Aerosols deposition

The basic operations in dust collection by any device are (1) separation of the gas-borne particles from the gas stream by deposition on a collecting surface (2) retention of the deposit on the surface and (3) removal of the deposit from the surface for recovery or disposal. The separation step requires (1) application of a force that produces a differential motion of a particle relative to the gas and (2) a gas retention time sufficient for the particle to migrate to the coUecting surface. The principal mechanisms of aerosol deposition that are apphed in dust collectors are (1) gravitational deposition, (2) flow-line interception, (3) inertial deposition, (4) diffusional deposition, and (5) electrostatic deposition. Thermal deposition is only a minor factor in practical dust-collectiou equipment because the thermophoretic force is small. Table 17-2 lists these six mechanisms and presents the characteristic... 

TABLE 17-2 Summary of Mechanisms and Parameters in Aerosol Deposition... 

The major effects of air pollution on fabrics are soiling and loss of tensile strength. Sulfur oxides are considered to cause the greatest loss of tensile strength. The most widely publicized example of this type of problem has been damage to women s nylon hose by air pollution, described in newspaper accounts. The mechanism is not understood, but it is postulated that fine droplets of sulfuric acid aerosol deposit on the very thin nylon... 

Kaufman, J. W. (1999). The role of upper airway heat and water vapor exchange in hygroscopic aerosol deposition iii the human airway. In Toxicity Assessment Alternatives Methods, Issues, Opportunities (H. Salem and S.A. Katz, Eds.), pp. 63-70. Humana Press Inc., Totow a, NJ. 

Most lung deposition models are based on the influence of particle size on aerosol deposition. Breathing parameters, such as breathing frequency and tidal volume, play a key role in lung deposition [15]. Table 2 shows the breathing parameters for healthy male volunteers subjected to various levels of exercise on a bicycle ergometer [16], There are known differences in these parameters based on gender, age, and disease... 

A variety of species of laboratory animal are employed to study aerosol deposition for both efficacy and toxicity. It is important to recognize that the breathing parameters [17], not to mention the anatomy [18], of these animals differ substantially from humans. Table 3 shows a range of breathing parameters for several species of laboratory animal. Clearly there is a matter of scale involved in that small animals cannot generate the same airflow volumes as humans and to some extent compensate by increasing their respiratory rate. 

Clair C. Patterson, T. J. Chow, and M. Murozumi. The Possibility of Measuring Variations in the Intensity of Worldwide Lead Smelting during Medieval and Ancient Times Using Lead Aerosol Deposits in Polar Snow Strata. In Scientific Methods in Medieval Archaeology. Rainer Berger, ed. Berkeley University of California Press, 1970, pp. 339-350. 

Most dosimetry models have incorporated the so-called Weibel A airway dimensions (Weibel, 1963) in order to calculate aerosol deposition, clearance and the density of alpha-decays per unit surface... 

The deposition model used here includes expressions for diffusion (Ingham, 1975) sedimentation (Pich, 1972) and impaction (Egan and Nixon, 1985) and a realistic treatment of lung ventilation. It can be shown that this predicts the aerosol deposition measured in the lungs of human subjects (summarised by Rudolf (1986)) over the range of aerosol size from 5 nm to 5 pm diameter, and for all breathing conditions tested, to within 207o of measured values. 

Egan, M.J. and W. Nixon, A Model of Aerosol Deposition in the Lung for Use in Inhalation Dose Assessments, Radiat. Prot. Dosim. 11 5-17 (1985)... 

An Empirical Formula Describing Aerosol Deposition in Man for Any Particle Size, J. Aerosol Sci. 17 350-355 (1986). 

After exposure, the outside surface of the cast was cleansed until the activity of the washes was less than 10X the background of a gamma well scintillation counter. The cast was cut into separate bifurcations and airway sections and each section was counted to determine the amount of aerosol deposited. Sane samples contained both airway and bifurcation sections because of the complex configuration of the cast. For combination samples, the total activity deposited was equally apportioned between each of the airways and bifurcations. End airways were included for determination or total deposition but not in any of the analyses because flow disturbances at open ends may have affected deposition. The surface area of each sample was measured separately. The surface density for each cast segment was calculated by dividing the activity measured in the sample by the interior surface area of that sample. 

Cuddihy et al. (1978) reviewed a set of experimental data on lung, liver, and skeletal radioactivity after inhalation of 144CeCla by beagles (Boecker and Cuddihy, 1974) to determine the possible range of individual organ burdens in the total population. A second study on variability of aerosol deposition patterns in dogs (Cuddihy and... 

The systematic removal of elements by runoff and the reimmobilization from solution by organic matter are continuously counterbalanced by the new input of chemical species, which maintain both biological and biogeochemical cycles. The main sources of water-soluble elements are oceanic aerosols deposited on the land surface and the weathering of rocks. The airborne input of the trace metals may be ranked as follows for the Spitzbergen island ecosystems (Table 4). 

Moropoulou, A., Bisbikou, K., Van Grieken, R., Torfs, K., and Polikreti, K. (2001). Correlation between aerosols, deposits and weathering crusts on ancient marbles. Environmental Technology 22 607-618. 

Soluble aerosols deposited on the epithelial linings of the respiratory tract are absorbed and metabolized in the same way as soluble gases and vapors. 

Cooney D, Kazantseva M, Hickey AJ (2004) Development of a size-dependent aerosol deposition model utilising human airway epithelial cells for evaluating aerosol drug delivery. Altern Lab Anim 32(6) 581-590. 

The second part describes different experimental approaches to simultaneously assess deposition and subsequent absorption of pharmaceutical aerosol formulations, typically by adapting some existing impactor/impinger devices to accommodate pulmonary epithelial cell culture systems. Differences between longtime and low-dose aerosol deposition in environmental toxicology and short time bolus inhalation of pharmaceutical aerosols are elucidated. 

Newman, S.P., Clark, A.R., Talaee, N., and Clarke, S.W., Pressurized aerosol deposition in the human lung with and without an open spacer device. Thorax, 44 706-710 (1989). Newman, S.P., Clark, A.R., Talaee, N., and Clarke, S.W., Lung deposition of 5 mg Intal from a pressurized metered dose inhaler assessed by radiotracer technique, Int. J. Pharm., 74 203-208 (1991). 

Farr, S.J., Rowe, A.M., Rubsamen, R., and Taylor, G., Aerosol deposition in the human lung following administration from a microprocessor controlled pressurised metered dose inhaler. Thorax, 50 639-644 (1995). 

Because of the complexity of the actual structures, the emphasis in modeling has been on obtaining an average representation, and the variability among individuals tends to be neglected. There are two experimental studies of variability of airway dimensions in living humans as revealed by aerosol-deposition studies. Lapp et al. assessed the size of alveolar spaces in terms of half-life of aerosol persistence during breath-... 

Bell, K. A. Aerosol Deposition in Models of a Human Lung Bifurcation. Ph.D. Thesis. Pasadena California Institute of Technology, 1974. 426 pp. 

Bell, K. A., and S. K. Friedlander. Aerosol deposition in models of a human lung bifurcation. Staub-Reinhalt Luft. 33 178-182, 1973. 

Kliment, V. Similarity and dimensional analysis, evaluation of aerosol deposition in the lungs of laboratory animals and man. Folia Morphol. 21 59-64, 1973. 

Palmes, E. D., and M. Lippmann. Influence of respiratory air space dimensions on aerosol deposition. In W. H. Walton, Ed. Inhaled Particles IV. Proceedings of the Fourth International Symposium on Inhaled Particles and Vapors, British Occupational Hygiene Society, Edinburgh. September, 1975. London Pergamon Press, Ltd. (in press)... 

---