Mental retardation and "nontoxic" lead levels

Abstract

The blood Pb concentrations of children with IQ of 55-84, divided according to the presence (n = 48) or absence (n = 35) of a probable etiology for their retardation, and of 40 control children were studied. The mean Pb level of the retarded children with unknown etiologies was 25.03 .mu.g/dl, which was significantly higher than those of the other 2 groups; 54% of the group with unknown etiologies had levels > 25 .mu.g/dl, compared with 15% of the retarded children with probable etiologies and 17% of the control children. In the group of retarded children with unknown etiologies there was a significant negative correlation between Pb levels and IQ.