"• George Monbiot's first thought - "it seemed preposterous" that lead could cause the rise and fall in violence - was worth holding on to. If lead did cause violence by affecting mental capacity, we have to presume its affect is over the life course of those afflicted. In fact, few people are persistently violent. Sampling delinquents for toxicity is all very well, but the correlation with violence is not so neat. The wide variance in the homicide rates between Russia, US, and Japan in 1998 is a good example. Even the Wilkinson and Pickett inequality argument, or Levitt's legalisation of abortion, have more logic. Historically violence has always been heavily overrepresented among socially disadvantaged groups. And there was more violence in the past - a Europe-wide drop of 10:1 to 50:1 from the 15th to the 20th century. The fact this pseudo-science has not received critical comment is probably because academics who study violence have held on to the belief that it is preposterous to reduce the complexity of violence to this simplistic causal mechanism.
Dr Andrew Wilson
Senior lecturer in criminology, Nottingham Trent University"
http://www.guardian.co.uk/environment/2013/jan/09/evidence-lead-poisoning-violence