead in paint and gasoline is banned in the U.S., but it persists in the environment in ubiquitous house dust and paint chips, particularly in poorer neighborhoods. Lead-based paints were commonly used in the 1950s and '60s. One group, the Alliance to End Childhood Lead Poisoning, estimates that 30 million U.S. homes built before 1960 still have lead in them.

Although universal lead screening is not available, it is recommended that children at high risk for lead exposure be screened. Blood lead concentrations of 10 micrograms per deciliter of blood or less are considered to be safe and acceptable levels.

But are these levels really safe?

Researchers looked at a cross-section of 276 children in Rochester, N.Y., over a five-year period. They measured the blood lead levels of the children seven times between birth and age 5 and conducted standard IQ tests to see if the children were performing at the appropriate level of development.

But what primary researcher Bruce Lanphear, MD, MPH, found was that even children with the "safe" level of lead in their blood, as defined by the Environmental Protection Agency and the CDC, had significant brain damage.

Specifically, at age 5, the children experienced a 5.5-point drop in IQ for every jump of 10 micrograms of lead per deciliter in their blood. What's worse, says Lanphear, is that the biggest drop in IQ occurred with 73% of the children who had the very lowest lead levels. The deficit was as high as 11 IQ points from normal.

"If there really is a 10-point drop in IQ with the initial 10 microgram per deciliter [of lead in the blood], that's huge," says Lanphear of Children's Hospital Medical Center in Cincinnati. And once the IQ points are lost, Lanphear says they never come back.

Daniel Coury, MD, professor of clinical pediatrics at Ohio State University, believes that Lanphear's findings will encourage public health officials to rethink the lead issue. "Technically, Dr. Lanphear's data say, no lead is good lead," Coury says.

Lanphear believes that poor neighborhoods endure a disproportionate share of lead toxicity.

"How much of that association of lead and IQ is really a factor of poverty?" asks Lanphear? "If there's a problem, fix it before a child moves in, using housing codes before a house is bought."

To keep children safe from lead poisoning, remember the following:

  • Keep areas where children play as dust-free and clean as possible.
  • Wash toys and stuffed animals regularly.
  • Make sure that children wash their hands before meals, naptime, and bedtime.
  • Try not to bring lead dust into the home. (If you work in construction, in demolition, in painting, with batteries, in a radiator repair shop, or in a lead factory, or if your hobbies involve lead, you may unknowingly bring lead into your home on your hands or clothes.)
  • If your home was built before 1950, ask your pediatrician to test your child for lead.
  • If your home was built before 1978, talk to your pediatrician or health department about safe ways to remodel before any work is done.
  • Clean and cover any chalking, flaking, or chipping paint with a new coat of paint, duct tape, or contact paper.
  • Repair areas where paint is dusting, chipping, or peeling before placing cribs, playpens, beds, or highchairs next to them.
  • Check with your pediatrician or health department to see if your area has a problem with lead in the water.

Even though small, Lanphear's study is consistent with larger population data, indicating that the existing lead standards need to be toughened. That is in spite of the fact that the EPA just toughened its latest recommendations for lead levels in blood in January. The new recommendations are 25 times as strict.

Lanphear views lead poisoning as a public health menace on par with tobacco and feels that the government needs to crack down on lead. In addition, Lanphear believes the lead industry needs to do more.

"Why wouldn't we demand that the lead industry association, and the pigment industry, and the petroleum industry pay for all the pollution and contamination in the environment to fix it up. It's a huge environmental justice issue," says Lanphear.

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