Concentrations Of Culturable Bacteria Research Articles

Optimization of slightly acidic electrolyzed water spray for airborne culturable bacteria reduction in animal housing

Slightly acidic electrolyzed water (SAEW) spray has been considered as a novel approach for airborne bacteria reduction in animal housing. This study aimed to optimize the operating parameters of SAEW spray based on the size distribution of sprayed aerosols, the available chlorine travelling loss in sprayed aerosols, and the reduction efficiency of airborne culturable bacteria (CB). The optimized operating parameters were the nozzle orifice diameter and the spray pressure. The size distribution characteristics of sprayed SAEW aerosols under different operating parameters were quantified. The pH and available chlorine concentrations of the original SAEW solution and the SAEW aerosols collected at 0 m, 0.25 m, 0.50 m, 0.75 m, and 1.00 m from the spray nozzle head were analyzed. A bioaerosol nebulizing generator was used to simulate animal housing environment in an environmentally-controlled chamber. Six SAEW spray trials under different operating parameters were conducted at a spray dosage of 80 mL/m2 in the chamber. Airborne CB concentrations before and after spray were measured to investigate the reduction efficiency of airborne CB. Dv(50), the volume-based diameter below which 50% of the particle being present, increased with the nozzle orifice diameter and decreased with the spray pressure. The travelling loss of available chlorine in the sprayed SAEW aerosols was greatly dependent on Dv(50). SAEW spray with medium size sprayed aerosols (Dv(50) = 86.62 μm, 67.94 μm, and 54.53 μm) showed significantly higher airborne CB reduction efficiencies than large (Dv(50)=121.80 μm and 96.00 μm) or small size aerosols (Dv(50) = 42.57 μm). The spray operating parameters that provide medium size sprayed aerosols (Dv(50) ~ 60-90 μm) are recommended for SAEW spray in animal housing. Keywords: animal housing, bioaerosol, available chlorine, size distribution, air quality, poultry and livestock DOI: 10.3965/j.ijabe.20160904.2366 Citation: Zheng W C, Ni L, Hui X, Li B M, Zhang J F. Optimization of slightly acidic electrolyzed water spray for airborne culturable bacteria reduction in animal housing. Int J Agric & Biol Eng, 2016; 9(4): 185－191.

Profile and Characteristics of Culturable Airborne Bacteria in Hangzhou, Southeast of China

ABSTRACTIncreased concentrations of airborne bacteria are known to be associated with decreased public health. As such, we evaluated the culturable concentration and distribution characteristics of airborne bacteria at four sampling sites in Hangzhou, southeast China. Results showed that the concentration of culturable bacteria in the air at selected sampling sites ranged from 0.05). Taken together these results provide a baseline for airborne culturable bacteria in southeast China, and will enable evaluation of the risks to human health from exposure to the atmosphere in the region.

Airborne Particulate Matter and Culturable Bacteria Reduction from Spraying Slightly Acidic Electrolyzed Water in an Experimental Aviary Laying-Hen Housing Chamber

Abstract. Compared to conventional cage laying-hen houses, aviary hen houses generally have much higher concentrations of airborne dust and bacteria due to generation of bioaerosols by the hens’ access to and activities on the litter floor. Hence, reducing these airborne agents is important to safeguard the health of the animals and workers in such housing systems. Spraying slightly acidic electrolyzed water (SAEW) is a novel approach to reducing airborne culturable bacteria (CB) and particulate matter (PM) levels in hen houses. The objective of this study was to evaluate the efficacy of reducing airborne CB and PM in an experimental aviary chamber by periodic spraying of SAEW (Trt), as compared to no spraying (Ctrl ns ) or spraying of tap water (Ctrl w ). The hens were provided 16 h light and 8 h dark (lights on at 6:00 h and off at 22:00 h) and were given access to the litter floor from 12:00 h to 22:00 h. The Trt regimen sprayed SAEW at 14:00 h for 15 min at a dosage of 80 mL m -2 ; the Ctrl ns regimen had no spraying; and the Ctrl w regimen sprayed tap water following the same procedure as with Trt. Concentrations of airborne CB and PM in six aerodynamic size ranges (0.65-1.1, 1.1-2.1, 2.1-3.3, 3.3-4.7, 4.7-7.1, and >7.1 I¼m) were measured at 1.5 m above the floor in the center of the room during the periods of 13:45-14:00 h and 14:45-15:00 h. Compared to Ctrl ns , spraying SAEW significantly reduced airborne CB (>2.1 I¼m) by up to 49% ±10% (p w did not show a reduction effect. No significant difference was found between Trt and Ctrl w in reducing airborne PM, although both reduced or tended to suppress PM >7.1 I¼m in size. The results show that spraying SAEW can inactivate airborne CB attached to PM. Thus, this is a promising technique for alleviating the adverse health impacts of bioaerosols in aviary laying-hen housing systems.

Winter Time Concentrations and Size Distribution of Bioaerosols in Different Residential Settings in the UK

The total concentration and size distribution of bioaerosols in three different types of housing (single room in shared accommodation [type I], single bedroom flat in three-storey building [type II] and two- or three-bedroom detached houses [type III]) was assessed during the winter. This research was an extension of a previous study carried out in the summer. The measurement campaign was undertaken in winter 2008 and 30 houses were sampled. Samples were taken from kitchens, living rooms, corridors (only in housing type I) and outdoors with an Anderson 6 stage viable impactor. In housing type I, the total geometric mean concentration was highest in the corridor for both bacteria and fungi (3,171 and 1,281 CFU/m3, respectively). In type II residences, both culturable bacteria and fungi were greatest in the living rooms (3,487 and 833 CFU/m3, respectively). The living rooms in type III residences had largest number of culturable bacteria (1,361 CFU/m3) while fungi were highest in kitchens (280 CFU/m3). The concentrations of culturable bacteria and fungi were greater in mouldy houses than non-mouldy houses. A considerable variation was seen in the size distribution of culturable bacteria in type I residences compared to types II and III. For all housing types more than half of culturable bacterial and fungal aerosol were respirable (<4.7 μm) and so have the potential to penetrate into lower respiratory system. Considerable variation in concentration and size distribution within different housing types in the same geographical region highlights the impact of differences in design, construction, use and management of residential built environment on bioaerosols levels and consequent varied risk of population exposure to airborne biological agents.

Bioaerosols in residential micro-environments in low income countries: A case study from Pakistan

Our knowledge of the concentrations of bioaerosols in residential micro-environments in low income countries is scanty. The present investigation was conducted to assess the culturable concentration and size distribution of bacteria, gram negative bacteria and fungi in two rural and an urban site in Pakistan. The highest indoor culturable bacteria concentration was found at Rural Site II (14,650 CFU/m3) while the outdoor maximum occurred at the urban site (16,416 CFU/m3). With reference to fungi, both indoor and outdoor concentrations were considerably higher at Rural Site I than the other sites. The size distribution of culturable bacteria at all sites showed greater variability than that of culturable fungi. At all sites more than the half (55–93%) of the culturable bacterial and fungal counts were observed in the respirable fraction (<4.7 μm) and so had the potential to penetrate into lower respiratory system.

Assessment of culturable airborne bacteria in a university campus in Hangzhou, Southeast of China

A systematic investigation on the varieties of culturable airborne bacteria component, concentration and size distribution was conducted in a university campus in Hangzhou, Southeast of China. Results obtained showed that Gram positive bacteria were much more than Gram negative bacteria, contributing to about 84 to 90% of the total number. 22 genera of Gram positive and 12 genera of Gram negative bacteria were identified.Micrococcus, Bacillus, Staphylococcus, and Corynebacterium were dominant in Gram positive bacteria, while Pseudomonas were most common in Gram negative bacteria, and these 5 dominant genus occupied about 60% of the total generally. The mean concentration of culturable bacteria in the university campus was 1224 CFU (Colony Forming Units) /m3. Bacterial concentration in living area was highest (1572 CFU/m3), while the concentration in office area was lowest (651 CFU/m3), obviously lower than other areas in the campus (**P 8.2 μm) to stage 5 (1.0 to 2.0 μm), and then was dramatically decreased at stage 6 (<1.0 μm) in the sampler. Moreover, airborne bacteria was mostly collected in stage 3 (3.0 to 6.0 μm), stage 4 (2.0 to 3.5 μm) and stage 5 (1.0 to 2.0 μm), and the highest proportions of culturable airborne bacteria were detected at stage 5. Key words: Airborne bacteria, Micrococcus, Bacillus, size distribution

Performance of photocatalytic lamps on reduction of culturable airborne microorganism concentration

Reduction of viable airborne Staphylococcus epidermidis and Aspergillus niger spore concentrations using two types of photocatalytic fluorescent lamps under controlled environmental conditions (25 vs. 35 °C and 55 vs. 75% relative humidity) were investigated. Visible white-light and UVA black light were in-house spray-coated with TiO 2 and then compared with a commercially coated visible white-light for microbial concentration reduction. The white-light photocatalytic lamps reduced the concentration of culturable S. epidermidis up to 92% independent of temperature or humidity change, while the black light photocatalytic lamps completely inactivated the culturable bacteria at 25 °C, 55% relative humidity. Humidity seemed to alleviate UVA damage since better bacteria survival was found. For A. niger spores, rising humidity or temperature could lower their concentration or drop their culturabilities so that a difference between the natural decay and photocatalytic disinfection could not be distinguished. Reductions of total bacteria and total fungi concentrations using these lamps were also examined under uncontrolled environmental conditions in an office and a waste-storage room. It was found that photocatalytic lamps could reduce total culturable bacteria concentration from 9 to 97% and total culturable fungi concentration from 3 to 95% within irradiation time of 30–480 min, respectively. Insignificant difference in concentration reduction among these photocatalytic lamps was pronounced.

Distribution characterization of microbial aerosols emitted from a wastewater treatment plant using the Orbal oxidation ditch process

Methods based on impaction and the polymerase chain reaction (PCR) were applied to monitor the concentrations, size distributions, and species diversity of bioaerosols at different treatment units in a Beijing municipal wastewater treatment plant (WWTP) that uses an Orbal oxidation ditch process. The concentrations of culturable bacteria and fungi recorded in the WWTP varied from 459 ± 88 to 5565 ± 571 CFU m −3 and 141 ± 41 to 1590 ± 152 CFU m −3, respectively. The highest concentrations of culturable bacteria were obtained in the sludge-dewatering house, whereas the highest fungi concentrations were found in the fine grit chamber (FGC). The particle size distributions showed that 27.6% of culturable bacteria were detected in particles of 2.1–3.3 μm in size, and 6.6% were in particles between 0.65 and 1.1 μm in size. More than 67% of the fungi were detected in particles ranging from 1.1 to 3.3 μm in size, with only 5.0% found in particles less than 1.1 μm in size. Both culturable and total airborne bacterial community in FGC samples demonstrated high microbial diversities. Airborne bacteria generated from adjacent treatment units showed a close genetic evolutionary relationship. Combination of pure-culture methods and PCR-based methods can provide additional information to verify the presence of bioaerosols.

Assessment of bioaerosols at a concentrated dairy operation

Increased bioaerosol loadings in downwind plumes from concentrated animal feeding operations (CAFOs) may increase the risk for allergy and infection in humans. In this study, we monitored airborne concentrations of culturable bacteria and fungi at upwind (background) and downwind sites at a 10,000 milking cow dairy over the course of a year. The average bacterial concentrations at the upwind site were 8.4 × 103 colony forming units (CFU) m−3 and increased to 9.9 × 105 CFU m−3 at the downwind edge of the cattle lots, decreasing to 6.3 × 104 CFU m−3 200 m farther downwind. At the same sites, the average fungal concentrations were 515, 945, and 1,010 CFU m−3, respectively. Significant correlations between the ambient weather conditions and airborne fungal and bacterial concentrations were identified. Sequence analysis of PCR-amplified DNA from bacterial clones and fungal isolates revealed genus and species level differences between upwind and downwind sites. Although we could not cultivate gram-negative bacteria, bacterial clones at downwind sites identified as being gram-negative matched with the following genera: Acinetobacter, Bradyrhizobium, Escherichia, Idiomarina, Methylobacterium, Ralstonia, and Novosphingobium. Fungal isolates from downwind matched with the following genera: Acremonium, Alternaria, Ascomycte, Aspergillus, Basidiomycete, Cladosporium, Davidiella, Doratomyces, Emericella, Lewia, Onygenales, Penicillium, Rhizopus, and Ulocladium. None of the bacterial and fungal sequence matches were affiliated with genera and species known to be pathogenic to humans. Overall, the data suggest that exposure to bioaerosols in the downwind environment decreases with increasing distance from the open-lot dairy.

Comparison of the biological content of air samples collected at ground level and at higher elevation

In this study, air samples were collected simultaneously at ground level and from a broadcast tower (open space) 238 m high using two BioSamplers and two portable Biostage impactors. The sampling lasted up to 5 h, from morning to afternoon, and the experiments were independently conducted twice. The samples collected by the BioSamplers were analyzed for bacterial diversity and concentration, endotoxin and (1,3)-β-d-glucan content. Denaturing gradient gel electrophoresis (DGGE) fingerprinting, DNA sequencing, real-time quantitative polymerase chain reaction (qPCR), and Limulus amebocyte lysate (LAL) were used for the analyses. Air samples collected by the portable Biostage impactors were directly incubated at 25°C, and the culturable bacteria and fungi concentrations were manually counted. The results from the culture analysis indicated that the ground air samples had higher (statistically significant) concentrations of culturable bacteria and fungi than those taken at an elevation of 238 m. DGGE profiles of PCR products showed similar bacterial diversity in both ground-level and elevated air samples. Pseudomonas was identified by DNA sequencing as the predominant bacterial genus present. The SYBR qPCR tests revealed that the pooled air samples from both the ground and elevated levels had similar total bacterial concentrations, about 1,000 times their culturable ones. Although the endotoxin and (1,3)-β-d-glucan concentrations were observed to vary over the time, no statistically significant differences were observed in the pooled air samples from the ground and elevated levels over the course of the day. The results from this study elucidated the microbial differences in air at different elevations, and added to the body of evidence of atmospheric mixing of biological agents.

Size-resolved culturable airborne bacteria sampled in rice field, sanitary landfill, and waste incineration sites

Size-resolved bacterial concentrations in atmospheric aerosols sampled by using a six stage viable impactor at rice field, sanitary landfill, and waste incinerator sites were determined. Culture-based and Polymerase Chain Reaction (PCR) methods were used to identify the airborne bacteria. The culturable bacteria concentration in total suspended particles (TSP) was found to be the highest (848 Colony Forming Unit (CFU)/m(3)) at the sanitary landfill sampling site, while the rice field sampling site has the lowest (125 CFU/m(3)). The closed landfill would be the main source of the observed bacteria concentration at the sanitary landfill. The rice field sampling site was fully covered by rice grain with wetted conditions before harvest and had no significant contribution to the airborne bacteria concentration. This might occur because the dry conditions favor suspension of soil particles and this area had limited personnel and vehicle flow. The respirable fraction calculated by particles less than 3.3 mum was highest (26%) at the sanitary landfill sampling site followed by waste incinerator (19%) and rice field (10%), which showed a lower level of respiratory fraction compared to previous literature values. We identified 58 species in 23 genera of culturable bacteria, and the Microbacterium, Staphylococcus, and Micrococcus were the most abundant genera at the sanitary landfill, waste incinerator, and rice field sites, respectively. An antibiotic resistant test for the above bacteria (Micrococcus sp., Microbacterium sp., and Staphylococcus sp.) showed that the Staphylococcus sp. had the strongest resistance to both antibiotics (25.0% resistance for 32 microg ml(-1) of Chloramphenicol and 62.5% resistance for 4 microg ml(-1) of Gentamicin).

Impact of Production Systems on Swine Confinement Buildings Bioaerosols

Hog production has been substantially intensified in Eastern Canada. Hogs are now fattened in swine confinement buildings with controlled ventilation systems and high animal densities. Newly designed buildings are equipped with conventional manure handling and management systems, shallow or deep litter systems, or source separation systems to manage the large volumes of waste. However, the impacts of those alternative production systems on bioaerosol concentrations within the barns have never been evaluated. Bioaerosols were characterized in 18 modern swine confinement buildings, and the differences in bioaerosol composition in the three different production systems were evaluated. Total dust, endotoxins, culturable actinomycetes, fungi, and bacteria were collected with various apparatuses. The total DNA of the air samples was extracted, and quantitative polymerase chain reaction (PCR) was used to assess the total number of bacterial genomes, as a total (culturable and nonculturable) bacterial assessment. The measured total dust and endotoxin concentrations were not statistically different in the three studied production systems. In buildings with sawdust beds, actinomycetes and molds were found in higher concentrations than in the conventional barns. Aspergillus, Cladosporium, Penicillium, and Scopulariopsis species were identified in all the studied swine confinement buildings. A. flavus, A. terreus, and A. versicolor were abundantly present in the facilities with sawdust beds. Thermotolerant A. fumigatus and Mucor were usually found in all the buildings. The culturable bacteria concentrations were higher in the barns with litters than in the conventional buildings, while real-time PCR revealed nonstatistically different concentrations of total bacteria in all the studied swine confinement buildings. In terms of workers' respiratory health, barns equipped with a solid/liquid separation system may offer better air quality than conventional buildings or barns with sawdust beds. The impact of ventilation rates, air distribution, or building design still has to be explored.

Bacteria in the global atmosphere – Part 1: Review and synthesis of literature data for different ecosystems

Abstract. Bacteria are ubiquitous in the atmosphere, with concentrations of bacterial cells typically exceeding 1×104 m−3 over land. Numerous studies have suggested that the presence of bacteria in the atmosphere may impact cloud development, atmospheric chemistry, and microbial biogeography. A sound knowledge of bacterial concentrations and distributions in the atmosphere is needed to evaluate these claims. This review focusses on published measurements of total and culturable bacteria concentrations in the atmospheric aerosol. We discuss emission mechanisms and the impacts of meteorological conditions and measurement techniques on measured bacteria concentrations. Based on the literature reviewed, we suggest representative values and ranges for the mean concentration in the near-surface air of nine natural ecosystems and three human-influenced land types. We discuss the gaps in current knowledge of bacterial concentrations in air, including the lack of reliable, long-term measurements of the total microbial concentrations in many regions and the scarcity of emission flux measurements.

Microbial Air Contamination in Farmhouses – Quantitative Aspects

AbstractThe aim of this study was to characterize the microbial contamination of the air in farmhouses (defined as residential buildings on farms) on the basis of volumetric (using a six‐stage Andersen impactor) measurements of bacterial and fungal aerosols. The microbial air quality (including both the total concentration of bioaerosols and their respirable fractions) in farmhouses was collated with the bacterial and fungal air contamination in urban dwellings. In comparison with the urban dwellings, the air in the farmhouses was characterized by significantly higher concentrations of culturable bacteria and fungi. However, respirable microorganisms in the farmhouses constituted the smaller fraction of all culturable bacteria and fungi. The results indicate that the microbial air quality in the farmhouses was most likely affected by the presence of farm buildings, which acted as additional bioaerosol emission sources. The smaller respirable bioaerosol fraction observed in the farmhouses could be explained by the indirect transfer of bacteria and fungi on workers' clothing and bodies from farm buildings to the habitable environments.

Culturable Airborne Bacteria in Outdoor Environments in Beijing, China

Airborne bacteria are important biological components of bioaerosol and play an important role in ecosystem. Bacteria at a high concentration in the atmosphere can result in biological air pollution and all kinds of diseases. In this study, a systematical survey on the culturable airborne bacteria was carried out for 1 year at three sites in Beijing urban area. Results showed that concentrations of culturable bacteria ranged from 71 colony forming units (CFU)/m(3) to 22,100 CFU/m(3), and the mean was 2,217 CFU/m(3). Bacterial concentrations at the human activity-enriched site (RCEES) and the highly trafficked site (XZM) were virtually the same point. They were significantly higher than those at the greener site (BBG). Significant variation in bacterial concentrations in different seasons was observed at RCEES and XZM with higher concentrations in summer and autumn. In a single day, significantly lower concentrations were detected at 13:00 hours through all sampling sites. In this study, 165 species in 47 genera of culturable bacteria were identified. Micrococcus was one of the most dominant bacterial groups and contributed to approximately 20 approximately 30% of the total bacterial concentration, followed by Staphylococcus, Bacillus, Corynebacterium, and Pseudomonas. The bacterial species with a high concentration percentage included Micrococcus luteus and Micrococcus roseus.

Culturable bacteria in Himalayan glacial ice in response to atmospheric circulation

Abstract. Only recently has specific attention been given to culturable bacteria in Tibetan glaciers, but their relation to atmospheric circulation is less understood yet. Here we present the results of culturable bacteria preserved in an ice core drilled from the East Rongbuk (ER) glacier, Himalayas. The average concentrations of culturable bacteria are 5.0, 0.8, 0.1 and 0.7 CFU mL−1 for the glacier ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively. The high concentration of culturable bacteria in ER glacier deposited during the premonsoon season is attributed to the transportation of continental dust stirred up by the frequent dust storms during spring. This is also confirmed by the spatial distribution of culturable bacteria in Tibetan glaciers. Continental dust originated from the Northwest China accounts for the high abundance of culturable bacteria in the northern Tibetan Plateau, while monsoon moisture exerts great influence on culturable bacteria with low abundance in the southern plateau. The numbers of representatives with different ARDRA patterns from RFLP analysis are 10, 15, 1 and 2 for the glacial ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively, suggesting that culturable bacteria deposited in ER glacier during monsoon season are more diverse than that deposited during the other seasons, possibly due to their derivation from both marine air masses and local or regional continental sources, while culturable bacteria deposited during the other seasons are from only one possible origin that is transported by westerlies. Our results show the first report of seasonal variations of abundance and species diversity of culturable bacteria recovered from glacial ice in the Himalayas, and we suggest that microorganisms in Himalayan ice might provide a potential new proxy for the reconstruction of atmospheric circulation.

Bioaerosol formation during grape stemming and crushing

Indoor formation of airborne particles during pre-fermentation grape processing was assessed by particle counting using laser particle sizers. Particle numbers of four different aerodynamic size classes (0.3 to 0.5 μm, 0.5 to 1 μm, 1 to 5 μm, and > 5 μm) were determined during unloading of harvest containers and subsequent grape stemming and crushing. Regarding these size classes, composition before grape handling was determined as 87.9%, 10.4%, 1.7%, and 0.1%, respectively, whereas the composition changed during grape handling to 50.4%, 15.2%, 33.0%, and 1.5%, respectively. Airborne bacteria and fungi originating from grape processing were collected by impactor and liquid impinger samplers. Grape handling resulted in a sixfold increase in total (biological and non-biological) airborne particles. The generation of bacterial and fungal aerosols was associated mostly with particles of aerodynamic diameters > 5 μm (mainly 7 to 11 μm) as determined by flow cytometry. This fraction was increased 150fold in relation to background levels before grape crushing. Maximum concentrations of culturable bacteria reached 485,000 colony forming units (cfu/m 3), whereas 146,000 cfu of fungi and yeasts were detected per cubic meter of air. Culturable Gram-negative bacteria occurred only in small numbers (180 cfu/m 3). In relation to the total number of airborne particles emitted, culturable microorganisms comprised 0.1% to 0.2%. As soon as grape crushing was stopped, particle concentrations decreased rapidly either due to passive settling or due to air currents in the occupational indoor environment reaching background levels.

Concentrations of airborne culturable bacteria in 100 large US office buildings from the BASE study

This paper presents summary statistics of airborne culturable bacteria from the US Environmental Protection Agency Building Assessment Survey and Evaluation (BASE) study. Air samples were collected with single-stage, multiple-hole, agar impactors in 100 large office buildings in 1994-1998 to obtain normative data on indoor environmental quality. Bacterial concentrations were compared by incubation temperature, location, season, and climate zone. Forty-one percent of the samples were below the 2- or 5-min detection limits (18 or 7 CFU/m3, respectively) but less than 1% were overgrown. Mesophilic bacteria (30 degrees C) accounted for >95% of culturable bacteria, both indoors and outdoors. Average concentrations were higher outdoors, except for Gram-positive cocci, which were the only group that were significantly higher indoors (39 vs. 24 CFU/m3), and Gram-negative cocci, for which both concentrations were low and the difference were not significant. Outdoor concentrations of culturable bacteria were somewhat higher in winter (194 vs.165 CFU/m3), and the two dominant outdoor groups were unknown bacteria and Gram-positive rods. Conversely, indoor concentrations were significantly higher in summer (116 vs. 87 CFU/m3), consisting primarily of unknown bacteria and Gram-positive cocci. Bacterial concentrations were within the ranges reported in previous studies of non-problem buildings, and the extreme aggregated indoor concentrations (e.g. the 90th percentile, 175 CFU/m3) of these 100 representative buildings may serve as upper bounds to develop interpretation guidelines for office environments and similar non-manufacturing workplaces in various climate zones. The Building Assessment Survey and Evaluation (BASE) study was one of the most comprehensive investigations of indoor environmental quality in which a standardized protocol was used to measure bioaerosols in 100 typical US office buildings. The information on the indoor and outdoor concentrations of airborne bacteria in different climate zones during the heating and cooling seasons has expanded the baseline data available for interpretation of measurements from building investigations. With suggested refinements, the BASE protocol may serve as a guide for future studies of bioaerosol concentrations, building characteristics, and occupant perceptions of the indoor environment.

Effects of Ceiling-Mounted HEPA-UV Air Filters on Airborne Bacteria Concentrations in an Indoor Therapy Pool Building

The purpose of this study was to assess the effectiveness of a new generation of high-volume, ceiling-mounted high-efficiency particulate air (HEPA)-ultraviolet (UV) air filters (HUVAFs) for their ability to remove or inactivate bacterial aerosol. In an environmentally controlled full-scale laboratory chamber (87 m3), and an indoor therapy pool building, the mitigation ability of air filters was assessed by comparing concentrations of total bacteria, culturable bacteria, and airborne endotoxin with and without the air filters operating under otherwise similar conditions. Controlled chamber tests with pure cultures of aerosolized Mycobacterium parafortuitum cells showed that the HUVAF unit tested provided an equivalent air-exchange rate of 11 hr−1. Using this equivalent air-exchange rate as a design basis, three HUVAFs were installed in an indoor therapy pool building for bioaerosol mitigation, and their effectiveness was studied over a 2-year period. The HUVAFs reduced concentrations of culturable bacteria by 69 and 80% during monitoring periods executed in respective years. The HUVAFs reduced concentrations of total bacteria by 12 and 76% during the same monitoring period, respectively. Airborne endotoxin concentrations were not affected by the HUVAF operation.

The seasonal distribution of bioaerosols in municipal landfill sites: a 3-yr study

Landfill is the most common way to dispose waste in many countries, and most landfill sites after closure are often considered for public recreation purposes. It is important that the pollutant levels of closed landfill areas are free of adverse health concerns. However, only limited studies have investigated the airborne biological contamination in closed landfill sites. The objective of this study was to document the bioaerosol levels in a closed landfill site while the temporal, seasonal, and meteorological effects were also taken into accounts. Study site was at one sanitary landfill, taking mostly municipal wastes, in southern Taiwan. Airborne bacteria and fungi were collected on tryptic soy agar (Difco) and malt extract agar (Difco) by a Burkard impactor (Burkard Manufacturing Co. Ltd.) operating at about 10 l m −3 for 30 s. Air samples were collected sequentially in winter, spring, summer and fall in 1998, winter, spring, summer in 1999, as well as summer and fall in 2000. In addition, sampling was conducted in the morning, at noon, in the evening and the following morning during each field assessment. Levels of airborne bacteria and fungi were all far above 10 3 CFU m −3. The concentrations of culturable bacteria and fungi were higher in winter than in other seasons. The difference of bioaerosol level and fungal percentages between the undergoing-closure and closed areas was obvious, and the concentrations were higher in closed area. We therefore recommend that before any complete investigation can be conducted to assure the safety, the closed area of landfill site is probably not ready for immediate public use.