The first study to follow lead-exposed children from before birth into adulthood has shown that even relatively low levels of lead permanently damage the brain and are linked to higher numbers of arrests, particularly for violent crime.

Previous studies linking lead to such problems have used indirect measures of lead and criminality, and critics have argued that socioeconomic and other factors may be responsible for the observed effects.

But by measuring blood levels of lead before birth and during the first seven years of life, then correlating the levels with arrest records and brain size, Cincinnati researchers have produced the strongest evidence yet that lead plays a major role in crime.

The team also found that lead exposure is a continuing problem despite the efforts to minimize exposure.

The average lead levels in the study "unfortunately are still seen in many thousands of children throughout the United States," said Dr. Philip Landrigan, director of the Children's Environmental Health Center at the Mount Sinai School of Medicine in New York.

The link between criminal behavior and lead exposure was found among even the least-contaminated children in the study, who were exposed to amounts of lead similar to what the average U.S. child is exposed to today, said Landrigan, who was not involved in the study published in the online journal PLoS Medicine.

Nationwide, about 310,000 children from age 1 to 5 have blood


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lead levels above the federal guideline of 10 micrograms per deciliter.

About 80 percent of lead exposure comes from houses built before 1978. Paint in such houses often contains as much as 50 percent lead and, even though it has been covered by newer, lead-free paints, it still flakes or rubs off.