Variability of Blood Lead Concentrations During Infancy

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Abstract
As part of a study of early childhood development, > 200 children had their blood Pb concentrations (PbB) determined semiannually during the 1st 2 yr of life. These children were selected from 11,837 consecutive births surveyed for umbilical cord PbB at Boston Lying-In Hospital [Massachusetts, USA]. Candidate subjects were drawn from the highest, lowest and middle deciles of PbB. The mean PbB was 7.2 .+-. 5.3 (SD) .mu.g/dl at birth and did not change appreciably with age. The average change in an individual''s PbB every 6 mo. was 4 .mu.g/dl, which was several-fold in excess of the analytical reproducibility. Only 25% of the children in the highest category at birth were in the highest category at 2 yr of age. Approximately 40% of the children remained in their immediately previous PbB tertile category. A stochastic description of these patterns of change fit the data. Results should caution investigators who might wish to rely on a single determination to categorize children with PbB.

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