Lead paint was only a problem for kids who ate paint chips.
An enviro writes at LiveScience:
But why is the murder rate falling?
There is a strong case to be a made that much of the decline is related to removing lead from the environment. As Nevin explains, there were two major spikes in the murder rate in the last century — first around the 1930s and later from the 1960s to 1970s. Shown on a timeline graph, those spikes appear as two big bumps, like a Bactrian camel. Significantly, the graph for lead exposure in our environment looks almost exactly the same, with a 21-year off-set. That is, peak lead exposure resulted in a spike in the murder rate 21 years later.