By Michelle Roberts
BBC News health reporter, in Washington DC
Lead pollution may be turning children into criminals, US experts fear.
Exposure to lead at low doses can cause aggression, it is claimed
Exposure even at low doses can cause aggression and behavioural problems in children, the scientist who first linked lead to lower IQ believes.
Dr Herbert Needleman, of Pittsburgh University, found youths arrested for delinquency had higher levels of lead in their bones than others.
Other psychosocial factors are likely to be important, but cutting lead could cut crime, he told a US conference.
Routinely checking lead levels in every child when they are aged one and two would also help, he told the annual meeting of the American Association for the Advancement of Science (AAAS).
"It's not expensive and you could pick up the ones who might develop problems early on before they appear," he said.
Those children found to have high lead levels could be given extra support at school, for example, as well as removing them from the source of the exposure, he said.
Lead is known to be toxic to the brain and governments around the world have taken steps to reduce environmental lead with measures such as unleaded petrol and by removing lead from paint.
But Dr Needleman claims growing evidence suggests even very low-level exposure is still doing harm.
"Lead is a poison," Dr Needleman said. "It affects the prefrontal lobes of the brain, which are important in the regulation of behaviour.
"We know that criminals have disturbances in the prefrontal lobes too, so the chain of evidence is pretty strong."
His research looking at lead levels and delinquency, published in the journal Neurotoxicology and Terotology in 2003, found teenagers arrested for crimes had readings four times higher than teenagers who did not have a criminal record.
However, Larry Silverman, an environmental attorney in the US, told the conference: "Even if you say it's down to lead... you are not doing them a favour. People are looking for personal responsibility."