Lung Retention of Metallic Fumes

Abstract

From the results of theoretical and experimental studies on the aerosol retention in lung, it has been assumed that the effect of particle size on the lung retention rate of aerosol would uniformly depend upon the aerodynamic mass median diameter (AMD or Da).In order to elucidate this assumption, the author made an inhalation experiment using lead (Pb) and tellurium (Te) fumes which had monodispersed spheric but different specific gravities for rats. In the experiment several particle sizes of Pb or Te fume generated by the high frequency electric furnace type fume generator were inhaled by SPF male rats of Sprague-Dawley strain in a head-only exposure chamber for 90min. After inhalation, the lung was taken out instantly from the rat's body, and the weights of metallic fumes retained in each rat lung were measured by atomic absorption analysis. The relative lung retention rates (RL) of metallic fumes in rats were calculated considering the exprimental conditions such as the fume concentration in the exposure chamber, the exposure period and respirating minute volume of rat. However, minute volume of each rat could not be measured easily, so that it was used uniformly 100ml/min for minute volume of rats because body weight of each rat showed little difference among each other.As results of the experiment, the following relationship was found to exist between RL and Da in both the cases of inhalation of Pb and Te fumes: RL=K⋅Da-n. The author named the index number of lung retention as n in this equation. According to the above assumption, n value should be constant regardless of the kind of aerosol material. However, n were 0.72 of Pb fume and 0.36 of Te fume in the present experiment. This difference might be produced by the physico-chemical properties and biological activity of metallic fumes.