Age at Lead Exposure Influences Lead Retention in Bone

Abstract

More than 90% of the body lead burden in rats and people is in the skeleton (1–3). The half-life of bone lead is long, 5–20 years or more, with lead in cortical bone having a longer biological residence time than lead in trabecular bone (1–3). The long half-life suggests that environmental exposure of children to lead can result in bone lead accumulation that may persist for many years. However, it has been hypothesized that the high rate of bone remodeling during childhood and the related high turnover of calcium and lead results in a substantial reduction in bone lead stores, so that much of the lead incorporated into bone during childhood does not persist into adulthood (4). We tested the alternative hypothesis that younger age at lead exposure results in a greater accumulation of lead stored in the skeleton as well as in soft tissues. The objective of this study was to determine the effect of age during lead exposure on blood and organ lead concentrations one month later. Organ concentrations of the essential divalent metals calcium, copper, iron, magnesium, and zinc were also measured for comparison to lead.