The subsequent evidence is so strong that I don't think it's appropriate to call it faulty. In the paper "Life After Lead" they study a boundary effect of children who were just above and just below treatment thresholds for blood lead levels and the outcomes in terms of crime, school success, etc are stark. Figure 4(F) particularly.
https://www.aeaweb.org/articles?id=10.1257/app.20160056