ABSTRACT
Early studies showed that during chronic exposure, lead is gradually fixed in the crystalline matrix of bone. Over 90% of total body lead in adult humans is found in the skeleton. The earliest efforts to model lead kinetics were based on observations of the rate of loss of intravenously-injected radiolabeled lead from the blood and other tissues of the rat. Like the models of lead kinetics in rats, all of these models of human lead kinetics are classical first-order compartmental models, with no allowance for nonlinearity of lead kinetics or for dependence of the rate of return of lead from bone on the timing of previous lead exposure. A variety of studies using calcium tracers have demonstrated that bone-seeking elements are initially deposited at all bone surfaces including endosteal, periosteal, haversian canal, and trabecular surfaces.
