Blood lead levels in normal and mentally deficiency children.

In Britain overt lead poisoning in childhood is uncommon, though it appears to be common in the industrial areas of the United States of America, where it may account for as many as 79% of childhood deaths due to accidental poisoning (Christian, Celewycz, and Andelman, 1964). A number of cases are probably missed (Mellins and Jenkins, 1955; McLaughlin, 1956) and mild cases undoubtedly go undetected because of the vague character of the illness in its less severe forms, and the difficulties involved in establishing a firm diagnosis (Jacobziner and Raybin, 1962). One of the problems in diagnosis is the technical difficulty of carrying out accurate lead analyses; an even greater one is that there is still no general agreement on the laboratory criteria for lead poisoning. Moncrieff, Koumides, Clayton, Patrick, Renwick, and Roberts (1964) studied a large unselected group ofmentally defective children, and found that no less than 45% of their series had biochemical evidence which they regarded as sufficient to suggest the diagnosis of lead intoxication. Lead poisoning is, to a large extent, an environmental disorder, occurring most often where housing standards are poor, and where the pre-school child has ready access to sources of ingestible lead, for example flaking painted plaster, or rusty lead-painted railings. Since these conditions are not uncommon in Glasgow an investigation has been carried out on the incidence of lead poisoning in mentally defective children in the Glasgow area. This initial study was planned with two objectives: (1) to define criteria for the diagnosis of lead poisoning in childhood; and (2) to compare the incidence of raised blood lead levels in normal children, in mentally retarded children in whom the cause was defined, and in children in whom there was mental deficiency without recognizable cause.