Deposition of 0.1 μm chain aggregate aerosols in beagle dogs

Abstract

Deposition and retention of ultrafine chain aggregate particles were studied in 20 beagle dogs. Aggregated particles of insoluble 67Ga 2O 3 in the 0.1 μm size range were generated by heat treatment of 67Ga tetramethylheptanedione. Size characterization was done using electron microscopy, diffusion battery and electrical aerosol analyzer measurements. The average equivalent diffusion diameter of the aerosol was 0.07 μm and the volume median diameter (electrical mobility measurement) was 0.10 μm with a geometric standard deviation of 1.6. Primary particles from which the aggregates were formed were 0.01–0.02 μm in diameter. Whole-body counting and gamma camera imaging were used to measure deposition. Total deposition in the whole body was 33 ± 16% (mean ± S.D.) of the inhaled particles; 82 ± 13% of this material was deposited in the lung. Retention studies showed that 77 ± 3% of the material deposited in the lung was in the pulmonary region. Thus, 21 % of the inhaled particles were deposited beyond ciliated airways in alveolar areas. The deposition in the deep lung has important implications for health risk assessments of particles in the environment of similar size and shape such as diesel exhaust emissions.