The Washington Post on Sunday had this article by Shankar Vedantam on a claimed link between lead exposure of children and crime rates years later when the children grow up. One red flag that immediately goes up is Vedantam's determined effort to spin the story into an anti-Giuliani piece. Another is that is seems unlikely that a factor such as this could explain a sharp drop in crime in a short period. If a cohort of children is exposed to sharply less lead than the cohort before, both cohorts are in the population for a long time, and if one is less crime-prone than the other, the drop would be gradual.

Steven Levitt has this skeptical post at Freakonomics Blog.