Lead Levels Linked to Lower IQ in Children

The harmful effects of lead poisoning on children are well-documented, but new research suggests that the danger is more widespread than ever imagined, and that exposure to levels currently deemed safe can lower children's IQ scores.

At age 2, Salissa Stallworth was already showing the effects of lead poisoning. In a lab study conducted at the University of Cincinnati college of medicine in 1995, the toddler was unable to respond to basic instructions that other girls her age were able to follow.

Experts say that Salissa was not born with developmental problems, nor were her problems genetic or the product of disease. Instead, she was poisoned right in her own home by lead. Eight years later, doctors say she is still suffering the effects of lead poisoning.

‘Safe’ Levels Now Deemed Dangerous

"She has ADHD (attention deficit hyperactivity disorder), she has behavioral problems, she has emotional problems, she has phobias," Latecia Stallworth, Salissa's mother said. "They told me that there could be long-term side effects to her having lead poisoning, and so far it has been true."

Lead-based paint chips and lead-contaminated dust found in deteriorating buildings are the culprits in lead poisoning for most American children. Lead-based paints have been banned from use in housing since 1978, but about 24 million housing units still have deteriorated lead paint, and elevated levels of lead-contaminated house dust, according to the Centers for Disease Control.

The CDC estimates that 1 million children in the United States suffer from dangerous levels of lead in their system. But new research indicates that the amount of lead that can lead to developmental problems is far lower than CDC-imposed legal "safe" limits. That means the number of affected children might jump dramatically from 1 million to 15 million children.

As a result, several U.S. senators are asking the CDC to lower their scale of what is a dangerous level of lead in kids' blood.

Three Disturbing Studies

A study recently published in the New England Journal of Medicine looked at the blood lead levels of 172 children in Rochester, N.Y., ranging in age from six months to 5 years.

Researchers tested the children's IQ at ages 3 and 5, and found that those whose blood levels of lead increase from one microgram per deciliter to 10 (the limit under CDC's safety guidelines) experienced an IQ drop of 7.4 points.

Children whose blood levels rose from 10 to 30 micrograms per deciliter lost an additional two to three IQ points. But the key point in the research is that even at levels below the limit deemed safe by the CDC, children were losing IQ points.

A separate study in the journal from the Environmental Protection Agency found that low levels of lead delay puberty for several months in young girls, especially African-Americans and Latinas. The concern is that the lead is interfering with hormonal processes during development.

In addition, a University of Pittsburgh study found that juvenile offenders had a much higher concentration of lead in their bones compared to their counterparts who were not in trouble with the law.

Damaging Effects on Young Children

"Lead impairs or destroys normal functions of brain tissue, of nerve cells, of the developing brain," said Dr. John Rosen, of The Children's Hospital at Montefiore in Bronx, N.Y. "And the developing brain in young children is extremely susceptible."

Although lead paint is typically found in older dwellings, often occupied by low-income families, Rosen said that lead, not money or poverty, is the key cause of the developmental problems.

"This is about lead paint," Rosen said. "This is about lead's toxic, damaging effect on the growth of the brain of young children."

Based on the new research, Rosen said that the CDC should reclassify what would make a child have a dangerous level of lead in their blood.

"I think from a public health standpoint, it's essential and mandatory for the CDC to lower the definition of childhood lead poisoning," Rosen said.

While lead is often found in paint, children don't need to eat paint chips to get infected. Just handling dust or residue may be enough. Unfortunately, children are all too often the first line of detection.

"Most cities use children as lead detectors," said Don Ryan, of the Alliance to End Childhood Lead Poisoning. "Rather than identifying hazards in the first place, they wait until a child has been poisoned and then after the fact go to look for the hazard."

It is too late, at that point, Rosen said.

"The biggest tragedy to me having supervised now the treatment of over 25,000 lead poisoned children is the fact that the child's life is gone," Rosen said. "It is wrecked forever as early as one or two years of age and there's no recovery."

Salissa's mother knows that all too well.

"Every parent wants their child to go to college, get a career, be happy, you know," Stallworth said. "I think she's going to have some problems with that. I hope and pray that no other parent really has to go through what I'm going through."

ABCNEWS' Chris Cuomo reported this story on Good Morning America.