Showing papers on "Bioaerosol published in 2001"

Effects of Relative Humidity on the Ultraviolet Induced Inactivation of Airborne Bacteria

Abstract: Ultraviolet germicidal irradiation (UVGI) as an engineering control against infectious bioaerosols necessitates a clear understanding of environmental effects on inactivation rates. The response of aerosolized Serratia marcescens, Bacillus subtilis, and Mycobacterium parafortuitum to ultraviolet irradiation was assessed at different relative humidity (RH)levels in a 0.8 m3 completely-mixed chamber. Bioaerosol response was characterized by physical factors including median cell aerodynamic diameter and cell water sorption capacity and by natural decay and UV-induced inactivation rate as determined by direct microscopic counts and standard plate counts. All organisms tested sorbed water from the atmosphere at RH levels between 20% and 95% (up to 70% of dry cell mass at 95% RH); however, no concomitant change in median aerodynamic diameter in this same RH range was observed. Variations in ultraviolet spherical irradiance were minor and not statistically significant in the 20-95% RH range. Cell water sorption...

Ambient air levels of Aspergillus fumigatus and thermophilic actinomycetes in a residential neighborhood near a yard-waste composting facility

Abstract: Composting is a biological process that has thepotential to emit large quantities ofbioaerosols and, therefore, could adverselyaffect public health. Numerous previousstudies have demonstrated bioaerosol levelselevated above background adjacent tocomposting waste materials, but effects onoffsite bioaerosol levels due tocomposting-facility bioaerosol emissions havenot been extensively investigated. Of the fewsuch studies published, most have not foundelevated compost-related bioaerosols downwindfrom the composting operation. We investigatedviable Aspergillus fumigatus andthermophilic actinomycete levels upwind anddownwind of a large yard-waste compostingfacility and sought to determine whether levelsin a residential neighborhood near the facilitywere elevated above background levels due tofacility bioaerosol emissions. Mean bioaerosollevels at the composting facility weresignificantly higher than the mean backgroundlevels, exceeding the background means byroughly 20-fold. When a neighborhood samplingsite about 500 m from the facility was in thedownwind direction mean levels weresignificantly higher than for other winddirections, and excursions well abovebackground levels were significantly morefrequent than at background sites. There was asignificant temporal correlation betweenbioaerosol levels at the composting facilityand the downwind sampling site. The resultsindicate that bioaerosol emissions from a largeyard-waste composting facility cansignificantly increase bioaerosol exposurelevels at least 500 m downwind from thefacility.

Bioaerosol emissions from a suburban yard waste composting facility.

Abstract: The purpose of this study was to assess worker and community exposure to bioaerosols emitted from a suburban yard waste composting facility in northern Illinois, USA. Characterization of on- and off-site viable bioaerosols was undertaken through a total of 288 on- and off-site Andersen samples conducted over 10 sampling days. A total of 46 dust samples and 38 Kramer-Collins spore samples were also collected in this period. Evaluation of the impact of the facility on community bioaerosol concentrations was undertaken by comparing on- and off-site measurements by sampling locations, wind direction, and site activity. On-site concentrations of total spores, Aspergillus/Penicillium spores, total bacteria, Gram-positive bacteria, Gram-negative bacteria, actinomycetes, total SDUWLFXODWHVHQGRWR(LQDQG-1,3 glucans were higher than off-site concentrations. Total fungal spores averaged 13,451 spores/m 3 (range 5,223-26,067) on-site and 8,772 spores/m 3

Exposure to airborne microorganisms and endotoxin in herb processing plants

Abstract: Microbiological air sampling was performed in two herb processing plants located in eastern Poland. Air samples for determination of the levels of bacteria, fungi, dust and endotoxin were collected at 14 sites during cleaning, cutting, grinding, sieving, sorting and packing of 11 kinds of herbs (nettle, caraway, birch, celandine, marjoram, mint, peppermint, sage, St. John's wort, calamus, yarrow), used for production of medications, cosmetics and spices. It was found that processing of herbs was associated with a very high pollution of the air with bacteria, fungi, dust and endotoxin. The numbers of microorganisms (bacteria and fungi) in the air of herb processing plants ranged within 40.6-627.4 x 10(3) cfu/m3 (mean +/- S.D = 231.4 +/- 181.0 x 10(3) cfu/m3). The greatest concentrations were noted at the initial stages of production cycle, during cleaning, cutting and grinding of herbs. The numbers of airborne microorganisms were also significantly (p<0.0001) related to the kind of processed herb, being the greatest at processing marjoram, nettle, yarrow and mint. The values of the respirable fraction of airborne microflora in the examined facilities varied within a fairly wide range and were between 14.7-67.7%. The dominant microorganisms in the air of herb processing plants were mesophilic bacteria, among which endospore-forming bacilli (Bacillus spp.) and actinomycetes of the species Streptomyces albus were most numerous. Among Gram-negative bacteria, the most common was endotoxin-producing species Alcaligenes faecalis. Altogether, 37 species or genera of bacteria and 23 species or genera of fungi were identified in the air of herb processing plants, of these, 11 and 10 species or genera respectively were reported as having allergenic and/or immunotoxic properties. The concentrations of dust and bacterial endotoxin in the air of herb processing plants were large with extremely high levels at some sampling sites. The concentrations of airborne dust ranged within 3.2-946.0 mg/m3 (median 18.1 mg/m3), exceeding at 13 out of 14 sampling sites the Polish OEL value of 4 mg/m3. The concentrations of airborne endotoxin ranged within 0.2-2681.0 microg/m3 (median 16.0 microg/m3), exceeding at all sampling sites the suggested OEL value of 0.1 microg/m3. In conclusion, the workers of herb processing plants could be exposed to large concentrations of airborne microorganisms, dust and endotoxin posing a risk of work-related respiratory disease.

Suspended particulates and bioaerosols emitted from an agricultural non-point source.

Abstract: Suspended particulate and bioaerosol levels were measured at three sites downwind of an agricultural non-point source during the wheat harvesting season. Suspended particulates were detected at mean values ranging from 10000 to 2420 µg m−3 at distances of from 20 to 60 m downwind of the source, respectively. Airborne viable bacterial counts were recorded at mean values ranging between 104 and 106 colony forming units (cfu) m−3, whereas, Gram negative (Gram −ve) bacteria varied between 103 and 105 cfu m−3. Fungi levels were detected at mean values varying between 105 and 106 cfu m−3. However, streptomycetes were found at lower counts than those recorded for viable bacteria and fungi. Total viable bacteria, Gram −ve bacteria, fungi and streptomycetes associated hay fragments were determined at mean values of 1.5 × 106, 1.6 × 103, 2.2 × 104 and 6 × 103 cfu g−1 of hay, respectively. Cladosporium, white and red yeasts as well as Alternaria were the predominant airborne fungi, whereas, Alternaria was the dominant species associated with hay fragments. Pseudomonas, Acinetobacter and Enterobacteriaceae were the dominant Gram −ve bacteria. The most common fungal genera, such as Cladosporium and Fusarium (minor short axis), as well as Streptomyces species have an aerodynamic diameter (dae) of less than 5 µm, which can penetrate and deposit in the alveoli. Farmers and nearby residents are exposed to high levels of organic dust and bioaerosols during the wheat harvesting season. This may cause health problems in exposed persons based on toxic or allergic reactions.

Field detection and identification of a bioaerosol suite by pyrolysis-gas chromatography-ion mobility spectrometry*

Abstract: Improvements were made to a pyrolysis-gas chromatography-ion mobility spectrometry (Py-GC-IMS) 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 compared to earlier work. These improvements allowed a greater degree of confidence in the correlation of biological aerosols obtained 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 (71%). 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 blank water sprays. Reproducible limits of detection were at a concentration of less than 0.5 bacterial analyte-containing particle per liter of air. In order to realize this low concentration, an aerosol concentrator was used to concentrate 2000 l of air in 2.2 min. Previous outdoor aerosol trials have shown the Py-GC-IMS device to be a credible detector with respect to determining the presence of a biological aerosol. The current series of outdoor trials has provided a platform to show that the Py-GC-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 (BG), a gram-negative bacterium (EH), and a protein (ovalbumin). © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 190–204, 2001

Collection of Bioaerosol Particles by Impaction: Effect of Fungal Spore Agglomeration and Bounce

Abstract: Calibration and performance evaluations of bioaerosol impactors are usually conducted with non-biological test aerosols, such as polydisperse liquid oleic acid particles or monodisperse solid polystyrene latex (PSL) particles. This study was undertaken to investigate to what degree surface properties and agglomeration of bioaerosol particles may result in different performance characteristics of impactors. The single-stage impaction of biological and non-biological particles on a sticky surface was studied utilizing Air-O-Cell sampling cassettes that are widely used to collect airborne fungal spores. The aerosol concentrations upstream and downstream of the sampler were measured with an aerodynamic particle size spectrometer. The collection efficiency was determined for the sampler operating at different flow rates ranging from 10 to 30 L/min. The tests were performed with aerosol particles of about 1 to 4 μm in diameter, including two fungal species of different surface properties (Penicillium brevicompactum and Penicillium melinii), and two types of non-biological aerosols (oleic acid and PSL). The 50% cut-off sizes determined experimentally with non-biological particles differed from the theoretical predictions by 11% or less. The data obtained with biological test particles, however, were found to show higher (at low sampling flow rates) or lower (at high flow rates) collection efficiencies than determined through the use of conventional non-biological test particles. E.g., at 30 L/min, the difference is about 50%. The differences were attributed to the presence of spore aggregates and their possible deaggregation during impaction. Inertial impaction, deaggregation, and bounce of fungal spores from the collection surface were studied experimentally and estimated theoretically utilizing experimental data on the percentages of singlets, doublets and triplets in specific bioaerosols. It is concluded that the calibration and performance of bioaerosol impactors may strongly depend on the surface characteristics, initial percentage of aggregates, and deaggregation rate of the specific bioaerosol particles being sampled.

An Analytical Method for the Measurement of Nonviable Bioaerosols

Abstract: Exposures from indoor environments are a major issue for evaluating total long-term personal exposures to the fine fraction (<2.5 microm in aerodynamic diameter) of particulate matter (PM). It is widely accepted in the indoor air quality (IAQ) research community that biocontamination is one of the important indoor air pollutants. Major indoor air biocontaminants include mold, bacteria, dust mites, and other antigens. Once the biocontaminants or their metabolites become airborne, IAQ could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, allergic, infectious, and chemical responses in exposed individuals. Biocontaminants, such as some mold spores or pollen grains, because of their size and mass, settle rapidly within the indoor environment. Over time they may become nonviable and fragmented by the process of desiccation. Desiccated nonviable fragments of organisms are common and can be toxic or allergenic, depending upon the specific organism or organism component. Once these smaller and lighter fragments of biological PM become suspended in air, they have a greater tendency to stay suspended. Although some bioaerosols have been identified, few have been quantitatively studied for their prevalence within the total indoor PM with time, or for their affinity to penetrate indoors. This paper describes a preliminary research effort to develop a methodology for the measurement of nonviable biologically based PM, analyzing for mold and ragweed antigens and endotoxins. The research objectives include the development of a set of analytical methods and the comparison of impactor media and sample size, and the quantification of the relationship between outdoor and indoor levels of bioaerosols. Indoor and outdoor air samples were passed through an Andersen nonviable cascade impactor in which particles from 0.2 to 9.0 microm were collected and analyzed. The presence of mold, ragweed, and endotoxin was found in all eight size ranges. The presence of respirable particles of mold and pollen found in the fine particle size range from 0.2 to 5.25 microm is evidence of fragmentation of larger source particles that are known allergens.

Method and device for detecting and identifying bio-aerosol particles in the air

Abstract: In a method for detecting and identifying bioaerosol particles in the air, the bioaerosol particles in a particle stream are selected in an ATOFMS (aerosol time-of-flight mass spectrometer) by means of fluorescence techniques, and only the selected bioaerosol particles are ionized, for instance on the basis of MALDI (matrix-assisted laser desorption/ionization), after which the resulting ions are detected and the bioaerosol particles are identified. The selection of bioaerosol particles takes place by means of laser radiation, generated by a first laser device, of a wavelength which in specific substances in bioaerosol particles effects a fluorescence, after which by means of a fluorescence detector the bioaerosol particles are selected and a second laser device is triggered to emit light of a wavelength which effects the ionization of the bioaerosol particles selected only by the fluorescence detector.

Comparison of Field Performance of the Andersen N6 Single Stage and the SAS Sampler for Airborne Fungal Propagules

Abstract: Comparisons of two common bioaerosol samplers were made after sampling and enumeration of airborne fungal propagules in several office structures on a university campus in Southern California. Data collected on five occasions throughout the year showed that a Surface Air Systems (SAS) high flow portable sampler recovered consistently lower levels of colony forming units (cfu) than an Andersen N6 single stage impactor. There was no difference statistically between the samplers when concentrations of Cladosporium were compared. Compared to the Andersen N6, the SAS sampler recovered about half the number of cfu for three other fungal categories, i.e. non-sporulating species, Aspergillus and Penicillium and others. Differences in sampler efficiencies are discussed in terms of effective particle diameters. Counts of culturable airborne fungal spores obtained with the SAS sampler should be interpreted with caution when genera other than Cladosporium predominate.

Effectiveness of HVAC duct cleaning procedures in improving indoor air quality.

Abstract: Indoor air quality has become one of the most serious environmental concerns as an average person spends about 22 hr indoors on a daily basis. The study reported in this article, was conducted to determine the effectiveness of three commercial HVAC (Heating Ventilation Air Conditioning) duct cleaning processes in reducing the level of airborne particulate matter and viable bioaerosols. The three HVAC sanitation processes were: (1) Contact method (use of conventional vacuum cleaning of interior duct surfaces); (2) Air sweep method (use of compressed air to dislodging dirt and debris); (3) Rotary brush method (insertion of a rotary brush into the ductwork to agitate and dislodge the debris). Effectiveness of these sanitation processes was evaluated in terms of airborne particulate and viable bioaerosol concentrations in residential homes. Eight identical homes were selected in the same neighborhood. Two homes were cleaned using each procedure and two were used as controls. It was found that both particle count readings and bioaerosol concentrations were higher when cleaning was being performed than before or after cleaning, which suggests that dirt, debris and other pollutants may become airborne as a result of disturbances caused by the cleaning processes. Particle count readings at 0.3 micron size were found to have increased due to cigarette smoking. Particle counts at 1.0 micron size were reduced due to HVAC duct cleaning. Post-level bioaerosol concentrations, taken two days after cleaning, were found to be lower than the pre-level concentrations suggesting that the cleaning procedures were effective to some extent. Homes cleaned with the Air Sweep procedure showed the highest degree of reduction in bioaerosol concentration among the three procedures investigated.

Emissions of chemical compounds and bioaerosols during the secondary treatment of paper mill effluents.

Abstract: This study identified and quantified the main chemical compounds—the substances responsible for the disagreeable odors—and the bioaerosols emitted during the biological treatment of paper mill effluents. It also identified the characteristics of the process that effects the generation or diffusion of these substances. All treatment stages were evaluated. Measuring sites were located as closely as possible to the potential emission sources. Measurements were taken in the summer in 11 paper mills during a 2- to 3-day period in each mill. Chemical compounds were evaluated by direct-reading instruments; bioaerosols were sampled by impaction and counted. Sulfur compounds, emitted into the air when the effluent or the sludge is stirred, had the highest concentrations; their presence was attributable to such things as kraft-type paper pulp. Next in concentration were the carbon and nitrogen oxides, ammonia, and some organic acids, produced by the action of microorganisms. These acids are found mainly in the slud...

Procedures for the characterisation of bioaerosol particles. Part II: Effects of environment on culturability

Abstract: The behaviour of bioaerosol particles in industrial and health-careapplications may be most effectively understood once they have beenquantitatively assessed using well-characterised sampling and assaytechniques. However, the large number of different conditions possiblein this wide range of applications makes the assessment of bioaerosolparticles very difficult. In addition to the effects of differentsampling and assay technologies, the mechanism of aerosolisation andenvironmental conditions can influence bioaerosol behaviour. The effectsof sampler selection and suspension aerosolisation on bioaerosolviability were reported earlier as ``Part I'' of two papers, and theeffects of the environment on the culturability of three different typesof microorganism are reported here as ``Part II''. The environmentalrelative factors considered in the present study are: relativehumidity (RH), aerosol-age, and a number of gaseous pollutants. A smallnumber of additional tests, examining the effects of aerosolisationmethod on culturability, are also reported. A combination of anenvironmentally controlled Bioaerosol Test Chamber and Goldberg RotatingDrum were shown to be an appropriate facility to carry out the study.Changing RH was shown to have a considerable effect on the culturablefraction of aerosolised Sacharomyces cerevisiae cells but notPenicillium expansum spores or Bacillus subtilis var.niger spores. In this text, ``culturable fraction'' is definedas the fraction of the total number of microorganisms in a sample thatwill form colonies (i.e. grow and reproduce) on a suitably preparedculture plate under optimum conditions for the species of microorganismunder consideration. After the initial shock of aerosolisation, theculturable fraction of S. cerevisiae cells and P.expansum spores is not further affected by increasing aerosol age.Results from an earlier study have shown spray suspension and collectedaerosol age also have no effect on culturability of P. expansumspores. The effects of gaseous pollutants are reflected in the reductionin culturability of P. expansum spores following exposure tosulphur dioxide, ozone and ozone hydrocarbon cocktail. This reductionwas never to less than 30% of the unpolluted control. All thetests show that P. expansum spores are fairly robust andbiologically stable. Examination of the effects of aerosolisationtechnique on the culturability of S. cerevisiae shows theCollison nebuliser produces aerosols with the highest culturabilitycompared with either a plain glass atomiser or a Unimed nebuliser usedin these tests.

Ausbreitung von Bioaerosolen aus Kompostierungsanlagen unterschiedlicher Bauart

Abstract: In order to assess the dispersal of cultivalable airborne microorganisms from composting plants, measurements were taken in the close proximity to three different types of plant. The downwind concentrations of dispersed microorganisms differed widely, 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 level of background concentrations. In contrast, spore concentrations comparable to those of a background concentration could be found at a distance of 500 metres from the partly open plant. For the open composting plant, higher levels of specific compost microorganisms than those of the control values were found at 500 metres. Moreover, the ranges of airborne concentrations at similar distances from the enclosed plant were much smaller in relation to the partly open plant. The highest ranges were found for the open composting plant. Furthermore, certain operations related to the production process at composting plants leading to increased emissions, cause higher bioaerosol concentrations in the vicinity of the composting plant. By taking measurements, establishing the sampling locations at various distances within an angle of 30° to 45° downwind from the composting plants, it was possible to record bioaerosol pollutions completely. On the basis of these results, recommendations for the assessment of bioaerosol pollution and standardization of measuring methods are given.

Fluorescence Spectra of Individual Flowing Airborne Biological Particles Measured in Real Time

Abstract: : The UV-excited fluorescence spectra of individual flowing biological aerosol particles as small as 2 pm in diameter have been measured in real time (rates up to 10 particles per second). The particles are illuminated with a single shot from a Q-switched 266- or 351-nm laser. The signal-to-noise ratio and resolution of the spectra are sufficient for observing small line-shape differences among various types of bioaerosols (e.g., bacteria versus pollens) and between the same types of bioaerosol prepared under different conditions (e.g., the unstarved and four-month-starved E. coli strain DH5). Multiple-wavelength excitation provides additional information for distinguishing bioaerosols based on their fluorescence spectra.

The vertical distribution and diurnal variation law of the bioaerosol concentration in Nanjing City

Abstract: ：Using the data observed in July 1998, the vertical distribution and variation law of the bioaerosol concentration in Nanjing is analyzed and studied. The result shows that the bioaerosol concentration decreases as the altitude increases; the maximum bacteria cncentration is 700 CFU/m3 and that of fungi is 1080 CFU/m3 ,which are lower than the data of some other domestic cities,but the fungi concentration is obviously higher than that of some foreign cities. The concentrations of farina,bacteria and fungi vary periodically in 24 hours.

Comparison of bioaerosol sampling methods for swine barns

Abstract: Two bioaerosol sampling methods (Andersen sampler and filtration sampler) were compared. The two samplers were used to assess the bioaerosol loads in two swine finishing barns. They were similar in terms of the species of microorganisms sampled. The persistent strains of microorganisms were various species of the following genera: Staphylococcus, Pseudomonas, Bacillus, Listeria, Enterococcus, Nocardia, Lactobacillus, and Penicillium. However, the use of Andersen sampler resulted in significantly higher bioaerosol concentrations than the filtration sampler. Thus, it appears that filtration sampling can be used for a qualitative survey of bioaerosols in swine barns while the Andersen sampler is suitable for both quantitative and qualitative assessments.

Bioaerosols and Disease

Abstract: Airborne contaminants in the workplace can include chemical, physical, and biological agents. Although the primary focus of the industrial hygienist and toxicologist in the past has been on the health effects of chemical and physical contaminants, there is renewed interest in the science of “aerobiology”—the study of airborne particles of biological origin. Millions of workers in hundreds of occupations are exposed to potential health hazards in their workplace because of substances they breathe in the air. Every year, an estimated 65,000 U.S. workers develop respiratory disease related to their jobs, and an estimated 25,000 persons die from occupational lung disease. Respiratory illness causes an estimated 657 million person-days of restricted activity and 324 million person-days of lost work. Occupational exposure to airborne particles (aerosols) is very common and may pose a potential hazard to human health because microbial cells are particulate matter, studies that deal with airborne microorganisms are concerned with aerosols. Many of the physical and chemical processes that describe aerosol behavior also apply to bioaerosols. The term bioaerosol is used to describe a colloidal suspension of liquid droplets or solid particles in air, that contain or have attached to them one or more living or dead organisms, certain products of bacterial and fungal metabolism, or other biological material. Bioaerosols are ubiquitous indoors and outdoors and may contain cell fragments, dust mites, animal dander, skin scales, and a wide variety of microscopic organisms, including bacteria, viruses, fungi, algae, amoebae, and protozoa. Other nonliving biological substances (e.g., cotton dust, pollen, hemp, jute, sugarcane) also produce respiratory illness in workers. These are not considered in this chapter but have been reviewed elsewhere. This chapter focuses on those bioaerosols most likely to be related to the workplace, although nonoccupational sources can be prevalent. Bioaerosols such as house dust mites, animal dander, or cockroach products that are very important in inducing diseases like asthma may be referred to but are not discussed in detail because of their strong association with the home environment. Attention is given to infectious agents (and their products) because many working conditions are conducive to transmitting of such agents. Although bioaerosols generally represent fewer hazards than those of a physical or chemical nature, there are certain occupations where the risk of such exposures may be more prevalent. Occupational settings of concern include agriculture, saw mills, textile manufacturing, meat and other food processing, biotechnology, research laboratories, waste disposal, construction, and health-care institutions. The extent of health problems caused by bioaerosols in the workplace is difficult to estimate partly because of the wide array of agents that evoke a variety of human responses. The workplace atmosphere may contain hundreds of different kinds of biological particles, both pathogens and nonpathogens, and today's technology cannot quantify all of them. The complexity is even greater because of the broad range of different types of industrial environments and because exposures are not often recognized until the workers experience illness. Understanding the cause and effect relationship associated with exposure to bioaerosols is a most difficult and vexing problem. Despite uncertainty about the magnitude of the health risk caused by exposure, the impact is appreciable and has been considered the largest single cause of morbidity. This chapter is intended primarily for those occupational health professionals who seek to understand the potential health risk of airborne biological agents in the workplace. It presents an overview of the basic concepts and methodologies useful in assessing the health effects of bioaerosols, including the (1) types and properties of bioaerosols; (2) sources of bioaerosols; (3) transmission, infections, and disease; (4) interaction with environmental and physiological factors; (5) health effects from the inhalation of bioaerosols; (6) sampling and identifying airborne microbial contaminates; (7) assessment of risk; and (8) control and prevention of airborne infectious disease. Keywords: Bioaerosols; Bacteria; Viruses; Fungi; Rickettsias; Nonliving contaminants; Sources; Transmission; Infection; Disease; Contributing factors; Workplace; Allergies; Sampling; Identification; Risk assessment; Control; Prevention