“…These depend on particle density, size, and shape as well as particle solubility and the rate and depth of respiration [National Academy of Sciences, 19721. It has been estimated that for most common lead aerosols of mixed particle size between 30% and 50% of the total inhaled lead mass will be retained in the alveolar region and completely absorbed [Kehoe, 1961;Task Group on Lung Dynamics, 1966;National Academy of Sciences, 1972;Chamberlain et al, 1975;Ratcliffe, 19811. The larger particles deposit in the nose, throat, and upper airways, where they are cleared to the gastrointestinal tract by ciliary action [Muir, 19721. CPA assumed that all lead particulates not deposited and absorbed through the alveoli are ingested.…”