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May 27 (Bloomberg) — This is Rob Waters’s article:
Young children exposed to high levels of lead 25 years ago were more likely as adults to have smaller- than-normal brain structures that regulate impulses and to commit violent crimes, studies found.
Lead is known to damage the developing brains of children, robbing them of IQ points and causing mental retardation in severe cases. In the U.S., lead was banned from house paint in 1978 and phased out of gasoline by 1996. Yet the toxic metal lingers on the walls in millions of dwellings built before the 1950s, especially in poor communities like those in Cincinnati where these studies were conducted.
The findings, released today in two papers in the journal PLOS Medicine, came from a study of children exposed to lead at least 25 years ago. The research documents the long-term behavioral damage from lead and, for the first time, the effects on key brain structures, said Kim Dietrich, professor of environmental health at the University of Cincinnati, and a co- author of both studies.
The results “provide a clear warning sign that early lead exposure disrupts brain development in ways that are likely to be permanent,” said David Bellinger, a neurology professor at Harvard Medical School, in an editorial that accompanied the two studies. He was not involved in the research.
Dietrich and his colleagues began the research by recruiting pregnant women in inner-city Cincinnati from 1979- 1984. The researchers measured the lead in the blood of the women during pregnancy and of their children throughout their youth.
Most of the families lived in rental housing or public housing projects where lead paint often flaked off the walls, joining the dust on the floor. The babies would put it in their mouths as part of “normal hand-to-mouth behavior we see in all kids between 6 months and 2 years of age,” Dietrich said in a telephone interview today.
Two decades later, Dietrich tracked the arrest records of 250 of the participants, by then ages 19 to 24, and found that the more lead they had in their blood as children, the greater the likelihood they were arrested as adults. That was especially true of arrests for violent offenses such as assault, rape and domestic violence.
Scientists have changed their views about what level of lead in a child’s bloodstream constitutes a threat. When Dietrich began his study, the threshold for danger was 30 micrograms of lead per deciliter of blood, he said. In 1991, the U.S. Centers for Disease Control slashed that number by two- thirds and set 10 micrograms of lead as the hazard level.
Blood Lead Levels
In Dietrich’s group, the average blood lead level of all the children in their early years was 13.4 micrograms. For each additional 5 micrograms of lead in their blood during their first six years of life, the chance that they would commit a violent crime after they turned 18 rose by 48 percent, the research found.
In the second study, collaborating researchers at Cincinnati Children’s Hospital used MRI imaging devices to map and measure the brains of 157 of the people who had been part of Dietrich’s project. The scientists focused on regions of the frontal lobe and cerebral cortex known to be involved in executive function, impulse control and regulation of hostility and aggression.
Though their technique was capable of detecting whether these areas were larger or smaller than expected, the scanning found only brain loss, said Kim Cecil, an imaging specialist at the hospital.
“It was all loss, no region became larger,” Cecil said in a telephone interview today. “The higher their blood lead levels when they were children, the greater their brain loss” as adults.
When lead gets into the bloodstream and reaches the brain, it takes the place of calcium inside cells, Cecil said. It may trigger a loss of brain volume by accelerating a normal process of planned cell death, she said.
“We don’t know if the damage occurred all at once during a critical time period or from many years of exposure,” she said.
The research also showed that males were far more likely than females to lose brain mass, Cecil said.
One possible explanation, she said, is that estrogen “offers some protection against cell destruction from lead.”
While the banning of lead from paint and gasoline and efforts by public health officials to safely remove lead paint from older buildings have lowered the number of children with elevated lead levels in their blood, there is still much work to be done, Dietrich said.
Today’s studies “are a warning from the past of things we need to avoid in the future,” Dietrich said. The threat “hasn’t gone away. We’ve learned that lead’s toxicities are expressed in a variety of ways and at lower levels of exposure than we ever would have imagined 10 years ago.”
source: this is Rob Waters’s article on May 27, 2008 at www.bloomberg.com
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