Evaluation of three portable samplers for monitoring airborne fungi

Airborne fungi were monitored at five sample sites with the Burkard portable, the RCS Plus, and the SAS Super 90 air samplers; the Andersen 2-stage impactor was used for comparison. All samplers were calibrated before being used simultaneously to collect 100-liter samples at each site. The Andersen and Burkard samplers retrieved equivalent volumes of airborne fungi; the SAS Super 90 and RCS Plus measurements did not differ from each other but were significantly lower than those obtained with the Andersen or Burkard samplers. Total fungal counts correlated linearly with Cladosporium and Penicillium counts. Alternaria species, although present at all sites, did not correlate with total count or with amounts of any other fungal genera. Sampler and location significantly influenced fungal counts, but no interactions between samplers and locations were found.     

Monitoring airborne fungal spores in an experimental indoor environment to evaluate sampling methods and the effects of human activity on air sampling.

Aerobiological monitoring was conducted in an experimental room to aid in the development of standardized sampling protocols for airborne microorganisms in the indoor environment. The objectives of this research were to evaluate the relative efficiencies of selected sampling methods for the retrieval of airborne fungal spores and to determine the effect of human activity on air sampling. Dry aerosols containing known concentrations of Penicillium chrysogenum spores were generated, and air samples were taken by using Andersen six-stage, Surface Air System, Burkard, and depositional samplers. The Andersen and Burkard samplers retrieved the highest numbers of spores compared with the measurement standard, an aerodynamic particle sizer located inside the room. Data from paired samplers demonstrated that the Andersen sampler had the highest levels of sensitivity and repeatability. With a carpet as the source of P. chrysogenum spores, the effects of human activity (walking or vacuuming near the sampling site) on air sampling were also examined. Air samples were taken under undisturbed conditions and after human activity in the room. Human activity resulted in retrieval of significantly higher concentrations of airborne spores. Surface sampling of the carpet revealed moderate to heavy contamination despite relatively low airborne counts. Therefore, in certain situations, air sampling without concomitant surface sampling may not adequately reflect the level of microbial contamination in indoor environments.     

Comparison of two biological aerosol sampling methods

Two biological aerosol samplers, the Andersen two-stage microbial impactor and the May three-stage glass impinger, were examined to determine the benefits and effectiveness of the May sampler compared with the Andersen sampler, one of the most widely accepted samplers. Side-by-side samples were collected during simulated wastewater spray irrigation dispersion studies. Escherichia coli colony counts and air concentrations were statistically treated to determine the dependability of the May results with respect to the Andersen results. After data pairs containing potentially overloaded Andersen counts were eliminated, a linear regression of the remaining data was performed. It indicates that although the May sampler reports 82% of the Andersen sampler value, the correlation between the two samplers is good with an r2 value of 0.84. This comparison indicates that although there are differences between the two samplers, they do give comparable results and that when both are used in a sampling program, they tend to complement each other.     

Comparison of two biological aerosol sampling methods.

Two biological aerosol samplers, the Andersen two-stage microbial impactor and the May three-stage glass impinger, were examined to determine the benefits and effectiveness of the May sampler compared with the Andersen sampler, one of the most widely accepted samplers. Side-by-side samples were collected during simulated wastewater spray irrigation dispersion studies. Escherichia coli colony counts and air concentrations were statistically treated to determine the dependability of the May results with respect to the Andersen results. After data pairs containing potentially overloaded Andersen counts were eliminated, a linear regression of the remaining data was performed. It indicates that although the May sampler reports 82% of the Andersen sampler value, the correlation between the two samplers is good with an r2 value of 0.84. This comparison indicates that although there are differences between the two samplers, they do give comparable results and that when both are used in a sampling program, they tend to complement each other.     

Preliminary studies on the effect of the Burkard alternate orifice on airborne fungal spore concentrations

The Burkard 7-day spore trap with standard orifice is commonly used by researchers in sampling outdoor air. The alternate orifice is reported to have higher efficiency in collecting small airborne fungal spores; however, no previous studies compared Burkard samplers with different orifices. This study was conducted to study the effect of the alternate orifice on the concentration of airborne fungal spores. Air samples were collected from July to October 2005 with two Burkard spore traps, one had the standard orifice and the second had the alternate orifice. The two spore traps were located on the roof of a building (12 m height) at the University of Tulsa, Oklahoma. Burkard daily slides were analyzed for airborne spores by light microscopy. The data from the two samplers were statistically analyzed using t-tests. The results indicated that the alternate orifice had significantly higher concentrations of Penicillium/Aspergillus-type spores and basidiospores than the standard orifice. By contrast, the standard orifice had significantly higher concentrations of Alternaria, ascospores, and other spores than the alternate orifice. The alternate orifice can be used to increase the efficiency of trapping small spores, which can be underestimated by using the standard orifice. However, additional comparison in other months of the year is recommended.     

Pollen and fungal spore sampling and analysis. Statistical evaluations

Statistical evaluations of samples obtained from a Burkard seven-day recording volumetric pollen/spore trap were performed to determine the precision of the sampling and analysis procedures. The reproducibility of co-located traps was also investigated. The results showed that pollen grain transect counting was not significantly different, while fungal spore counting produced statistically different results. There was no statistical difference in the number of pollen and fungal spores counted between the co-located samplers. Reasons for the differences in the fungal spore counts are presented.     

Fungi associated with three houses in Havana (Cuba)

Aerobiological sampling was carried out during two consecutive years, 2000 and 2001, in order to ascertain the level of fungal spores present in indoor and outdoor environments in the city of Havana. The samples were collected using Burkard (Burkard Personal Culture and Burkard Personal Slide) and Andersen traps. Sampling was completed by using adhesive tape. We identified 19 spore types, of which the most frequent were Aspergillus (A. flavus, A. niger and A. clavatus), Penicillium (P. citrinum) and Cladosporium (Cl. cladosporioides) . The other fungal types identified include important potential allergens and/or phytopathogens.     

Evaluation of Four Aerobiological Sampling Methods for the Retrieval of Aerosolized Pseudomonas syringae

The Andersen six-stage impactor, the SAS (Surface Air System) impactor, the AGI-30 impinger, and gravity plates were evaluated for the retrieval of aerosol-released Pseudomonas syringae. The upper limits of the impactor samplers were exceeded at a spray concentration of 10⁷ CFU/ml, indicating that these samplers are not appropriate for monitoring high airborne concentrations. Decreased cell concentrations were retrieved with increased sampling time for the Andersen and AGI samplers, indicating that a minimum sampling time is preferable for monitoring aerosolized vegetative cells.     

Enumeration of airborne molds in some indoor environments of Madras city (India) by cultural and non-cultural volumetric samplers

The air mycoflora of six indoor environments in Madras city (India) has been investigated by sampling air with an Andersen sampler and a Burkard personal sampler. Forty-eight species assignable to 24 genera were recorded by Andersen sampler. Spores belonging to 14 genera in addition toPenicillium andAspergillus were identified from Burkard trap slides. Species ofAspergillus, Penicillium, Mucor andRhizopus were most frequently isolated in considerable numbers. As a single genusAspergillus ranked first followed byPenicillium at some sites, andCladosporium at some other sites. The predominance ofPenicillium andAspergillus was also confirmed by Burkard trap data. Spores belonging toGanoderma, Nigrospora, Epicoccum, andTetraploa were recorded only by Burkard sampler, thereby suggesting the necessity of using two complimentary spore traps, cultural and non-cultural, in any aerobiological investigation.     

Dispersal of fungal spores from three types of air handling system duct material

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

Airborne fungi in the hospitals of metropolitan Delhi

Summary The fungal airspora of a large hospital in Delhi Metropolis was studied from May 1989 – April 1991, using Andersen Six Stage Volumetric Sampler and Burkard Personal Slide Sampler. Simultaneously, samples were also collected from outside the hospital to act as a control. Samplers were operated for 10 min. each time, at 10 - day intervals. Additional samples were also collected from different sections of 3 other hospitals. Some of the dominant forms encountered wereCladosporium spp.,Aspergillus flavus, Smut,Fusarium spp.,Aspergillus niger, Alternaria spp.,Penicillium citrinum, Aspergillus versicolor, andPenicillium oxalicum. Aspergillus flavus showed significantly high concentration inside hospital (n=66, x=53 CFU m^–3, p<0.05) as compared to outside air. The peak period for fungi was observed to be from June – September. The spore concentration was much lower in hospital units receiving filtered air as compared to control environment, but in naturally ventilated hospitals the concentration was similar to that of outside air.     

Fungal spores are an important component of library air

The airborne fungal spore types were studied in different libraries in Delhi, using an Andersen sampler and a Burkard personal sampler, for culturable and non-culturable fungi respectively. The concentration inside the libraries, before and after the agitation of books, were compared with outside air. The major contributors to the library air areCladosporium, aspergilli/penicillia, smuts andAlternaria, varying from 50 to 14%. Some fungi (Cladosporium, Alternaria, smut,Penicillium chrysogenum andnigricans) showed seasonal occurrence, corresponding to their occurrence in the extramural environment. Aspergilli/penicillia,Drechslera, Curvularia andAspergillus flavus had a significantly higher concentration (P<0.01) inside the library, and recorded a significant increase in concentration after agitation of books. Air-conditioned libraries have low fungal spore concentrations, as compared to naturally ventilated libraries.     

Airborne Fungi in a Bakery and the Prevalence of Respiratory Dysfunction among Workers

Concentrations of fungi in different sections of a bakery in Delhi were studied for two years (May 1989–April 1991). Andersen Volumetric and Burkard Personal Slide samplers, were used to collect samples at 10 day intervals. Aspergilli/penicillia, smuts and Cladosporium spp. predominated, contributing about 90% of the total fungi. Aspergillus flavus was characteristic in the storage section and Aspergillus niger in the packing section. In general, concentrations inside the bakery were higher than in the outdoor air. Aspergillus flavus, Aspergillus niger, Alternaria spp. and ustilaginales were predominant in the summer months, whereas Cladosporium spp., Penicillium citrinum and Penicillium chrysogenum were prevalent in winter. The seasonal differences observed in the first year were seen again in the second year. A survey of the prevalence of respiratory dysfunction among the bakery workers (n=279) revealed that 40.1% of the workers were suffering from respiratory disorders and 8.2% had a family history of respiratory disorders. The prevalence of various symptoms was: cough with phlegm, 37.5%; cough without phlegm, 16.1%; breathlessness/wheeze, 34.7%; rhinitis, 53.6%; conjunctivitis, 20.5%; eczema, 16.1%. Age, period of association with the job and smoking habits significantly influence the incidence of breathlessness, rhinitis and cough (p<0.05). Thirtynine individuals reported their symptoms to be work related, of which 35 reported aggravation of symptoms during work hours.     

Viable fungi in corn dust

Numbers of viable fungal propagules in corn dusts in southern Georgia were estimated during various farm and grain elevator operations in 1979, 1980, and 1982. A six-stage Andersen sampler for viable microbial particles was used to sample the dusts with various agar media. The most abundant fungi in corn dusts were species of yeasts: Aspergillus, Penicillium, Cladosporium, Alternaria. Helminthosporium, and Fusarium. However, the relative abundance of these fungi differed between years. There was a greater incidence of the Aspergillus flavus group in the hot, dry year of 1980 compared with the cooler, wetter years of 1979 and 1982. Fungi in the corn dusts sampled numbered between 10(4) and 10(9) viable propagules per m3 of air. By contrast, outdoor air often contained fewer than 10(4) viable fungal propagules per m3. Most A. flavus propagules were deposited at stages three and four of the Andersen sampler, with correspond to the trachea, primary bronchi, and secondary bronchi in the human respiratory system. In an assessment of the air spores by exposing sterile petri dishes, more large-spored fungi, like Alternaria tenuis, and fewer small-spored fungi, such as A. flavus, were detected when compared with colony counts from petri dishes exposed to air in the Anderson sampler.     

Viable fungi in corn dust.

Numbers of viable fungal propagules in corn dusts in southern Georgia were estimated during various farm and grain elevator operations in 1979, 1980, and 1982. A six-stage Andersen sampler for viable microbial particles was used to sample the dusts with various agar media. The most abundant fungi in corn dusts were species of yeasts: Aspergillus, Penicillium, Cladosporium, Alternaria. Helminthosporium, and Fusarium. However, the relative abundance of these fungi differed between years. There was a greater incidence of the Aspergillus flavus group in the hot, dry year of 1980 compared with the cooler, wetter years of 1979 and 1982. Fungi in the corn dusts sampled numbered between 10(4) and 10(9) viable propagules per m3 of air. By contrast, outdoor air often contained fewer than 10(4) viable fungal propagules per m3. Most A. flavus propagules were deposited at stages three and four of the Andersen sampler, with correspond to the trachea, primary bronchi, and secondary bronchi in the human respiratory system. In an assessment of the air spores by exposing sterile petri dishes, more large-spored fungi, like Alternaria tenuis, and fewer small-spored fungi, such as A. flavus, were detected when compared with colony counts from petri dishes exposed to air in the Anderson sampler.     

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.     

Airborne fungal spores in 80 homes in the Latrobe Valley, Australia: levels, seasonality and indoor-outdoor relationship

Airborne viable and total fungal spores were sampled inside and outside 80 houses in the Latrobe Valley, Victoria, Australia as part of a larger indoor environmental study. Each residence was visited six times over a period of 1 year for sample collection, and fungal spore samples were collected from at least three indoor sites and from an outdoor site. Viable spores were sampled using an Andersen sampler, while total spores were assessed using a Burkard spore trap. Identification of fungal colonies to genera level was performed in two seasons; winter and late spring. The most common fungal genera/groups wereCladosporium, Penicillium, and yeasts, both indoors and outdoors in winter and late spring. Outdoor levels were higher than those indoors throughout the year, and a significant seasonal variation in spore levels was seen both indoors and outdoors with overall maxima in summer. Contrary to this trend, the levels ofAspergillus, yeasts,Cephalosporium andGliocladium were higher in winter. Most fungal genera were found in greater concentrations outdoors compared to indoors, butPenicillium was more common indoors. Outdoor spore levels were a significant influence on indoor levels, but seasonal differences suggest that other influences are important.     

The effects of transported Asian dust on the composition and concentration of ambient fungi in Taiwan

This study was conducted to evaluate the effects of transported Asian dust and other environmental parameters on the levels and compositions of ambient fungi in the atmosphere of northern Taiwan. We monitored Asian dust events in Taipei County, Taiwan from January 2003 to June 2004. We used duplicate Burkard portable air samplers to collect ambient fungi before, during, and after dust events. Six transported Asian dust events were monitored during the study period. Elevated concentrations of Aspergillus (A. niger, specifically), Coelomycetes, Rhinocladiella, Sporothrix and Verticillium were noted (p < 0.05) during Asian dust periods. Botryosporium and Trichothecium were only recovered during dust event days. Multiple regression analysis showed that fungal levels were positively associated with temperature, wind speed, rainfall, non-methane hydrocarbons and particulates with aerodynamic diameters ≤10 μm (PM₁₀), and negatively correlated with relative humidity and ozone. Our results demonstrated that Asian dust events affected ambient fungal concentrations and compositions in northern Taiwan. Ambient fungi also had complex dynamics with air pollutants and meteorological factors. Future studies should explore the health impacts of ambient fungi during Asian dust events, adjusting for the synergistic/antagonistic effects of weather and air pollutants.     

Evaluation of the environmental impact of microbial aerosols generated by wastewater treatment plants utilizing different aeration systems

Using three sampler devices (SAS, Andersen Six-Stages and All Glass Impinger), the environmental impact of bacterial and fungal aerosols generated by municipal wastewater treatment plants operating with different methods of sludge oxygenation were evaluated. The highest microbial concentrations were recovered above the tanks (2247 cfu m-3) and in downwind positions (1425 cfu m-3), where a linear correlation (P < 0.05) was found between the quantity of sewage treated and the entities of microbial aerosol dispersion. Moreover, an exponential increase (P < 0.05) in the bacteria recovered from the air occurred at increasing times of treatment. However, after long-term plant operation, high bacterial and fungal concentrations were found in almost all of the sites around the plant. Coliforms, enterococci, Escherichia coli and staphylococci were almost always recovered in downwind positions. Considerable fractions (20-40%) of sampled bacteria were able to penetrate the final stages of the Andersen apparatus and thus, are likely to be able to penetrate the lungs. The plant operating with a fine bubble diffused air system instead was found to generate rather low concentrations of bacteria and fungi; moreover, staphylococci and indicator micro-organisms were almost absent. Finally, salmonellae, Shigella, Pseudomonas aeruginosa and Aeromonas spp. were not detected in either of the plants. The results indicate a remarkable dispersion of airborne bacteria and fungi from tanks in which oxygen is supplied via a mechanical agitation of sludge, and suggest the need to convert them to diffused aeration systems which pose a lesser hazard for human health.     

Contribution of leaf surface fungi to the air spora

High concentrations of airborne fungal spores frequently occur from spring through fall in temperate areas of the world. Although it is generally assumed that fungi on leaf surfaces are contributors to the air spora, little data are available comparing the types of fungi found on leaf surfaces with those in the atmosphere. Air sampling was carried out with a Burkard Spore Trap located on the roof of a building on the University of Tulsa campus using standard methods. Leaf samples were aseptically collected from Ulmus americana and Quercus palustris trees on campus, placed in sterile plastic bags, and brought to the lab. For each leaf, 4 cm² areas of both upper and lower leaf surfaces were swabbed and plated on malt extract agar with streptomycin. Cultures were incubated at room temperature for 5–7 days and then examined microscopically. Results were expressed as colony forming units (CFU)/cm². Twenty-one fungal taxa were identified from the air samples. The most abundant taxa were Cladosporium, ascospores, basidiospores, and Alternaria; together these four spore types comprised over 90% of the yearly total. Yeasts were the most abundant fungi isolated from both leaf types. Among the mycelial fungi were Phoma species, followed by Cladosporium and Alternaria. Overall twenty genera of filamentous fungi were identified. Yeasts and Phoma are normally splash dispersed and were not identified in the Burkard air samples. However, 10 taxa isolated from leaf surfaces were registered in air samples. Crude estimates of the leaf surface area of each tree suggest that the total fungal load was approximately 5.04×10⁸ CFU for Ulmus and 2.71×10⁸ CFU for Quercus. Of these levels, 19% were from fungi also detected in air samples. The data suggest that some leaf-surface fungi are major contributors to the air spora.