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PubMedDate not supplied

Study on size distribution of total aerosol and water-soluble ions during an Asian dust storm event at Jeju Island, Korea.

Soil dust particles transported from loess regions of the Asian continent, called Asian dust, highly influences the air quality of north-eastern Asia and the northern Pacific Ocean. In order to investigate the effects of these dust storms on the chemical composition of atmospheric aerosol particles with different size, measurements of size distributions of total aerosol and major ion species were carried out on Jeju Island, Korea during April 2001. Juju Island was chosen for the study because the levels of emissions of anthropogenic air pollutants are very low. A 5-stage cascade impactor was used to sample size-fractionated aerosol particles. Samples were analyzed for major water-soluble ions using Dionex DX-120 ion chromatograph. The average mass concentration of total aerosol was found to be 24.4 and 108.3 microg m(-3) for non-Asian dust and Asian dust periods, respectively. The total aerosol size distribution, measured during the non-Asian dust period, was bimodal, whereas the coarse particles dominated the size distribution of total aerosol during the Asian dust period. It was found that SO4(2-), NH4+ and K+ were mainly distributed in fine particles, while Cl-, NO3-, Na+, Mg2+ and Ca2+ were in coarse particles. Although SO4(2-) was mainly distributed in fine particles, during the Asian dust period, the concentrations in coarse particles were significantly increased. This indicates heterogeneous oxidation of SO2 on wet surfaces of basic soil dust particles. The NH4+ was found to exist as (NH4)2SO4 in fine particles, with a molar ratio of NH4+ to SO4(2-) of 2.37 and 1.52 for non-Asian dust and Asian dust periods, respectively. Taking into account the proximity of the sampling site to the sea, and the observed chloride depletion, coarse mode nitrate, during the non-Asian dust period, is assumed to originate from the reaction of nitric acid with sodium chloride on the surfaces of sea-salt particles although the chloride depletion was not shown to be large enough to prove this assumption. During the Asian dust period, however, chloride depletion was much smaller, indicating coarse nitrate particles were mainly produced by the reaction of nitric acid with surfaces of basic soil particles. Most chloride and sodium components were shown to originate from sea-salt particles. Asian dust aerosols, arriving at Jeju Island, contained considerable amounts of sea-salt particles as they passed over the Yellow Sea. Ca2+ was shown to be the most abundant species in Asian dust particles.

Aerosols↗
PubMed2004

Aerosol dispersion of respirable particles in narrow size distributions produced by jet-milling and spray-drying techniques.

PURPOSE: To examine the effect of particle size and morphology on aerosol dispersion using jet-milled and spray-dried mannitol particles in narrow size distributions within the respirable range. METHODS: Particle size and morphology were examined by laser diffraction and scanning electron microscopy, respectively. Aerosol dispersion was examined using a cascade impactor with a preseparator operating at a flow rate of 60 L/min, using two inhaler devices: Rotahaler (low-resistance device) and Inhalator (high-resistance device). Powder flow was examined using static and dynamic methods (Carr's compressibility index and vibrating spatula, respectively). RESULTS: Narrow size distributions of jet-milled and spray-dried particles were produced (d50% = 1.4 to 10.3 microm, GSD = 1.8 to 2.1, and d50% = 1.6 to 7.5 microm; GSD = 1.5 to 1.9, respectively). All particles were highly crystalline. Differences in particle shape were observed between jet-milled and spray-dried particles. Higher fine particle fraction (FPF) and relative fine particle fraction (FPFrel) (greater aerosol dispersion) and lower geometric standard deviation (GSD) (less variation) were obtained using particles with d50% between 2 and 5 microm. Higher mass median aerodynamic diameter were obtained with larger d50%. Spray-dried particles produced greater aerosol dispersion compared with jet-milled particles. Greater aerosol dispersion was obtained using the Inhalator than the Rotahaler. CONCLUSIONS: Small changes in the particle size within the 1-10-microm range produced a major impact in the aerosol dispersion of jet-milled and spray-dried particles. Even in these narrow size ranges, aggregation plays an important role in aerosol dispersion.

Administration, Inhalation↗
PubMed1999

Correlation of urinary nickel excretion with observed 'total' and inhalable aerosol exposures of nickel refinery workers.

An investigation of the relationship between observed nickel aerosol exposures and urinary nickel excretion was undertaken at a Scandinavian nickel refinery. The goal of the study was to assess the impact of nickel aerosol speciation, the use of particle size-selective sampling instrumentation and adjustment of urinary levels for creatinine excretion on the usefulness of urinary nickel excretion as a marker for exposure. Urinary nickel measurements and paired 'total' and inhalable aerosol exposure measurements were collected each day for one week from refinery workers in four process areas. The mean observed urinary nickel concentration was 12 micrograms L-1 (11 micrograms of Ni per g of creatinine). The strongest relationships between urinary excretion and aerosol exposure were found when urinary nickel levels were adjusted for creatinine excretion and when exposure to only soluble forms of nickel aerosol was considered. No significant difference was observed between measures of 'total' and inhalable aerosol in the ability to predict urinary excretion patterns. In the light of these results, it is recommended that consideration be given to the chemical species distribution of nickel aerosol in the use of urinary nickel measurements as a screening tool for cancer risk in occupationally-exposed populations.

Adult↗
PubMed2005

Stratospheric temperature monitoring using a vibrational Raman lidar. Part 1: aerosols and ozone interferences.

Lidar measurements of temperature for the upper troposphere and lower stratosphere are commonly derived by the Raman technique. Lidar signals derived from vibrational Raman processes have been subjected to numerous simulation tests to examine their sensitivity to the presence of aerosols and ozone in the atmosphere. The influence of aerosols characteristics (wavelength dependence of aerosol extinction and particle phase function) and of ozone concentration on Raman temperature profiles is estimated. Simulations indicate large temperature deviations for post-volcanic conditions. For a Raman backscatter at 607 nm, bias is below 1 K for a total optical depth less than 9 x 10(-3) in the case of a stratospheric contamination and less than 6 x 10(-3) for a tropospheric contamination. The effect of aerosols depends on phase function and a few parameters such as altitude, optical depth and the shape of the high-altitude cloud. The wavelength dependence of aerosol extinction has some influence only for severe post-volcanic conditions (Scattering Ratio, SR >2). For a Raman backscatter at 387 nm, bias is larger and can be significant even in background aerosol conditions. Changes in the ozone density profile lead to significant Raman temperature deviations only for some specific conditions. Results suggest that both aerosol and ozone corrections are necessary to obtain an accuracy better than the 1 K requested for most atmospheric applications.

Aerosols↗
PubMed1985

Effects of aerosol corticosteroids on the voice: triamcinolone acetonide and beclomethasone dipropionate.

The present investigation compared the effects of triamcinolone acetonide (Aristocort Aerosol) and beclomethasone dipropionate (Vanceril Inhaler) on the vocal functioning of 11 chronic asthmatics. Using conventional aero-acoustic techniques, subjects' vocal fundamental frequency, maximum phonation time, and oral air volume velocity were sampled at baseline (oral corticosteroid use) and at the end of the first and second year of aerosol triamcinolone acetonide use. At the end of the second year of aerosol triamcinolone acetonide use, all subjects discontinued use of this compound and began use of aerosol beclomethasone dipropionate. Subjects' vocal performance then was sampled after 1 year of aerosol beclomethasone dipropionate use. Results of this study suggest that aerosol triamcinolone acetonide reduced the vocal dysfunction observed during the baseline period. When aerosol beclomethasone dipropionate was used, however, subjects' vocal performance was similar to that observed during the baseline period (oral steroid use).

Aerosols↗
PubMed1996

Pharmacodynamics and pharmacokinetics of BAY x 7195 aerosol, a new and selective receptor antagonist of cysteinyl-leukotrienes, in normal volunteers.

1. The safety, tolerability and pharmacokinetics of BAY x 7195 aerosol, a new selective receptor antagonist of cysteinyl-leukotrienes, were investigated in healthy male volunteers in two observational studies (1 and 2 mg; n = 5 each) and two double blind, placebo-controlled two way crossover studies (4 and 8 mg; n = 6 each) using the commercially available Inhaler Ingelheim M. 2. The pharmacodynamic effect was assessed by testing the ability of BAY x 7195 aerosol to inhibit leukotriene-D4 (LTD4) induced bronchoconstriction in healthy volunteers. Using a double-blind, placebo-controlled three way crossover design, volunteers received 2 and 4 mg of BAY x 7195 by means of a newly developed metered dose dry powder inhaler. Bronchoprovocation with nebulized LTD4 was performed 20 min and 8 h (n = 6 each) after drug administration. Specific airways of conductance (SGaw) served to assess the airway's response. 3. BAY x 7195 aerosol was safe and well tolerated. Inhalation of the aerosol had no effect on baseline lung function. Only one volunteer reported cough following the inhalation of the 8 mg dose. 4. The pharmacokinetics of unchanged drug following the administration of BAY x 7195 aerosol were linear in the investigated range of doses and in general very similar to a previously investigated tablet formulation. Plasma-concentration vs time courses followed a two-compartment body model. Compared with oral administration of the tablet formulation absorption tended to be more rapid with the aerosol formulation. 5. Compared with placebo, 2 and 4 mg BAY x 7195 increased the concentration of LTD4 needed to produce a 35% decrease in SGaw 20 min after drug administration by a mean (geometric) of 14.2 and 29.7 fold, respectively. For both doses only three volunteers showed a protective effect against LTD4 induced bronchoconstriction 8 h after drug administration. Individual shifts in the concentration-response curve ranged between 0.4 and 7.2 fold. 6. In conclusion, the present results suggest that BAY x 7195 aerosol is a safe and potent but short acting receptor antagonist of cysteinyl leukotrienes in man.

Administration, Inhalation↗
PubMed2002

Aerosol delivery of virulent Mycobacterium bovis to cattle.

SETTING: Although animal models of aerosol inoculation of Mycobacterium tuberculosis and M. bovis have been reported using laboratory animals, a model of aerosol delivery of M. bovis to cattle has not been reported previously. OBJECTIVE: Develop and characterize a model of aerosol delivery of M. bovis to cattle, and compare the distribution of lesions in cattle infected with either of two different strains of M. bovis, one isolated from cattle (HC2005T), and the other isolated from white-tailed deer (1315). DESIGN: Cattle (n=20, female and castrated males) aged 4 months, were infected with 1 x 10(3) (n=5) or 1 x 10(5) (n=5) colony-forming units (CFU) of M. bovis 1315 or 1 x 10(3) (n=5) or 1x10(5) (n=5) CFU of M. bovis HC2005T. Calves were infected using a commercially available aerosol delivery system. One hundred fifty-five days after infection, calves were euthanized, examined and tissues collected for microscopic analysis and bacteriologic culture. RESULTS: Nineteen of 20 calves developed tuberculosis. Typical tuberculous lesions were most pronounced in the lungs and tracheobronchial and mediastinal lymph nodes. CONCLUSION: The system described provides a reliable method of aerosol delivery of M. bovis to cattle. Lesion distribution suggests that the aerosolized inoculum was delivered deep into pulmonary alveoli and thus represents true aerosol exposure. Disease was more severe in groups receiving the highest dose of either inoculum strain; however, differences between strains were not seen. Published by Elsevier Science Ltd.

Aerosols↗
PubMedDate not supplied

Analysis of aerosol deposition in the healthy human lung.

Wide variation in the pattern of deposition of inhaled aerosols has previously been described in both healthy and diseased humans. To investigate the factors responsible for such variation, the authors studied a group of 13 healthy nonsmoking subjects. One two occasions each subject inhaled a monodisperse 8.1 mm (mass median aerodynamic diameter) Fe2O3 aerosol labelled with 99mTc using a standardized breathing pattern. Pulmonary function was defined by tests of forced expiratory airflow. Total activity in the right lung at 0 hr and at 24 hr (24-hr percent retention) was measured using a gamma camera. Numerical indices of deposition pattern were derived in several ways from the initial gamma camera image of the right lung by comparing the ratio of activity within a mid- and peripheral lung region of interest, by analyzing the profile of radioactivity within a horizontal band across the right lung from the midline to the lung edge, and by analysis of a distribution histogram of activity within the whole lung (skew and kurtosis). The 24-hr percent retention of aerosol showed considerable intrasubject variability unlike the deposition indices. The various deposition indices were found to correlate with the 24-hr percent retention, FEV1.0, FEV1.0/FVC%, and MMFR at varying levels of significance. Results indicate that the pattern of aerosol deposition in healthy humans is influenced by mild degrees of obstruction to airflow, as reflected by tests of forced expiratory airflow, increasing airways obstruction being associated with more central deposition of the inhaled aerosol. Deposition indices derived from the initial pattern of aerosol distribution within the lung may prove to be more reliable and sensitive than measurements of 24-hr percent retention in defining aerosol deposition pattern.

Adult↗
PubMed2004

Aerosolization of Mycoplasma synoviae compared with Mycoplasma gallisepticum and Enterococcus faecalis.

In order to study the airborne transmission of an arthropathic strain of Mycoplasma synoviae, preliminary aerosol experiments were performed. They were conducted in duplicate in an empty isolator (1.3 m3) to assess the yield and viability of M. synoviae with time compared with Mycoplasma gallisepticum and Enterococcus faecalis. After aerosol generation air samples were taken with two different devices using gelatine or cellulose nitrate filters. There was no difference between the devices, but cellulose nitrate filters yielded very low bacterial counts. The aerosolized dose per isolator for M. synoviae was 3.4 x 10(10) colony-forming units (cfu), for M. gallisepticum was 2.6 x 10(10) cfu and for E. faecalis was 3 x 10(10) cfu. Immediately after aerosolization, concentrations of about 10(6) to 10(7) cfu/m3, 10(7) to 10(8) cfu/m3 and 10(8) to 10(9) cfu/m3 air of M. synoviae, M. gallisepticum and E. faecalis were found, respectively. At 25 min M. synoviae concentrations dropped below the detection level (<4 x 10(4) cfu), while 10(5) to 10(6) and 10(8) to 10(9) cfu were found for M. gallisepticum and E. faecalis, respectively. The average M. synoviae concentration during the experiment was estimated at 10(2) to 10(3) cfu/l. The M. gallisepticum and E. faecalis aerosol generated an average of approximately 10(3) to 10(4) cfu/l air and 10(5) to 10(6) cfu/l air, respectively. Thus mycoplasma and E. faecalis aerosols were successfully generated despite considerable initial loss as measured by culture. The loss was greater in the mycoplasma aerosols, especially those of M. synoviae.

Aerosols↗
PubMed2002

Pulmonary effects of ultrafine and fine ammonium salts aerosols in healthy and monocrotaline-treated rats following short-term exposure.

In the present study the effects of a 3-day inhalation exposure to model compounds for ambient particulate matter were investigated: ammonium bisulfate, ammonium ferrosulfate, and ammonium nitrate, all components of the secondary aerosol fraction of ambient particulate matter (PM), and carbon black (CB, model aerosol for primary PM). The objective of this study was to test the hypothesis that secondary model aerosols exert acute pulmonary adverse effects in rats, and that rats with pulmonary hypertension (PH), induced by monocrotaline (MCT), are more sensitive to these components than normal healthy animals. An additional aim was to test the hypothesis that fine particles exert more effects than ultrafines. Healthy and PH rats were exposed to ultrafine (mass median diameter [MMD] approximate, equals 0.07-0.10 microm; 4 x 10(5) particles/cm(3)) and fine (MMD approximate, equals 0.57-0.64 micro;m; 9 x 10(3) particles/cm(3)) ammonium aerosols during 4 h/day for 3 consecutive days. The mean mass concentrations ranged from 70 to 420 microg/m(3), respectively, for ultrafine ammonium bisulfate, nitrate, and ferrosulfate and from 275 to 410 microg/m(3) for fine-mode aerosols. In an additional experiment, simultaneous exposure to a fine CB aerosol (0.6 microm; 2-9 mg/m(3)) and ammonium nitrate (0.4-18 mg/m(3)) was performed. Bronchoalveolar lavage fluid (BALF) analysis and histopathological examination were performed on animals sacrificed 1 day after the last exposure. Histopathology of the lungs did not reveal test atmosphere-related abnormalities in either healthy or PH rats exposed to the ammonium salts, or to a combination of CB + nitrate. Alveolar macrophages in rats exposed to CB only revealed the presence of black material in their cytoplasm. There were no signs of cytotoxicity due to the aerosol exposures (as measured with lactate dehydrogenase [LDH], protein, and albumin contents in BALF). Macrophages were not activated after MCT treatment or the test atmospheres, since no changes were observed in N-acetyl glucosaminidase (NAG). Cell differentiation profiles were inconsistent, partly caused by an already present infection with Haemophilus sp. However, we believe that the test atmospheres did not affect cell differentiation or total cell counts. The results show that at exposure levels of ammonium salts at least one order of magnitude higher than ambient levels, marked adverse health effects were absent in both healthy and PH rats.

Administration, Inhalation↗
PubMedDate not supplied

Chemoprevention of tobacco smoke-induced lung tumors by inhalation of an epigallocatechin gallate (EGCG) aerosol: a pilot study.

We investigated whether inhalation of aerosolized epigallocatechin gallate (EGCG) would prevent the development of lung tumors produced by tobacco smoke (TS). Male strain A/J mice were exposed for 5 mo, 6 h/day, 5 days/wk, to a mixture of tobacco sidestream and mainstream smoke. At the end of this exposure, 3 groups were formed: (a) mice exposed to TS and left undisturbed in air; (b) animals exposed to TS and given EGCG aerosol by nose-only inhalation for 30 min per session; and (c) animals exposed to TS and then exposed by nose-only inhalation to water aerosol without any EGCG (sham-exposed group). Three similar groups were formed from animals that previously had been kept in filtered air. In experiment 1, the EGCG concentration in the aerosol was 80 microg/L and administered 3 times a week and in experiment 2 it was 191 microg/L administered twice a week. Inhalation of EGCG did not modulate TS-induced tumorigenesis. In two accompanying positive control experiments, animals treated with the tobacco-specific carcinogen NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone] were given the same EGCG or water aerosol treatment. In both experiments, EGCG aerosol significantly reduced lung tumor multiplicity by 20% to 30% However, exposure of NNK-treated animals to water solvent alone (sham exposure) produced an even greater reduction in tumor multiplicities (40%). A reduction of lung tumor multiplicities was also observed in animals exposed nose-only once or five times a week to either water aerosols or to filtered air. It is concluded that water-soluble chemopreventive agents that need to be ingested in comparatively high doses are not the most suitable candidates for administration by inhalation.

Aerosols↗
PubMed2000

Electrostatic N-95 respirator filter media efficiency degradation resulting from intermittent sodium chloride aerosol exposure.

The effects of intermittently loading small masses of sodium chloride aerosol on the filtration efficiency of N-95 filtering facepiece respirators was investigated. The National Institute for Occupational Safety and Health (NIOSH) certifies that N-95 respirators must provide at least 95 percent filtration efficiency against a sodium chloride aerosol challenge as per the respirator certification (42 CFR 84) test criteria. N-95 respirators are specified for protection against solid and water-based particulates (i.e., non-oil aerosols). New N-95 respirators from three different manufacturers were loaded with 5 +/- 1 mg of sodium chloride aerosol one day a week, over a period of weeks. Aerosol loading and penetration measurements were performed using the TSI 8130 Filter Tester. Respirators were stored uncovered on an office desktop outside the laboratory. To investigate environmental and temporal effects of filters being stored without sodium chloride exposure, control respirators were stored on the desk for various lengths of time before being initiated into weekly testing. For all manufacturers' respirators, the controls showed similar initial penetrations on their day of initiation (day zero) to those of the study samples on day zero. As the controls were tested weekly, they showed similar degradation rates to those of the study samples. Results show that some of the manufacturers' models had penetrations of greater than 5 percent when intermittently exposed to sodium chloride aerosol. It is concluded that intermittent, low-level sodium chloride aerosol loading of N-95 respirators has a degrading effect on filter efficiency. This reduction in filter efficiency was not accompanied by a significant increase in breathing resistance that would signal the user that the filter needs to be replaced. Furthermore, it was noted that the effect of room storage time prior to initial exposure was much less significant.

Aerosols↗
PubMed2001

Fusion of SeaWiFS and TOMS satellite data with surface observations and topographic data during extreme aerosol events.

Spaceborne sensors allow near-continuous aerosol monitoring throughout the world. This paper illustrates the fusion of Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and TOMS satellite data with surface observations and topographic data during four extreme aerosol events: (1) the April 1998 Asian dust storm that impacted the west coast of North America, (2) the May 1998 Central American forest fire smoke that impacted eastern North America, (3) the intense fall 1999 northern California fires, and (4) the massive February 2000 Sahara dust storm. During these dust and smoke events, the aerosol was visualized on true color SeaWiFS images as a distinct yellowish dye, the result of the aerosol increasing the reflectance of darker surfaces (ocean and land) and decreasing the reflectance of clouds. TOMS imagery also indicated increased aerosol absorption in the affected areas, while surface monitors measured major reductions in visual range. Fusing these data aids in the determination of the aerosol's spatial, temporal, and optical properties and provides supporting evidence for characterizing what is being visualized as dust or smoke. A 3-dimensional perspective of the events is obtained when incorporating topographic data and provides insight into the vertical properties of the aerosol plumes.

Aerosols↗
PubMed2005

Modeling inorganic aerosols and their response to changes in precursor concentration in Mexico City.

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.

Aerosols↗
PubMedDate not supplied

Generation and characterization of condensation aerosols of benzo[alpha]pyrene.

Condensation aerosols of benzo[a]pyrene (BAP) with particle sizes ranging from 0.1 to 2 micrometers (aerodynamic diameter) were produced and studied. These aerosols were generated in a glove box by direct vaporization of BaP and homogeneous condensation of the vapor. The aerosol concentration ranged from 50 to 700 micrograms/l with aerosol production rates up to 15 mg BaP per minute. The effects of vaporization temperature and flow rate of diluting air on the particle size distribution and aerosol output were studied. The BaP aerosol was produced with relatively constant mass concentration and particle size distribution for more than 5 h. The aerosol was physicochemically and thermally stable. Data on the in vitro dissolution of BaP particles in aqueous solvents and in different dissolution systems suggested that the organic BaP particle does not dissolve in simple aqueous solvents. Proteins, surfactants, or ethyl alcohol enhanced the rate of dissolution of BaP. The rate of dissolution of BaP particles was inversely proportional to particle size.

Aerosols↗
PubMed1980

Laboratory production of ammonium and ferric sulfate aerosols.

Since sulfate aerosol particles are an environmental factor of possible concern, laboratory studies are being conducted to determine their health effects. It is important in such studies that aerosols be controlled and monitored. Submicron sulfate aerosols at high (greater than 80%) and low (30-40%) relative humidities were generated and characterized in support of animal inhalation experiments. Aqueous solutions of ammonium sulfate and ferric sulfate were aerosolized with a compressed air nebulizer, dried, discharged and passed into an aerosol chamber. Aerosol characterization was performed using cascade impactors, electron microscopy, filter samples and an electrical mobility analyzer. Parameters measured included particle size distribution and mass concentration. Instruments used for sizing the aerosols were compared. The electrical mobility analyzer provided useful information on the time stability of the particle size and the mass concentration, but agreement between this instrument and electron microscopy or cascade impaction was poor.

Aerosols↗
PubMed1980

The interaction of bromine with micron and submicron aerosols.

This study was undertaken to gain a better understanding of the reactions of aerosols with gases and vapors. The experimental system was designed in which both phases were dispersed. A collision-type nebulizer was used to generate monodisperse aerosols of 0.234, 0.500, 0.804, 1.101 and 2.020 microns diameter. Bromine concentrations of 100 and 200 ppm were produced to interact with the aerosolS. A light-scattering optical particle counter was used to determine the particle number concentration. Reacted aerosol collected on Teflon filters was analyzed by energy-dispersive x-ray fluorescence. Two temperature regimes were selected: approximately 26 degrees C and 60 degrees C. Separate runs were also conducted for the extreme case of zero curvature using 25 microns thick polystyrene sheet. Data generated from this study show a strong dependence of bromine levels on particle size. As the particle size increased, the amount of bromine per particle (ng Br/particle) also increased. However, on a weight-to-weight basis (ng Br/ng aerosol), the amount of bromine was found to increase with decreasing particle size. The concentration dependence on particle diameter was more strongly associated with values between d2 and d3. This dependence, together with other experimental data, supports a shrinking-unreacted core physical model for the actual reaction. When Br2 concentration or reaction temperature was increased, higher levels of bromine resulted in the aerosol. Runs where both temperature and concentration were increased showed lower levels of bromine than with an increase in either variable. One possible explanation is that the relative rates of reaction on the surface of the particle and diffusion through the reacted shell may be the influencing factors. Brominated polystyrene sheet material showed substantially lower bromine levels than the aerosols.

Adsorption↗
PubMed1986

Studies of the temporal and spatial distribution of aerosols in multi-tiered inhalation exposure chambers.

Two multi-tiered whole body inhalation exposure chambers with nominal volumes of 1 m3 (H-1000) and 2 m3 (H-2000) were evaluated for their performance in terms of the temporal and spatial distribution of test aerosols within the chamber. Parameters investigated included chamber type, single-chamber-single-aerosol generator versus two-chamber-single-aerosol generator systems, chamber air supply and exhaust systems, particle size, and aerosol diluter type. Results indicated that: 1) particle size has an effect on chamber aerosol concentration distribution, with the larger particle resulting in a higher variation; 2) the single-chamber-single-generator system is more stable than the two-chamber-single-generator system; 3) the H-2000 chamber has a lower aerosol spatial variability than the H-1000 chamber; and 4) the aerosol distribution within the chamber could be improved with the use of a newly designed diluter.

Aerosols↗