It has been suggested that highly concentrated aerosols exhibit colligative behavior due to hydrodynamic interactions among particles. Such behavior includes enhanced settling rates (cloud settling) and possibly increased deposition efficiency upon inhalation. The purpose of our study was to determine whether or not concentrated sidestream cigarette smoke would deposit in an enhanced manner in hollow models that represented human nasal airways. Sidestream smoke wisps were generated by smoldering 1R3 University of Kentucky research cigarettes and were drawn horizontally through the models. The smoke aerosol had a mass median aerodynamic diameter of about 0.45 μm and a geometric standard deviation of about 1.3. Photographs indicated that the smoke consisted primarily of wisps that had characteristic diameters of about 0.3 mm and lengths that were typically greater than 1 cm. These wisps, which were surrounded by relatively particle-free air, were the entities that might exhibit cloud-like behavior. The average measured percentage deposition efficiency of cigarette smoke in the nasal casts was 4.5 ± 0.2 (SE). This value is close to what one would expect for particles of 0.45 μm aerodynamic diameter. Colligative behavior did not appear to produce measurably enhanced deposition in the surrogate nasal models. © 1994.

This study was performed to assess the effects of sulfuric acid inhalation, and partly to examine the potential suitability of the laboratory ferret as a respiratory tract clearance model. Separate groups of ferrets were first exposed nose-only to purified air, 0.5 mg/m3 ofsulfuric acid aerosol, and 1.0 mg/m3 ofsulfuric acid aerosol for 4 h. Following the deposition of radiolabeled tracer microspheres, the clearance rates from the head and chest regions were monitored using collimated radiation detection equipment. The results indicate that (1) neither of the acid atmospheres produced a statistically significant effect on the clearance rate of the head region; (2) the high-acid atmosphere produced a significant acceleration in the clearance rate of the lung region; and (3) the long-term lung clearance rate of the purified air-exposed ferrets was very close to that observed with humans. Also, the ferrets were docile and easy to handle, and seemed to be well suited to this type of study. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.

Experiments were performed to study the physical characteristics of smoke aerosols generated by burning three types of stick incense in a 4 m3 clean room. Sidestream cigarette smoke was also examined under the same conditions to provide a comparison. Among the parameters measured were (a) masses of aerosol, carbon monoxide and nitrogen oxides generated by burning the incense or cigarettes, (b) rates of decay of the particles from the air, and (c) estimates of count median particle size during a 7 h period post-burning. There was variability among the types of incense studied with respect to many of the parameters. Also, as a general trend, the greater the initial particulate mass concentration, the more rapid the rate of decay of the smoke. In relation to the quantity of particulate generated, cigarette smoke was found to produce proportionally larger quantities of carbon monoxide and nitrogen oxides than did incense. Due to the fact that burning incense was found to generate large quantities of particulate (an average of greater than 45 mg/g burned, as opposed to about 10 mg/g burned for the cigarettes), it is likely, in cases in which incense is habitually burned in indoor settings, that such a practice would produce substantial airborne particulate concentrations.

During growth and development, young children are periodically exposed to relatively high concentrations of various air contaminants, including tobacco smoke and environmental pollutants generated by fossil fuel use. The effects of these exposures on respiratory function and lung development are difficult to determine because of interindividual variation and lack of accurate dosimetry. To provide information on the effects of chronic exposure to a common indoor and outdoor pollutant during lung development, a study was performed to assess the effects of exposure to two concentrations of nitrogen dioxide (NO2; 0.5 or 10 ppm) on tracer particle clearance from the airways of ferrets exposed during postnatal respiratory tract development. Separate groups of ferrets were exposed nose-only to the test atmospheres or clean air 4 h/d, 5 d/wk, for either 8 or 15 wk. Those animals exposed for 8 wk were subsequently housed in a filtered air environment until the particle clearance measurements commenced at 3 wk prior to the end of the 15-wk exposure protocol. Radiolabeled (51Cr) tracer particles were deposited in the respiratory tract of all animals by inhalation, and the clearance rates from the head and thoracic regions were separately monitored for 18 d. No significant effects of the NO2 exposure on head airways clearance were seen. In contrast, the rates of particle clearance from the thorax of both the 8- and 15-wk groups exposed to 10 ppm NO2 were significantly reduced, and did not differ from each other. Thoracic clearance was also reduced in animals exposed to 0.5 ppm, but the rate was not significantly different from that of the clean air exposed controls. These results show that NO2 at moderate concentrations caused highly significant changes in the deep lung of the juvenile ferret, and suggest that impairment of the clearance function may be only slowly recovered after chronic exposure.

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

This study assessed the effects of repeated exposure to environmentally realistic levels of two urban air pollutants nitric acid vapor (HNO3) and ozone (O3) - on tracer particle clearance from the rat respiratory tract. The measurement of particle clearance efficiency is important because failure of this function could contribute to a buildup of foreign matter in the respiratory tract. Separate groups of rats (30 rats per group) were exposed nose-only for 4 h/day, 3 days/wk (a surrogate for an air pollution episode) for 40 wk to 4 atmospheres: purified air; 0.15 ppm O3; 50 μg/m3 HNO3; and 0.15 ppm O3 + 50 μg/m3 HNO3. At 4 wk prior to the end of the exposure, the rats inhaled radiolabeled tracer particles nose-only for 30 min. A clearance measurement protocol was then followed to estimate the rates of early and late clearance. Early (presumably upper respiratory tract) clearance was monitored during the 48 h following tracer deposition by the analysis of radioactivity excreted in the feces, while late (presumably deep lung) clearance was characterized by a combination of chest counting and 30 day postexposure sacrifice radioactivity analyses. The exposure to O3, both alone and in combination with HNO3, produced a more than 30% (statistically significant) delay during the initial phase of upper respiratory tract clearance, and all of the pollutant exposures may have stimulated deep lung clearance. The directions of these effects were the same as those observed previously when rats were acutely exposed to O3- containing atmospheres.

The effects of a 4 hour exposure to a model sulfur pollutant atmosphere on the clearance of inhaled insoluble tracer particles from the lungs of rats has been studied. The pollutant combination consisted of 5 ppm of sulfur dioxide gas and 1.5 mg/m3 of sulfate aerosol at 80-85% relative humidity. The exposure atmosphere was aged for 30 minutes upstream of the exposure chamber in an aging line in order to provide for gas/ particle interactions such as those occurring in industrial and environmental atmosphere. Results indicate that the sulfur pollutant atmosphere did not produce a statistically significant alteration in early (nasopharyngeal and tracheobronchial) or late (parenchymal) clearance rates such as those which have been identified in this laboratory following exposure to ozone-containing atmospheres.

The effects of variations in cyclic breathing parameters (i.e., tidal volume and breath frequency) have been the subject of few studies devoted to the deposition of submicrometer aerosols in the human respiratory tract. Therefore, a series of experiments was performed to investigate whether the deposition efficiency (DE) of sidestream cigarette smoke is altered by varying tidal volume and breath frequency in a child-size hollow tracheobronchial (TB) model while maintaining a fixed minute ventilation rate of 5 L/min. Under cyclic flow conditions with tidal volumes of 100 mL (50 breaths/min), 250 mL (20 breaths/min), 500 mL (10 breaths/min) and 750 mL (6.7 breaths/min), sidestream cigarette smoke was passed through replicas of an idealized hollow TB model. The smoke deposits were extracted and then quantitated spectrophotometrically. The experiments revealed a significant difference in DE between the 100-mL tidal volume (DE = 6.0%) and the 750-mL tidal volume (DE = 11.1%). Under equivalent steady flow conditions, the mean DE was 21.5%. A trend was evident in the data--DE increased as tidal volume increased (and breathing frequency decreased)--suggesting that the influence of diffusion and secondary flows on DE becomes greater as the air residence time increases and the degree of air turbulence decreases. The results provide evidence of the importance of breathing parameters when attempting to model in vivo deposition of environmental tobacco smoke and other similar-size respirable aerosols.

The objective of this study was to evaluate the toxicity of inhaled diesel engine–generated fine carbon particles, when an acid mixture of the type found in California's air was also present. Rats were exposed nose–only for 5 hours per day for 5 consecutive days. The target concentrations of the pollutants in the three atmospheres studied were: (a) 0.5 mg/m3 diesel exhaust soot, (b) 0.35 mg/m3 nitric acid + 0.15 mg/m3 sulfuric acid, and (c) 0.5 mg/m3 diesel exhaust soot + 0.35 mg/m3 nitric acid + 0.15 mg/m3 sulfuric acid. Control rats were exposed using the same schedule to purified air. The evaluation of potential toxic effects in exposed rats included: (a) measurement of respiratory tract clearance of insoluble tracer particles; (b) histopathologic examination of respiratory tract tissues, including autoradiographic measures of cell turnover as an index of cell killing; and (c) measurement of functional effects on pulmonary alveolar macrophages. Biological effects were observed for each of the atmospheres studied. None of the atmospheres produced significant lung cell damage, but retained soot deposits were seen in the lung after exposure to atmospheres that contained soot. Although the diesel soot + acids atmosphere did not alter early or late clearance of tracer particles, this atmosphere – and the other two atmospheres studied – depressed pulmonary macrophage functions. This interference with macrophage functions may have significant implications to human health. © 1991, Mary Ann Liebert, Inc. All rights reserved.

This study was performed to assess the effects of two high concentrations (about 380 mg/m3 and about 38 mg/m3) of inhaled cigarette smoke on tracer particle clearance from the head airways region and the thoracic (primarily deep lung) region of ferrets exposed during postnatal respiratory tract development. Ferrets were exposed 2 h/days, 5 days/wk to purified air or to the smoke aerosols starting at 5 wk of age, for a total of 15 wk of exposure. Three weeks prior to the end of the 15-wk exposure regimen, radiolabeled tracer particles were deposited by inhalation, and the clearance rates from the head airways and thoracic regions were monitored for 18 days. The head airways counting data were accurately fit by a double exponential function, reflecting fast-clearing and slow-clearing components. The thoracic counting data were adequately fit by a single exponential function. Statistically significant accelerations of particle clearance rates were observed for the slow-clearing and fast-clearing phases of clearance from the head airways region for both the higher and lower concentration groups; the results implied a dose-response relationship. Only in the case of the higher concentration group was significant slowing observed in the thoracic region analysis, indicating that the head airways region was perhaps the area of greater impact of the smoke aerosol. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.