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CHICAGO -- Lead exposure in childhood leads to permanent brain damage and life-long problems with attention and impulsivity control, researchers said here.

The higher a person's childhood blood lead levels, the more likely they were to have decreased activity in parts of their brain responsible for executive functioning, Kim M. Cecil, PhD, of Cincinnati Children's Hospital, and colleagues reported at the meeting of the Radiological Society of North America.

"Many people think that once lead blood levels decrease, the effects should be reversible," Cecil said. "But in fact, lead exposure has harmful and lasting effects."

Lead exposure has been widespread because of decades of airborne emissions from cars that ran on leaded gasoline and because lead paint was used on walls and woodwork in many houses built before 1970.

Previous research has shown that lead exposure in childhood is associated with diminished intelligence -- most commonly low IQ scores.

But less is known about lead's effect on other functional areas of the brain, including attention, impulse control, decision-making, abstract thinking, and motivation rewards.

So the researchers assessed participants from the Cincinnati Lead Study, which followed 376 infants born between 1979 and 1987 who lived in a region of Cincinnati historically known for dangerous lead levels.

They performed functional MRI on a selection of these patients. The continuous performance task (CPT) assessed attention in 33 patients, and the Go-No-Go test looked at impulsivity in 26 patients.

The study included 14 women and 19 men, whose mean age was 21. Their mean childhood blood lead level averaged 14.2 mcg/dL, and their mean group IQ score was low at 86.7.

The researchers found that on the attention task, higher blood lead levels were associated with decreased activity in parts of the brain associated with attention.

The same was true on the impulsivity task, Cecil said.

However, the brain attempted to "compensate" for deficiencies, she added, as unexpected brain areas lit up during executive functioning task performance.

She noted, however, that there were significant differences between men and women, as most of the findings were being driven by men.

"We are seeing this clinically in criminality studies," Cecil said. "Men are up to six times more likely to be involved in criminality than women."

She said this finding starts to build the case that there are different biological effects of lead exposure based on gender. One explanation may be that estrogen is neuroprotective, she added.