The deposition patterns of large-particle microbiological aerosols within the respiratory tract are not well characterized. A novel system (the flow-focusing aerosol generator [FFAG]) which enables the generation of large (>10-m) aerosol particles containing microorganisms under laboratory conditions was characterized to permit determination of deposition profiles within the murine respiratory tract. Unlike other systems for generating large aerosol particles, the FFAG is compatible with microbiological containment and the inhalational challenge of animals. By use of entrapped Escherichia coli cells, Bacillus atrophaeus spores, or FluoSphere beads, the properties of aerosols generated by the FFAG were compared with the properties of aerosols generated using the commonly available Collison nebulizer, which preferentially generates small (1-to 3-m) aerosol particles. More entrapped particulates (15.9-to 19.2-fold) were incorporated into 9-to 17-m particles generated by the FFAG than by the Collison nebulizer. The 1-to 3-m particles generated by the Collison nebulizer were more likely to contain a particulate than those generated by the FFAG. E. coli cells aerosolized using the FFAG survived better than those aerosolized using the Collison nebulizer. Aerosols generated by the Collison nebulizer and the FFAG preferentially deposited in the lungs and nasal passages of the murine respiratory tract, respectively. However, significant deposition of material also occurred in the gastrointestinal tract after inhalation of both the small (89.7%)-and large (61.5%)-particle aerosols. The aerosols generated by the Collison nebulizer and the FFAG differ with respect to mass distribution, distribution of the entrapped particulates, bacterial survival, and deposition within the murine respiratory tract.Environmental bioaerosols can have a profound influence on human health, due to infectious disease, hypersensitivity conditions (e.g., hay fever), and acute inflammatory responses resulting from the inhalation of irritants. Environmental aerosols comprise a polydisperse distribution composed of a range of particle sizes from submicron to large droplets thousands of microns in diameter. Hence, such aerosols contain a proportion of particles of Ͼ10 m, herein defined as "large particles." Indeed, analysis of the particle sizes containing bacteria within the atmosphere indicated that ϳ40% are greater than 7 m, due to adherence to debris (27). Environmental microbial aerosols can arise from a number of sources, including food processing (13,19,40); water sources, e.g., contaminated air conditioning systems, shower heads, water faucets, and cooling towers (2, 42, 53); pesticide sprayers (1); and fungal-spore generation (15, 26). The importance of bioaerosols from a civilian biodefense perspective was highlighted by the U.S. anthrax mail attacks in 2001 (3).In health care settings, nosocomial transmission may occur by patients coughing or sneezing, generating respirable particles within the diameter range of 0.5 to 12 m (6, 14); alternat...
This is an Open Access article, distributed under the terms of the Open Government Licence. http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Crown Copyright ?? 2016. Published by Elsevier Ltd. All rights reserved. The version of record (T. G. Foat, et al, 'A prototype personal aerosol sampler based on electrostatic precipitation and electrowetting-on-dielectric actuation of droplets', Journal of Aerosol Science, Vol. 95, pp. 43-53, May 2016) is available online at doi: https://doi.org/10.1016/j.jaerosci.2016.01.007.An electrostatic precipitator (ESP) based personal sampler with a laboratory based electrowetting-on-dielectric (EWOD) concentrator could provide a high concentration rate personal aerosol sampler system. A prototype system has been developed based on the concept of a lightweight personal ESP collecting aerosol particles onto a hydrophobic surface followed by the use of an EWOD actuated droplet system to transfer the deposited sample into a microlitre size water droplet.A personal sampler system could provide military or civilian personnel with a wide area biological monitoring capability supplying information on who has been infected, what they have been infected with, how much material they were exposed to and possibly where and when they were infected. Current commercial-off-the-shelf (COTS) personal sampler solutions can be bulky and use volumes of water to extract the sample that are typically a thousand times greater than the proposed method.Testing of the prototype ESP at a sample flow rate of 5Lmin-1 demonstrated collection efficiencies greater than 80% for sodium fluorescein particles larger than 4??m diameter and of approximately 50% at 1.5??m. The ESP-EWOD system collection efficiency measured for Bacillus atrophaeus (BG) spores with an air sample flow rate of 20L min-1 was 2.7% with a concentration rate of 1.9??105 min-1. This was lower than expected due to the corona ions from the ESP affecting the hydrophobicity of the collection surface and hence the EWOD efficiency. However, even with this low efficiency the concentration rate is more than an order of magnitude higher than the theoretical maximum of the best current COTS personal sampler. For an optimised system, ESP-EWOD system efficiency should be higher than 32% with a comparable increase in concentration rate
Following the malicious and/or accidental release of an aerosol of Bacillus anthracis spores, the immediate risk of human inhalation would decrease as the spores were deposited on surfaces or diluted by wind flow. There is, however, a concern that the deposited spores could become re-aerosolized and so present an ongoing hazard. Using an accurate simulant for B. anthracis spores a method is reported here that allowed the enumeration of re-aerosolized spores from concrete and turf by wind flow and footfall. Under the conditions used, the rates of re-aerosolization were low. These findings will need to be verified under real outdoor conditions before the true significance in terms of secondary exposure to pathogenic spores can be assessed.
Flow-focussing technology was harnessed to enable generation of large droplet aerosols within high-level microbiological containment. The Collison nebuliser and flow-focussing aerosol generator (FFAG) produced aerosols from distilled water with average mass median aerodynamic diameters (MMAD) of 4.19 and 11.93 lm, respectively. The medium type [water, phosphate buffered saline (PBS) or microbiological broth] had minimal effect on the droplet size generated by the FFAG. The FFAG can be modulated to generate reproducible aerosols with a wide range of MMADs (9-105 lm). The number of particulates (i.e. fluospheres) contained within the droplets increased as the MMAD increased from 12 to 50 lm. The technology described can be used for the exposure of small-animal models to large droplet aerosols ([10 lm) and has applications in healthcare, pharmaceutical, agricultural and biodefence environments.
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