Pock Model Simulations of Pulmonary Quartz Dust Retention Data in Extended Inhalation Exposures of Rats

Abstract

In recent years, a physiology-oriented multicompartmental kinetics (POCK) model was developed to simulate pulmonary retention data of biopersistent, noncytotoxic aerosols in long-term inhalation exposures of rats. Experimental data were successfully simulated for submicrometer-sized aerosols like carbon black, diesel soot, and titanium dioxide and for a micrometer-sized xerographic toner aerosol (Stöber et al., 1994, 1995). This article describes for various rat strains successful POCK model simulations of experimental pulmonary retention data of micrometer-sized aerosols of biopersistent cytotoxic SiO2 modifications like quartz and quartzite. In the past, the POCK model was not applied to cytotoxic aerosols and dusts. Cytotoxicity was considered incompatible with the model assumption of a constant macrophage lifetime independent of the macrophage aerosol load. The few relevant experimental retention studies with biopersistent silica found in the open literature showed particulate lung burdens up to some 15 mg per rat lung. Apparently, at these loads, pulmonary burdens could be simulated because the fraction of alveolar macrophages killed by the cytotoxic particles was possibly still small compared to the total number of viable macrophages. Of necessity, however, the classical alveolar clearance in these studies was exclusively performed by alveolar macrophages that were burdened with cytotoxic particles, and the cells appeared to suffer from a substantial initial decrease of their inherent mobility. Thus a sizeable reduction of the alveolar clearance rate coefficient in comparison to nontoxic aerosol was found. The results for the model parameters of several different exposure studies are shown and interpreted in comparison to nontoxic titanium dioxide retention parameters.

Controlled synthesis of EuPO4 nano/microstructures and core–shell SiO2@EuPO4 nanostructures with improved photoluminescence

“…31 First, deionized water and absolute ethanol were mixed, followed by the addition of aqueous ammonia and tetraethoxysilane. A white silica colloidal suspension was formed and stirred with 3.5 h. The SiO 2 submicro-spheres were centrifugally separated from the suspension and washed with ethanol and deionized water several times, prior to drying in air at 60 C for 12 h. Aer that, a certain amount of SiO 2 submicro-spheres is mixed with the prepared 0.1 mol L À1 europium nitrate solution.…”

Luminescence Studies and Judd–Ofelt Analysis on SiO2@LaPO4:Eu@SiO2 Submicro-spheres with Different Size of Intermediate Shells

“…The SiO 2 @LaPO 4 :Eu@SiO 2 submicro-spheres are core-shell-shell structures, which were synthesized according to our earlier report 46 . First, the synthesis progress of SiO 2 @LaPO 4 :Eu was briefly described as follows: (1) The Stöber method was employed to synthesize the SiO 2 submicro-spheres 47 . (2) The MABA-Si (bridging ligand organosilane) was prepared by using the method reported in literature 48 .…”