The uptake and excretion of lead by young children.

The fractional absorption of ingested lead by adults has been found from both balance studies and isotope studies. However, insofar as endogenous fecal lead cannot be measured in the balance studies, such studies do not permit the determination of true uptake from gut to blood. For children, only balance studies have been reported, but it is possible to make an estimate of their true uptake by making some allowance for endogenous fecal lead. The estimate made in this way suggests a higher fractional uptake than is usually quoted, but the clearance rate of lead from blood is probably also high for children. An estimate is made of the half-life of lead in blood for children which suggests a value several times shorter than that for adults. The estimates of uptake and half-life made here are very speculative but are of interest in the absence of any direct measurements.