**Abstract**

The ability of lead to cause brain damage and reduce intelligence quotient has been established. However, transport of lead through brain capillary has not been elucidated. Hence, plasma and brain tissue kinetics of lead was studied mathematically. Literatures were searched for formulas that could be used for the determination of relationship between plasma and brain tissue kinetics of lead with an interest to discovering the residence time of lead residues in brain. Findings have shown that 5 *μg=dl* of lead in plasma permeates the brain of human weighing 20 kg faster than that of 40 kg and 70 kg body weight, respectively. The surface area of permeability of brain cell is higher, in low body weight human than in high body weight human. Time of exposure and concentration of lead are higher in low body weight human as compared to high body weight human. Hence, neonates and children are more vulnerable to brain damage than adult human.

**Keywords:** encephalopathy, lead, brain capillary, toxicokinetics, encephalization quotient, transport
