VOA标准英语2009年-Lead Poisoning Study Shows Damage Grea

Brain scans of men and women exposed to lead during childhood shows residual 1 damage less severe in females

Rose Hoban | Washington, DC 18 December 2009

Ever since the ancient Roman era, people have known that lead, a heavy metal long used in paints, ceramics 2 and construction, is very bad for you.  Acute lead exposure, particularly in children, leads to neurological and behavioral problems. Nonetheless, young people continue to be exposed to lead, and new research shows the serious long-term effects of this childhood lead exposure.

In the past, many common household items contained lead, everything from water pipes, to drinking vessels 3, to eating utensils 4. Most people had lead in their blood, but it was believed that some amount of lead was acceptable. Over the past few decades, however, scientists have determined 5 that even trace amounts of lead in children's bodies leads to long-term neurological and behavioral problems.

Study followed toddlers into adulthood 6

Kim Cecil, from the University of Cincinnati is one of those scientists.  She was part of a team of researchers who took annual blood samples from several hundred lead-exposed children for more than 20 years. The children lived in a Cincinnati neighborhood located near a busy highway.

"The neighborhood that [these kids] were recruited from is adjacent to an interstate.  So their playgrounds are contaminated, outside the homes," Cecil says.  Inside the older rental 7 housing where many live, she adds, "the lead would chip off and eventually become dust that settles on the floors in the windowsills.  And then as they become toddlers as they started crawling around, they get that lead dust on their hands from the windowsills in the floors, they put it in their mouth."

Lead poisoning damages thinking and concentration

Now these toddlers are young adults in their 20s, and Cecil and her colleagues brought them into the hospital for brain scans.  While they were in the brain-scanning machine, they were asked to do tasks that required concentration and attention. The researchers were able to see which parts of their brains were most active.

"When we plotted the circuits in the brain against their childhood lead blood lead levels, we found that those with a higher blood lead measurement had less activity in the part of the brain normally left to do the attention tasks," Cecil notes.

These problems existed years after the lead exposure, long after their blood lead levels had decreased.

   

Hormones 8 may shield women from some damage

What Cecil found most interesting was that there were differences in the brains of the males and the females exposed to lead as children.  The male brains, especially nerve cell rich parts of the brain associated with thinking and remembering, seemed to have sustained more long term damage from high lead levels than the brains of the young women.

"We see that men have greater volume loss, the men have greater changes in their white matter," she says.

Cecil also saw that the brains of the young women did a better job of compensating 9 for the damage.  She says this will be her next line of inquiry 10 – whether female hormones, such as estrogen, somehow protect young women from the neurological damage created by exposure to lead.

Cecil presented her findings at the annual meeting of the Radiological Society of North America.