Concentrations of lead in the tissues of children.

Twenty-four different tissues from 73 children and infants, including stillbirths, were analysed for lead content. In the youngest group of 49 infants aged under 1 year, including 14 stillbirths, the mean concentrations of lead in their soft tissues were all less than 0.3 ppm and nearly all less than the concentrations found in the soft tissues of older children, or of adults. The mean concentrations of lead in the bones in the infant group were greater than in their soft tissues, but still less than 1 ppm, and were 10-40 times less than in adult bones and about three times less than in the bones of older children. Lower concentrations of lead were observed in the tissues of stillbirths than in those of neonatal live births, at a 95% level of significance by analysis of variance. In 24 children aged 1-16 there was no clear evidence of increase of lead concentrations in the bones with increasing age; neither was there evidence of a difference in the concentrations of lead in types of bone. Although the mean concentrations in the bones were greater in the children aged 1-16 than in those of infants aged under 1 year, the data did not suggest that a progressive accumulation of lead occurred in the bones, probably before the end of the second decade of life, by which time the growing phase will be nearing completion. In 18 children aged 1-9 and in six children aged 11-16 the concentrations of lead in the soft tissues were similar, and comparable with those observed in women. The ratio differences between ash-weight and wet-weight measurement in the different types of bone in children did not differ proportionately from the adult ratios, suggesting a similarity in the patterns of deposition of lead in bone, irrespective of age. No differences in tissue lead concentrations by sex were observed in the infant group of children, or when the concentrations in the tissues were related to the years in which the samples were obtained. Individual tissues showed different concentrations and patterns of distribution of lead, which were skewed more towards low values in the infant group than in older children. The results of other studies, of which there have not been many, were found to be in general agreement with those reported here. The exposure of infants to lead appeared to be less than in older children or in adults, probably for reasons associated with lack of availability and parental care.