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Abstract Objectives--To investigate the risk of silicosis among tin miners and to investigate the relation between silicosis and cumulative exposure to dust (Chinese total dust and respirable crystalline silica dust). [...]

Mainstream cigarette smoke generated using different puffing profiles and delivered under different exposure modes was characterized for particle size distribution, vaporlgas concentration, and chemical composition. Three exposure modes were compared: (1) nose-only, intermittent (NO-I), which simulated a periodic exposure; (2) nose-only, continuous (NO-C), in which a constant smoke concentration was maintained for several hours; and (3) whole-body, continuous (WB-C), which was similar to the NO-C mode except that the smoke was routed to a whole-body instead of to a nose-only exposure chamber. Three different puffing profiles were compared: (1) a standard (SP), 2-s, 35-ml puff once per minute; (2) a puff of double the standard volume (70 ml) once per minute (OP); and (3) a double puff twice per minute (2-DP). Results from multijet Mercer impactor samples indicated that the mass median aerodynamic diameter of smoke particles increased with mass concentration and decreased with puff volume. Gas samples showed no substantive differences between exposure modes with or without rats in the exposure chambers, except for CO2 concentrations in the WE-C chambers, NO2 concentrations in the NO-I chambers, and NO concentrations in the NO-C chambers. Linear relationships were observed between the concentration of total particulate matter and that of CO, NO, and volatile organic hydrocarbons under all exposure and puffing modes. Concentrations of six different organic vapors (acetone, 2-methylfuran, benzene, meta- and para-xylene, ortho-xylene, and limonene) were measured using Tenax trapping technique. The results showed no substantive differences among the three exposure modes or three puffing profiles, except that the concentrations of toluene, orthoxylene, and limonene were higher in smoke from the WE-C than from the NO-C (or NO-I) modes. The amounts of four particulate-phase constituents (nicotine, glycerol, hydroquinone, and palmitic acid) were analyzed chemically; good agreement was found in the amounts resulting from all of the puffing profiles and most of the exposure modes, except that nicotine was found to be slightly lower in the WE-C mode than in the other exposure modes.Sampling results indicated that there were few substantive differences in smoke composition among the different exposure and puffing modes used in this study We concluded that WB-C exposures to the cigarette smoke generated under 2-DP profiles might produce biological effects similar to those produced under SP profiles by nose-only exposures, and might be useful for chronic animal exposures.

This study was designed to compare the internal and external deposition of cigarette smoke particles in F344IN rats after nose-only or whole-body exposures and to provide information on how grooming affects the amount of smoke particles that pass through the gastrointestinal (GI) tract. Female rats were exposed to mainstream cigarette smoke by - four different modes: nose-only, tube-restrained (NOT); pelt-only, tube-restrained (POT); whole-body, tube-restrained (WBT); and whole-body, cage-housed (WBC). Croups of rats were exposed simultaneously for 40 min by 1 of the 4 modes to [14C]ldotriacontane (DTC) labeled cigarette smoke at a mean mass concentration of 327 mglm3. Half of the rats from each group were sacrificed immediately after exposure, and the others were sacrificed 24 h later. Head skin, a sample of subcutaneous fat, GI tract, trachea/lobar bronchi, lungs, depelted head, depelted carcass, and remaining pelt were analyzed to determine their UC content. About 60% of the 14C activity in the respiratory tract in the NOT and WBT groups was deposited in the pulmonary region, and about 40% was in the head airways and trachea. The radiolabeled DTC was cleared very slowly from the pulmonary region. The initial total body burdens of 14C in the rats exposed by the WBT and WBC modes were higher than those in the rats exposed by the NOT mode as a consequence of pelt contamination by the 14C-DTC. Crooming resulted in the ingestion of about 80-90% and 60% of the 14C activity originally deposited on the head skin and pelt, respectively, by 24 h after exposure. The ratio of the amount of smoke particles either contained within or passing through the CI tract to the amount in lung after 24 h was 2.6 for WBC-exposed rats and 1.3 for NOT-exposed rats. We concluded that compared to rats exposed using the NOT mode, WBC exposures increased the amount of smoke particles passing into the CI tract by about a factor of two.

A seven-cell, screen-type, parallel-flow diffusion battery (PFDB) was calibrated with monodisperse, yellow-green fluorescent, polystyrene latex particles. The particles were aerosolized and introduced into the PFDB with a flow that was uniformly distributed among the seven cells. The particles penetrating the screens in each cell were then collected on backup filters. To determine the mass of particles able to penetrate each cell, the particles were removed from the filters by dissolving them in ethyl acetate, and the fluorescence intensity of the solubilized material was determined using a fluorescence spectrophotometer. The results showed that the median sizes of the latex spheres could be estimated accurately from the mass penetration curves of the cells, even though the geometric standard deviations of the size distributions were overestimated. Particles in diluted main-stream cigarette smoke were sized using both diffusion battery and multijet Mercer impactor techniques. For smoke particles generated from a 2-see, 70-mL puff/min having a mean concentration of 161 mg/m3, the mass median diameter was estimated to be 0.35 µm by both techniques. However, for cigarette smoke containing >18% (by mass) of particles larger than 0.656 µm (the upper operable size of the PFDB at a flow rate of 1.58 L/min Per cell), the diffusion battery cannot provide accurate size measurements and only the impactor technique should be used.

The calibration curve of an optical particle counter (OPC) normally is established based on the relationship between the optical responses of spherical particles (e.g., polystyrene latex spheres) and the particle sizes. This calibration curve, however, cannot be used to size unknown aerosol particles accurately in the field. A new technique was developed that allowed calibration of OPCs by using aerosol particles that the instruments will be measuring. A two-stage virtual impactor was used to classify aerodynamically monodisperse aerosols of fly ash, oil shale, triphenyl phosphate, tale, glass microspheres, and alumina for calibrations of a Royco 226 OPC. Particles with the same aerodynamic diameter produced optical responses in the OPC that depended not only on the geometric size but on the refractive index, density, and morphology. Calibration curves of test aerosols, except that of the triphenyl phosphate, were different from that of polystyrene latex spheres. The results indicated that OPCs can be calibrated accurately for field aerosols by using a two-stage virtual impactor as a sampling inlet and, thus, OPC applications can be enhanced greatly.

The aerodynamic behavior of aggregates consisting of uniform polystyrene latex (PSL) spheres and unaggregated cuboidal Natrojarosite particles in a TSI aerodynamic particle sizer (Model APS33B) has been studied. In initial tests, monodisperse PSL micro-spheres ranging from 0.3 to 7 μm in geometric diameter were generated from aqueous suspensions using a Lovelace nebulizer. APS33B responses for these uniform-sized particles showed multiple peaks. The major (primary) peak, which resulted from the smallest particle, corresponded to the unaggregated single spheres (singlets); the second, third, and fourth peaks were identified as doublets, triangular triplets, and tetrahedral quadruplets, respectively. Both doublets and triplets moved with their long axes in perpendicular (maximum drag) orientation to the flow direction in the APS33B. In contrast, the tetrahedral particles were isometric and had the same dynamic shape factor (drag resistance) for all three primary orientations. The particle Reynolds numbers (Rep) for these particles were calculated and ranged from 0.2 to 30 in the sensing volume of the APS33B detector (i.e., ultra-Stokesian conditions). Ultra-Stokesian drag forces for all three types of aggregates were, therefore, estimated and expressed as a function of an empirical factor (1 + aRebp) to the Stokesian drag force. The ultra-Stokesian drag of a Natrojarosite particle was measured in the range 20 Rep < 50 and could be described with a similar expression. This approach facilitates the study of the dynamic behavior of nonspherical particles and yields new information about the characteristics of drag forces in the ultra-Stokesian regime

This report describes an experimental study to classify fiberlike particles by length based on their electrical properties. Carbon fibers with monodisperse diameters and polydisperse lengths were passed through a unipolar charger. The charged fibers were then segregated in an electrical mobility analyzer based on their mobilities. They were collected on Mylar segments, which were placed at different precipitating lengths on a central rod of the analyzer. The results showed that carbon fibers with a narrow length range attached themselves to many of the Mylar segments on the rod, demonstrating the fibers with monodisperse lengths can be classified by using this technique. In addition, the results indicated that the longer the precipitating length of the segment, the shorter the length of the fibers collected. The effects of flow rate, charging time, and analyzer voltage on fiber classification were also investigated. The results showed that, at a fixed precipitating length, the longer fibers were collected under a higher flow rate or a lower analyzer voltage. However, no effect of charging time was observed. Further analysis illustrated that all data obtained from the various operating conditions could be consolidated by a function relating electrical mobility to fiber length. This relationship was then used to estimate the charge distribution of carbon fibers in a unipolar charging mechanism. Based on our results, the number of charges on a carbon fiber increases monotonically with the aspect ratio of the fiber.

A cylindrical, Pyrex glass chamber with stable temperature control was evaluated to determine the residence time of aerosol particles within an enclosure, and to compare our results to the theoretical expression derived by Crump and Seinfeld (1981). Monodisperse polystyrene latex particles with diameters between 0.04 and 3 μm were used to determine the particle deposition rates under different water temperature gradients (δTw) between the top and bottom water layers of the chamber. The water layers and an insulating fiberglass jacket around the side wall helped to maintain a steady temperature gradient in the chamber and this was found to be very important in controlling particle deposition. Results indicated that the minimal deposition losses occurred at δTw = 0°C for particles between 0.2 and 0.3 μm, with a residence time as long as 38 h. Results also showed that particle deposition rate can be described by the theory of Crump and Seinfeld with an exponent n = 2.02 and a turbulence intensity ke = 0.0039/s at δTw = 0°C, and n = 2.04 and ke = 0.020/s at δTw = 10°C gradient. Preliminary results also indicated that a slightly higher temperature at the bottom of the chamber (e.g., δTw = 5°C for 0.62-μm particles) might induce an upward thermophoretic force which would reduce particle settling.

Effects of particle density and droplet deformation on the performance of a TSI aerodynamic particle sizer (APS) were studied using polystyrene latex (PSL), dioctyl phthalate (DOP), ammonium fluorescein (AF), fused aluminosilicate (FAP), and fused cerium oxide (FCO) monodisperse aerosols. Results indicated that, because of the sensitivity of the instrument, periodic cleaning of the APS inner nozzle is needed to maintain the consistency of its calibration curve. Density effects were experimentally confirmed with PSL, AF, FAP, and FCO aerosols of particle densities ranging from 1.05 to 4.33 g/cm3. Results, however, showed that this effect can only be experimentally detected for particles of density greater than 2 g/cm3 and aerodynamic diameter greater than 5 (μm. Effects of droplet deformation were studied with DOP.

Mainstream cigarette smoke generated using a Walton smoking machine and Kentucky 2R1 research cigarettes was studied. Results showed that puff volume and total particulate matter were consistent after the first puff, with average values of 35.6 cm3 and 3.37 mg, respectively. The particle size distribution, measured with a multijet cascade impactor, was not related to butt length or relative humidity (≤95%), but was strongly dependent on the aging time. Based on simple monodisperse coagulation, the mass median aerodynamic diameter was calculated to be 0.45 μm at a dilution ratio of 21.7. Using a technique based on the dimensional change of collected droplet particles at various viewing angles of a scanning electron microscope, the count median diameter was estimated to be 0.22 μm. These values were in good agreement with those reported by others. The results suggest that there is a dilution value critical to the rapid evaporation and final particle size of the cigarette smoke aerosol. Once reaching this value, further dilution has little effect on the final particle size. By using the derived mass concentration and size distribution, the particle density, number concentration, and coagulation coefficient of the cigarette smoke aerosol were estimated to be 1.12 g/cm3, 7.20 × 109 particles/cm3, and 6.64 × 10 -10 cm3/s respectively. Solid particles > 1 μm were found in the first few puffs. These were considered to consist of tobacco debris.

The performance of a modified virtual impactor with a clean air core in the center of an aerosol flow is described. With this feature, the modified virtual impactor has overcome the inherent disadvantage of conventional designs which have fine particle contamination in the coarse particle fraction. Furthermore, the separation efficiency of this impactor can be predicted from the efficiency curve of the conventional type virtual impactor and the ratio of clean air flow to the total flow rate. With a higher clean air flow, the 50% cutoff Stokes number slightly increases and the efficiency curve has better separation characteristics. Internal wall losses in the impactor are a function of particle size and reach a local maximum near the 50% cutoff size.

Calibration curves of the aerodynamic particle sizer (APS) under different sets of operating conditions (i.e., pressure drop across the nozzle, flow rate, and ambient pressure) were obtained. Materials used included oleic acid (OA), dioctyl phthalate (DOP), polystyrene latex (PSL), and fused aluminosilicate particles (FAP). The effect of particle density on the calibration was not found to be significant among test aerosols (in the density range from 0.89 to 2.3 g/cm3). Calibration curves obtained at reduced ambient pressure were different from the manufacturer's curve, indicating that recalibration of the APS is required if other than standard operating conditions are used. However, all the curves can be consolidated into a unique curve that relates the Stokes number at the nozzle exit to the normalized particle velocity (particle velocity divided by gas velocity). Methods for calculating gas velocity, particle velocity, and other pertinent parameters for the APS were developed and the results are presented. Consequently, these parameters together with the unique curve can be used to generate calibration curves for any set of operating conditions without performing the experimental calibration in the laboratory. The geometric standard deviations of monodisperse aerosols measured by the APS are generally in good agreement (< 2%) with those determined by other methods, thus demonstrating the good resolution of the instrument.

The fractional deposition of cigarette smoke particles in the respiratory tracts of rats was studied. Male and female rats were conditioned in nose-only exposure tubes 25 min/day for 2 days, exposed to cigarette smoke at mass concentrations of 95 or 341 mg/m3 25 min/day for 3 days, and then exposed to smoke at mass concentrations of 212 and 657 mg/m3, 25 min/day for 5 days. Mainstream cigarette smoke was generated by a modified Walton smoking machine from two 1R3 research cigarettes burned sequentially for each exposure. Deposition studies were conducted by placing the rats in plethysmograph tubes to allow respiratory minute volume measurements during exposure, then exposing them to [14C] cigarette smoke at mass concentrations of 202 or 624 mg/m3 for 25 min, using the same smoking machine. Size distribution, real-time concentration, and 14C activity of the smoke particles were determined using a multijet Mercer impactor, a real-time aerosol monitor, and filter samples, respectively. Immediately after the exposure, the rats were terminated to determine the distribution of the 14C. Individual lung lobes, trachea and lobar bronchi, head, larynx, kidneys, liver, gastrointestinal (GI) tract, blood, and depelted carcass of each rat were analyzed for 14C content. Results showed that the GI tract contained 16–31% of the total activity, indicating significant clearance from the large airways and nose to the GI tract during the exposure and during the 10–15 min between the cessation of the exposure and the removal ofthe organs. Total deposition of the inhaled 14C activity was 20.1 � 1.6% for both exposure concentrations. The intrapulmonary deposition fractions (lung lobes plus airways below the lobar bronchi) were 12.4 � 0.9 and 15.9 � 1.4% for concentrations of 202 and 624 mg/m3 respectively, suggesting a slight enhancement in upper airway deposition for animals exposed to the higher smoke concentration.

Cigarette smoking can influence the pulmonary disposition of other inhaled materials in humans and laboratory animals. This study was undertaken to investigate the influence of cigarette smoke exposures of rats on the pulmonary clearance of inhaled, relatively insoluble radioactive tracer particles. Following 13 weeks of whole-body exposure to air or mainstream cigarette smoke for 6 hr/day, 5 days/week at concentrations of 0, 100, or 250 mg total particulate matter (TPM)/m3, rats were acutely exposed pernasally to 85Sr-labeled fused aluminosilicate (85Sr-FAP) tracer particles, then air or smoke exposures were resumed. A separate group of rats was exposed to the 85Sr-FAP then serially euthanized through 6 months after exposure to confirm the relative insolubility of the tracer particles. We observed decreased tracer particle clearance from the lungs that was smoke concentration-dependent. By 180 days after exposure to the tracer aerosol, about 14, 20, and 40% of the initial activity of tracer was present in control, 100 mg TPM/m3, and 250 mg TPM/m3 groups, respectively. Body weight gains were less in smoke-exposed rats than in controls. Smoke exposure produced lung lesions which included increased numbers of pigmented alveolar macrophages distributed throughout the parenchyma and focal collections of enlarged alveolar macrophages with concomitant alveolar epithelial hyperplasia and neutro-philic alveolitis. The severity of the lesions increased with smoke exposure duration and concentration to include interstitial aggregates of pigmented macrophages and interstitial fibrosis. Our data confirm previous findings that exposure to cigarette smoke decreases the ability of the lungs to clear inhaled materials. We further demonstrate an exposure-concentration related magnitude of effect, suggesting that the cigarette smoke-exposed rat constitutes a useful model for studies of the effects of cigarette smoke on the disposition of inhaled particles.