When I was in school in Greensboro, we were told that certain segments of the population (re poor) were behind in academics because they ate lead paint. If it hadn't been for the lead paint, they would be as smart as everyone else.
It may not be in lead paint at all. It may be a preservative used in inoculations. There is a theory that lead may contribute to autism. Any statistics from the testing of lead in children may prove or disprove that theory.