Showing papers on "Bioaerosol published in 1999"

Real-time measurement of fluorescence spectra from single airborne biological particles

Abstract: Improved real-time methods for characterizing airborne biological particles are needed. Here we review our efforts in developing techniques for measuring the laser-induced fluorescence (total and spectrally dispersed) of individual airborne particles, and describe our present system, which can measure fluorescence spectra of single micrometer-sized bioaerosol particles with good signal-to-noise ratios. We demonstrate the capability of this system by showing measured spectra of a variety of airborne particles generated in the laboratory from road dust, ammonium sulfate, Bacillus subtilis and other bacteria prepared under various conditions, allergens, cigarette smoke, and chicken-house dust. These spectra illustrate the capability of the system to distinguish between some biological and nonbiological aerosols, and among several types of laboratory-generated biological aerosols. We suggest improvements needed to make our system field portable. © 1999 John Wiley & Sons, Inc.* Field Analyt Chem Technol 3: 221–239, 1999

Collection of Airborne Microorganisms by Electrostatic Precipitation

Abstract: The applicability of electrostatic precipitation as a method for bioaerosol collection was investigated by using a modified Electrostatic Aerosol Sampler (EAS) (Model 3100, TSI Inc., St. Paul, MN). The physical and biological efficiencies of this method were determined. The tests were performed using three bacterial species which were collected onto agar, into water, and onto filters. The physical collection efficiency was higher than 80% when using a sampling flow rate of 1 L/min. When the Bacillus subtilis var niger (BG) spores were collected on agar, about 50-60% of the collected culturable organisms formed colonies. The bioefficiency exceeded 90% when the BG spores were collected on a filter, but was only 15-22% when collected into water. The Mycobacterium bovis BCG bacteria recovered at the 0-8% level on all three collection media. The least number of colonies were formed when Pseudomonas fluorescens bacteria were collected on any of the collection media. The data show that the process of electrostat...

Sampling Performance of Impactors for Bacterial Bioaerosols

Abstract: Impactor is more commonly used than impinger and filter for bioaerosol sampling because of direct collection without post-collection sample processing. In this study, sampling bacterial performance of microbial impactors with different sampling velocities and cut-point diameters was assessed. By the evaluated impactors, the recoveries of hardy bacterial spores was observed to be much higher than those of sensitive gram-negative bacteria. In addition, it was demonstrated that sampling biological recoveries of Andersen 1-STG sampler were much higher than those of MAS-100 and Burkard samplers. These might be related to lower cut-point diameter of Andersen 1-STG sampler with higher collection efficiency. Moreover, a sampling time of < 40 min was not indicated to significantly influence bacterial recoveries of the evaluated impactors.

Field testing of a personal size-selective bioaerosol sampler

Abstract: Existing samplers for the collection of bioaerosols have been designed with the aim of maintaining biological stability of the collected material, and in general do not select particles in accordance with international conventions for aerosol sampling. Many have uncharacterised sampling efficiencies and few are designed as personal samplers. If standard personal dust samplers are used for bioaerosols the viability of collected microorganisms may be compromised by dehydration. The objective of this study was to evaluate a novel personal bioaerosol sampler designed to collect the inhalable dust fraction and further subdivide the sample into thoracic and respirable fractions. The new sampler was tested to see whether it enhanced the survival of the collected microorganisms, and was assessed for ease of use in the field and in subsequent laboratory analyses. A number of occupation-related field sites were selected where large concentrations of bioaerosols were to be expected. The prototype sampler was found to be simple to use. Analysis could be carried out with similar efficiency either with all three fractions together for a total count, or separately for size selective data. The sampler performed at least as well as the standard IOM filter method but with the added advantage of size fractionation. The field trials showed that for sampling periods lasting several hours, microorganism survival within the sampler was adequate for culture and identification of the organisms present. This new sampler is now commercially available. In addition to bioaerosol sampling, the principle of size selective sampling using porous foams can be applied to other occupational hygiene problems, and also to indoor air monitoring of PM10 and PM2.5 concentrations.

Bioaerosol Concentration at an Outdoor Composting Center.

Abstract: Compost centers are one of many environments that produce airborne microorganisms. The objective of this study was to compare the bacterial, fungal, and acti-nomycete concentrations at the Norman, OK, compost center to background concentration of these same microorganisms. For this comparison, a modified Andersen Microbial Sampler was used. Sampling was performed at three sites at the outdoor compost center and at two background sites. The concentration of each microorganism was measured as total colony forming units per cubic meter (CFU/m3). The predominantly downwind compost center site had a 10-fold increase in all the microorganisms in comparison with the other sites (p < 0.05). The median concentrations (95% confidence interval) of total viable bacteria, Gram-negative bacteria, fungi, and actinomycetes at this site were 5059 (CI95= 4952-9600) CFU/m3, 2023 (CI95= 2586-6806) CFU/m3, 972 (CI95= 964-1943) CFU/m3, and 2159 (CI95= 1755-4190) CFU/m3, respectively.

An indoor bio-contaminants air quality

Abstract: Both the quantity and quality of microorganisms (mold, actinomycetes and bacteria) were investigated in the air of five clean rooms indoors, outdoor air sampling was a routine work of the present study. Total viable bacterial counts were recorded in a mean value of 103 cfu/m3, whereas mold counts ranged between 102-103 cfu/m3. The highest mold counts were recorded at some places investigated such as research laboratories and a library. Moreover, the types, percentages and frequencies of occurance of viable mold were studied. Penicillium, Cladosporium and Aspergillus were the predominant mold genera. These organisms are aeroallergens. Actinomycetes were detected in low numbers compared with other organisms (range between 0-102 cfu/m3). Yellow, grey and white colour series were dominant streptomycetes. The mold and streptomycetes spore sizes were measured microscopically. The sizes of major mold spores ranged between 2.5-10 mum, whereas that of streptomycetes spores ranged between 1.2-2.5 mum. The particles...

Collection Efficiency and Culturability of Impingement into a Liquid for Bioaerosols of Fungal Spores and Yeast Cells

Abstract: Collection efficiency of AGI-30 impingers and culturability of collected fungal bioaerosols were evaluated in a laboratory test system. A Pitt-3 generator and a Collison nebulizer aerosolized spores of Penicillium citrinum (P. citrinum) and yeast cells of Candida famata (C. famata) var. flareri , respectively. A 37-mm 3-piece cassette containing a 0.4- mu m Nuclepore filter was adapted to the outlet of the test impinger to collect the particles penetrating the sampler. The particles deposited on the inlet tube were also extracted to evaluate the wall loss effect. The physical collection efficiency was evaluated by counting the fungal particles of three portions of the impinger (inlet tube, AGI-30, and outlet) using a haemocytometer. In addition, the culturability was determined as the ratio of CFU concentration to total concentration measured by the haemocytometer. Our results demonstrated that the impinger could collect more than 90% of the particles, and less than 1% of the particles were found in the i...

Evaluation of Impingement and Filtration Methods for Yeast Bioaerosol Sampling

Abstract: Yeast was one of the most prevalent groups isolated from field fungal samples. To provide a quantitative basis for determining the airborne yeast concentration, the bioefficiency of three sampling methods as well as the effects of relative humidity, sampling time, and flow rates were evaluated. The experiments were performed on the basis of total recovery, which was the ratio of CFU concentration and total particle concentration measured by an aerodynamic particle sizer. The bioefficiency results demonstrated that the total recovery of airborne yeast collected by the AGI-30 impinger was above 80% at 70% relative humidity, while it decreased rapidly as relative humidity decreased beneath 60%. This might be related to undergoing desiccation and losing culturability before collection for yeast cells following bioaerosol generation from liquid suspension. The filtration outcome indicated that dehydration effects were significant and total recovery was < 20% for Nuclepore and gelatin filters. In addition, no s...

Dispersal of Fungal Spores from Three Types of Air Handling System Duct Material

Abstract: Exposure to airborne microorganisms in indoor environments may result in infectious disease or elicit an allergic or irritant response. Air handling system components contaminated by fungi have been implicated in the dispersal of spores into the indoor environment, thereby serving as a route of exposure to occupants. This study was conducted to provide quantitative data on the dispersal of spores from fungal colonies growing on three types of duct material. Galvanized metal, rigid fibrous glass ductboard, and fiberglass duct liner were soiled and contaminated with a known concentration of Penicillium chrysogenum spores. The duct materials were incubated in humidity chambers to provide a matrix of growing, sporulating fungal colonies at a contamination level of 109 colony forming units (CFU) per duct section, consistent for all materials. For each experiment a contaminated duct section was inserted into the air handling system of an experimental room, and the air handling system was operated for three 5-minute cycles with an air flow of 4.2 m3 min−1. The duct air velocity was approximately 2.8 m sec−1. The airborne concentration of culturable P. chrysogenum spores (CFU m−3), total P. chrysogenum spores (spores m−3), and total P. chrysogenum-sized particles (particles m−3) were measured in the room using Andersen single-stage impactor samplers, Burkard slide impactor samplers, and an aerodynamic particle sizer, respectively. The highest airborne concentrations (104 CFU m−3; 105 spores m−3; 104 particles m−3) were measured during the first operating cycle of the air handling system for all duct materials with decreasing airborne concentrations measured during the second and third cycles. There was no significant difference in spore dispersal from the three contaminated duct materials. These data demonstrate the potential exposure for building occupants to high concentrations of spores dispersed from fungal colonies on air handling system duct materials during normal operation of the system.

The Effect of Phosphate Buffer on Aerosol Size Distribution of Nebulized Bacillus subtilis and Pseudomonas fluorescens Bacteria

Abstract: During bioaerosol research microorganisms are frequently aerosolized from phosphate-buffered suspension via air-jet nebulization. Buffer will therefore be present in organism-free droplets (''empties") as solutes in hydrous surface coatings of airborne organisms or as dry surface coatings on organisms. It might be expected that the buffer would influence the resulting aerosol size distribution and that the influence might vary with relative humidity. In this work we examined the effect of various buffer concentrations on the aerosol size distribution of Bacillus subtilis (B. subtilis) and Pseudomonas fluorescens ( P. fluorescens ) at various relative humidities. Microorganism suspensions in distilled deionized water and phosphate-buffered water were prepared and nebulized from a 3-jet Collison nebulizer into a sampling chamber maintained at 10% relative humidity. The aerosol was then conducted to a second chamber to which moist air was added to achieve the target relative humidity. Particle aerodynamic si...

Worker Exposures to Particulates, Endotoxins, and Bioaerosols in Two Refuse-Derived Fuel Plants

Abstract: Exposures of refuse-derived fuel (RDF) production workers to total particulates, endotoxin, and total (viable plus nonviable) bioaerosols were characterized at two RDF production plants. Full-shift personal air monitoring for 35 workers was conducted for total particulates, analyzed by gravimetric analysis; endotoxin, analyzed by chromogenic endpoint assay; and total bioaerosols, analyzed by fluorescent microscopy (FM). Geometric mean values of personal air samples were 0.50 mg/m3 for total dust, 29.0 EU/m3 (2.9 ng/m3) for endotoxin, and 6.8 × 105 organisms/m3 for bioaerosols. Significant differences were observed between the two plants only for total endotoxin exposures. The mean concentrations for total particulates, total FM bioaerosols, and endotoxins did not differ among the day, evening, or night shifts. Interjob differences were found for exposures to total dust, total endotoxin, and FM bioaerosols. Individual comparisons for total particulates and endotoxin exposures were significant for compariso...

Sampling performance of impactors for fungal spores and yeast cells

Abstract: Impactor than impinger and filter is more commonly used for bioaerosol sampling because of direct collection without post-collection sample processing. In this study, sampling fungal performance of microbial impactors with different sampling velocities and cut-point diameters was assessed. It was demonstrated that biological recoveries of Penicillium citrinum spores were ob served to be similar to those of two yeast cells, Candida famata var. flareri and Rhodotorula mucilaginosa . In addition, it was indicated that sampling performance of Burkard samplers was relatively better than those of Andersen 1-STG and MAS-100 samplers. Moreover, sampling time was indicated to not significantly influence fungal recoveries of the three evaluated impactors.

Air sampling of fungal spores on filters. An investigation on passive sampling and viability.

Abstract: In this study, glycerol was tested as a collection substrate for passive bioaerosol sampling. Filters (mixed cellulose acetate and nitrate) were soaked in glycerol and exposed for an aerosol from three different fungal species: Penicillum commune, Aspergillus versicolor and Paecilomyces variotii. The passive sampling method was compared with a closed-face polycarbonate filter sampling method. Exposure was performed in an exposure chamber. The total number of spores was determined by microscopic techniques, and the cultivable number was determined by cultivation on Malt Extract Agar dishes. The glycerol soaked filter demonstrated a good correlation with the closed-face sampler with regard to the total count. Spores stored in a pumped filter cassette were not affected by storage for up to 7 days. On the other hand, the culturability of the spores was markedly decreased after 1 day when stored on glycerol soaked filters.

Real-time detection and characterization of individual flowing airborne biological particles: fluorescence spectra and elastic scattering measurements

Abstract: Real-time methods which is reagentless and could detect and partially characterize bioaerosols are of current interest. We present a technique for real-time measurement of UV-excited fluorescence spectra and two-dimensional angular optical scattering (TAOS) from individual flowing biological aerosol particles. The fluorescence spectra have been observed from more than 20 samples including Bacillus subtilis, Escherichia coli, Erwinia herbicola, allergens, dust, and smoke. The S/N and resolution of the spectra are sufficient for observing small lineshape differences among the same type of bioaerosol prepared under different conditions. The additional information from TAOS regarding particle size, shape, and granularity has the potential of aiding in distinguishing bacterial aerosols from other aerosols, such as diesel and cigarette smoke.

Monitoring biological aerosols using UV fluorescence

Abstract: An apparatus has been designed and constructed to continuously monitor the number density, size, and fluorescent emission of ambient aerosol particles. The application of fluorescence to biological particles suspended in the atmosphere requires laser excitation in the UV spectral region. In this study, a Nd:YAG laser is quadrupled to provide a 266 nm wavelength to excite emission from single micrometer-sized particles in air. Fluorescent emission is used to continuously identify aerosol particles of biological origin. For calibration, biological samples of Bacillus subtilis spores and vegetative cells, Esherichia coli, Bacillus thuringiensis and Erwinia herbicola vegetative cells were prepared as suspensions in water and nebulized to produce aerosols. Detection of single aerosol particles, provides elastic scattering response as well as fluorescent emission in two spectral bands simultaneously. Our efforts have focuses on empirical characterization of the emission and scattering characteristics of various bacterial samples to determine the feasibility of optical discrimination between different cell types. Preliminary spectroscopic evidence suggest that different samples can be distinguished as separate bio-aerosol groups. In addition to controlled sample results, we will also discuss the most recent result on the effectiveness of detection outdoor releases and variations in environmental backgrounds.

[The microbiological characterization of the bioaerosol and leachate from an urban solid refuse dump: preliminary data].

Abstract: The present paper shows the results of an experimental study aimed at arranging a microbiological characterization of bioaerosol and leachate resulting from a sanitary landfill for solid urban waste situated near Rome. Bioaerosol sampling was performed by using the active sampling method referred to as surface air system, that is extensively used during indoor environmental monitoring. The microorganisms (bacteria and fungi) believed to be of relevance on bioaerosol and leachate with a view to hygienic risks, were investigated in order to estimate the potential risks to which the population and the workers can be exposed and consequently to allow corrective measures by monitoring campaigns of the examined matrices and by models of low environmental impact landfill.

Procedures for the characterisation of bioaerosol particles. Part I: aerosolisation and recovery agent effects

Abstract: The sampling and assay of bioaerosols are important ina number of industrial and health-care applications. Airborne microorganisms are notoriously difficult toenumerate accurately under such conditions and nosingle procedure is suitable for all applications. Problems are compounded by the differences in assaymethod or sampler type selected, making theinterpretation of results difficult.Understanding the airborne behaviour of microorganismsover a range of environmental conditions is vital ifprocedures are to be defined and recommended for theassessment of bioaerosols. Microorganisms that arerobust over a wide range of conditions are ideal astracer particles. Unfortunately, the large majorityof non-fungal bioaerosols are susceptible to damage. A predictable assessment procedure is required whichwill not affect the viability of the collectedsample. This paper examines how aerosolisation may affect the characteristics of two speciesof microorganism (Pseudomonas fluorescens andMS2 coliphage). It forms part of a larger programmeto develop standards for the assessment of biologicalparticles. The aim of the work was to develop procedures toexamine the effects of aerosolisation onmicroorganisms, with particular reference topre-aerosolisation protocol (spray suspension age) andpost-sampling handling protocol (aerosol age incollection solution). These procedures were then usedto examine the effect of recovery agents, addedto the spray suspension prior to aerosolisation, onthe culturability of E.coli. Aerosolisation reduces the culturability of P. fluorescensand the viability of viability of MS2coliphage. Pre-sampling and post-collection handlingand storage of these aerosolised microorganisms werealso found to have an effect. This and earlierstudies have shown that the culturable fraction ofmicroorganisms can be affected by the same factorsdescribed above. Of five microorganisms tested so farin the main programme, only Penicillium expansumspores were shown to be robust and stable with aconstant culturable fraction. Therefore, recommendinga particular microorganism (apart from P. expansum) as an airborne biological standard foraerosol studies is not advised. It is recommendedthat a microorganism, representative of the envisagedapplication, be characterised it in terms of theaerosolisation parameters, storage time and conditionsin the manner reported in this study. This can beachieved using the experimental equipment described.The addition of 0.1 mM concentrations of the sugarsinositol, trehalose and raffinose to spray suspensionsof Escherichia coli, prior to aerosolisation,made no significant difference to the culturablefraction of the aerosol.

Determining the emission of microorganisms from biofilters and emission concentrations at the site of composting areas

Abstract: In order to assess source emissions and dispersal of airborne culturable microorganisms from composting plants, measurements at three composting plants have been carried out. The downwind concentrations of dispersed microorganisms differed greatly, depending on the type of plant design. At 200 metres downwind from the totally enclosed composting plant, levels of spore concentrations of thermotolerant fungi and Aspergillus fumigatus, which may be regarded as characteristic for composting operations, were not above the magnitude of background concentrations. In contrast, spore concentrations in excess of the background level occurred within 500 metres of the partly open plant. Moreover, the ranges of airborne concentrations at similar distances from the enclosed plant were much smaller relative to the partly open plant. Measurement of source emissions from biofilters showed concentrations in the raw and purified gases in the range of up to three orders of magnitude. The operational characteristics of the plants generally contributing to bioaerosol emissions on-site were found to have an influence on the concentration levels in the raw gas. A decrease in the microbiological parameters which may be regarded as specific for composting operations, was attributed to a reduced rate of passage through the biofilters. The magnitude of reduction as well as the concentrations varied greatly.