Airborne bacteria and fungal spores in the indoor environment. A case study in Singapore

The concentration of airborne fungal spores and bacteria as related to room temperature, humidity and occupancy levels within a library building in Singapore was determined. Measurement of indoor air quality with respect to microorganisms is of particular importance in tropical environments due to the extensive use of air‐conditioning systems and the potential implications for human health. This study has revealed a number of interesting relationships between the concentrations of fungal spores and bacteria in relation to both environmental and human factors. The levels of fungal spores measured in the indoor environment were approximately fifty times lower than those measured outside, probably because of the lowered humidity caused by air‐conditioning in the indoor environment. The variation in fungal spore concentration in the outdoor environment is likely to be due to the diurnal periodicity of spore release and the response to environmental factors such as light temperature and humidity. The indoor concentration of fungal spores in air was not clearly correlated to concentrations measured in air outside of the library building and remained relatively constant, unaffected by the difference in the numbers of occupants in the library. In contrast, the indoor concentrations of bacteria in air were approximately ten times higher than those measured outdoors, indicating a signficant internal source of bacteria. The elevated levels of indoor bacteria were primarily attributed to the number of library occupants. Increased human shedding of skin cells, ejection of microorganisms and particulates from the respiratory tract, and the transport of bacteria on suspended dust particles from floor surfaces probably accounts for the strong positive correlation between occupancy levels and the concentration of bacteria in internal air.     

Characterization of airborne bacteria at an underground subway station

The reliable detection of airborne biological threat agents depends on several factors, including the performance criteria of the detector and its operational environment. One step in improving the detector's performance is to increase our knowledge of the biological aerosol background in potential operational environments. Subway stations are enclosed public environments, which may be regarded as potential targets for incidents involving biological threat agents. In this study, the airborne bacterial community at a subway station in Norway was characterized (concentration level, diversity, and virulence- and survival-associated properties). In addition, a SASS 3100 high-volume air sampler and a matrix-assisted laser desorption ionization-time of flight mass spectrometry-based isolate screening procedure was used for these studies. The daytime level of airborne bacteria at the station was higher than the nighttime and outdoor levels, and the relative bacterial spore number was higher in outdoor air than at the station. The bacterial content, particle concentration, and size distribution were stable within each environment throughout the study (May to September 2010). The majority of the airborne bacteria belonged to the genera Bacillus, Micrococcus, and Staphylococcus, but a total of 37 different genera were identified in the air. These results suggest that anthropogenic sources are major contributors to airborne bacteria at subway stations and that such airborne communities could harbor virulence- and survival-associated properties of potential relevance for biological detection and surveillance, as well as for public health. Our findings also contribute to the development of realistic testing and evaluation schemes for biological detection/surveillance systems by providing information that can be used to mimic real-life operational airborne environments in controlled aerosol test chambers.     

Architectural design influences the diversity and structure of the built environment microbiome

Buildings are complex ecosystems that house trillions of microorganisms interacting with each other, with humans and with their environment. Understanding the ecological and evolutionary processes that determine the diversity and composition of the built environment microbiome—the community of microorganisms that live indoors—is important for understanding the relationship between building design, biodiversity and human health. In this study, we used high-throughput sequencing of the bacterial 16S rRNA gene to quantify relationships between building attributes and airborne bacterial communities at a health-care facility. We quantified airborne bacterial community structure and environmental conditions in patient rooms exposed to mechanical or window ventilation and in outdoor air. The phylogenetic diversity of airborne bacterial communities was lower indoors than outdoors, and mechanically ventilated rooms contained less diverse microbial communities than did window-ventilated rooms. Bacterial communities in indoor environments contained many taxa that are absent or rare outdoors, including taxa closely related to potential human pathogens. Building attributes, specifically the source of ventilation air, airflow rates, relative humidity and temperature, were correlated with the diversity and composition of indoor bacterial communities. The relative abundance of bacteria closely related to human pathogens was higher indoors than outdoors, and higher in rooms with lower airflow rates and lower relative humidity. The observed relationship between building design and airborne bacterial diversity suggests that we can manage indoor environments, altering through building design and operation the community of microbial species that potentially colonize the human microbiome during our time indoors.     

Influence of meteorological factors on the level and characteristics of culturable bacteria in the air in Gliwice,Upper Silesia (Poland)

Numerous studies have focused on occupational and indoor environments because people spend more than 90% of their time in them. Nevertheless, air is the main source of bacteria in indoors, and outdoor exposure is also crucial. Worldwide studies have indicated that bacterial concentrations vary among different types of outdoor environments, with considerable seasonal variations as well. Conducting comprehensive monitoring of atmospheric aerosol concentrations is very important not only for environmental management but also for the assessment of the health impacts of air pollution. To our knowledge, this is the first study to present outdoor and seasonal changes of bioaerosol data regarding an urban area of Poland. This study aimed to characterize culturable bacteria populations present in outdoor air in Gliwice, Upper Silesia Region, Poland, over the course of four seasons (spring, summer, autumn and winter) through quantification and identification procedures. In this study, the samples of bioaerosol were collected using a six-stage Andersen cascade impactor (with aerodynamic cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1 and 0.65 μm). Results showed that the concentration of airborne bacteria ranged from 4 CFU m^?3, measured on one winter day, to a maximum equal to 669 CFU m^?3 on a spring day. The average size of culturable bacterial aerosol over the study period was 199 CFU m^?3. The maximal seasonally averaged concentration was found in the spring season and reached 306 CFU m^?3, and the minimal seasonally averaged concentration was found in the winter 49 CFU m^?3. The most prevalent bacteria found outdoors were gram-positive rods that form endospores. Statistically, the most important meteorological factors related to the viability of airborne bacteria were temperature and UV radiation. These results may contribute to the promotion and implementation of preventative public health programmes and the formulation of recommendations aimed at providing healthier outdoor environments.     

Monitoring of bacterial sugars and hydroxy Fatty acids in dust from air conditioners by gas chromatography-mass spectrometry

Bacterial levels in dust collected from hospital air-conditioning filters were examined by chemical analysis (without prior culture). The dust was analyzed by gas chromatography-mass spectrometry after hydrolysis and derivatization. l-Glycero-d-mannoheptose and hydroxy fatty acids (3-OH 12:0 and 3-OH 14:0) (primarily found in lipopolysaccharide) and muramic acid (a chemical marker for bacterial peptidoglycan) were present at higher levels in dust collected from filters primarily contacting outdoor (as opposed to indoor) air. The ratio of l-glycero-d-mannoheptose to muramic acid in dust (compared with those of a group of gram-positive and gram-negative bacteria) suggested that both dust types contained appreciable numbers of gram-negative bacteria. There is potential for the chemical assessment of the microbial content of airborne dust.     

Microbial Contents of Vacuum Cleaner Bag Dust and Emitted Bioaerosols and Their Implications for Human Exposure Indoors

Vacuum cleaners can release large concentrations of particles, both in their exhaust air and from resuspension of settled dust. However, the size, variability, and microbial diversity of these emissions are unknown, despite evidence to suggest they may contribute to allergic responses and infection transmission indoors. This study aimed to evaluate bioaerosol emission from various vacuum cleaners. We sampled the air in an experimental flow tunnel where vacuum cleaners were run, and their airborne emissions were sampled with closed-face cassettes. Dust samples were also collected from the dust bag. Total bacteria, total archaea, Penicillium/Aspergillus, and total Clostridium cluster 1 were quantified with specific quantitative PCR protocols, and emission rates were calculated. Clostridium botulinum and antibiotic resistance genes were detected in each sample using endpoint PCR. Bacterial diversity was also analyzed using denaturing gradient gel electrophoresis (DGGE), image analysis, and band sequencing. We demonstrated that emission of bacteria and molds (Penicillium/Aspergillus) can reach values as high as 1E5 cell equivalents/min and that those emissions are not related to each other. The bag dust bacterial and mold content was also consistent across the vacuums we assessed, reaching up to 1E7 bacterial or mold cell equivalents/g. Antibiotic resistance genes were detected in several samples. No archaea or C. botulinum was detected in any air samples. Diversity analyses showed that most bacteria are from human sources, in keeping with other recent results. These results highlight the potential capability of vacuum cleaners to disseminate appreciable quantities of molds and human-associated bacteria indoors and their role as a source of exposure to bioaerosols.     

Evaluation of media for recovery of aerosolized bacteria

Disease transmission by airborne bacteria is well known. Bacterial burden in indoor air is estimated by sampling the air and estimating Colony Forming Units (CFU) using a variety of media. In this study, the recovery of bacteria, after aerosolization in an aerosol chamber, and employing a variety of media, was compared to that achieved using Tryptic Soy Agar medium. The total number of cells present was determined by direct microscopy. All trials were conducted at approximately the same relative humidity (RH) and temperature using the same collection device. Twelve species of bacteria were tested and a total of 120 media or media combinations were evaluated. Recovery on 64 media formulations was significantly lower for all strains examined, and therefore, excluded from further consideration for the purposes of this study. Data for 56 of the media are presented. Three species (Bacillus subtilis, Staphylococcus aureus andSerratia marcescens) were selected as representative for reporting and testing recovery success. It is concluded that, for the media included in the study, there are large differences in recovery and successful recovery is related both to the effect of aerosolization and the type of medium employed for recovery. Brain Heart Infusion Agar (with horse serum), Tryptic Soy Agar and Mueller Hinton Agar yielded the best recoveries of aerosolized cultures. The most important finding was that only a small fraction of the airborne bacterial populations, enumerated by direct microscopy, could be recovered on any of the media tested, suggesting that culturable bacterial count is not a satisfactory means of estimating air microbial pollution.     

重庆中国三峡博物馆临时展厅内空气微生物调查检测

目的调查重庆中国三峡博物馆临时展厅内空气微生物的数量和种类,进而为博物馆等公共场所的环境安全提供评估依据。方法利用空气采样器对博物馆不同楼层的临时展厅进行空气微生物采样,利用纯培养的方法对空气微生物进行数量检测,利用全自动生化鉴定仪对微生物种类进行生化鉴定。,结果四楼临时展厅中的细菌数量达到（509±65．06）CFU／m3,显著高于其他楼层的临时展厅（P〈0．05）,而一楼临时展厅内的真菌数量为（14±5．29）CFU／m3,显著高于二楼和i楼临时展厅（P〈0．05）,但与四楼临展内比较差异尤统计学意义（P〉0．05）。临时展厅内空气微生物中的真菌以曲霉属（Aspergillus）为主,还包括毛霉属（Mucor）、青霉属（Penicillium）、孢子丝菌属（Sporothrix）以及根霉属（Rhizopus）;细菌则以微球菌属（Micrococcus）为主,还包括芽孢杆菌属（BaciUus）、假单胞菌属（Pseudomonadaceae）、葡萄球菌属（Staphylococcus）、棒状杆菌属（Corynebacterium）、放线菌属（Actinomyces）、苏黎世菌属（Turicella）和黄杆菌属（Flavobacterium）。结论普通参观日内,重庆中国三峡博物馆临时展厅内空气微生物浓度能够满足我国《室内空气质量标准》（GBT18883—2002）的要求,且微生物种类以条件性致病菌为主,正常条件下不会导致传染性疾病的发生。     

Suitability of poor medium in counting total viable airborne bacteria

The purpose of this study was to test the effect of incubation temperature and culture medium on viable counts of airborne bacteria. The incubation temperature had different effect on indoor and outdoor air bacteria. Indoor air bacteria grew as well at 20°C as 37°C, but less at 10°C. Outdoor air bacteria grew equally well at 10°C and 20°C, but less at 37°C. Both indoor and outdoor air bacteria grew differently on poor and rich media. The counts of both indoor and outdoor air bacteria were higher on poor R2A medium (low nutrient concentration) than on rich TYG and blood media (high nutrient concentration). The results indicate that a poor medium incubated at 20°C is adequate for counting viable airborne bacteria.     

Airborne bacterial emission fluxes from manure-fertilized agricultural soil

This is the first study to quantify the dependence on wind velocity of airborne bacterial emission fluxes from soil. It demonstrates that manure bacteria get aerosolized from fertilized soil more easily than soil bacteria, and it applies bacterial genomic sequencing for the first time to trace environmental faecal contamination back to its source in the chicken barn. We report quantitative, airborne emission fluxes of bacteria during and following the fertilization of agricultural soil with manure from broiler chickens. During the fertilization process, the concentration of airborne bacteria culturable on blood agar medium increased more than 600 000-fold, and 1 m³ of air carried 2.9 × 10⁵ viable enterococci, i.e. indicators of faecal contamination which had been undetectable in background air samples. Trajectory modelling suggested that atmospheric residence times and dispersion pathways were dependent on the time of day at which fertilization was performed. Measurements in a wind tunnel indicated that airborne bacterial emission fluxes from freshly fertilized soil under local climatic conditions on average were 100-fold higher than a previous estimate of average emissions from land. Faecal bacteria collected from soil and dust up to seven weeks after fertilization could be traced to their origins in the poultry barn by genomic sequencing. Comparative analyses of 16S rRNA gene sequences from manure, soil and dust showed that manure bacteria got aerosolized preferably, likely due to their attachment to low-density manure particles. Our data show that fertilization with manure may cause substantial increases of bacterial emissions from agricultural land. After mechanical incorporation of manure into soil, however, the associated risk of airborne infection is low.     

Bioaerosols of subterraneotherapy chambers at salt mine health resort

Nowadays, an inhalation of naturally generated aerosols has again become a widely practiced method of balneological treatment of various respiratory diseases. The aim of this study was to characterize the microbial aerosol of subterraneotherapy chambers at the Bochnia Salt Mine Health Resort in southern Poland. The measurements were carried out using a 6-stage Andersen impactor over a period of 1 year in both indoor (i.e., two subterranean chambers, where curative treatments took place) and outdoor air. The maximum bacterial aerosol concentrations in the chambers reached 11,688 cfu/m³. In such interiors, a high-performance method of microbial contaminant reduction need be introduced, especially when large groups of young patients are medically cured. Respecting fungal aerosol, its average indoor concentration (88 cfu/m³) was significantly lower than outdoor level (538 cfu/m³). It confirms that ventilation system provides efficient barrier against this type of biologically active propagules. Among identified micro-organisms, the most prevalent indoors were Gram-positive cocci, which constituted up to 80 % of airborne microflora. As highly adapted to the diverse environments of its human host (skin, respiratory tract), they can be easily released in high quantities into the air. The number of people introduced into such subterranean chambers should be in some way limited. The analysis of microclimate parameters revealed that temperature and relative humidity influenced significantly the level of bacterial aerosol only. Hence, a constant control of these parameters should be scrupulously superintended at this type of subterranean premises.     

Particulate matter and bacteria characteristics of the Middle East Dust (MED) storms over Ahvaz,Iran

The Middle East Dust storms have greatly affected the south and west parts of Iran during the last decade. The main purpose of this study was to examine and compare culturable airborne bacteria concentration in particulate matter (PM) during normal, semi-dust, and dust event days in different places and seasons in Ahvaz from November 2011 to May 2012. Sampling was performed every 6 days and on dust event days at different sampling stations. The overall mean concentrations of PM₁₀, PM_2.5, and PM₁ for the entire study period were 598.92, 114.8, and 34.5 μg/m³, respectively. The PM concentrations during the dust event days were much higher than normal and semi-dust event days. The highest mean PM concentrations were observed in March 2011. The low PM_2.5/PM₁₀ ratios indicate that these PM are mostly originating from natural sources such as dust storms. The overall mean concentration of total bacteria during the study period was 620.6 CFU/m³. The greatest bacterial concentrations were observed during dust event days and at areas with high traffic and more human activities compared with normal days and greener areas. The percentage of gram-positive bacteria was significantly higher than that during the study period (89 vs 11 %). During this study, 26 genera of culturable bacteria were identified from all the sampling stations. The most dominant genera in all sampling stations were Streptomyces, Bacillus, Kocuria, Corynebacterium, and Paenibacillus. The results also showed that there were positive correlations between PM and bacterial concentrations during the study period (p < 0.05).     

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.     

Assessment of airborne endotoxin in sandstorm dust and indoor environments using a novel passive sampling device in Al Zulfi city,Saudi Arabia – Establishing threshold exposure levels

The impact of sandstorm dust events affects local air quality and public health. These issues are becoming of greater concern in Saudi Arabia. There is a significant lack of research on airborne endotoxin exposure and analysis in the Middle East countries and no coherent body of research exists focusing on sandstorm dust in worldwide. In this study, we used a novel design of an aluminum foil plate (AFP) electrostatic dust cloth (EDC) for the passive air sampling of sandstorm dust. A total of 38 sandstorm dust samples were collected during sandstorm episodes occurring between January and April 2020 in both indoor (7 days, n = 20) and outdoor environments (24 h, n = 18). After exposure, and following an extraction procedure, bacterial endotoxin levels were measured using the Limulus Amoebocyte Lysate (LAL) gel clot method. The study highlights that the airborne endotoxin level observed was between 10 and 200 EU/m² in both indoor and outdoor environments, during a sandstorm event. Agricultural activities and farmhouses observed higher airborne endotoxin levels. In general, increased endotoxin levels were related to the severity of the sandstorms. Given that the observed values were high as per existing guidelines for respiratory health, we recommend the setting an occupational airborne exposure limit for bacterial endotoxin. This is the first report and further studies across various sandstorm-hit regions will need to be undertaken, together with various sampling methods, in order to assess for seasonal and geographic trends.     

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 x 10(5) and 143.7 CFU/m(3), respectively. The concentration of airborne culturable fungi was about 10(3) CFU/m(3), 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.     

Air pollution combustion emissions: characterization of causative agents and mechanisms associated with cancer, reproductive, and cardiovascular effects

Combustion emissions account for over half of the fine particle (PM(2.5)) air pollution and most of the primary particulate organic matter. Human exposure to combustion emissions including the associated airborne fine particles and mutagenic and carcinogenic constituents (e.g., polycyclic aromatic compounds (PAC), nitro-PAC) have been studied in populations in Europe, America, Asia, and increasingly in third-world counties. Bioassay-directed fractionation studies of particulate organic air pollution have identified mutagenic and carcinogenic polycyclic aromatic hydrocarbons (PAH), nitrated PAH, nitro-lactones, and lower molecular weight compounds from cooking. A number of these components are significant sources of human exposure to mutagenic and carcinogenic chemicals that may also cause oxidative and DNA damage that can lead to reproductive and cardiovascular effects. Chemical and physical tracers have been used to apportion outdoor and indoor and personal exposures to airborne particles between various combustion emissions and other sources. These sources include vehicles (e.g., diesel and gasoline vehicles), heating and power sources (e.g., including coal, oil, and biomass), indoor sources (e.g., cooking, heating, and tobacco smoke), as well as secondary organic aerosols and pollutants derived from long-range transport. Biomarkers of exposure, dose and susceptibility have been measured in populations exposed to air pollution combustion emissions. Biomarkers have included metabolic genotype, DNA adducts, PAH metabolites, and urinary mutagenic activity. A number of studies have shown a significant correlation of exposure to PM(2.5) with these biomarkers. In addition, stratification by genotype increased this correlation. New multivariate receptor models, recently used to determine the sources of ambient particles, are now being explored in the analysis of human exposure and biomarker data. Human studies of both short- and long-term exposures to combustion emissions and ambient fine particulate air pollution have been associated with measures of genetic damage. Long-term epidemiologic studies have reported an increased risk of all causes of mortality, cardiopulmonary mortality, and lung cancer mortality associated with increasing exposures to air pollution. Adverse reproductive effects (e.g., risk for low birth weight) have also recently been reported in Eastern Europe and North America. Although there is substantial evidence that PAH or substituted PAH may be causative agents in cancer and reproductive effects, an increasing number of studies investigating cardiopulmonary and cardiovascular effects are investigating these and other potential causative agents from air pollution combustion sources.     

Community structure of bacteria and fungi in aerosols of a pig confinement building

Modern intensive husbandry practices can create poor indoor air quality, with high levels of airborne dust, endotoxins, ammonia, and microorganisms. Air in a sow breeding barn was investigated to determine the biomass composition of bioaerosols using molecular methods supplemented with microscopic and cultivation-dependent approaches. A total of 2.7?±?0.7?×?10(7) bacterial cells?m(-3) air and 1.2?±?0.3?×?10(6) fungi spores?m(-3) were detected, corresponding to the fungal biovolume constituted 98% of the total microbial biovolume (fungal and bacterial). Fifty-two percent of all 4',6-diamidino-2-phenyl indole-stained cells were detectable with fluorescence in situ hybridization (FISH) with a general bacterial probe mixture. Quantitative FISH of the bacterial consortium revealed Firmicutes as the dominant group with Streptococcus as the major genus, while Actinobacteria constituted 10% of the detectable bacteria. Additionally, the study revealed an abundant and diverse fungal community including species not previously found in similar environments. The most abundant fungal 18S rRNA gene clone sequences identified affiliated with the Aspergillus-Eurotium cluster, but among others, species of Wallemia, Mucorales, and Russulales were detected. For both fungi and anaerobic bacteria, a hitherto undescribed diversity was found in bioaerosols from a modern sow breeding barn, which potentially could create poor indoor air quality, although their effect on the health of farmworkers and stock still is not resolved.     

Viable airborne microbial counts from air-cooling units with and without complaints of urine and body odors

Viable airborne microbial counts are commonly used in indoor air quality (IAQ) assessment, but studies linking the microbial counts to a specific type of indoor microbial contamination are limited. We hypothesize that the airborne microbial counts can differentiate air-cooling units with and without complaints of urine and body odors. The keratinolytic property of some isolated bacteria prompts to the hypothesis that keratinase is present in the units to break down keratins, structural proteins that form human skin scales, as sources of amino acids and ammonium to produce the odors. Seven bacterial species and four fungal species were identified in the units and room air. Airborne Staphylococcus haemolyticus and Methylobacterium organophilum counts contributed the most to the microbial dissimilarities of units with and without odor complaints. Keratinolytic bacteria and a methylotrophic bacterium were abundant in the units. All the units contained ammonium, and keratinase activity was higher in the units with odor complaints. Extracellular keratinase activity was more effective at 20 °C than at 30 or 4 °C. Keratinolytic bacteria produced high levels of ammonium in the culture with skin cells. Viable airborne microbial counts can help IAQ inspectors to identify potential odor-causing air-cooling units. Keratins may be broken down in the units and associated with the odor complaints.     

(1 → 3)-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucan in different background environments and seasons

This study was undertaken to investigate how the length of the extraction period influences the (1 → 3)-β-d-glucan (β-glucan) yield and also to examine the background concentration of β-glucan as airborne β-glucan in outdoor environments in different seasons and as concentrations in airborne and floor dust in offices. To ensure compatibility between results obtained in different laboratories, it is important to use optimal and standardised methods to extract and quantify β-glucan. In this study, an extraction period of 60 min gave the highest β-glucan yield. The median concentration of β-glucan in 44 floor dust samples was 597 μg g⁻¹ dust. The median concentration of airborne β-glucan in offices was 5.1 ng m⁻³ in the summer and 2.3 ng m⁻³ in the winter, and the outdoor median concentration in towns was 6.8 ng m⁻³. The outdoor airborne concentration of β-glucan was significantly lower in January, November and December than during the rest of year. In July, the median airborne concentration of β-glucan was 14 times higher than in January. Furthermore, the airborne concentration of β-glucan was significantly higher in July than in March, April, May, September and October. In the summertime, we found that the indoor airborne concentration of β-glucan was lower than outdoor concentrations. This is in accordance with measurements of concentrations of airborne pollen and culturable fungal spores showing higher outdoor than indoor concentrations during the summer months.     

Indoor moulds in asthmatic patients homes

Summary A study was conducted in 29 households with asthmatic patients in order to analyse the indoor mould concentration; an important contamination was found in both the air and the dust. Although it is known that the outdoor mould concentration in the air decreases during winter, we found that the indoor one did not vary throughout the year. Moreover, the indoor mould concentration increased during the winter in recently built houses, probably because of the poor ventilation. The immunological study showed a lack of correlation between the moulds collected and the patients sensitization.