ABSTRACT: Air samples from in and around one thousand eight hundred fifty five (1, 855) buildings were collected by spore trap technique (Air-O-Cell) over a period of 10 years (1995-2005) covering 45 states of North America. Nine thousand two hundred thirty two (9,232) samples were analyzed qualitatively as well as quantitatively to study the air-borne fungi in and around building environment. Qualitatively one hundred fifteen (115) types of air-borne fungi were recorded where as quantitatively a mean value of 382.8 cts/m
3i was observed during the period of study.
Based on this study a reference number 385 cts/m
3 is established for the determination of baseline condition of a building under normal condition for the general acceptability of Indoor Environmental Quality (IEQ).
INTRODUCTION
There are several known and unknown factors that, collectively, can adversely affect the quality of the indoor environment. Many of these known factors such as Temperature and Relative Humidity have measurable standards as defined by associations such as American National Standards Institute (ANSI), American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), and the like. However, incase of other known factors such as fungi (mold) and bacteria, there are no universally accepted standards for their measurement. Therefore, Diagnosticians, Facility Managers and others responsible for testing or maintaining residential and commercial property rely heavily on interpretation of the laboratory results derived from environmental samples they collect. The interpreted data plays an important role in formulating an educated scientific opinion with regards to the totality of the Indoor Environmental Quality (IEQ) of dwellings.
One important part of IEQ is that of airborne fungi. Airborne fungi have the capability of producing mold in a building environment that can range from small scale, relatively inexpensive contamination, like that found on a shower curtain in a common residential bathroom, to that of a full-blown, costly infestation of epic proportions resulting in the complete demolition of a building. Through an effective Proactive Maintenance Plan (PMP) that encompasses routine sampling of both air and surfaces within a building structure, the early detection and proper identification of airborne fungi found in the indoor environment can be an effective tool to understand the basis of the problem in a more accurate and authentic way, as well as to help foster an understanding as to how mold relates to the totality of the building’s IEQ.
During the present endeavor, an attempt has been made to study airborne fungal diversity both qualitatively and quantitatively by using spore trap technique under normal conditions in a building to establish a reliable reference concentration of Airborne Fungi to evaluate buildings in order to address fungal infestation or mold related issues, which may influence the IEQ.
MATERIALS AND METHODS
All togetherone thousand eight hundred fifty five (1,855) commercial and residential buildings across the United States covering forty-five (45) states were identified and selected (based upon the customer’s calls) for this study. On the basis of use, buildings were categorized into two different types: Residential and Commercial. Residential buildings were considered mostly dwelling houses whereas commercial buildings were considered mostly the work place.
A total of nine thousand two hundred thirty two (9,232) air samples from eight thousand four hundred and six sampling sites (8,406) were collected over a period of ten years (1995 to 2005) using Air-O-Cell cassettes. All the samples were collected from breathing zone (4’-5’ from the floor surface). This sampling cassette specifically designed for the rapid collection of a wide range of airborne aerosols including air-borne fungi/elements. The collected air samples were processed and specimens were identified in the Environmental Diagnostics Laboratory (EDLab™) an American Industrial Hygiene Association accredited Laboratory (EMLAP # 102795) in Clearwater, Florida, USA.
Microscopic specimen slides were prepared from laboratory accepted Air-O-Cell cassettes. The glass slip with collected sample removed carefully from the Air-O-Cell cassette and placed in the centre of a clean, sterilized and labeled microscopic slide containing a drop of lacto phenol cotton blue stain directly onto the drop of staining solution (collection surface of the glass slip down) with the help of needle so that the stains evenly disperse. These slides were allowed to sit about 5-10 min prior to analysis.
Microscopy is used for the identification and enumeration of air-trapped fungal spores/elements. A preliminary examination of the trace under low magnification (10 x 10) is performed to confirm that sample is uniform and the staining has been properly achieved. Identification and quantification of air-mycoflora was performed under 400-X magnification. Phase contrast objectives were used for identifying the hyaline or colorless spores. When the identification of the spore/elements was not certain in 400-X, a higher magnification of 1000-X is applied. Trapped fungal spore/element is identified up to certain taxon (Genus or Class) based on the identification parameter, which includes but not limited to the gross morphology (spore shape, size etc.), color, surface texture, internal morphology, septation, presence and location of the attachment point if any. Some fungi produce spores, which are taxonomically/morphologically indistinguishable specially when they trapped on the Air-O-Cell. These spores were grouped and recorded together for the analysis (Aspergillus/Penicillium-like spores, Mucor/Rhizophous-like, Bipolaris/Dreschlera/Helminthosporium-like spore). However, the final identification of the trapped bio-particulate is made after comparing it against standard reference slides, photos and/or publications. Actual spore count was converted to airborne concentration by using the following formula:
L P
Cp = ---------- X -----------
W X N (F x T)/1000
Where,
Cp = Concentration of particles per cubic meter volume of the air
L = Length of the entire sample deposited
P = Number of particle counted
W = Width of one field (longitudinal transverse)
N = Number of field transverse counted
F = sample flow rate in liters per minutes
T = Elapse sampling time in minute
RESULTS AND DISCUSSTION
A total of nine thousand two hundred thirty-two (9,232) air samples obtained from eight thousand four hundred and six (8,406) different sampling sites belonging to one thousand eight hundred fifty-five (1,855) commercial and residential buildings from forty-five states within the United States were analyzed during the entire period of study (1995-2005).
Qualitatively, altogether one hundred fifteen (115) different taxa of airborne fungi were identified during this investigation. The top fifteen airborne fungi identified from both indoor and outdoor samples were found to be Dematiaceous Fungal Hyphal Elements, Aspergillus/Penicillium-like spores, Cladosporium species, Ascospores, Dematiaceous Fungal spores, Fungal spore elements, Curvularia species, Asomycetes with no further identification, Fungal hyphal elements, Fusarium species, Nigrospora species, Ganoderma species, Epicoccum Species, Alternaria species, and Curvularialunata. Dematiaceous Fungal Hyphal Elements were reported as the most predominant fungal derivate from indoor air, followed by Aspergillus/Penicillium-like spores, Cladosporium species, Ascospores, Dematiaceous fungal spores, fungal spores,
Ascomycetes, Curvulariaspecies, Fungal Hyphal Elements, and Epicoccum species in that order. Cladosporium species dominated the outdoor mycoflora followed by Dematiaceous Fungal Hyphal Elements, Aspergillus/Penicillium-like spores, Ascospores, Dematiaceous spores, Fungal Spores, Fusarium species, Ganoderma species, Curvulariaspecies, and Fungal Hyphal Elements in that order. Quantitatively, indoor fungal concentration ranges between Below Detectable Limit (BDL) to eight thousand ninety-seven (8,097) cts/m
3, with a mean value of 382.8 cts/m
3. In contrast, outdoor concentration range was BDL to twenty nine thousand one hundred fifty-nine (29,159) cts/m
3 with a mean value of 2027.9 cts/m
3.
The concentration of airborne fungi at different percentile of samples has been recorded. Results from indoor air samples collected indicate that three thousand nine hundred sixty-six (3,966) samples out of a total of seven thousand seven hundred thirty-eight (7,738) have a maximum concentration up to 125 cts/m
3. Only two hundred eighty-eight (288) samples were reported where maximum concentration exceeded over 2,000 cts/m
3. In case of outdoor samples (a total of one thousand four hundred ninety-four (1,494) samples), six hundred seventeen (617) samples were recorded with a maximum concentration up to 500 cts/m
3 and eighty-eight (88) samples with a concentration more than 8,000 cts/m
3. Samples from fifty-one percent of the total number of buildings tested reported airborne fungal concentrations of less than 200 cts/m
3, while four percent reported high airborne fungal concentrations of 2,000 cts/m
3 or greater as seen in
The indoor to outdoor air fungal concentration ratio is approximately 1:5 (one: five).
CONCLUSIONS
The present endeavor is a unique and a median approach to determine the reference level of airborne fungi in and around dwellings. This study is also unique because it described airborne fungal concentration both qualitatively as well as quantitatively as a tool for evaluating the Indoor Environmental Quality (IEQ).
Out of several known factors, biological contamination, especially fungi may adversely influence the Indoor Environmental Quality (IEQ). There is no universally accepted reference to determine the acceptability of IEQ. Although, attempts have been made to compile criteria to assess the fungal contaminant
1, 2, 3, 6 in building environment. Compilation of these types of criteria is not an easy task due to the complexity and variability of conditions and sampling methodologies
3. For example, the concentration and variety of fungi may differ substantially when different sampling techniques are used. Factors like exposure time, period, place, volume of air and other environmental conditions (Temperature, Relative humidity and others) play a pivotal role in air sampling. Data obtained during the period of investigation indicates that the concentration of fungi may vary depending upon the nature of the building, like residential or commercial.
During the present endeavor our goal was to study the airborne fungal concentration under normal conditions (without disturbing the nature of the dwelling place i.e. residential or commercial). All of the buildings investigated during this study, quantitatively only 4% percent of the buildings had remarkably elevated number of fungal population in indoor air in comparison to the other samples . Qualitatively, Dematiaceous Fugal Hyphal Elements (55.8%), Aspergillus/ Penicillium like spore (55.3%), Cladosporium sp. (50.1%), Ascospores (35.9%), Dematiaceous Spores (34.2%), Fugal Spores (26.9%) (includingbasidiospore), other Ascomycetes (16.8%),. Curvularia sp. (15.3%) Fungal Hyphal Elements (13.3%) and Epicoccum (7.4%) noticed as most frequently isolated airborne fungi. However, Aspergillus/Penicillium like spore dominated the list of prevailing fungi in terms of highest overall concentration (1,141,008 count/m
3). This indicates that the spore of Aspergillus/Penicillium group is highly suitable to become airborne in comparison to the others.
The above observation indicates that it is not uncommon to report the above taxa of the fungi in and around buildings. A comparison of spore concentration of air-borne fungi is made between outdoor sites with that of indoor site and a ratio of 5:1 is obtained. This ratio reflects that normally microbiological activity is greater out site in comparison to indoors. These criteria may also be adapted while evaluating a building environment for fungal contaminant.
Results of this study reflects that
< 380 cts/m
3 is an appropriate reference number that may be used as a tool to determine the baseline (under normal conditions) of airborne fungi in indoor environments. However, numeric reference plays a secondary role when the results revel the presence of well-recognized pathogenic or allergenic taxa.
Relatively little is known about the air-borne fungal spore concentration in buildings, but it is generally considered that if survive it may influence the building conditions and health of the dwellers. Findings of this investigation suggest that a lower percentage of the buildings harbor very high concentration of fungal population. Only 4% of the buildings during this study showed a fungal concentration of 2000 cts/m
3 or more however; 63% of the buildings were reported with relatively low concentration (between less than 100 cts/m
3 to 300 cts/m
3) of air-borne fungi. As a result of the observation during the present endeavor it is proposed that buildings can be categories into three different levels based on the fungal population
. Level I with a upper limit of 400 cts/m
3,
Level II with a maximum concentration between 401- 1000 cts/m3 and
Level III with a concentration of more than 1001 cts/m
3 (Graph-9)
The outcome of this study provides numeric and qualitative data on “Airborne Fungi” that may be considered by building scientists, industrial hygienists, medical professionals, IAQ practitioners when assessing the condition of a building specially for fungal contaminants.
references
1. National Institute for Occupational Safety and Health (2005): NIOSH Safety and Health Topic: Indoor Environmental Quality
2. U.S. Environmental Protection Agency, Office of Air and Radiation. Report to Congress on Indoor Air Quality, Volume II: Assessment and Control of Indoor Air Pollution, pp. I, 4-14. EPA 400-1-89-001C, 1989.
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7. Burge, H.(1996): Health Effect of Biological Contaminants. In: Indoor Air and Human Health, PP.171-178. R.B. Gammage and B.A. Berven, Eds. CRS press, Boca Raton, FL.
8. Spicer, R and Gangloff (2005): Establishing Site Specific Reference Levels for Fungi in Outdoor Air for Building Evaluation. Journal of Occupation and Environmental Hygiene.
2 : 257-266
9. Lee, Shu-An., Willeke, K., Mainelis, G., Adhikari, A., Wang, W., Reponen, T., and Grinshpun, S. A. (2004): Assessment of Electrical Charge on Airborne Microorganism by a New Bioaerosol Sampling Method. Journal of Occupation and Environmental Hygiene. 1:: 127-138
10. Maclntosh, D. L., Brightman, H.S., Baker, B. J., Myatt, T.A., Stewart, J.H., and McCarthy (2006): Airborne Fungal Spore in a Cross-Section Study of Office Buildings. Journal of Occupation and Environmental Hygiene. 3: 379-389.
11. Baxter, D. M., Perkins, J. L., McGhee, C.R. and Seltzer, J. M. (2005): A Regional Comparison of Mold Spore Concentrations Outdoors and Inside “Clean” and “Mold Contaminated” Southern California Buildings. Journal of Occupation and Environmental Hygiene. 2: 8-18.
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