1) Maybe lead in the ground has the same general level of danger as lead paint? Other sources of lead were covered in the article.
2) It is possible (probable even) that the levels of lead have been retarding the growth of IQ, but not reversing it.
3) Ignoring that even your link mentions that the data is skewed due to higher survivability as medical technology has gotten better, this is a separate trend on a separate scale and not really all that relevant. It could possibly be explained by lead from other sources (plumbing maybe?) or other factors outside of the scope of this particular study. If anything, your link reinforces that there was an issue as the homicide rates climbed sharply before suddenly dropping off again.
1) Maybe lead in the ground has the same general level of danger as lead paint? Other sources of lead were covered in the article.
2) It is possible (probable even) that the levels of lead have been retarding the growth of IQ, but not reversing it.
3) Ignoring that even your link mentions that the data is skewed due to higher survivability as medical technology has gotten better, this is a separate trend on a separate scale and not really all that relevant. It could possibly be explained by lead from other sources (plumbing maybe?) or other factors outside of the scope of this particular study. If anything, your link reinforces that there was an issue as the homicide rates climbed sharply before suddenly dropping off again.