Development of exposure chamber for investigation of inhaled chronic health effect of airbone particles

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As a result of improved dust control in work and atmospheric environments, investigations of the chronic health effects of inhaled dust have become much more important than the acute ones. In animal experiments, therefore, the dust concentration and size distribution in the exposure chamber must be kept constant over a long period. Also, it is desirable that the particles be unagglomerated and evenly dispersed. In this study a new fluidized bed dust generator with continuous screw feeder and overflow pipe was developed for long-term chronic inhalation toxicity studies. This generator has the following advantages:1. It is possible to operate for a long time.2. The dust concentration can be changed arbitrarily.3. Many kinds of aerosol particles can be generated.4. Maintenance and operation are easy.The performance of inhalation system, consisted of dust generator, exposure chambers and gas-liquid-solid separator, were investigated by Wister male rats exposed to coal fly ash aerosol for one-year.The following results were observed.1. The daily average concentrations in the exposure chamber for one-year were 38.5 <+!-> 11.1 mg/ <m^3> (high exposure group) and 5.0 <+!-> 2.1 mg/ <m^3> (low exposure group).2. The mass median aerodynamic diameter of coal fly ash aerosol in the exposure chamber was 2.7 <micro> m during the exposure.3. Many coal fly ash particles were observed in exposed rat lung.4. The body burdens of coal fly ash were measured quantitatively by an analysis of aluminium contained in coal fly ash.5. The deposed coal fly ash in exposed rat lung was significantly incresed.I believe that the inhalation system developed in this study is extremely useful for investigating chronic health effects of inhaled dusts.