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Showing papers on "Bioaerosol published in 2002"


Journal Article
TL;DR: The lack of reference limit values for bioaerosols seriously hinders interpretation of results obtained in various countries and should always be inadmissible and result in preventive actions.
Abstract: Studies of indoor bioaerosols conducted in Central and Eastern European countries, as a result of the scarcity of funding, mostly do not attain the level presented by similar studies in Northern America and Western Europe. For socio-economic reasons, most of the intense studies on indoor bioaerosols in Central and Eastern European countries were carried out in industrial facilities and have contributed significantly to occupational health science. In contrast, until recently, insufficient of studies have been conducted on bioaerosols of residential and communal premises (dwellings, offices, schools, etc.) and no network for monitoring the microbiological quality of air in such premises exists. In Poland, in the mid-1990s complex bioaerosol investigations were carried out by the Bioaerosol Group at the Institute of Occupational Medicine and Environmental Health in Sosnowiec. The concentrations of airborne bacteria and fungi in dwellings without mold problems were between 88-4297 cfu/m(3) and 0-1997 cfu/m(3), while in moldy homes they were 178-4751 cfu/m(3) and 49-16,968 cfu/m(3), respectively. As many as 167 microbial species were isolated from the air of examined dwellings. Most frequently occurred Gram-positive cocci (Micrococcus/ Kocuria spp., Staphylococcus spp.), endospore-forming bacilli (Bacillus spp.), Gram-negative bacteria (Pseudomonadaceae, Aeromonas spp.), filamentous fungi (Penicillium spp., Aspergillus spp.), and yeasts. Notable studies of indoor bioaerosols have also been performed in the other Central and Eastern European countries: Lithuania, Latvia, Estonia, Russian Federation, Ukraine, Czech Republic, Slovakia, Bulgaria and Hungary, are reviewed in this article. The lack of reference limit values for bioaerosols seriously hinders interpretation of results obtained in various countries. The following residential limit values (RLV) for dwellings and communal premises are proposed for the concentration of airborne bacteria, fungi and bacterial endotoxin: 5 x 10(3) cfu/m(3), 5 x 10(3) cfu/m(3) and 5 ng/m(3) (50 EU), respectively. The proposed values of occupational exposure limit (OEL) for industrial settings contaminated by organic dust are 100 x (3) cfu/m(3), 50 x (3) cfu/m(3) and 200 ng/m(3) (2000 EU), respectively. It is also proposed that the presence in indoor air of microorganisms from risk groups 3 and 4 of European Community Directive 2000/54/EC (e.g., Mycobacterium tuberculosis, Bacillus anthracis, Coxiella burnetii), independently of the concentration, should always be inadmissible and result in preventive actions.

245 citations


Journal ArticleDOI
TL;DR: The results show that particle mass concentrations, absorption coefficient and fungi were higher in personal exposure samples than in home and workplace samples, and these concentrations were usually lower in the home than in the workplace.
Abstract: The aim of this study was to compare the personal exposure to particles and bioaerosols with that measured by stationary samplers in the main microenvironments, i.e., the home and the workplace. A random sample of 81 elementary school teachers was selected from the 823 teachers working for two councils in eastern Finland for the winter time measurement period. Bioaerosol and other particles were collected on filters by button samplers using personal sampling and microenvironmental measurements in homes and workplaces. The 24-hour sampling period was repeated twice for each teacher. Particle mass, absorption coefficient of the filter and the concentration of viable and total microorganisms were analyzed from each filter. In this paper, the study design, quality assurance principles and results of particle and bioaerosol exposure are described. The results show that particle mass concentrations, absorption coefficient and fungi were higher in personal exposure samples than in home and workplace samples. Furthermore, these concentrations were usually lower in the home than in the workplace. Bacterial concentrations were highest in heavily populated workplaces, while the viable fungi concentrations were lowest in workplaces. The fungi and bacteria results showed high variation, which emphasises the importance of quality assurance (duplicates and field blanks) in the microbial field measurements. Our results indicate that personal exposure measurements of bioaerosols in indoor environments are feasible and supplement the information obtained by stationary samplers.

140 citations


Journal ArticleDOI
TL;DR: In this paper, a new bio-aerosol sampler was evaluated and it was found that 80-90% of initially charge-neutralized biological particles were removed from the air, when a small amount of ionization was generated in the electrostatic precipitator's (ESP) inlet and a precipitation voltage of ±4000 V was applied across the agar plates.

105 citations


Journal ArticleDOI
TL;DR: In this article, the bioaerosol levels in a closed landfill site while the temporal, seasonal, and meteorological effects were also taken into account, and the concentrations of culturable bacteria and fungi were higher in winter than in other seasons.

101 citations


Journal ArticleDOI
TL;DR: Total airborne fungal concentrations varied significantly by season and were positively correlated with relative humidity and negatively related to CO2 concentrations and the first and second PCA factors had similar correlations with environmental variables compared with total fungi.
Abstract: Bioaerosol concentrations in office environments and their roles in causing building-related symptoms have drawn much attention in recent years Most bioaerosol studies have been cross-sectional We conducted a longitudinal study to examine the characteristics of airborne fungal populations and correlations with other environmental parameters in office environments We investigated four office buildings in Boston, Massachusetts, during 1 year beginning May 1997, recruiting 21 offices with open workstations We conducted intensive bioaerosol sampling every 6 weeks resulting in 10 sets of measurement events at each workstation, and recorded relative humidity, temperature, and CO2 concentrations continuously We used principal component analysis (PCA) to identify groups of culturable fungal taxa that covaried in air Four major groupings (PCA factors) were derived where the fungal taxa in the same groupings shared similar ecological requirements Total airborne fungal concentrations varied significantly by season (highest in summer, lowest in winter) and were positively correlated with relative humidity and negatively related to CO2 concentrations The first and second PCA factors had similar correlations with environmental variables compared with total fungi The results of this study provide essential information on the variability within airborne fungal populations in office environments over time These data also provide background against which cross-sectional data can be compared to facilitate interpretation More studies are needed to correlate airborne fungi and occupants' health, controlling for seasonal effects and other important environmental factors

99 citations


Journal ArticleDOI
TL;DR: In this article, a new bioaerosol sampler was developed and tested in which airborne microorganisms are collected by electrostatic means, where two ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection.
Abstract: We have developed and tested a new bioaerosol sampler in which airborne microorganisms are collected by electrostatic means. In this sampler, 2 ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection. The organisms are then subjected to a precipitating electric field and are collected onto 2 square agar plates positioned along the flow axis. Tests with nonbiological NaCl particles versus B. subtilis var. niger (BG) spores and vegetative cells have shown that airborne microorganisms are collected more efficiently than nonbiological particles, even when the microorganisms have first passed through an electric charge neutralizer with no additional charging applied. The difference was attributed to the natural charges contained in cell membranes or spore coats of the microorganisms. Charge-neutralized BG spores and vegetative cells were collected at 4 L/min with efficiencies close to 80%, depending on the precipitation voltage, versus 50-60% for NaCl test par...

81 citations


Journal ArticleDOI
TL;DR: The findings from this study facilitate applications of electric charging for environmental control purposes involving sterilization of bacterial cells by imposing high electric charges on them and can be used in the development of new bioaerosol sampling methods based on electrostatic principles.
Abstract: In this study, the effects of the electric charges and fields on the viability of airborne microorganisms were investigated. The electric charges of different magnitude and polarity were imparted on airborne microbial cells by a means of induction charging. The airborne microorganisms carrying different electric charge levels were then extracted by an electric mobility analyzer and collected using a microbial sampler. It was found that the viability of Pseudomonas fluorescens bacteria, used as a model for sensitive bacteria, carrying a net charge from 4100 negative to 30 positive elementary charges ranged between 40% and 60%; the viability of the cells carrying >2700 positive charges was below 1.5%. In contrast, the viability of the stress-resistant spores of Bacillus subtilis var. niger (used as simulant of anthrax-causing Bacillus anthracis spores when testing bioaerosol sensors in various studies), was not affected by the amount of electric charges on the spores. Because bacterial cells depend on their membrane potential for basic metabolic activities, drastic changes occurring in the membrane potential during aerosolization and the local electric fields induced by the imposed charges appeared to affect the sensitive cells' viability. These findings facilitate applications of electric charging for environmental control purposes involving sterilization of bacterial cells by imposing high electric charges on them. The findings from this study can also be used in the development of new bioaerosol sampling methods based on electrostatic principles.

76 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed a personal sampler for viable airborne microorganisms and evaluated its performance under controlled laboratory conditions and in a field using a simplified human manikin in an office environment.

66 citations


Journal ArticleDOI
TL;DR: This molecular approach can support bioaerosol risk evaluation and compare oral cavity isolates against isolates collected from aerosol surrounding the aeration basin to evaluate microbial contamination in plant workers.

54 citations


Journal ArticleDOI
TL;DR: In this article, an experimental setup that allows us to analyze electrobiological properties of airborne microorganisms was developed and built, which imparts electric charges on airborne biological and nonbiological particles by aerosolizing them in the presence of an electric field.
Abstract: Our earlier studies have shown that the electrostatic collection technique, a potentially "gentle" bioaerosol collection method, allows for efficient collection of airborne bacteria, but sensitive bacteria such as Pseudomonas fluorescens ( P. fluorescens ) lose their culturability during collection. We hypothesized that excessive stress was imposed on the sensitive bacteria by the sampler's conventional corona charging mechanism. In this research, we developed and built an experimental setup that allows us to analyze electrobiological properties of airborne microorganisms. In this experimental system, we imparted electric charges on airborne biological and nonbiological particles by aerosolizing them in the presence of an electric field. The charged P. fluorescens test bacteria and NaCl test particles were then channeled into a parallel plate mobility analyzer, which we have designed so that bacteria and inert particles carrying specific charge ranges can be extracted and made available for further analys...

49 citations


Journal Article
TL;DR: The workers of potato processing facilities could be exposed to large concentrations of microorganisms, dust and endotoxin posing a risk of work-related respiratory disease.
Abstract: Microbiological air sampling was performed in a big potato processing plant located in eastern Poland. Air samples for determination of concentrations of microorganisms, dust and endotoxin were collected at 6 sites in the division producing potato flakes and meal from dried potato pulp and at 2 sites in the division producing potato syrup from imported starch. The concentrations of total airborne microorganisms were within a range of 28.3-93.1 ◊ 10 3 cfu/m 3 . Mesophilic bacteria were dominant at all sampling sites, forming 73.1-98.8% of the total count. Among them, distinctly prevailed corynebacteria (irregular Gram-positive rods) that accounted for 54.3-81.1% of the total airborne microflora. The most common were strains of Corynebacterium spp., followed by strains of Arthrobacter spp., Microbacterium spp., and Agromyces ramosus. The latter species, so far not reported from the air of occupational environments, abundantly develops in the parenchyma of potato tubers. Its airborne concentration increased rapidly after peeling of potatoes, and attained maximal values at cutting and blanching (steaming and sulfuration) of potatoes, and at sacking of potato meal. The proportions of Gram-negative bacteria and endospore-forming bacilli were low, respectively 0.6-7.6% and 2.0-8.1% of total count. Fungi constituted 1.2-26.9% of total count. The dominant species was Aspergillus niger that formed 99.8% of total airborne fungi. The values of the respirable fraction of airborne microflora varied between 25.3-73.2%. The concentrations of airborne dust were 1.4-26.6 mg/m 3 in the division producing potato flakes and meal and 114.9-200.5 mg/m

Journal ArticleDOI
TL;DR: In this paper, a method for automated monitoring of airborne endospores, which combines an aerosol capture technique with endospore detection based on terbium luminescence turn-on, is presented.
Abstract: We report a method for automated monitoring of airborne endospores, which combines an aerosol capture technique with endospore detection based on terbium luminescence turn-on. We have demonstrated quantification of aerosolized bacterial spores with a response time of /spl sim/15 min, a sensitivity of 10/sup 4/ spores/ml, and a dynamic range of 4 orders of magnitude using a bioaerosol sampler, a microwave, and a lifetime-gated fluorimeter. Ultimately, the most attractive feature we have demonstrated is the unattended monitoring of aerosolized bacterial spores for the duration of a workday (/spl sim/8 hours).

Journal ArticleDOI
TL;DR: The early stage of textile processing seems to generate high endotoxin and bacteria contamination, and priorities should be given to occupational hygiene programs for workers at various sites in textile plants.

Book ChapterDOI
01 Jan 2002
TL;DR: The dispersion and composition of microbial aerosols in the surrounding of three composting plants in central Germany were examined in this article, where only sampling days (nights) were chosen for which the meteorological situation allowed a minimum dilution of the bioaerosol emissions downwind to the plants.
Abstract: The dispersion and composition of microbial aerosols in the surrounding of three composting plants in central Germany were examined. Immission measurements were carried out at specifically chosen sampling points downwind to the plants including reference points upwind. Only sampling days (nights) were chosen for which the meteorological situation allowed a minimum dilution of the bioaerosol emissions downwind to the plants. The samples were analysed for the presence of six groups of organisms by selective cultivation, including mesophilic bacteria and moulds, xerophilic moulds as well as thermophilic moulds and thermophilic actinomycetes.

Journal ArticleDOI
TL;DR: Results of this simulation indicate that, for a passive remote sensing measurement, it is unlikely that bioaerosol clouds can be identified from the spectral signature alone.
Abstract: At first glance, an examination of the bulk refractive indices for the 8–12 μm waveband of various bioaerosols suggests differentiation with respect to common background aerosols based upon the spectral characteristics of the absorption. The question of whether there is a spectral signature of bioaerosol clouds when those clouds are immersed in a typical atmosphere, including the boundary layer background aerosols, has been addressed in a simulation using the Weather and Atmospheric Visualization Effects for Simulation (WAVES) suite of codes. Using measured values of the refractive index for common bacterial spores, and their typical size distributions, the single-scattering, ensemble-averaged optical properties such as extinction/absorption coefficients, albedo, and the scattering phase function was computed for bioaerosol clouds at a resolution of 1 cm-1. WAVES was then used to calculate the radiative transfer for a finite sized cloud immersed in background. Results of this simulation indicate that, for a passive remote sensing measurement, it is unlikely that bioaerosol clouds can be identified from the spectral signature alone.

Journal ArticleDOI
TL;DR: There was a wide range of recoveries ranging from 0–100% when the cellulose acetate filter was used to detect phages in bioaerosols within and around broiler houses, and further studies are needed to accurately determine the collection efficiencies of viruses.
Abstract: Air quality within and around confined animal housing operations is important from both occupational exposure and environmental quality perspectives. Appropriate sampling equipment should be available so that bioaerosols are adequately characterized in terms of their component microbial populations. In this study the efficacy of a commercially available impaction-based bioaerosol sampler (SAS-100) was evaluated in terms of its ability to detect male-specific coliphages within and around poultry broiler houses. In addition to the manufacturer recommended agar medium, cellulose and cellulose-acetate filter media were also used as the collection surface. The agar medium and the cellulose ester filters provided very high recoveries of phages as compared to the cellulose filter (P<0.05). There was a wide range of recoveries ranging from 0–100% when the cellulose acetate filter was used to detect phages in bioaerosols within and around broiler houses. The results suggest that the sampler is capable of concentrating male-specific coliphages from bioaerosols. However, further studies are still needed to accurately determine the collection efficiencies of viruses.

Proceedings ArticleDOI
27 Jun 2002
TL;DR: The Py-GC-IMS was tested for its ability to detect the biological aerosols of Gram-negative Erwinia herbicola (EH) and ovalbumin protein as compared to previous studies as mentioned in this paper.
Abstract: Improvements were made to a pyrolysis-gas chromatography-ion mobility spectrometry stand-alone biodetector to provide more pyrolyzate compound information to the IMS detector module. Air carrier gas flowing continuously through the pyrolysis tube, the rate of air flow, and pyrolysis rate were found to improve the relative quality and quantity of pyrolyzate compounds detected by the IMS detector compare to earlier work. These improvements allowed a greater degree of confidence in the correlation of biological aerosols obtain in outdoor testing scenarios to a standard GC-IMS biological aerosol dataset. The airflow improvement allowed more biomarker compounds to be observed in the GC-IMS data domain for aerosols of Gram-negative Erwinia herbicola (EH) and ovalbumin protein as compared to previous studies. Minimal differences were observed for Gram-positive spores of Bacillus subtilis var. globigii (BG) from that of earlier work. Prior outdoor aerosol challenges dealt with the detection of one organism, either EH or BG. Biological aerosols were disseminated in a Western Canadian prairie and the Py-GC-IMS was tested for its ability to detect the biological aerosols. The current series of outdoor trials consisted of three different biological aerosol challenges. Forty-two trials were conducted and a simple area calculation of the GC-IMS data domain biomarker peaks correlated with the correct bioaerosol challenge in 30 trials. In another 7 trials, the status of an aerosol was determined to be biological in origin. Two additional trials had no discernible, unambiguous GC-IMS biological response, because they were black water sprays. Reproducible limits of detection were at a concentration of less than 0.5 bacterial analyte-containing particles per liter of air (ACPLA). In order to realize this low concentration, an aerosol concentrator was used to concentrate 2000 liters of air in 2.2 minutes. Previous outdoor aerosol trials have shown the Py-GC-IMS device to be a credible detector with response to determining the presence of a biological aerosol. The current series of outdoor trials has provided a platform to show that the Py-PC-IMS can provide information more specific than a biological or non-biological analysis to an aerosol when the time of dissemination is unknown to the operator. The Py-GC-IMS is shown to be able to discriminate between aerosols of a Gram-positive spore, a Gram-negative bacterium and a protein.

DOI
01 Nov 2002
TL;DR: A field comparison of four bioaerosol samplers, the Reuter Centrifugal Sampler (RCS), the Andersen N6 Single Stage (N6), the Surface Air System Super 90, and the Air-o-Cell sampler (AOC), was conducted in a variety of public buildings for the measurement of fungal aerosols to compare sampling performance efficiencies and to collect baseline data for a pool of buildings as mentioned in this paper.
Abstract: Introduction: No standard method exists for enumerating fungal aerosols, impeding the development of reliable exposure-response data. A field comparison of four bioaerosol samplers, the Reuter Centrifugal Sampler (RCS), the Andersen N6 Single Stage (N6), the Surface Air System Super 90, and the Air-o-Cell sampler (AOC), was conducted in a variety of public buildings for the measurement of fungal aerosols to compare sampling performance efficiencies and to collect baseline data for a pool of buildings Methods: Sampling was conducted at 75 sites in public buildings from June-October 2001 in the greater Vancouver area, British Columbia. Four locations were sampled at each site (1 common area, 2 offices, and 1 outdoor sample). Each location was sampled in parallel, collecting approximately 150 litres of air for each sample. Malt extract agar was used for all growth media. Sequential duplicates were taken at each location. Simple linear regressions were calculated for each method pair to develop betweensampler calibration equations. Results: Data from approximately 592 samples (60 different buildings) were available for analysis from each instrument. Differences were found between samplers for overall yield, detection limits, and reproducibility. The highest spore concentrations were returned by the non-viable method, the AOC. The N6 and RCS were comparable in colony concentrations, but the N6 was more efficient at capturing small particulate such as Penicillium and Aspergillus spores. The SAS-90 returned concentrations that were significantly lower than all other samplers. The surrogate chemicals, ergosterol and (1→3) β D glucan were below the limit of detection of the method for these samples. Conclusions: Concentration data is dependent on the sampling methodology utilized for assessment and should be considered before conducting investigations of bioaerosols in different environments. Exposure guidelines cannot be created until a standard methodology is available. All of the bioaerosol sampling devices tested had unique characteristics which could be seen as beneficial or detrimental depending on the sampling environment and the conclusions drawn from the sample data.

Journal ArticleDOI
TL;DR: The results of the study and preliminary results of their generalization showed that there is a significant scatter of the value of the biogenic component of tropospheric aerosol within the altitude range from 0.5 to 7 km.
Abstract: Although statistical aspects of the distribution of atmospheric impurity concentration have long been a subject of extensive discussion in the literature, this problem is still of considerable theoretical and applied importance. The biogenic component of tropospheric aerosol in the southern regions of Western Siberia is a subject of systematic research at the Research Institute of Aerobiology, Vector State Research Center for Virology and Biotechnology, in collaboration with the Institute of Atmosphere Optics, Siberian Division, Russian Academy of Sciences [1, 2]. The term “biogenic component” is assumed to include only two fractions of atmospheric aerosol: total protein and live microorganisms. The results of the study and preliminary results of their generalization showed that there is a significant scatter of the value of the biogenic component of tropospheric aerosol within the altitude range from 0.5 to 7 km. This effect cannot be attributed to the measuring error alone. Therefore, it should be explained by the statistical nature of the scatter.

01 Jan 2002
TL;DR: A method for automated monitoring of airborne endospores, which combines an aerosol capture technique with endospore detection based on terbium luminescence turn-on is reported, which is similar to firemen inspecting your home periodically to ensure that there is no fire.
Abstract: 2001 have highlighted the need for new methods of detecting bioaerosols including airborne Bacillus anthracis spores. Current methods of bacterial spore (endospore) detection, such as colony counting and PCR, require trained personnel for sampling and analysis. The labor requirement obviates these methods for continuous, online endospore monitoring; it would be like firemen inspecting your home periodically to ensure that there is no fire. Here we report a method for automated monitoring of airborne endospores, which combines an aerosol capture technique with endospore detection based on terbium luminescence turn-on. Endospores can be formed by certain bacteria during times of stress or lack of nutrients. This dormant bacterial form can survive harsh conditions such as boiling, freezing, and des icca t ion tha t readily kill vegetative bacteria [1]. Indeed, Bacillus stearothermophilus and Bacillus subtilis spores are used to check the performance of autoclaves. Two spore-forming genera of medical importance, Bacillus and Clostridium, are the causative agents of anthrax, tetanus, botulism, and gas gangrene. The fact that endospores are so durable is the primary reason for time-consuming and expensive sterilization procedures employed in hospitals, canneries, and other food preparation facilities. Although the vegetative cells of endosporeforming bacteria are most commonly found in the soil, endospores exist almost everywhere, including the atmosphere, where they are frequently carried on dust particles [2]. Online monitoring of aerosol ized bacter ia l spores is essential in locations such as mail sorting, food preparation, and heal thcare faci l i t ies . Among the desired characteristics for bacterial spore alarm systems are online operation, minimal maintenance, few false alarms, and no false negatives. Methods for bioaerosol sampling [3], [4] such as filtering, suspending, or impacting, coupled to methods of monitoring such as PCR analysis of gene segments [5], culturing and analysis of the colonies using standard microbiolocal assays (e.g., shape, staining), pyrolysis-GC-IMS [6], or fluores-

Book ChapterDOI
01 Jan 2002
TL;DR: Temperatureotolerant and thermophilic actinomycetes, e.g. Saccharopolyspora rectivirgula, are selected as target organisms for rRNA probing and highly specific detection of the cellular fraction of bioaerosols within 1 to 2 working days instead of the present 1 to 3 weeks is feasible.
Abstract: Exposure to bioaerosols from composting facilities can have severe effects on the occupational health of workers and can also influence residents living in the close vicinity of these plants. New methods for the specific detection of airborne microorganisms originating from these plants need to be developed as standards. Present techniques for analyses of microbial bioaerosols are based on cultivation using selective agar media, whereby the non-culturable cells and cell fragments are not detected. In contrast to this methodology, cultivation-independent approaches are adapted here for a more direct assessment of bioaerosol concentrations. For this purpose different sampling methods, such as filtration, impingement and impaction, are evaluated. Direct detection following sampling is performed by epifluorescence microscopy. This means in particular the determination of whole cell numbers and identification of key organisms with taxon-specific ribosomal RNA (rRNA)-targeted oligonucleotide probes by fluorescence in situ hybridization (FISH). In a comparative study, suitable combinations of sampling and detection methods will be developed. Due to their significance in composting processes, thermotolerant and thermophilic actinomycetes, e.g. Saccharopolyspora rectivirgula, are selected as target organisms for rRNA probing. Using such molecular techniques, highly specific detection of the cellular fraction of bioaerosols within 1 to 2 working days instead of the present 1 to 3 weeks should be feasible.




01 Jan 2002
TL;DR: In this article, a new bio-aerosol sampler was developed and evaluated in which the microorganisms were collected by electrostatic means, and the results of field measurements parallel those obtained through laboratory experiments.
Abstract: Many aerobiological measurements and the protection of governmental/military establishments from bioterrorism require the development of new bioaerosol collectors that can be operated efficiently at low power. We have developed and evaluated a new bioaerosol sampler in which the microorganisms are collected by electrostatic means. An ionizer charges the incoming microorganisms, if they carry insufficient charge for efficient collection in the device. The microorganisms are collected on two square agar plates placed along the flow axis. Laboratory experiments have shown that bacterial cells and spores are generally collected more efficiently than inert particles. We attribute this difference to the natural negative charge contained in the cell membranes of microorganisms. The results of field measurements parallel those obtained through laboratory experiments.