ronan ciosoig moraighmaccom ban leaded petrol cut crime rates around world geoffrey lean environment editor published 28 october 2007 banning lead petrol responsible declining crime rates britain united states countries startling new research suggests astonishing conclusion threatens overturn current thinking crime punishment could undermine reputations leading politicians including rudy giuliani frontrunning republican presidential candidate basing much appeal reduction crime new york city 1990s served mayor published peerreviewed journal environmental research study reports strong association 50 years exposure young children toxic metal crime rates 20 years later young adults says association holds true wide variety countries differing social conditions law order policies rates violent crimes began falling sharply us early 1990s continued followed similar tends elsewhere reducing crime proved foundation careers many politicians embraced tough law order policies none mr giuliani long ago boasted reduced homicides 67 per cent reduced overall crime 57 per cent yet evidence growing banning lead take much credit reducing crime rates toxic metal long known damage brains lead criminal aggressive behaviour research pittsburgh university found adolescents arrested crime city lead levels four times higher law abiding contemporaries study 3000 possible causes criminality 1000 young people fordham university new york found high lead levels best predictor delinquent violent behaviour metal first added petrol 1920s boost engine power use grew rapidly levels blood rose parallelit phased first us starting 1974 followed countries britain one last get rid toxic metal one latest enjoy decline crime thu 07 aug 2008 065326 0100 ierant lead head makes criminal