bioterrorism & homeland security2007

Bioterrorism & Homeland Security2007 AAAR Annual Conference Abstracts

11B.1Estimating Exposure Risk for Escaping Office Personnel.ALFRED EISNER, Alion Life and Environmental Sciences;Russell Wiener, US EPA, NHSRC.

The Ricin Technical Assistance Document prepared byERT and U.S. EPA in response to the ricin attack onCapitol Hill on February 2, 2004, and subsequent analysisof the case revealed the need to develop quantitativemethods to estimate risk resulting from exposure ofrapidly evacuating (escaping) occupants to threat agentsresuspended from surfaces in offices. The goal of thisresearch effort is to determine quantitative estimates ofrisk to escaping occupants resulting from exposure toresuspended chemical and biological agents like ricin.

A study designed to elucidate the processes of exposuregenerated by escaping individuals was initiated using aspecially designed articulated, heated, breathing manikin.The adult-sized manikin was \upgraded\ to enable it toexecute fast movements such as walking or running downor up stairs, which we believe are the most effectivemotions for stirring agents from the floor. Motioncapability was achieved by attaching electric actuators tothe manikin's limbs.

Three Aerodynamic Particle Sizers (APSs) were set up tomeasure particle size distribution and concentration in 1 sintervals. A sampling tube imbedded in the shoe allowedthe particles to be sampled from the space under the footin real time. The other APSs were set to measure particleconcentration and distribution simultaneously from otherareas along the manikin's body.

This study revealed that a particle-laden bolus isgenerated in the space opening during a step forward,moving rapidly from heel to toe. We found that a singlefootstep generated a bolus that typically lasted 3 seconds,with particle concentrations easily reaching 4000/cm3.Further investigation of particle transport is currently inprogress, using PIV to investigate transport from underthe foot space into the area above the foot space andfurther along the manikin's body into the breathing zone.

11B.2Electrical Enrichment of Bioaerosols near Ground Level.DAVID ALBURTY, Zachary Packingham, Alburtylab; AndrewPage, Page Applied Research.

During fair weather, a population of particles has beenobserved near ground level with a size distributionskewed in favor of fine (<2.5 microns AD) particles,when compared to the particle population at two meters.Investigation of this layer, at a height (altitude) of 20 cmabove ground level, shows that it can contain adisproportionately elevated concentration of viablebioaerosols. The ability to predict and better understandthis phenomenon may be of significant importance inbioaerosol sampling and in children’s health, and inbioaerosol source attribution.

Concurrent ambient aerosol samples were taken outdoorsat heights of 20 cm above ground level and 200 cm aboveground level. The samples were taken in a rural setting inMissouri, USA over a period of three years, using particlecounters, APS, and a 6-stage viable impactor.Atmospheric electrical measurements were taken at 20 cmand 200 cm using an ion gauge and a static meter.Meteorological data were taken and weather patterns wererecorded. Biological samples were cultured, enumerated,gram stained and classified. Particle counter data werereduced and compared to bioaerosol particulate matterconcentrations.

Results show that the concentration ratio of fine particlesnear the ground during fair weather varies fromapproximately 200% to 1000% that of the population attwo meters. The formation of this concentration ofmicron-sized biological particles is theorized to be due tolevitation due to the typical net negative natural charge ofthe earth and the biological particles. The net negativenatural charge present on populations of biologicalaerosols near the ground appears to be increased byaccumulation of negative charges produced during theevaporation of water in the environment.

References: Yao, M. and Mainelis, G. Utilization ofNatural Electrical Charges on Airborne Microorganismsfor their Collection by Electrostatic Means, JAS, 37(4)2006, Shalat, S., Lioy, Schmeelck, and Mainelis,Improving Estimation of Indoor Exposure to InhalableParticles for Children in the First Year of Life, J. Air andWaste Mgt. Assoc. 57(8) 2007.

Copyright © 2007 by the American Association for Aerosol Research (AAAR).AAAR hereby grants contributing authors full rights to use of their own abstracts.


11B.3Control-Volume Numerical Simulation of BioaerosolDispersion in the Atmospheric Surface Layer. JOSHHUBBARD, John Haglund, Ofodike Ezekoye, University ofTexas at Austin.

Most biological aerosol sampling devices are designed tocollect particles in the 1-10 micrometer aerodynamicdiameter (AD) size range. It has been suggested that thisrange be extended to include particles 0.5-30 micrometerAD for real-time bioaerosol detection (NRC 2005).When the method of detection depends on the mass ofbioaerosol collected, increasing the upper limit of theparticle size range may offer a net benefit. However, onemay also consider that particles larger than 10 micrometerAD experience greater sedimentation, and thus would notwarrant design of samplers for collection of particles inthis range. In this study we estimate the change in themass distribution function of a polydisperse aerosol over arange of distances down-wind from a release point.Particle transport is modeled by a two-dimensionalconvection-diffusion process including gravitationalsedimentation. The transport of the aerosol release in theatmospheric surface layer is approximated with a control-volume numerical simulation. To characterize the windspeed and turbulent diffusivities we adopt the empiricalrelations proposed by Businger et al. (1971) which arebased on Monin-Okhubov similarity theory. Weacknowledge the presence of more sophisticateddispersion models; however, the current approach allowsfor a large number of initial distributions and flowconditions to be investigated, providing physical insightthat would not be easily realized using more advancedmodels. Our data suggests that a significant mass fractionof particle sizes greater than 10 micrometer AD maytransport distances on the order of several kilometers froma release point, and that a substantial increase in theaerosol mass collected may result if particles larger than10 micrometer were included in the operating envelope ofthe sampling device.

National Research Council (2005). Sensor Systems forBiological Agent Attacks: Protecting Buildings andMilitary Bases. pp. 46-70.

Businger et al. (1971). Journal of the AtmosphericSciences: 28: 181-189.

11B.4Development of an Aerosol System for Uniformly DepositingBacillus anthracis Spore Particles on Surfaces. PAUL A.BARON, Cherie F. Estill, Gregory J. Deye, Misty J. Hein,National Institute for Occupational Safety and Health; JeremyK. Beard, John D. Wright, Lloyd. D. Larsen, Gregory E.Dahlstrom, U.S. Army Dugway Proving Ground.

After the anthrax incidents in October 2001, severaltechniques used for sampling surfaces for biologicalagents were found to be inadequately validated, especiallyat low surface loadings. Therefore a system wasdeveloped to produce sample sets having targeted surfaceconcentrations of dry biological agent simulant. A largetest chamber was constructed and particles of dry agentsimulant were aerosolized using a venturi aspirator. Theaerosol was initially dispersed into the chamber atrelatively high air concentrations, monitored in real time,and stirred using several fans. The concentration decay(stirred settling and dilution) was measured and when thetargeted air concentration was reached, the samplingsurfaces were uncovered and exposed to the settlingparticles until <99% of the particles had settled.Subsequently, the chamber was opened and the surfaceswere sampled or removed for evaluation. Three types ofsurface samples could be exposed: agar plates, stainlesssteel, and carpet squares. The agar settle plates were usedto estimate the true colony-forming-unit (CFU) surfaceconcentration. The uniformity of surface loadings waslimited by random deposition of small numbers ofparticles on the surfaces (Poisson distribution) and wascharacterized by how much greater the observedvariability was than that predicted by Poisson statistics.The age of flow enhancer mixed with the spores appearedto affect the spores' ability to grow on the agar medium.The presence of spore agglomerates re-suspended byvarious sample handling activities in the chamber furtherincreased the variability of deposited particles. Whenmeasures to reduce variability of the deposits were inplace, the concentration of airborne particles measuredusing a particle spectrometer could be used to predict themean surface concentration of viable spores within about+/- 20% at higher concentrations (>20 CFU/agar plate)and within about a factor of two at lower concentrations(1 to 10 CFU/agar plate).



14C.1Can HEPA Filters Effectively Protect us from ViralAerosols? Brian Heimbuch, Jacqueline Hodge, Joseph Wander,Air Force Research Laboratory, MLQL, Tyndall Air Force Base;CHANG-YU WU, University of Florida.

High Efficiency Particulate Air (HEPA) filters are theprimary technology used for particulate removal inindividual and collective protection applications. HEPAfilters are commonly thought to be impenetrable, but infact they are only 99.97% efficient at collecting the mostpenetrating particle (~ 0.3 micrometer). While this is animpressive collection efficiency, HEPA filters may bepenetrated by certain threats: Viruses are submicron insize and have small minimum infections doses (MID).Thus, an appropriate viral challenge may yield penetrationthat will lead to infection of personnel. However, theoverall particle size (agglomerated viruses and/or virusesattached to inert carriers) will determine the captureefficiency. Aerosolized viruses are commonly thought toexist as agglomerates, which would increase the particlesize and consequently increase their capture efficiency.However, many of the threat agent viruses can be highlyagglomerated and still exist as submicron particles.Furthermore the stability of aggregates is not wellunderstood, and they may fragment during filtration.We have demonstrated in our laboratory that MS2 coliphage aerosols penetrate Carbon HEPA Aerosol Canistersand flat sheet HEPA material. A nebulized challenge of~100,000 viable plaque forming units (PFU) per liter ofair results in penetration of ~1-2 viable PFU. Thepenetration is linear over time, thus viral penetration isexpected to occur in minutes following a viral challenge.AFRL is currently investigating the particle sizedistribution of the MS2 aerosol and our aim is to adjustthe size distribution to measure its effect on penetration.Preliminary results indicate that 200-300-nm particlesaccount for ~7.5% of the total number of particles. We arealso evaluating the penetration characteristics of amammalian virus, which may better represent the threatagent viruses. This study will expand our knowledge ofthe tactical threat posed by viral aerosols to HEPA filtersystems.

14C.2Re-Aerosolization During Doffing of ContaminatedGarments. JASON HILL, James Hanley, RTI International;James Hanzelka, U.S. Army Dugway Proving Ground.

An exploratory study was conducted to measure the re-aerosolization of particles during doffing of contaminatedprotective garments. The tests involved seven differentgarment systems utilizing either permeable or semi-permeable fabrics. Each test began with a system-level,human-subject aerosol exposure followed by controlled,assisted doffing. The tests used a non-toxic fluorescentaerosol simulant and were conducted in accordance withan approved human-use protocol.

The test method developed for the study employed twounique facilities: an aerosol exposure wind tunnel and anemissions quantification chamber. The exposure windtunnel provided controlled contamination of the garmentby the fluorescent aerosol. After exposure, the testparticipant entered the emission quantification chamber.The HEPA-filtered emissions chamber operated as ahorizontal-flow cleanroom with focused exhaust flow toallow representative sampling of emissions as a functionof time.

Re-aerosolization during the doffing process wasmeasured by both filter-based and continuous samplers.Fluorometric analysis of the full-duration, filter-basedsamples provided data on total downstream emissions,fallout, and personal exposure of the doffers. Sequentialfilter samples obtained over subsets of the full test werecompared to the continuous instruments (optical particlecounter, Aerodynamic Particle Sizer, and photometer) tocharacterize emissions from portions of the doffingroutine.

Results showed that the re-aerosolized mass was withinmeasurement range of the various samplers. Evidencesuggests dependencies of the re-aerosolized mass on thegarment design (coverall vs. separate coat and trousers),doffing method (pull off vs. cut off), and permeability ofgarment fabric. Results for total fallout, the downstreamairborne mass, the personal samplers on the doffers andthe aerosol analyzers will be presented.



14C.3Bioaerosol Detect-to-Warn Concept Based on CombinedUV-fluorescence and background Aerosol Monitoring.TARMO HUMPPI, Finnish Defence Forces Technical ResearchCentre; Kauko Janka, Riku Reinivaara, Juha Tikkanen, DekatiLtd.; Antti Rostedt, Matti Putkiranta, Jaakko Laaksonen, JormaKeskinen, Tampere University of Technology.

One of the major challenges in real time detection ofairborne biological threat agents (ABTA) is to distinguishthe benign natural or man made bioaerosols fromintentional release of ABTA.

No single available real-time detection technique gives asatisfactory criterion for detection. Thus the reliablebiodection have to rely on more than one detectiontechnology giving diverse information from aerosolbackground, concentration, size distribution and intrinsicfluorescence.The most commonly used techniques are based on themeasurement of intrinsic UV-fluorescence and the size ofbioparticles. For any reliable alarming criteria the timelybehaviour of the measured parameters compared tonormal conditions is significant. This requires continuousmeasurement with fast response. Because extremely lowconcentrations of harmful bio agents can cause infection,sensitivity in terms of agent containing particles per literair (ACPLA) is of a crucial importance.In addition to the background bioaerosol, other aerosols(e.g. diesel soot) may yield also fluorescent response. Thetimely behaviour or this kind of aerosol typicallyresembles that of artificially spred bioaerosols. For thatreason it is extremely difficult to distinguish using onlysofware based algoritms.

Developed concept combines UV-fluorescence detectionoptics with a special background-aerosol detectionsystem. The light source for exciting fluorescence is aCW semiconductor diode laser with 405 nm wavelength.The optical system detects both fluorescence andscattered light, indicating both the fluorescence tendencyand concentration of particles. The practical systemincludes also a particle concentrator (CF = 500). Thebackground aerosol detection system measures theconcentration of particles causing typically false signalsfor UV-fluorescence detection unit. Characteristics forthis technique are fast response time and sensitivity. It canbe easily integrated into a robust biodetector for fieldoperation. The practical realisation of the developedbiodetector, as well as, the experimental results arepresented.

14C.4Rapid Detection and Identification of AirborneMicroorganisms by a High-Throughput AtmosphericPressure MALDI-MS. BERK OKTEM, Appavu K. Sundaram,Vladimir M. Doroshenko; Science and Engineering ServicesInc.

Rapid detection and identification of pathogenicmicroorganisms in contaminated food and environmentalsamples, especially after bio-terrorism related events, iscritical for treatment of the infected patients as well as forproper decontamination efforts. Traditionalmicrobiological methods to identify pathogens are timeconsuming, taking 24 to 48 hours for the confirmatoryresults to arrive. Matrix assisted laser desorptionionization mass spectrometry (MALDI-MS) has oftenbeen successfully used for rapid characterization ofmicroorganisms. However due to introduction of thesamples into vacuum, this often requires humanintervention. In this work, we report development of ahigh-throughput atmospheric pressure (AP) MALDI-MSbased assay with aerosol collection capability. It offersimportant benefits such as seamless integration of samplepreparation with MS and fast overall analysis, on theorder of minutes. It has an aerosol collector which collectsairborne aerosols directly on the chemical processingplate. The input flow rate is 450 L/min, suitable forambient sampling with low particle numberconcentration. For initial studies, a modified laboratoryworkstation is used for sample preparation withcustomized liquid handling. All sample processing iscarried out on AP-MALDI target probe at 50C. To 2 mmof particle spot on the target surface 1 microliter of anagent specific extraction reagent is added. Digestion ofproteins is then carried out in-situ using trypsin enzyme.Salts and other contaminants are then removed bywashing with water. Matrix solution is then added. AP-MALDI MS and MS/MS spectra are acquired using anion trap MS. MS/MS data is used to search in the publiclyavailable database using MASCOT search engine toobtain species specific identification based on the peptidesequence. We have successfully tested this setup with AP-MALDI MS/MS based analysis to detect and identifysimulants of threat agents such as Bacillus globigii spores,MS2 bacteriophage in different environments.



14C.5Ambient aerosol measurements and field testing of a twowavelength fluorescence Excitation and Elastic Scatterbioaersol system. V. SIVAPRAKASAM, A. Huston, H.B Lin,J. Eversole, J.Willey, Naval Research Laboratory, WashingtonDC

A bioaerosol sensor based on dual wavelengthfluorescence excitation and multiple wavelength elasticscattering - has been developed and characterized forclassifying micron-sized bioaerosols on the fly. We havebeen able to successfully classify different types ofbioaerosols including proteins and bacteria (vegetativecells and spores) and distinguish them from severalcommon interferents. We have studied a variety ofsimulants and interferents grown under varying conditionsto characterize the performance of the instrument.Simulant and interferent aerosols were generated usingseveral different techniques.

The UV-LIF instrument was tested during a two-week-long, blind field trial at the Edgewood, MD breeze tunnel.The instrument operated unattended while simulants andinterferents were released at various random times duringthe test period. The results of the field trial will behighlighted in this presentation. We detected andcorrectly identified over 90 % of the simulant releases andhad zero false alarms over the 2 week testing period. Inorder to gain a better understanding of the characteristicsof aerosols in the ambient air, we conducted backgroundaerosol measurements for over 2 months and havecollected over 700 hours of data. These measurementswill aid us in steering the algorithm development andunderstands the dynamics of the background aerosols.Some of the preliminary results from our bioaerosolclassification algorithm effort will be presented.

14C.6Developoment and Characterization of a Sulfur MustardAerosol CounterMeasures Laboratory. Jake McDonald,Yung-Sung Cheng, WAYLON WEBER, Yue Zhou, LovelaceRespiratory Research Institute.

A Sulfur Mustard (SM) synthesis, analysis and aerosoldelivery laboratory was developed and characterized. Thelaboratory supports a COUNTERACT Center ofExcellence that is aimed at developing therapies tocounteract SM induced injury to eye, skin, and therespiratory tract. The laboratory provides the first knownsystem for developing and studying SM vapors andaerosols directly. SM was synthesized and purified bypublished techniques. SM aerosol/vapor generation wasconducted using a delivery system to best mimic potentialhuman exposures. Characterization of vapor/droplets wasconducted with a cryo focusing-thermal desorption gaschromatgraph, providing analysis of both the gas andparticle phase. Droplet size, which was modulated by acounter current heat exchanger, was characterized byimpaction and differential mobility analysis. Initialfindings and laboroatory design will be reported.


bioterrorism & homeland security2007

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