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Evaluation of a novel bioaerosol generation device for the use in studies requiring airborne microorganism agglomerates
J Aerosol Sci Vol. 31, Suppl. 1, pp. $80-$8 l, 2000
Pergamon
www.elsevier.com/locate/jaerosci
Session 2 B - I n s t r u m e n t
evaluation
II
EVALUATION OF A NOVEL BIOAEROSOL GENERATION DEVICE FOR THE USE IN
STUDIES l~QUIRING AIRBORNE MICROORGANISM A G G L O M E R A T E S E. C. BELL, T. L. HALE, M. J. SHAW AND R. S. BLACK Battelle Memorial Institute, Aerosol Science and Technology Assessment Group Columbus, Ohio, USA.
Keywords: BIOAEROSOL, AEROSOL GENERATION
INTRODUCTION
Airborne microorganisms of epidemioiogical interest often occur in nature as agglomerates, as opposed to individual organisms. Further, the physiological effects of inhaled aerosols are often related to their site of deposition within the human respiratory tract, which depends primarily on particle size. As a result, studies evaluating human health effects often require controlled generation of larger respirable (3-10 ~tm) organism agglomerates, as well as the more commonly examined smaller bioaerosols (1-3 ~tm) consisting of single organisms. Typical methods of aerosol generation from a liquid suspension, such as the Collison nebulizer, do not permit adequate control of both the particle size and the amount of aerosol delivered without the addition of bulking agents that may alter important bioaerosol characteristics. A device developed by ECBC (Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD) has been evaluated at Battelle for its capability to control both the size and concentration of a generated bioaerosol. This device, the Ink Jet Aerosol Generator (IJAG), has been evaluated with respect to reproducible trace level output concentration, size distribution, and generation stability over time with the aerosolization of a selected virus and several bacteria.
METHODS The IJAG device uses technology from ink jet printing devices to generate an aerosol. Nozzles are fired at varying rates, generating droplets approximately 50 p.m in size. Prior to leaving the IJAG, droplets are carried through a drying section to evaporate the liquid, leaving only the agglomerated material. The resulting agglomerate size (typically between 1 and 10 p.m) is dependent upon the concentration in the liquid suspension. Tests were conducted using the bacteria Bacillus globigii and Erwinia herbicola, and the virus MS2. The aerosols were generated into a test system comprising a drying chamber and subsequent sampling chamber. The aerosol was characterized using the Aerodynamic Particle Sizing (APS) instrument (ThermoSystems Inc.) for determination of the overall particle size distribution. Several bioaerosol collection methods were used to examine the culturable aspects of the aerosol. A series of filters was used to determine the total culturable aerosol concentration. The Andersen viable cascade impactor and the Battelle cascade impactor were both used to obtain information regarding the size distribution of the culturable organisms. Tests were also performed with the Collison nebulizer (BGI, Inc.) for comparison. Experimentation was performed to identify the appropriate liquid concentration of a material to deliver a desired agglomerate size. Studies were performed with several concentrations of Bacillus globigii, Erwinia herbicola, and MS2 suspensions to generate these relationships. The particle size of the aerosol
$80
Abstracts of the 2000 EuropeanAerosol Conference
$81
was further characterized using scanning electron microscope imagery of the collected organism agglomerates. The I JAG output over a long period of time was established, with only a small amount of drift over several hours observed. The ability of this device to reproducibly generate trace levels of the bioaerosols at varying particle sizes was demonstrated.
CONCLUSIONS The IJAG device can be used to generate a consistent amount of aerosol of a desired particle size in the respirable size range. When properly established and maintained, a test system with an HAG aerosol can be a valuable test and evaluation tool, especially when very low air concentrations or when narrow, controlled size distributions are required. This type of bioaerosoi generation device would be invaluable for studies involving human health effects, where infectivity by larger organism agglomerates may play an important role.
ACKNOWLEDGEMENTS We would like to acknowledge the Edgewood Chemical and Biological Center for the use of the IJAG device.
REFERENCES Cascade Impactor, Delron Cascade lmpactor Model DCI-6 and DCI-5, Specification Sheet, Delron Research Products Co. Cox, C.S., C.M. Wathes (1995). Bioaerosols Handbook, (CRC Press, Inc., London). Lighthart, B., A.J. Mohr (1998). Atmospheric MicrobialAerosols, (Chapman & Hall, London). Lundholm, I.M. (1982). Comparison of Methods for Quantitative Determinations of Airborne Bacteria and Evaluation of Total Viable Counts, Applied and Environmental Microbiology 44, 179-183. May, K. R. (1973). The Collison Nebulizer: Description, Performance and Application, Aerosol Science 4, 235-243. Qian, Y., K. Willeke, V. Ulevicius, S.A. Grinshpun, and J. Donnelly (1995). Dynamic Size Spectrometry of Airborne Microorganisms: Laboratory Evaluation and Calibration, Atmospheric Environment 29, 1123-1129.
Scheuermann, E.A. (1973). The Geletin Membrane Filter Method for the Determination of Airborne Bacteria, Drugs Made Get., 16, 59-68. Schlesinger, R.B. (1985). Comparative Deposition of Inhaled Aerosols in Experimental Animals and Humans: A Review, Journal of Toxicology and Environmental Health 15, 197-214.
Pergamon
www.elsevier.com/locate/jaerosci
Session 2 B - I n s t r u m e n t
evaluation
II
EVALUATION OF A NOVEL BIOAEROSOL GENERATION DEVICE FOR THE USE IN
STUDIES l~QUIRING AIRBORNE MICROORGANISM A G G L O M E R A T E S E. C. BELL, T. L. HALE, M. J. SHAW AND R. S. BLACK Battelle Memorial Institute, Aerosol Science and Technology Assessment Group Columbus, Ohio, USA.
Keywords: BIOAEROSOL, AEROSOL GENERATION
INTRODUCTION
Airborne microorganisms of epidemioiogical interest often occur in nature as agglomerates, as opposed to individual organisms. Further, the physiological effects of inhaled aerosols are often related to their site of deposition within the human respiratory tract, which depends primarily on particle size. As a result, studies evaluating human health effects often require controlled generation of larger respirable (3-10 ~tm) organism agglomerates, as well as the more commonly examined smaller bioaerosols (1-3 ~tm) consisting of single organisms. Typical methods of aerosol generation from a liquid suspension, such as the Collison nebulizer, do not permit adequate control of both the particle size and the amount of aerosol delivered without the addition of bulking agents that may alter important bioaerosol characteristics. A device developed by ECBC (Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD) has been evaluated at Battelle for its capability to control both the size and concentration of a generated bioaerosol. This device, the Ink Jet Aerosol Generator (IJAG), has been evaluated with respect to reproducible trace level output concentration, size distribution, and generation stability over time with the aerosolization of a selected virus and several bacteria.
METHODS The IJAG device uses technology from ink jet printing devices to generate an aerosol. Nozzles are fired at varying rates, generating droplets approximately 50 p.m in size. Prior to leaving the IJAG, droplets are carried through a drying section to evaporate the liquid, leaving only the agglomerated material. The resulting agglomerate size (typically between 1 and 10 p.m) is dependent upon the concentration in the liquid suspension. Tests were conducted using the bacteria Bacillus globigii and Erwinia herbicola, and the virus MS2. The aerosols were generated into a test system comprising a drying chamber and subsequent sampling chamber. The aerosol was characterized using the Aerodynamic Particle Sizing (APS) instrument (ThermoSystems Inc.) for determination of the overall particle size distribution. Several bioaerosol collection methods were used to examine the culturable aspects of the aerosol. A series of filters was used to determine the total culturable aerosol concentration. The Andersen viable cascade impactor and the Battelle cascade impactor were both used to obtain information regarding the size distribution of the culturable organisms. Tests were also performed with the Collison nebulizer (BGI, Inc.) for comparison. Experimentation was performed to identify the appropriate liquid concentration of a material to deliver a desired agglomerate size. Studies were performed with several concentrations of Bacillus globigii, Erwinia herbicola, and MS2 suspensions to generate these relationships. The particle size of the aerosol
$80
Abstracts of the 2000 EuropeanAerosol Conference
$81
was further characterized using scanning electron microscope imagery of the collected organism agglomerates. The I JAG output over a long period of time was established, with only a small amount of drift over several hours observed. The ability of this device to reproducibly generate trace levels of the bioaerosols at varying particle sizes was demonstrated.
CONCLUSIONS The IJAG device can be used to generate a consistent amount of aerosol of a desired particle size in the respirable size range. When properly established and maintained, a test system with an HAG aerosol can be a valuable test and evaluation tool, especially when very low air concentrations or when narrow, controlled size distributions are required. This type of bioaerosoi generation device would be invaluable for studies involving human health effects, where infectivity by larger organism agglomerates may play an important role.
ACKNOWLEDGEMENTS We would like to acknowledge the Edgewood Chemical and Biological Center for the use of the IJAG device.
REFERENCES Cascade Impactor, Delron Cascade lmpactor Model DCI-6 and DCI-5, Specification Sheet, Delron Research Products Co. Cox, C.S., C.M. Wathes (1995). Bioaerosols Handbook, (CRC Press, Inc., London). Lighthart, B., A.J. Mohr (1998). Atmospheric MicrobialAerosols, (Chapman & Hall, London). Lundholm, I.M. (1982). Comparison of Methods for Quantitative Determinations of Airborne Bacteria and Evaluation of Total Viable Counts, Applied and Environmental Microbiology 44, 179-183. May, K. R. (1973). The Collison Nebulizer: Description, Performance and Application, Aerosol Science 4, 235-243. Qian, Y., K. Willeke, V. Ulevicius, S.A. Grinshpun, and J. Donnelly (1995). Dynamic Size Spectrometry of Airborne Microorganisms: Laboratory Evaluation and Calibration, Atmospheric Environment 29, 1123-1129.
Scheuermann, E.A. (1973). The Geletin Membrane Filter Method for the Determination of Airborne Bacteria, Drugs Made Get., 16, 59-68. Schlesinger, R.B. (1985). Comparative Deposition of Inhaled Aerosols in Experimental Animals and Humans: A Review, Journal of Toxicology and Environmental Health 15, 197-214.