Diluted diesel engine exhaust was mixed with sulfur trioxide and the resulting acid-soot aerosol characterized. The generation system, which is suitable for inhalation toxicology studies, was characterized at a soot concentration of approximately 0.5 mg m-3 and H2SO4 coating levels from 0 to 5 mg m-3. Aerosol characterization included measurement of particle size (cascade impactor + electrical aerosol analyzer tandem sampler) and acid-soot association (electron microscopy of BaCl2-coated sample grids). The mass distribution of both acid-coated and uncoated diesel soot was unimodal and approximately lognormal. The acid coating increased both the size and monodispersity of the soot aerosol. The mass median Stokes equivalent diameter and geometric standard deviation were 0.12 μm and 2.4 for the uncoated soot, and 0.28 μm and 1.9 at 5.0 mg m-3 H2SO4. Approximately 95% of the soot particles were coated with H2SO4; the remainder appeared uncoated. Some H2SO4 droplets without a visible nucleus were also observed. © 1988.

An aging line especially designed for the aging of pollutant atmospheres is described. The line essentially is a nearly-square stainless steel duct with periodic 100-mesh stainless steel screens to promote plug flow. The line has been tested for uniformity of aging, aerosol losses, and ease of atmosphere control, Results show that a close approximation to plug flow can be achieved with excellent atmosphere control; aerosol losses in the particle size range 0.22-2.0 μm are less than 30% except at very long (96 min.) aging times, when significant sedimentation losses occur for larger particles. Copyright 1982, American Industrial Hygiene Association

The effects of exposures to sulfur dioxide and formaldehyde atmospheres on the clearance of inhaled, insoluble tracer particles from the lungs of rats have been studied. The tracer particles employed were polystyrene latex microspheres radio-labeled with 51Cr. Following the deposition of the 1.9-micron activity median aerodynamic diameter (AMAD) particles, the rats were divided into 3 groups for a single 4-h exposure to purified air, 20 ppm sulfur dioxide, or 20 ppm formaldehyde. Early, presumably upper-respiratory-tract, clearance was monitored by analysis of radioactivity excreted in feces, while late, presumably deep-lung, clearance was followed by thoracic counting of the animals. Both the sulfur dioxide and formaldehyde atmospheres did significantly delay early clearance (p less than 0.1, two-tailed t-test). However, the late clearance rates of the two pollutant-exposed groups of rats were not significantly different from that of the purified air-exposed group of rats. Although sulfur dioxide had numerically greater effects than formaldehyde, the differences were not statistically significant at the p less than 0.1 level.