Blood lead levels in normal and mentally deficiency children.

Abstract

A series of prepubertal children were investigated for evidence of exposure to Pb. Comprising the series were 20 children of normal intelligence (Group A), 20 with mental deficiency of known etiology (Group B), and 20 who were mentally deficient from unknown etiology (Group C). Nine of these children, 3 in Group A and 6 in Group C, had levels greater than 40 [mu]g/100 g blood. In these the urinary Pb excretion was normal but was increased significantly after an oral dose of 300 mg penicillamine. This test (the penicillamine-Pb excretion test) and the blood Pb levels are the most helpful procedures in the diagnosis of Pb exposure in childhood. The presence of a raised erythrocyte protoporphyrin level was suggestive of Pb, but in contrast to adult Pb poisoning urinary coproporphyrin and [delta]-amino levulic acid estimations were of no value in the detection of this state. All of the 9 children with raised blood Pb levels had a history of pica and with 1 exception lived in old houses. Furthermore, there were no children with raised blood Pb levels in Group B which contained children with organic brain damage some of whom were severely immobilized and consequently were more closely supervised than those in the other 2 groups. This emphasizes the importance of pica and of access to environmental Pb in the development ot Pb intoxication. There is evidence that Pb inhibits an important haem enzyme in the brain (ALA dehydrase) and that acute Pb intoxication leads in some cases to mental deficiency or aggravates a pre-existent mentally deficient state. The growing brain of young animals is more susceptible to damage by Pb than that of adult animals. These consideration are: weight to the suggestion that Pb poisoning may be a factor in the development of some cases of mental deficiency.