Concentration and distribution characteristics of airborne fungi in indoor and outdoor air of Tehran subway stations

The concentration and distribution characteristics of airborne fungi were investigated in indoor and outdoor air of two metro stations (Imam Khomeini and Sadeghiyeh stations) in Tehran subway. Samples were taken from indoor air at each station from platform and ticket office area also from adjacent outdoor air of each station. Indoor sampling was conducted for two types of trains, old and new. The concentration of airborne fungi ranged from 21 CFU/m³ at the outdoor air of Imam Khomeini station to 1,402 CFU/m³ in the air samples collected from the platform of this station. Results showed that airborne fungi concentrations at indoor air were higher than the outdoor air (p < 0.05), and fungal levels significantly correlated with the number of passengers (p < 0.05; r = 0.68) and RH % (p < 0.05; r = 0.43). Sixteen genera of fungi were isolated in all sampled environments. The predominant genera identified in indoor and outdoor air were Penicillium spp. (34.88 % of total airborne fungi) and Alternaria spp. (29.33 % of total airborne fungi), respectively. The results of this study showed that the indoor air quality in subway is worse than the outdoor air.     

Triazole Susceptibilities in Thermotolerant Fungal Isolates from Outdoor Air in the Seoul Capital Area in South Korea

Emerging fungi resistant to triazoles are a concern because of the increased use of medical triazoles and exposure to agricultural triazoles. However, little is known about the levels of triazole susceptibility in outdoor airborne fungi making it difficult to assess the risks of inhalation exposure to airborne, antifungal-resistant fungi. This study examined triazole susceptibilities of the airborne thermotolerant fungi isolated from the ambient air of the Seoul Capital Area of South Korea. We used impactor air sampling with triazole-containing nutrient agar plates as the collection substrates to screen for airborne fungal isolates based on their triazole susceptibilities. This study estimated that 0.17% of all the culturable fungi belong to the pathogenic thermotolerant taxa, among which each isolate of Aspergillus niger and Aspergillus tubingensis showed a minimum inhibitory concentration (MIC) of 2 μg/mL or greater for itraconazole. Their concentration in air was 0.4 CFU/m³. Seven human pathogenic Paecilomyces variotii isolates had MICs of 32 μg/mL or greater and lower than 2 μg/mL for the agricultural fungicide tebuconazole and the medical triazole itraconazole, respectively. Though the concentration was low, our results confirm the presence of airborne fungi with high MICs for itraconazole in ambient air. Inhalation is an important exposure route because people inhale more than 10 m³ of air each day. Vigilance is preferred over monitoring for the emergence of triazole-resistant fungal pathogens in ambient outdoor air.     

Airborne bacteria, fungi, and endotoxin levels in residential microenvironments: a case study

Limited data are currently available on the concentrations of airborne bacteria, fungi, and endotoxins in indoor environments. The levels of aerial bacteria and fungi were measured at several microenvironments within a well-ventilated residential apartment in Singapore including the living room, kitchen, bedroom, toilet, and at a workplace environment by sampling indoor air onto culture medium plates using the 6-stage Andersen sampler. Total microbial counts were determined by collecting the air samples in water with the Andersen sampler, staining the resultant extracts with a fluorescent dye, acridine orange, and counting the microbes using a fluorescent microscope. The levels of airborne endotoxins were also determined by sampling the airborne microorganisms onto 0.4?μm polycarbonate membrane filter using the MiniVol sampler at 5?l/min for 20?h with a PM_2.5 cut-off device. The aerial bacterial and fungal concentrations were found to be in the ranges of 117–2,873?CFU/m³ and 160–1,897?CFU/m³, respectively. The total microbial levels ranged from 49,000 to 218,000?microbes/m³. The predominant fungi occurring in the apartment were Aspergillus and Penicillium while the predominant bacterial strains appeared to be Staphylococcus and Micrococcus. The average indoor endotoxin level was detectable in the range of 6–39?EU/m³. The amount of ventilation and the types of human activities carried out in the indoor environment appeared to be important factors affecting the level of these airborne biological contaminants.     

Bioaerosol emissions in a poultry litter burning plant

This study investigates the exposure of workers to biological particles in a poultry litter burning plant in operation. The microorganism concentrations were examined at different workplaces during procedures leading to increased emissions. The concentrations of culturable airborne mesophilic, xerophilic and thermophilic microorganisms in the ambient air were tested inside and outside of the burning plant using two different methods of measuring. The focus of this study was on the quantitative evaluation of culturable bacteria as well as the quantitative and qualitative evaluation of gram-negative bacteria, fungi and thermophilic actinomycetes. The maximum airborne concentrations were found in the delivery hall. Mesophilic bacteria concentrations reached up to 1.7 × 10⁶ CFU/m³; gram-negative bacteria up to 9.1 × 10² CFU/m³. Fungal propagule concentrations for xerophilic fungi were between 1.2 × 10³ and 2.9 × 10⁴ CFU/m³ and for mesophilic fungi between 4.4 × 10² and 2.9 × 10⁴ CFU/m³. Among fungi, Aspergillus niger, Eurotium herbariorum and Scopulariopsis brevicaulis species were dominant. Thermophilic actinomycetes reached airborne concentrations of 8.7 × 10⁴ CFU/m³, with increased concentrations of the pathogens causing extrinsic allergic alveolitis. The high concentrations of airborne microorganisms in poultry litter burning plants and the potential hazard of the intake of microorganisms including potential pathogens require the introduction of consistent measures in both technical areas and personnel management.     

Exposure of Workers to Airborne Microorganisms in Open-Air Swine Houses

This study quantified the levels of airborne microorganisms in six swine farms with more than 10,000 pigs in subtropical Taiwan. We evaluated breeding, growing, and finishing stalls, which were primarily open-air buildings, as well as partially enclosed farrowing and nursery piggeries. Airborne culturable bacteria, gram-negative bacteria, and fungi were placed on appropriate media by using an all-glass impinger or single-stage Andersen microbial sampler. Results showed that mean concentrations of culturable bacteria and gram-negative bacteria were 3.3 × 10⁵ and 143.7 CFU/m³, respectively. The concentration of airborne culturable fungi was about 10³ CFU/m³, with Cladosporium the predominant genus. The highest airborne levels of culturable bacteria and gram-negative bacteria were identified in the finishing units. The air of the nursery stalls was the least contaminated with culturable and gram-negative bacteria. Irregular and infrequent cleaning, high pig density, no separation of wastes from pen floors, and accumulation of water as a result of the processes for cleaning and reducing pig temperature possibly compromise the benefits of the open characteristic of the finishing units with respect to airborne bacterial concentration.     

A comparative study on the airborne fungi in Athens,Greece, by viable and non-viable sampling methods

Airborne fungi were studied in the city of Athens using two complementary methods in which 136 concurrent samplings were carried out during the 12-month period from January until December 1998. A portable Burkard air sampler for agar plates was used for trapping the culturable portion of the mycobiota. Nineteen genera of fungi were identified and assessed in terms of total numbers and fluctuations in concentration (Alternaria, Arthrinium, Aspergillus, Aureobasidium, Botrytis, Chrysonilia, Cladosporium, Drechslera, Epicoccum, Fusarium, Mucor, Nigrospora, Paecilomyces, Penicillium, Rhizopus, Sclerotinia, Scopulariopsis, Trichoderma and Ulocladium), with the exception of those included in the Sphaeropsidales, the yeasts, and the non-sporulating fungi, which were counted as groups. A volumetric Burkard air sampler for glass slides was operating simultaneously for detecting the total mycobiota, including the non-culturable and the non-viable portion. Ascospores, basidiospores, spores of Myxomycetes, Ustilaginales, Uredinales and Erysiphales, teliospores of Puccinia, as well as conidia of the genera Curvularia, Helminthosporium, Periconia, Pestalotiopsis, Pithomyces, Polythrincium, Stachybotrys, Stemphylium and Torula were also recorded. Only seven of the genera were recovered by both samplers. The total numbers of fungal spores, which had a maximum concentration of 3,175 spores/m³, as well as the spore concentrations of the genera Cladosporium (2,565 spores/m³) and Alternaria (280 spores/m³) were underestimated by the viable method (2,435 CFU/m³ for the total, 2,169 CFU/m³ for Cladosporium and 180 CFU/m³ for Alternaria). The non-viable method fails to resolve the identification of the genera Penicillium and Aspergillus, which are major components of the airborne mycobiota (1,068 CFU/m³ and 204 CFU/m³, respectively) based on recovery by the viable method.     

Identification and seasonal distribution of airborne fungi in three horse stables in Italy

Fungal agents are responsible for a variety of respiratory diseases both in humans and animals. The nature and seasonal variations of fungi have been investigated in many environments with wide ranging results. The aims of the present report were (i) to evaluate the quality and magnitude of exposure to airborne fungi in three differently structured equine stalls (open air, partially and completely enclosed buildings) during a one-year period, using an air sampling technique and (ii) to compare the distribution and frequency of fungal species, with regards to these different environments. Air samples were collected monthly from December 2001 to November 2002 by means of a surface air sampler (SAS) Super-90, (PBI International, Milan, Italy). Penicillium and Aspergillus spp. were cultured from all the stables in all seasons. Mucoraceae were also recovered in all seasons in stalls 1 and 2, while they were not isolated in spring and fall in stall 3. These fungi were detected in 28.4%, 72.9% and 60.5% of the total number of samples, respectively. Other fungal genera such as Alternaria, Cladosporium, Fusarium, Beauveria and Drechslera were also occasionally recovered.Viable fungal concentrations varied greatly, ranging from below the limit of detection to more than 3000 CFU/m³ for stables 1 and 2, and 1750 CFU/m³ for stable 3. The median fungal concentration was approximately 178 CFU/m³. Total fungal concentration appeared to be highest in summer, winter and spring, and lowest in the fall.     

Opportunistic fungi in soils and surface air of a megalopolis (for the Tushino Region,Moscow)

The number and composition of opportunistic microscopic fungi was studied in soils and surface air (0.2 and 1.5 m above the surface) in the megalopolis districts (Tushino, Moscow) of different age of construction (6 and 40 years) and in urban recreational forests. The highest number (up to 1500 CFU/m³) determined by plating from air was found in the summer in new-built quarters. Direct count of fungal diaspores in airborne dust yielded significantly higher values (up to 4 × 10⁵/m³). The composition of the soil fungal population differed significantly from that of the air. In soil, the diversity of potentially pathogenic fungi was higher, while in air, their abundance was greater. The highest content of opportunistic fungi in soil and air was observed in spring and late summer-autumn, respectively. The fungi known as allergenic (mostly Cladosporium spp.) predominate in the air in autumn, especially in the new-built quarters.     

Airborne concentrations of bacteria and fungi in Thailand border market

Thailand border market is where the local Thais, Cambodians, Laotians, and Burmeses exchange their goods and culture at the border checkpoints. It is considered to be the source of aerial disease transmission especially for foreigners because it is always very crowded with people from all walks of life. Unhealthy air quality makes this area high risk of spread of airborne diseases. This study assessed airborne concentrations of bacteria and fungi in a border market to improve exposure estimates and develop efficient control strategies to reduce health risk. The density and distribution of airborne bacteria and fungi were investigated in the Chong Chom border market in Surin Province, Thailand. Eighteen air sampling sites were taken from outdoors and various work environments including indoor footpaths, wooden handicraft shops, electronic shops, the secondhand clothing shops, and fruit market areas. Exposed Petri plate method and liquid impinger sampler were used for sampling at the breathing zone, 1.5 m above the floor level, during weekend and holiday. Meteorological factors such as relative humidity, temperature, and light intensity were collected by portable data logger. The relative humidity was 67–73%, and temperature 29–33°C, and light varied between 18 and 270 Lux m⁻². Gram-positive and Gram-negative bacteria were found at a mean value of 10⁴ CFU m⁻³, and airborne fungi of 10³ CFU m⁻³ were recorded. The highest concentration of culturable airborne microorganisms was found along the indoor footpath (9.62 × 10⁴ CFU m⁻³ and 750.00 CFU/plate/h for impingement and sedimentation methods, respectively), the fruit market area (7.86 × 10⁴ CFU m⁻³ and 592.42 CFU/plate/h for impingement and sedimentation methods, respectively), and the secondhand clothing shop (4.59 × 10³ CFU m⁻³ and 335.42 CFU/plate/h for impingement and sedimentation methods, respectively) for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The lowest concentration of Gram-positive bacteria, Gram-negative bacteria, and fungi was found only at the outdoor area at 1.53 × 10⁴ CFU m⁻³, 0.93 × 10⁴ CFU m⁻³ and 0.80 × 10³ CFU m⁻³ by means of impingement method and 136.67 CFU/plate/h, 69.25 CFU/plate/h, and 62.00 CFU/plate/h by means of sedimentation methods for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The most frequently present airborne bacteria were identified as Bacillus, Corynebacteria, Diplococcus, Micrococcus, Acinetobacter, Alcaligenes, Enterobacter, and spore former rods. Acremonium, Aspergillus, Cladosporium, Penicillium, and Sporotrichum were the most frequently found aerosol fungi genera. The distribution of airborne microorganisms correlated with relative humidity and light factors based on principal component analysis. In conclusion, the border market is a potential source of aerial disease transmission and a various hazards of bioaerosols for workers, consumers, sellers, and tourists. The bioaerosol concentration exceeded the standard of occupational exposure limit. Many major indicators of allergenic and toxigenic airborne bacteria and fungi, Acinetobacter, Enterobacter, Pseudomonas, Cladosporium, Alternaria, Aspergillus, and Penicillium, were found in the various market environments.     

Outdoor airborne fungi: sampling strategies

Summary A six-stage Andersens's sampler was compared with a single stage type (SAS) for the collection of airborne fungi particles. The efficiency of two non selective culture media, and namely malt agar (MA) and potato dextrose agar (PDA), which were both modified in order to inhibit bacterial growth, was compared as well. An overall assessment of quantitative results suggests that the two samplers have a comparable degree of efficiency. However, the SAS appears to collect a greater number of CFU/m³ in absence of wind and viceversa the Andersen one appears to be more efficient in the presence of wind. The number of species detected with the SAS device is smaller, thus requiring an increased number of suctions. Andersen sampler sieving, according to the aerodynamic characteristics of the particles, appears to be not too accurate: there is an overlap from stage to stage of the sampler and some larger particles settle on smaller particle-collecting stages and viceversa. The PDA, with streptomycin and chloramphenicol, is better and closer to the natural distribution pattern: the number of CFU/m³ is higher although the number of the collected species is about the same.     

Assessment of Bioaerosols in Swine Barns by Filtration and Impaction

Bioaerosol concentrations inside one naturally ventilated and one mechanically ventilated swine finishing barn were assessed by sampling air using membrane filtration and impaction (six-stage Andersen sampler), and assayed by culture method. The barns, located on the same commercial farm in northeast Kansas, did not show any significant difference (p > 0.05) in concentrations of total and respirable airborne microorganisms. The overall mean total concentrations inside the two barns were 6.6 × 10⁴ colony forming units (CFU)/m³ (SD = 3.8 × 10⁴ CFU/m³) as measured by filtration and 8.6 × 10⁴ CFU/m³ (SD = 5.1 × 10⁴ CFU/m³) by impaction. The overall mean respirable concentrations were 9.0 × 10³ CFU/m³ (SD = 4.1 × 10³ CFU/m³) measured by filtration and 2.8 × 10⁴ CFU/m³ (SD = 2.2 × 10⁴ CFU/m³) by impaction. Total and respirable CFU concentrations measured by impaction were significantly (p < 0.05) higher than that by filtration. The persistent strains of microorganisms were various species of the following genera: Staphylococcus, Pseudomonas, Bacillus, Listeria, Enterococcus, Nocardia, Lactobacillus, and Penicillium. 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. Received: 2 April 2001 / Accepted: 13 June 2001     

Influence of meteorological parameters and PM2.5 on the level of culturable airborne bacteria and fungi in Abadan,Iran

In recent years, monitoring of airborne bacteria and fungi concentrations has obtained increasing universal attraction not only for influences on ecological balance but also for evaluating their public health consequences. In this study, we aimed to investigate culturable airborne bacteria and fungi levels in different sites of Abadan, and their association with meteorological parameters and PM_2.5 levels. Abadan is one of the most industrialized cities in the southwest of Iran where over the current decade has experienced lots of dust storm episodes. In total, 400 air samples were collected in 6 months (autumn and winter) using a single-stage viable Andersen cascade impactor for sampling airborne bacteria and fungi and portable DustTrak Aerosol Monitor 8520 for measuring PM_2.5 concentrations and meteorological parameters. Microbial concentrations showed a significant difference between various sites over the study period with averages of 569.57?±?312.64 and 482.73?±?242.86 CFU/M³ for bacteria and fungi, respectively. The air temperature had a significant effect on the concentration of both airborne bacteria and fungi. A significant positive correlation between relative humidity and fungi but no correlation between relative humidity and bacteria concentrations were observed. The average airborne PM_2.5 concentrations of all sites among the study period was 93.24?±?116.72 μg/m³. The atmospheric bacterial and fungal communities were strongly positively correlated with the ambient PM_2.5 level. The levels of airborne bacteria and fungi along with PM_2.5 in the air of the city were relatively higher than the recommended levels. Therefore, the best course of action is needed to control emission sources. Further studies are also needed to evaluate the clinical analysis of the health effects of exposure to these pollutants.

     

Indoor air quality in schools: exposure to fungal allergens

This study examined indoor air quality within schools in Kansas City, Spokane, Santa Fe, and Orlando. Air sampling was undertaken with both Andersen Single Stage Samplers and Burkard Personal Air Samplers. The data show a wide range of indoor exposures ranging from less than 100 colony forming units (CFU/m³) for viable fungi and 100 spores/m³ for total spores in Spokane and Santa Fe to concentrations over 6000 CFU/m³ for viable fungi and 15 000 spores/m³ for total fungi in Orlando and Kansas City, respectively. In the majority of sites the indoor airspora reflected the outdoor taxa withCladosporium the most abundant genus identified; however, several indoor locations had elevated levels ofPenicillium andAspergillus indicating possible sources of indoor contamination. Airborne basidiospores and smut spores were also fairly abundant in the schools and were among the top five taxa identified. The data also indicated that the airborne concentrations vary significantly during the day and between classrooms within each school. Continued studies in schools are needed to fully assess both the exposure levels and the clinical significance to atopic children allergic to these spores.     

Assessment of microbial aerosol emissions in an urban wastewater treatment plant operated with activated sludge process

Wastewater that enters wastewater treatment plants contains lots of pathogenic and nonpathogenic microorganisms which can become bioaerosols during treatment processes and pose health hazard to workers and nearby residents. The emission of the bioaerosols from an urban wastewater treatment plant in spring and summer in different locations and downwind of the plant adopting an extended mechanical aeration system was investigated. Samples of bacteria and fungi were collected within 6 months at 10 selected points by an Anderson one-stage impactor. The highest concentration of bacteria (mean 1373 CFU/m³, 741–2817 CFU/m³) and fungi (mean 1384 CFU/m³, 212–1610 CFU/m³) was found in downwind of the aeration basins. Statistical analysis showed a significant relationship between concentration of bacterial bioaerosols at downwind side of the aeration basins and wind speed (p value <0.05) and temperature (p value <0.05). Also, in the spring and summer, between the number of bacteria and fungi inside the plant and outside the plant (downwind) a significant correlation was observed (p value ≤0.05). The concentrations of bacteria at a distance of 500 m downwind were much higher than those at the background (upwind) point in spring and summer. The processes of wastewater treatment especially using mechanical equipment to create turbulence can be considered as a major source of spreading airborne microorganisms to ambient air of wastewater treatment plants, and the bioaerosols can be dispersed to downwind distances affecting the nearby neighboring. Therefore, in order to decrease the bioaerosols emission, doing some course of actions such as covering the surface of aeration basins, changing the aeration methods and aeration equipment (e. g using diffuser aerator) may be effective.     

Bioaerosols and Particle Release During Composting of Contaminated Sawmill Soil

Compost windrows for bioremediation of soil were built at a wood-preserving site contaminated with chlorophenols, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). Sampling of airborne particles during the mixing of the compost windrows found concentrations of PCDDs and PCDFs in different particle sizes. The congener distribution of PCDDs and PCDFs in the collected air particle fractions was similar to that in the compost windrows, and the level of PCDDs and PCDFs was 1000-fold higher than the atmospheric background values reported previously. Viable particle-sizing samplers and several selective growth media were used to enumerate bacteria and fungi in the airborne particles. From the collected air samples, 40 bacteria were isolated and identified. Among the isolated bacteria, 80% were Gram-positive and spore-forming. Two of the identified airborne bacteria, Pseudomonas aeruginosa and Bacillus cereus, may cause human disease and are classified in biological agent hazard group 2. The amounts of airborne fungi, molds, and yeasts were 1000 to 2000 colony-forming units (CFUs) per m³. The number of actinomycetes was up to 6-fold, and the number of bacteria was 2- to 20-fold compared to background values. The overall level of airborne bacteria (200 to 3500 CFUs per m³) was low compared to the level of bacteria (10⁵ to 10⁸ CFUs per m³) found when composting municipal waste.     

Assessing waste collectors' exposure to bioaerosols

Published studies on household wastecollectors' exposure to airborne biologicalagents (bioaerosols) do not indicate highexposures to these agents. However, thesestudies did not consider several factors. Theobjective of this study was to characterize theexposure of waste collectors to bioaerosols andto propose solutions to control exposures tothese agents.Personal exposures of waste collectors tobioaerosols (total bacteria, endotoxins andmolds) were measured for seven types ofcollection during the summer, which representsthe worst conditions. The effect of truckcleaning was also evaluated. Meanconcentrations of bacteria were all in theorder of 10³–10⁴ CFU/m³ of air. Theintervention threshold was exceeded forendotoxins during the collection of compostonce every two weeks in the country. Meanconcentrations varied from 8.5 to 100 endotoxinunits per cubic meter of air (EU/m³). Measuredmean concentrations of molds were between 8,300and 98,170 CFU/m³ of air. Also, the cleaningof an empty garbage truck does not improve thequality of the air. On the other hand, a dirtytruck is not a major source of bioaerosols.The sources of these bioaerosols are leachate,particularly if the waste in the truck is oforganic origin, as well as the garbage pailsthat contain this waste. Unnecessary exposuresto these sources should therefore be avoided. For bioaerosols, stringent personal hygienemeasures remain one of the best means ofprevention.     

Air biocontamination in a variety of agricultural industry environments in Egypt: a pilot study

Inhalation of airborne microorganisms and organic dust is an occupational concern among workers in agricultural industries. Airborne microorganisms and particulate matter samples were collected from poultry house, flourmill, textile, and food industry sites by use of liquid impinger and gravimetric samplers. Particulate matter concentrations were recorded at median concentrations of 1.56, 1.92, 4.39, and 0.7 mg/m³ in the occupied poultry house, textile, flourmill, and food indoor working environments, respectively. The highest median particulate matter concentration (27.9 mg/m³) was detected at the flourmill’s stack site. The highest median indoor concentration of culturable airborne bacteria (6.23 × 10⁵ CFU/m³) was found at the occupied poultry-house site and the lowest concentration (4.6 × 10³ CFU/m³) was found at the food industry site. The highest median indoor concentration of culturable airborne fungi (3.15 × 10⁴ CFU/m³) was found at the flourmill site whereas the lowest (1.24 × 10³ CFU/m³) was found at the textile industry site. Bacillus and Staphylococcus were the predominant Gram-positive bacteria whereas Acinetobacter and Klebsiella were the predominant Gram-negative bacteria. Escherichia coli and Salmonella were only detected in the indoor air at the poultry house site. Aspergillus flavus, Aspergillus niger, Penicillium, and yeast were the predominant fungal types at flourmill, textile, food industry, and poultry house, respectively. Workers were continuously exposed to airborne microorganisms at a median value of 10⁴ CFU/m³ in all the industries studied.     

The assessment of airborne microorganisms in large-scale composting facilities and their immediate surroundings

The number of airborne microorganisms in the area of large-scale composting facilities with different composting techniques (A: open facility using the intensive decomposition process [4000 t/year]. B: closed facility with compost containers [7000 t/year], C: closed facility with table-pile compositing and automatic turning equipment [22 000 t/year]) was investigated using impactor sampling systems (Andersen samplers). All counts carried out inside the closed facilities, especially during the turning process, showed values of >5.0 × 10⁵ CFU/m³ for viable bacteria and moulds with a proportion ofAspergillus fumigatus of up to 64%. Depending on the type of facility, different median values were determined inside the plant area. Counts were highest in the immediate area around the biofilter outside of Facility C (1.7 × 10⁴ CFU/m³ for bacteria and 9.5 × 10³ CFU/m³ for moulds). In view of the high load of ambient airborne microorganisms inside the composting facilities, adequate occupational health measures are urgently required. Counts determining the hazard to neighbourhood residents at distances of between 150 and 2000 m showed, depending on the facility, annual median values of 170–330 CFU/m³ for bacteria, 75–340 CFU/m³ for moulds, and 15–52 CFU/m³ forA. fumigatus. Higher individual counts — up to 3 × 10³ CFU/m³ for moulds and up to 350 CFU/m³ forA. fumigatus — were found as a result of specific climatic influences, (e.g. winds) and activities as well poor operation. Given the high proportion ofA. fumigatus in the exhaust air, this mould can serve as an indicator for the evaluation of the health risk. However, the maximum values found in the present study, may also be caused by other events in rural areas, (e.g. agricultural activities). With regard to neighbourhood residents, odour complaints are more important than pollution by microorganisms.     

Composition and variability of airborne fungi in an enclosed rabbit house in China

Sampling was conducted from June 2007 to May 2008 in an enclosed rabbit house to investigate composition and variability of airborne fungi. Samples were collected using an Andersen-6 sampler, with Sabouraud culture medium as sampling medium. The results showed that monthly mean concentration was 2.79–5.46 × 10³ colony forming unit/m³ air (CFU/m³ air), with the maximum level in October, and the minimum level in January. Within a day, the maximum level occurred at 09:00, followed by 17:00 and then 13:00. A total of 6,523 fungal colonies, belonging to 17 genera and 36 species, were obtained. The predominant genera included Cladosporium, Penicillium, Aspergillus and Altemaria, comprising 71.45% of the colony count. The obtained fungi of the year were mainly centralized in the stage D of the sampler (2.0–3.0 μm), accounting for 37.8% of the colonies. The minimum value occurred at stage F (<0.65 μm), accounting for 1.10% of the colonies.     

Seasonal Variations of Indoor Microbial Exposures and Their Relation to Temperature,Relative Humidity,and Air Exchange Rate

Indoor microbial exposure has been related to adverse pulmonary health effects. Exposure assessment is not standardized, and various factors may affect the measured exposure. The aim of this study was to investigate the seasonal variation of selected microbial exposures and their associations with temperature, relative humidity, and air exchange rates in Danish homes. Airborne inhalable dust was sampled in five Danish homes throughout the four seasons of 1 year (indoors, n = 127; outdoors, n = 37). Measurements included culturable fungi and bacteria, endotoxin, N-acetyl-beta-d-glucosaminidase, total inflammatory potential, particles (0.75 to 15 μm), temperature, relative humidity, and air exchange rates. Significant seasonal variation was found for all indoor microbial exposures, excluding endotoxin. Indoor fungi peaked in summer (median, 235 CFU/m³) and were lowest in winter (median, 26 CFU/m³). Indoor bacteria peaked in spring (median, 2,165 CFU/m³) and were lowest in summer (median, 240 CFU/m³). Concentrations of fungi were predominately higher outdoors than indoors, whereas bacteria, endotoxin, and inhalable dust concentrations were highest indoors. Bacteria and endotoxin correlated with the mass of inhalable dust and number of particles. Temperature and air exchange rates were positively associated with fungi and N-acetyl-beta-d-glucosaminidase and negatively with bacteria and the total inflammatory potential. Although temperature, relative humidity, and air exchange rates were significantly associated with several indoor microbial exposures, they could not fully explain the observed seasonal variations when tested in a mixed statistical model. In conclusion, the season significantly affects indoor microbial exposures, which are influenced by temperature, relative humidity, and air exchange rates.