QUARTZ DUST RETENTION IN RAT LUNGS UNDER CHRONIC EXPOSURE SIMULATED BY A MULTICOMPARTMENTAL MODEL: FURTHER EVIDENCE OF THE KEY ROLE OF THE CYTOTOXICITY OF QUARTZ PARTICLES

Abstract

Several years ago, Bellmann et al. (1991) obtained data on pulmonary lung burdens and tracheobronchial lymph node burdens of quartz dust in long-term inhalation studies with Fischer 344 rats exposed for 30 h/wk to 1 g/m3 of DQ12 quartz particles. The pooled retention data of male and female rats are used here for a simulation study by means of a previously developed multicompartmental mechanistic model that has been successfully applied to long-term retention studies with different samples of quartzite and titanium dioxide. The relative alveolar deposition rate of the DQ12 aerosol as assessed by the model approximation proved to be identical with the relative deposition rate in our previous quartzite study. All the transfer rate coefficients that presumably are affected by inherent particle cytotoxicity, which is higher for DQ12 quartz than for quartzite dust, were changed accordingly, and the model gave a satisfactory simulation of the time patterns of DQ12 quartz mass burden in the pulmonary region and in the lung-associated lymph nodes. Together with the modeling results with far less cytotoxic titanium dioxide particles, our successful simulation seems to corroborate the hypothesis underlying our model, that is, the key role of cytotoxicity in the retention kinetics of insoluble dusts and their disposition in lungs and lung-associated lymph nodes.