Did Unleaded Gas lead to the crime reductions of the 1990s?

A new study is claiming that the removal of lead from gasoline may have more to do with the crime reductions we saw in the 1990s than any other factor. The theory goes that even small amounts of lead in the bloodstream can cause brain damage in the parts of the brain dealing with aggresion and impulse-control. Thus, by removing it from the environment, it was (demonstrably) reduced in American bloodstreams. The children born since the end of leaded gasoline would have grown up and reached their most aggressive years in the 90s. The years when crime dropped, despite the coming of teenhood of a baby boom that greatly increased the teenaged population.

At first glance, I am almost tempted to view this as an attack on Rudy Giuliani's run for president, since much of his run is based on the crime reductions he accomplished as Mayor of New York. But reading deeper, it seems like a serious study. Especially when they show that States with slower declines were those States which took longer to phase out leaded gas. At the very least, it makes you wonder what else may be out there influencing our behavior.