Lead left in paint, water, soil and elsewhere may not only be affecting children’s intelligence but may cause a significant proportion of violent crime, a U.S. researcher argued Friday.

He said the U.S. government needs to do more to lower lead levels in the environment and parents need to think more about where their children may be getting exposed to lead.

“When environmental lead finds its way into the developing brain, it disturbs neural mechanisms responsible for regulation of impulse.

That can lead to antisocial and criminal behavior,” said Dr. Herbert Needleman, a professor of psychiatry and pediatrics at the University of Pittsburgh School of Medicine.

Needleman’s team, using a technique called X-ray fluorescence, found very low levels of lead in the bones of children.

Needleman cited several studies that associate crime with high levels of lead either in the bodies of those accused or in the environments they came from, including one that showed the average bone lead levels of 190 juvenile delinquents were higher than those of adolescents not charged with crimes.

His study suggested that between 18 percent and 38 percent of delinquent crimes in the Pittsburgh area could be attributed to lead toxicity in the adolescents.

Another one tested 300 delinquents and found those with higher lead levels reported more aggressive feelings or behavior disorders.

“The brain, particularly the frontal lobes, are important in the regulation of behavior,” Needleman told a meeting of the American Association for the Advancement of Science.

“Exposure to lead, at doses below those which bring children to medical attention, is associated with increased aggression, disturbed attention and delinquency. A meaningful strategy to reduce crime is to eliminate lead from the environment of children.”

Taking lead out of most gasoline has contributed to a sharp reduction in the level of lead in the blood of Americans over the past 30 years.

But lead is still found in paint, some types of fuel for older vehicles, older water pipes and in the soil.