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Fungi and bacteria in mould-damaged and non-damaged office environments in a subarctic climate
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Atmospheric Environment 41 (2007) 6797–6807 www.elsevier.com/locate/atmosenv
Fungi and bacteria in mould-damaged and non-damaged office environments in a subarctic climate Heidi Salonen, Sanna Lappalainen, Outi Lindroos, Riitta Harju, Kari Reijula Finnish Institute of Occupational Health, Arinatie 3 A, 00370 Helsinki, Finland Received 18 October 2006; received in revised form 17 April 2007; accepted 20 April 2007
Abstract The fungi and bacterial levels of the indoor air environments of 77 office buildings were measured in winter and a comparison was made between the buildings with microbe sources in their structures and those without such sources. Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in the indoor air and in settled dust, in both the mould-damaged and control buildings. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in environmental samples from the mould-damaged buildings. Some other fungi, with growth requiring of water activity, aw, above 0.85, occurred in both the reference and mould-damaged buildings, but such fungi were commoner in the latter type of buildings. The airborne concentrations of Penicillium, Aspergillus versicolor and yeasts were the best indicators of mould damage in the buildings studied. Penicillium species and A. versicolor were also the most abundant fungi in the material samples. This study showed that the fungi concentrations were very low (2–45 cfu m3 90% of the concentrations being o15 cfu m3) in the indoor air of the normal office buildings. Although the concentration range of airborne fungi was wider for the mould-damaged buildings (2–2470 cfu m3), only about 20% of the samples exceeded 100 cfu m3. The concentrations of airborne bacteria ranged from 12 to 540 cfu m3 in the control buildings and from 14 to 1550 cfu m3 in the mould-damaged buildings. A statistical analysis of the results indicated that bacteria levels are generally o600 cfu m3 in office buildings in winter and fungi levels are o50 cfu m3. These normal levels are applicable to subarctic climates for urban, modern office buildings when measurements are made using a six-stage impactor. These levels should not be used in evaluations of health risks, but elevated levels may indicate the presence of abnormal microbe sources in indoor air and a need for additional environmental investigations. r 2007 Elsevier Ltd. All rights reserved. Keywords: Fungi; Bacteria; Indoor air; Office building; Concentration
1. Introduction In Finland, more than 420,000 workers were employed in the office and administration sector in Corresponding author. Tel.: +358 304 742 937; fax: +358 9 506 108 7. E-mail address: Heidi.Salonen@ttl.fi (H. Salonen).
1352-2310/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2007.04.043
2005; 143,000 of these employees worked in the Helsinki area. The number of office workers has grown over the past few years (Central Statistical Office of Finland, 2006). Building-related moisture and mould damage are significant indoor air problems in Finland, as well as in other countries (Nevalainen et al., 1998; Brunekreef et al., 1989; Spengler et al., 1994). According to Finnish studies,
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moisture problems have been estimated to occur in over 50% of apartments, schools and day-care centres (Teijonsalo et al., 1991; Ruotsalainen et al., 1995; Koivisto et al., 1996; Nevalainen et al., 1998). Although estimates for office buildings are unavailable, moisture problems are obviously common also in these buildings since they have been built according to practices generally used for public buildings. It has been estimated that about 20,000–50,000 people in Finland experience symptoms associated with exposure to micro-organisms in water-damaged homes and workplaces (Haahtela and Reijula, 1997; Tuomisto, 2000). Moisture problems leading to microbe growth in the structures of buildings (Brunekreef et al., 1989; Hodgson et al., 1998; Platt et al., 1989; Taskinen et al., 1999; Wieslander et al., 1999; Mahmoudi and Gershwin 2000; Trout et al., 2001) and exposure to fungi from these sources may cause adverse health effects such as respiratory symptoms (coughing, wheezing), rhinitis, asthma, tiredness and headache (Peat et al., 1998; Bornehag et al., 2001). The causal relationship between damp housing and illness is still unclear (Garrett et al., 1998; Peat et al., 1998; Seuri et al., 2005). The causes of the health effects may be associated with complex interactions between bacteria and fungi and environmental growth substrates and other micro-organisms that lead to a wide variety of exposures (Nevalainen and Seuri, 2005). Currently, there are no generally accepted or suitable numerical ‘standards’ or official ‘criteria’ for acceptable concentrations of fungi and bacteria (Rao et al., 1996; Horner et al., 2004). Some of the proposed quantitative guidelines or standards are based mainly on domestic environments (Reponen et al., 1992). The home, however, differs in many ways from work or office environments. Home environments have sources of micro-organisms (e.g., cooking, firewood and pets) that are absent in the work environment (Lehtonen et al., 1993). In addition, technical features, such as ventilation systems, differ in dwellings and public buildings. Thus, it is obvious that a higher background level of fungi and bacteria exists in domestic environments than in office environments (industrial work environments excluded). Although there are no dose–response data available for use as a reference, microbe measurements are often used to describe the general quality of indoor air. In addition, fungi, with water activity, aw, above 0.85, as a growth requirement, have been
regarded as indicator organisms for the presence of moisture problems (Samson, 1994). Therefore, measurements of fungi and Actinobacteria are often used to reveal mould problems in buildings. There are very few data available on the range of microbe levels in normal office environments in Europe. This study presents the wintertime concentrations of fungi and bacteria, as well as fungal flora in moulddamaged and control office buildings in a subarctic climate. These findings can be used as reference values when abnormal indoor microbe sources are assessed for such a climate. 2. Materials and methods 2.1. Buildings and moisture investigation This study included a total of 77 office buildings in Southern Finland. All of the buildings were selected from the database of the Finnish Institute of Occupational Health (FIOH), Helsinki. Experienced construction engineers carried out inspections of the buildings for damage caused by moisture and mould. An inspection included an interview of building maintenance and management personnel and workers, a survey of the construction drawings, an inspection for signs of moisture and mould, and the opening of structures if needed. Microbe growth in the structures was primarily verified with microbe analyses. A surface moisture indicator (Tramex Moisture Enco 11860 ME 5970165, Tramex Moisture Encounter Plus 31262 MEP 9057587) and a humidity and temperature indicator (HM141 (ID), serial no. X4440092) with a measurement sensor (HMP42, X5040003) were used to detect moisture. The inspection revealed dampness or visible mould damage in 34 of the 77 office buildings. These 34 buildings were selected as ‘mould-damaged buildings’ in this study. The 43 buildings without any dampness or visible mould damage were selected as ‘control buildings’. Environmental samples were taken to clarify hazard identification when the results of a walk-through inspection revealed no significant moisture or mould construction damage (damaged area p1 m2) in the moulddamaged buildings. Settled dust samples were collected from all of the control buildings, and indoor air samples were collected from 20 of the buildings. The office buildings represented the typical Finnish urban style, and most of them had a concrete framework, flat roof and several floors.
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Altogether 86% of the buildings were equipped with supply and exhaust air ventilation systems; the rest had only an exhaust air system or natural ventilation. Samples of indoor air (34 buildings), settled dust (55 buildings) and building material (33 buildings) were collected from the buildings during the winter (November–March) within a period of 5 years. 2.2. Airborne fungi samples Indoor air samples of airborne fungi were collected from 14 of the 34 mould-damaged buildings (46 samples) and from 20 of the 43 control buildings (56 samples) with the use of an Andersen six-stage cascade impactor and a volume flow rate of 28.3 l min1 (Andersen, 1958). All of the samples were taken at a height of about 1.5 m, and the sampling time was 15 min. The samples were collected on 2% malt extract agar (MEA) and 18dichloran glycerol agar (DG18) for fungi and tryptone glucose yeast agar (TYG) for bacteria. The plates were incubated at 25 1C for 7 days (14 days for Actinobacteria). Fungi were identified at the genus/species/type level with the use of a light microscope. The air concentrations of fungi and bacteria were expressed as colony-forming units (cfu) m3. No outdoor air samples were taken because outdoor air levels of fungi and Actinobacteria are very low in subarctic climates during winter, and thus outdoor air has a negligible impact on the micro-organism levels of indoor air (Reponen et al., 1992). 2.3. Settled dust samples Dust samples from 55 buildings (47 settled dust samples from 15 mould-damaged buildings and 126 samples from 40 control buildings) were collected from horizontal surfaces (e.g., book shelves), at a height of about 1.5 m, over a 2-week period during normal office activities. The settled dust samples indicated somewhat cumulated air samples. Samples were taken with a sterile moisture swab from a sampling area of 100 cm2 and directly cultivated on MEA and DG18 for fungi and on TYG for Actinobacteria. The samples were incubated at 25 1C for 7 days (14 days for Actinobacteria), after which the fungi were identified according to the previously described method. The results were expressed according to the following semi-quantitative scale:
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+ ¼ 1–9 cfu 100 cm2; ++ ¼ 10–49 cfu 100 cm2; and +++ ¼ 449 cfu 100 cm2. 2.4. Material samples For the microbe analyses, the material samples were collected from different types of building materials (wood, gypsum boards, mineral insulation materials, paints, glues, etc.) in 23 mould-damaged buildings (70 samples). The micro-organisms were extracted from the material samples (weight about 10 g) into sterile Tween buffer solution with dilutions of 101–105. Fungi were determined on MEA and DG18 agar plates, and TYG agar plates were used for bacteria. The samples were incubated at 25 1C for 7 days (14 days for Actinobacteria); the fungi were identified according to the previously described method. The concentrations of fungi and bacteria in the material samples were expressed as colony-forming units (cfu) g1. 2.5. Statistical analysis Statistical tests were carried out using the SAS program package (version 9.1, SAS Inc., Cary, NC, USA). The Kolmogorov–Smirnov test was applied to check the normality of the concentration distributions (three agar plate types: MEA, DG18 and TYG). The distribution of the bacteria concentrations was lognormal, but the fungi concentrations were not. Therefore, upper limits based on a lognormal distribution were not used. Instead, the distributions were illustrated using the Box and Whisker plot diagram and the percentiles of the distributions. The differences in the distributions between the concentrations of Penicillium in the settled dust samples were tested with the chi-square test. The differences in the distributions between the mould-damaged and control buildings were tested with the Wilcoxon rank-sum test (Fig. 1). The statistical significance of the differences in the different fungal genera groups were calculated between the mould-damaged and control buildings (Figs. 2 and 3). 3. Results 3.1. Indoor air samples The indoor air concentrations of fungi spores and bacteria in the mould-damaged and control buildings are presented in Fig. 1. The median fungi
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6800
10000
cfu/m3
1000
100
10
1 DG-18
DG-18
MEA
MEA
moulddamaged buildings
control buildings
moulddamaged buildings
control buildings
Bacteria (TYG)
Bacteria (TYG)
moulddamaged buildings
control buildings
Fig. 1. Median spore concentrations of fungi and bacteria for the indoor air of mould-damaged (46 samples) and control (56 samples) buildings. The figure also shows the minimum, maximum and quartiles of the distributions.
% 0
20
40
60
80
100
*** Penicillium * Yeasts Cladosporium * Sterile ** Aspergillus versicolor Aspergillus penicillioides Engyodontium Aspergillus sydowii Wallemia sebig * Paecilomyces variotii * Rhizopus stolonifer Aspergillus fumigatus Eurotium herbariorum * Aspergillus niger Aspergillus ochraceus Other fungi (13 species) <5 %
Mould-damaged buildings Control buildings
Fig. 2. Prevalence of 29 different fungal genera or groups found in the indoor air of the mould-damaged and control buildings (cultivated on DG18 agar): *po0.05, **po0.01, ***po0.001.
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% 0
20
40
60
80
100
** Penicillium Sterile Yeasts Cladosporium ** Aspergillus versicolor * Aspergillus fumigatus Arthrographis Engyodontium * Acremonium Aspergillus sydowii Aspergillus ochraceus Other fungi (22 species) <5 %
Mould-damaged buildings Control buildings
Fig. 3. Prevalence of 32 different fungal genera or groups found in the air samples from the mould-damaged and control buildings (cultivated on MEA agar): *po0.05, **po0.01, ***po0.001.
concentrations were statistically significantly higher (DG18: po0.001; MEA: po0.001) in the moulddamaged buildings than in the control buildings. Such a clear difference was not detected for the bacteria concentrations because the concentration range was greater for the mould-damaged buildings than for the control buildings. Actinobacteria were detected in only 34% of the indoor air samples. The median concentration range was clearly greater (po0.001) for Actinobacteria in the moulddamaged buildings than for Actinobacteria in the control buildings, the average values being 16 and 3 cfu m3, respectively. The results are presented in more detail in Table 1. They show that 90% of the fungi concentrations in the control buildings were o15 cfu m3, whereas, in the mould-damaged buildings, 90% of the concentrations were o210 cfu m3 and 70% were o55 cfu m3. The geometric mean of the fungi counts was about six-fold higher in the moulddamaged buildings than in the control buildings. The fungi concentration of 100 cfu m3 was exceeded in only about 20% of the air samples from the mould-damaged buildings. The bacteria concentrations were higher in all of the buildings than
the fungi concentrations were. Altogether 90% of the bacteria concentrations were o309 cfu m3 in the control buildings and o584 cfu m3 in the mould-damaged buildings. The maximum bacteria concentration in the mould-damaged buildings was about 2.9-fold greater than that of the control buildings. The prevalence of fungal genera or groups in comparison with the total viable spore count is shown in Figs. 2 and 3 for the mould-damaged and control buildings. The commonest fungi in both the mould-damaged and control buildings were Penicillium, yeasts, Cladosporium, non-sporing isolates and Aspergillus versicolor. The occurrence of airborne fungal spores in the mould-damaged and control buildings differed significantly (po0.05) for seven species on DG18 agar and five species on MEA agar. The concentrations of Penicillium, A. versicolor and yeasts indicated the presence of mould damage in the buildings studied (po0.001). The median concentration (arithmetic average for the DG18 and MEA samples, respectively) of A. versicolor was 61–66 cfu m3 for the moulddamaged buildings and 2–5 cfu m3 for the control buildings. Several fungal genera were detected in
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Table 1 Basic statistics and percentiles for the fungal and bacterial concentrations in the mould-damaged (n ¼ 46) and control buildings (n ¼ 56) Fungi (DG18) Mould-damaged buildings
Control buildings
Mould-damaged buildings
Bacteria (TYG) Control buildings
Mould-damaged buildings
Control buildings
22
4
20
3
122
62
6
3
6
3
4
5
24 33 43 73 208 2468
5 5 7 12 15 45
21 31 54 94 199 2431
2 5 7 9 14 26
114 209 264 348 582 1551
80 118 156 207 309 536
Geometric mean (cfu m3) Geometric S.D. (cfu m3) Percentiles (cfu m3) Median P60 P70 P80 P90 Maximum
Fungi (MEA)
S.D.: standard deviation.
both the damaged and control buildings, but the concentrations were significantly higher in the mould-damaged buildings. These genera included Aspercillus penicillioides, Engyodontium, Aspergillus sydowii, Wallemia sebi, Aspergillus fumigatus, Eurotium herbariorum, Aspergillus nidulans, Phoma, Arthrographis, Aspergillus ustus, Aureobasidium and Geomyces pannorus. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in the mould-damaged buildings.
of indicator fungi (Samson, 1994) were detected: A. versicolor, Trichoderma, Exophiala, Phialophora, Ulocladium, Stachybotrys, Fusarium, A. fumigatus and yeasts. A. versicolor occurred in more than 25% of the samples. Other fungi that were detected in greater concentrations in damaged materials were A. sydowii, Cladosporium, yeasts, Acremoniun and sterile. The other identified fungi were detected in o15% of the material samples. 4. Discussion
3.2. Settled dust samples The prevalence of fungi in the settled dust samples is indicated in Tables 2 (DG18 agar) and 3 (MEA agar). The tables show that the predominant fungi in the settled dust samples were Penicillium, yeasts, sterile and Cladosporium in both the mould-damaged and control buildings. The semi-quantitative amount of Penicillium was higher (po0.001) in the mould-damaged buildings than in the control buildings. A. versicolor, Aureobasidium, Phialophora and Trichoderma viride occurred more often in the samples collected from the moulddamaged buildings than in those from the control buildings. A. ochraceus was found only in settled dust samples from the mould-damaged buildings. 3.3. Material samples Penicillium species were the predominant fungi in the material samples (on both MEA and DG18). The following nine fungal genera or groups
Because fungi concentrations vary over a wide range, threshold values are difficult to determine (Gots et al., 2003). Much data on fungi concentrations and flora have been published with respect to home environments. For example, Miller et al. (1988) suggested that fungi concentrations should be below 150 cfu m3 in home environments. According to Finnish guidelines for urban or suburban residences (Reponen et al., 1992), spore concentrations exceeding 500 cfu m3 in the indoor air during subarctic winter, and bacteria concentrations of over 5000 cfu m3, indicate abnormal microbe sources indoors. The concentrations of viable fungal spores, especially in the indoor air of moisture-damaged offices, and also in schools and day-care centres, have been reported as being fairly low in comparison with the suggested guidelines (Reponen et al., 1994; Koskinen et al., 1995; Meklin et al., 1996; Lindroos et al., 1998; Lappalainen et al., 2001). In our study, special attention was paid to the differences in bacteria and fungi
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Table 2 Prevalence of fungi in the settled dust samples (DG18 agar) taken from the mould-damaged and control buildings
Penicillium Yeasts Sterile Cladosporium Aspergillus versicolor Rhizopus stolonifer Eurotium herbariorum Aspergillus sydowii Aureobasidium Phialophora Ulocladium Other fungi (6 species)
% of samples
% of samples
Mould-damaged buildings (47 samples)
Control buildings (126 samples)
+
++
+++
+
++
+++
34.0 38.3 23.4 21.3 12.8 8.5 8.5 4.3 4.3 4.3 4.3 o2.1
19.1 – – – – 2.1 – – – – – o2.1
2.1 – – – – – – – – – – –
23.0 15.1 13.5 13.5 4.8 3.2 2.4 1.6 1.6 1.6 1.6 o0.8
– 1.6 – – – – – – – – –
– – – – – – – – – – –
Penicillium Cladosporium Sterile Yeasts Alternaria Aspergillus versicolor Aureobasidium Rhizopus stolonifer Aspergillus sydowii Acremonium Chrysonilia sitophila Other fungi (4 species)
Incidence: + ¼ 1–9 cfu 100 cm2, ++ ¼ 10–49 cfu 100 cm2, +++ ¼ 449 cfu 100 cm2. po0.001 (chi-square test).
Table 3 Prevalence of fungi in the settled dust samples (MEA agar) taken from the mould-damaged and control buildings
Penicillium Yeasts Sterile Cladosporium Aspergillus versicolor Rhizopus stolonifer Exophiala Trichoderma viride Chaetomium globosum Aspergillus ochraceus Aspergillus sydowii Aureobasidium Other fungi (8 species)
% of samples
% of samples
Mould-damaged buildings (47 samples)
Control buildings (126 samples)
+
++
+++
+
++
+++
29.8 38.3 19.1 8.5 10.6 10.6 8.5 8.5 6.4 4.3 4.3 4.3 o2.1
17.0 – – 6.4 2.1 – – – – – – – –
2.1 – – – – – – – – – – – –
20.6 17.5 15.1 4.8 3.2 1.6 1.6 1.6 o0.8
– – – – – – – – –
– – – – – – – – –
Yeasts Penicillium Cladosporium Aspergillus versicolor Aureobasidium Chaetomium globosum Alternaria Chrysonilia sitophila Other fungi (16 species)
Incidence: + ¼ 1–9 cfu 100 cm2, ++ ¼ 10–49 cfu 100 cm2, +++ ¼ 449 cfu 100 cm2 (see Table 2). po0.001 (chi-square test).
concentrations between office work environments with and without mould damage. An abnormal range of microbe concentrations and mycoflora that can be associated with mould damage in office buildings were detected. According to the results, airborne fungi concentrations above 50 cfu m3 indicated abnormal microbe sources in modern office environments (i.e., those with efficient ventilation). In control offices, about 90% of the fungi
concentrations measured were below 15 cfu m3, the highest level being 45 cfu m3. Thus this normal maximum fungi concentration (50 cfu m3) is applicable to urban office buildings in subarctic climates when the measurements are performed with a six-stage impactor during winter. It has been recognised that the qualitative determination of microbes provides more information about possible abnormal microbe sources than
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merely concentrations of viable fungi. The following list of fungi and bacteria associated with water damage has been published by Samson (1994): Trichoderma, Exophiala, Phialophora, Ulocladium, Stachybotrys, Fusarium, Wallemia, A. versicolor, A. fumigatus, Actinobacteria, Gram-negative bacteria and yeasts (e.g., Rhodotorula and Sporobolomyces). Our study shows, however, that low concentrations of many indicator micro-organisms could also be found in the control buildings. In the study of Hyva¨rinen et al. (2001a), the total concentrations of viable fungi and the concentrations of Penicillium, Aspergillus, and A. versicolor were significantly higher in the residences with moisture problems than in the reference buildings. In another study, these authors found that yeasts and Penicillium were the most frequently detected fungi types in moist building materials (Hyva¨rinen et al., 2001b). Penicillium has been reported to be associated with moisture damage also in other studies (Li and Kendrick, 1995; Mahooti-Brooks et al., 2004). The findings agree with the results of this study (i.e., increased concentrations or occurrences of the Penicillium species were the commonest indicators of abnormal indoor sources of microbes, according to air, settled dust and material samples). Higher airborne concentrations of Aspergillus, Cladosporium, Penicillium, non-sporing fungi (including basidiomycetes) or yeasts have previously been observed in buildings with moisture damage or visible mould growth than in control buildings (Pasanen, 1992; Pasanen et al., 1992a; DeKoster and Thorne, 1995; Garrett et al., 1998). In our study, Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in indoor air and in settled dust in both the mould-damaged and control buildings. The airborne concentrations of Penicillium and yeasts were statistically significantly higher in the moulddamaged buildings than in the control buildings. Apart from these common fungi, A. versicolor, A. sydowii and Acremonium were the most predominant fungi in the material samples collected from the mould-damaged buildings. Penicillium is a typical indoor air fungus that may originate from building materials (e.g., Pasanen et al., 1992b). Thus substantial amounts of Penicillium can easily grow in wet materials. Of the non-sporing isolates, in addition to the Penicillium species, Aureobasidium, Acremonium and Sphaeropsidales are the commonest fungi found in damaged material samples (Hyva¨rinen et al., 2002).
The bacteria levels reported for residences have varied between 10 and 104 cfu m3 (Macher et al., 1991; Nevalainen et al., 1991; Reponen et al., 1992; DeKoster and Thorne, 1995; Rautiala et al., 1996; Ross et al., 2000; Pessi et al., 2002). In our study, the highest concentration of airborne bacteria measured in the control buildings was 540 cfu m3. Most of the buildings were equipped with a modern ventilation system with a design value for the outdoor airflow of 1.5 dm3 s1 m2 (Finnish Ministry of the Environment, 2003). On the basis of these findings, we agree that the highest normal level of bacteria in offices is 600 cfu m3. If this level is exceeded, the building conditions need to be evaluated. The result may indicate insufficient ventilation or abnormal sources of micro-organisms. Moreover, additional assessments may be necessary in cases when a concentration of 300 cfu m3 (90 percentile level) is exceeded. Thus far, the occurrence of Actinobacteria in indoor air has been found to be associated with the presence of water damage (Nevalainen et al., 1991). The airborne concentrations of viable Actinobacteria are usually low (o4–154 cfu m3) even in moulddamaged buildings in winter (Nevalainen et al., 1991; Rautiala et al., 1996; Lappalainen et al., 2001), and they have rarely been found in reference buildings (Nevalainen et al., 1991). In our study, very low concentrations of Actinobacteria (geometric mean (GM) 3 cfu m3) were detected in the control buildings, but the concentrations in the mould-damaged buildings were about five times higher (GM 16 cfu m3). The sampling of settled dust has proved to be useful in characterising the microbial status of buildings (Gravesen, 1978). Chao et al. (2003) reported that viable fungal propagules accumulate in dust and are likely to have fewer variables than airborne fungi. In addition, Hyva¨rinen et al. (1993) and Niemeier et al. (2006) reported that more fungi species were identified by air sampling than by swab sampling. In our study, we found similar fungi in the air samples, swab samples from settled dust, and material samples. All of these methods complement each other and may be useful in specific cases. The advantage of cultivation methods is that they enable the identification of major fungi species, the equipment for analyses is simple, and there is a great deal of reference data. However, cultivation methods also have some weaknesses. They are slow and always selective, and therefore lead to underestimates of total fungi counts and overestimates of the
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most tolerant species. It has been reported that airborne culturable fungi comprise only 0.002–25% of total spore concentrations, and therefore the use of viable measurements may lead to significant error in calculations of total exposure (Pasanen, 2001). Another important error is variation in fungi concentrations over time (and space). As for other error sources, the error range of samplers and pumps, the transport of samples and human errors with the sampling and analyses should be mentioned. The presence of spore aggregates increases the variation of the counting processes, although, in our study, the correction table for multiple impaction was used. The total error is a sum of systematic and random errors (Lappalainen, 2002). New DNA techniques may revolutionise the environmental assessment of micro-organisms in the future (Pasanen, 2001), but thus far, viable spore methods are widely used for indoor air environments. The Finnish guidelines for the microbial quality of indoor air in residences are based on the concentrations of viable spores. The guidelines are also used for identifying abnormal indoor sources of fungi in office buildings and, therefore, may be misleading in many cases. This study offers some reference values for indoor office environments in subarctic climates. On the basis of our results, we suggest that additional investigations are needed if the bacteria levels exceed 600 cfu m3 or the fungal spore levels exceed 50 cfu m3 in the indoor air of office buildings during winter. Elevated fungi concentrations may indicate hidden mould damage in structures, while bacteria concentrations may be associated with insufficient ventilation or abnormal indoor air sources of micro-organisms in office buildings. The recommended levels should not be used for evaluating health risks. Acknowledgements The authors warmly thank Mr. Henri Riuttala for his skilful statistical advice, the indoor air researchers of FIOH Uusimaa for their excellent field investigations and Professor Anna-Liisa Pasanen for her valuable comments and advice.
References Andersen, A.A., 1958. New sampler for the collection, sizing and enumeration of viable inhaled particles. Journal of Bacteriology 76, 471–484.
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Bornehag, C.-G., Blomquist, G., Gyntelberg, F., Ja¨rvholm, B., Malmberg, P., Nordvall, L., Nielsen, A., Pershagen, G., Sundell, J., 2001. Dampness in buildings and health. Indoor Air 11, 72–86. Brunekreef, B., Dockery, D.W., Speizer, F.E., Ware, J.H., Spengler, J.D., Ferris, B.G., 1989. Home dampness and respiratory morbidity in children. American Review of Respiratory Disease 140, 1363–1367. Chao, H.J., Schwartz, J., Milton, D.K., Burge, H.A., 2003. The work environment and workers’ health in four large office buildings. Environmental Health Perspectives 111, 1242–1248. DeKoster, J.A., Thorne, P.S., 1995. Bioaerosol concentrations in noncomplaint, complaint and intervention homes in the Midwest. American Industrial Hygiene Association Journal 56, 573–580. Finnish Ministry of the Environment (YM, Ympa¨risto¨ministerio¨), 2003. Suomen rakentamisma¨a¨ra¨yskokoelma, Rakennusten sisa¨ilmasto ja ilmanvaihto, ma¨a¨ra¨ykset ja ohjeet (National Building Code of Finland, D2. Indoor climate and ventilation in buildings, regulations and guidelines). Finnish Ministry of the Environment, Helsinki (in Finnish). Garrett, M.H., Rayment, P.R., Hooper, M.A., Abramson, M.J., Hooper, B.M., 1998. Indoor airborne fungal spores, house dampness and associations with environmental factors and respiratory health in children. Clinical and Experimental Allergy 28 (4), 459–467. Gots, R.E., Layton, N.J., Pirages, S.W., 2003. Indoor health: background levels of fungi. American Industrial Hygiene Association Journal 64, 427–438. Gravesen, S., 1978. Identification and prevalence of culturable mesophilic microfungi in house dust from 100 Danish homes. Allergy 33, 268–272. Haahtela, T., Reijula, K., 1997. Sisa¨ilman terveyshaitat ja ehdotukset niiden va¨henta¨miseksi. AT-Julkaisutoimisto Oy, Helsinki (in Finnish). Hodgson, M.J., Morey, P., Leung, W.Y., Morrow, L., Miller, D., Jarvis, B.B., Robbins, H., Halsey, J.F., Storey, E., 1998. Building-associated pulmonary disease from exposure to Stachybotrys chartarum and Aspergillus versicolor. Journal of Occupational Environmental Medicine 40, 241–249. Horner, E.W., Worthan, A.G., Morey, P.R., 2004. Air- and dustborne mycoflora in houses free of water damage and fungal growth. Applied and Environmental Microbiology 70 (11), 6394–6400. Hyva¨rinen, A., Reponen, T., Husman, T., Ruuskanen, J., Nevalainen, A., 1993. Characterizing mould problem buildings-concentrations and flora of viable fungi. Indoor Air 3, 337–343. Hyva¨rinen, A., Vahteristo, M., Meklin, T., Jantunen, M., Nevalainen, A., Moschandreas, D., 2001a. Temporal and spatial variation of fungal concentrations in indoor air. Aerosol Science and Technology 35, 688–695. Hyva¨rinen, A., Reponen, T., Husman, T., Nevalainen, A., 2001b. Comparison of the indoor air quality in mould damaged and reference buildings in a subarctic climate. European Journal of Public Health 9 (3), 133–139. Hyva¨rinen, A., Meklin, T., Vepsa¨la¨inen, A., Nevalainen, A., 2002. Fungi and Actinobacteria in moisture-damaged building materials-concentrations and diversity. International Biodeterioration and Biodegradation 49, 27–37.
ARTICLE IN PRESS 6806
H. Salonen et al. / Atmospheric Environment 41 (2007) 6797–6807
Koivisto, J., Ja¨a¨skela¨inen, E., Nevalainen, A., 1996. Asuinkerrostalojen kosteusvauriot-yleisyyden ja korjauskustannusten selvitta¨minen (in Finnish). Kuopio: Kansanterveyslaitoksen julkaisuja B9/1996. Koskinen, O., Husman, T., Hyva¨rinen, A., Reponen, T., 1995. Respiratory symptoms and infections among children in day care center with mould problems. Indoor Air 5, 3–9. Lappalainen, S., 2002. Occupational exposure to fungi and methods to assess the exposure. Doctoral dissertation, Kuopio University Publications C. Natural End Environmental Sciences, vol. 141. University of Kuopio, Kuopio, Finland. Lappalainen, S., Ka¨hko¨nen, E., Loikkanen, P., Paloma¨ki, E., Lindroos, O., Reijula, K., 2001. Evaluation of priorities for repairing in moisture-damaged school buildings in Finland. Building and Environment 36, 981–986. Lehtonen, M., Reponen, T., Nevalainen, A., 1993. Everyday activities and variation of fungal spore concentrations in indoor air. International Biodeterioration and Biodegradation 31, 25–39. Li, D., Kendrick, B., 1995. Indoor aeromycota in relation to residential characteristics and allergic symptoms. Mycopathologia 131, 149–157. Lindroos, O., Lappalainen, S., Reijula, K., 1998. Concentrations of viable spores of fungi and a ventilation channels. In: Proceedings of Third International Conference on Bioaerosols, Fungi and Mycotoxins, 23–25 September 1998, Saratoga Springs, New York, USA. Macher, J.M., Huang, F.-Y., Flores, M., 1991. A two-year study of microbiological indoor air quality in a new apartment. Archives of Environmental Health 46, 25–29. Mahmoudi, M., Gershwin, M.E., 2000. Sick building syndrome. III. Stachybotrys chartarum. Journal of Asthma 37, 191–198. Mahooti-Brooks, N., Storey, E., Yang, C., Simcox, N.J., Turner, W., Hodgson, M., 2004. Characterization of mold and moisture indicators in the home. Journal of Occupational and Environmental Hygiene 1, 826–839. Meklin, T., Taskinen, T., Nevalainen, A., 1996. Microbial characterization of four school buildings. In: Proceedings of Indoor Air’96. The Seventh International Conference on Indoor Air Quality and Climate, vol. 2. Nagoya, Japan, pp. 1083–1088. Miller, J.D., Laflamme, A.M., Sobol, Y., Lafontaine, P., Greenhalg, R., 1988. Fungi and fungal products in some Canadian houses. International Biodeterioration 24, 103–120. Nevalainen, A., Seuri, M., 2005. Of microbes and men. Indoor Air 15 (9), 58–64. Nevalainen, A., Pasanen, A.-L., Niininen, M., Reponen, T., Kalliokoski, P., Jantunen, M.J., 1991. The indoor air quality in Finnish homes with mould problems. Environment International 17, 299–302. Nevalainen, A., Partanen, P., Ja¨a¨skela¨inen, E., Hyva¨rinen, A., Koskinen, O., Meklin, T., Vaahteristo, M., Koivisto, J., Husman, T., 1998. Prevalence of moisture problems in Finnish houses. Indoor Air 4, 45–49. Niemeier, R.T., Satheesh, K., Sivasubramani, K., Reponen, T., Grinshpun, S.A., 2006. Assessment of fungal contamination in mouldy homes: comparison of different methods. Journal of Occupational and Environmental Hygiene 3, 262–273. Pasanen, A.-L., 1992. Airborne mesophilic fungal spores in various residential environments. Atmospheric Environment 26A (16), 2861–2868.
Pasanen, A.-L., 2001. A review: fungal exposure assessment in indoor environments. Indoor Air 11, 87–98. Pasanen, A.-L., Niininen, M., Kalliokoski, P., Nevalainen, A., Jantunen, M.J., 1992a. Airborne Cladosporium and other fungi in damp versus reference residences. Atmospheric Environment 26B (1), 117–120. Pasanen, A.-L., Juutinen, T., Jantunen, M.J., Kalliokoski, P., 1992b. Occurrence and moisture requirements of microbial growth in building materials. International Biodeterioration and Biodegradation 30, 273–283. Peat, J.K., Dickerson, J., Li, J., 1998. Effects of damp and mould in the home on respiratory health: a review of the literature. Allergy 53, 120–128. Pessi, A.-M., Suonketo, J., Pentti, M., Kurkilahti, M., Peltola, K., Rantio-Lehtima¨ki, A., 2002. Microbial growth inside insulated external walls as an indoor air biocontamination source. Applied and Environmental Microbiology 68 (2), 963–967. Platt, S.D., Martin, C.D., Hunt, S.M., Lewis, C.W., 1989. Damp housing, mould growth, and symptomatic health state. British Medical Journal 298, 1673–1678. Rao, C.Y., Burge, H.A., Chang, J.C., 1996. Review of quantitative standards and guidelines for fungi in indoor air. Journal of the Air and Waste Management Association 46, 899–908. Rautiala, S., Reponen, T., Hyva¨rinen, A., Nevalainen, A., Husman, T., Vehvila¨inen, A., Kalliokoski, P., 1996. Exposure to airborne microbes during the repair of moldy buildings. American Industrial Hygiene Association Journal 57, 279–284. Reponen, T., Nevalainen, A., Jantunen, M., Pellikka, M., Kalliokoski, P., 1992. Normal range criteria for indoor air bacteria and fungal spores in a subarctic climate. Indoor Air 2, 26–31. Reponen, T., Hyva¨rinen, A., Ruuskanen, J., Raunemaa, T., Nevalainen, A., 1994. Comparison of concentrations and size distributions of fungal spores in buildings with and without mould problems. Journal of Aerosol Science 25, 1595–1603. Ross, M.A., Curtis, L., Scheff, P.A., 2000. Association of asthma symptoms and severity with indoor bioaerosols. Allergy 55, 705–711. Ruotsalainen, R., Jaakkola, N., Jaakkola, J.J., 1995. Dampness and moulds in day-care centers as an occupational health problem. International Archives of Occupational and Environmental Health 66 (6), 369–374. Samson, R.A., 1994. Recommendations. In: Samson, R.A., Flannigan, B., Flannigan, M.E., Verhoeff, A.P., Adan, O., Hoekstra, E.S. (Eds.), Health Implications of Fungi in Indoor Environments. Elsevier, Amsterdam, The Netherlands, pp. 529–538. Seuri, M., Paldanius, M., Leinonen, M., Roponen, M., Hirvonen, M.-R., Saikku, P., 2005. Chlamydophila pneumoniae antibodies in office workers with and without inflammatory rheumatic diseases in a moisture-damaged building. European Journal of Clinical and Microbiological Infectious Diseases 24, 236–237. Spengler, J., Neas, L., Nakai, S., et al., 1994. Respiratory symptoms and housing characteristics. Indoor Air 4, 72–82. Statistics Finland, 2006. Tyo¨voimatilasto 2005: vuosikatsaus, ennakkotietoja. Tyo¨markkinat. Statistics Finland, Helsinki. Taskinen, T., Hyva¨rinen, A., Meklin, T., 1999. Asthma and respiratory infections in school children with special reference
ARTICLE IN PRESS H. Salonen et al. / Atmospheric Environment 41 (2007) 6797–6807 to moisture and mould problems in the school. Acta Paediatria 88, 1373–1379. Teijonsalo, J., Kurnitski, J., Miettinen, P., Ruotsalainen, R., 1991. Luokkahuoneiden ilmanlaatu-alustava kartoitus (in Finnish). Paper presented at the Sisa¨ilmasto-ja ilmastointiseminaari, Espoo. Trout, D., Bernstein, J., Martinez, K., Biagini, R., Wallingford, K., 2001. Bioaerosol lung damage in a worker with repeated exposure to fungi in a water-damaged building. Environmental Health Perspectives 109, 641–644.
6807
Tuomisto, J., 2000. SYTTY Sytyke Suomen ympa¨risto¨terveyden tutkimukselle. In: Va¨likyla¨, T. (Ed.), Ympa¨risto¨ ja terveys, vol. 6, pp. 5–9. Wieslander, G., Norback, D., Nordstrom, K., Walinder, R., Venge, P., 1999. Nasal and ocular symptoms, tear film stability and biomarkers in nasal lavage, in relation to building-dampness and building design in hospitals. International Archives of Occupational and Environmental Health 72, 451–461.
Atmospheric Environment 41 (2007) 6797–6807 www.elsevier.com/locate/atmosenv
Fungi and bacteria in mould-damaged and non-damaged office environments in a subarctic climate Heidi Salonen, Sanna Lappalainen, Outi Lindroos, Riitta Harju, Kari Reijula Finnish Institute of Occupational Health, Arinatie 3 A, 00370 Helsinki, Finland Received 18 October 2006; received in revised form 17 April 2007; accepted 20 April 2007
Abstract The fungi and bacterial levels of the indoor air environments of 77 office buildings were measured in winter and a comparison was made between the buildings with microbe sources in their structures and those without such sources. Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in the indoor air and in settled dust, in both the mould-damaged and control buildings. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in environmental samples from the mould-damaged buildings. Some other fungi, with growth requiring of water activity, aw, above 0.85, occurred in both the reference and mould-damaged buildings, but such fungi were commoner in the latter type of buildings. The airborne concentrations of Penicillium, Aspergillus versicolor and yeasts were the best indicators of mould damage in the buildings studied. Penicillium species and A. versicolor were also the most abundant fungi in the material samples. This study showed that the fungi concentrations were very low (2–45 cfu m3 90% of the concentrations being o15 cfu m3) in the indoor air of the normal office buildings. Although the concentration range of airborne fungi was wider for the mould-damaged buildings (2–2470 cfu m3), only about 20% of the samples exceeded 100 cfu m3. The concentrations of airborne bacteria ranged from 12 to 540 cfu m3 in the control buildings and from 14 to 1550 cfu m3 in the mould-damaged buildings. A statistical analysis of the results indicated that bacteria levels are generally o600 cfu m3 in office buildings in winter and fungi levels are o50 cfu m3. These normal levels are applicable to subarctic climates for urban, modern office buildings when measurements are made using a six-stage impactor. These levels should not be used in evaluations of health risks, but elevated levels may indicate the presence of abnormal microbe sources in indoor air and a need for additional environmental investigations. r 2007 Elsevier Ltd. All rights reserved. Keywords: Fungi; Bacteria; Indoor air; Office building; Concentration
1. Introduction In Finland, more than 420,000 workers were employed in the office and administration sector in Corresponding author. Tel.: +358 304 742 937; fax: +358 9 506 108 7. E-mail address: Heidi.Salonen@ttl.fi (H. Salonen).
1352-2310/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2007.04.043
2005; 143,000 of these employees worked in the Helsinki area. The number of office workers has grown over the past few years (Central Statistical Office of Finland, 2006). Building-related moisture and mould damage are significant indoor air problems in Finland, as well as in other countries (Nevalainen et al., 1998; Brunekreef et al., 1989; Spengler et al., 1994). According to Finnish studies,
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moisture problems have been estimated to occur in over 50% of apartments, schools and day-care centres (Teijonsalo et al., 1991; Ruotsalainen et al., 1995; Koivisto et al., 1996; Nevalainen et al., 1998). Although estimates for office buildings are unavailable, moisture problems are obviously common also in these buildings since they have been built according to practices generally used for public buildings. It has been estimated that about 20,000–50,000 people in Finland experience symptoms associated with exposure to micro-organisms in water-damaged homes and workplaces (Haahtela and Reijula, 1997; Tuomisto, 2000). Moisture problems leading to microbe growth in the structures of buildings (Brunekreef et al., 1989; Hodgson et al., 1998; Platt et al., 1989; Taskinen et al., 1999; Wieslander et al., 1999; Mahmoudi and Gershwin 2000; Trout et al., 2001) and exposure to fungi from these sources may cause adverse health effects such as respiratory symptoms (coughing, wheezing), rhinitis, asthma, tiredness and headache (Peat et al., 1998; Bornehag et al., 2001). The causal relationship between damp housing and illness is still unclear (Garrett et al., 1998; Peat et al., 1998; Seuri et al., 2005). The causes of the health effects may be associated with complex interactions between bacteria and fungi and environmental growth substrates and other micro-organisms that lead to a wide variety of exposures (Nevalainen and Seuri, 2005). Currently, there are no generally accepted or suitable numerical ‘standards’ or official ‘criteria’ for acceptable concentrations of fungi and bacteria (Rao et al., 1996; Horner et al., 2004). Some of the proposed quantitative guidelines or standards are based mainly on domestic environments (Reponen et al., 1992). The home, however, differs in many ways from work or office environments. Home environments have sources of micro-organisms (e.g., cooking, firewood and pets) that are absent in the work environment (Lehtonen et al., 1993). In addition, technical features, such as ventilation systems, differ in dwellings and public buildings. Thus, it is obvious that a higher background level of fungi and bacteria exists in domestic environments than in office environments (industrial work environments excluded). Although there are no dose–response data available for use as a reference, microbe measurements are often used to describe the general quality of indoor air. In addition, fungi, with water activity, aw, above 0.85, as a growth requirement, have been
regarded as indicator organisms for the presence of moisture problems (Samson, 1994). Therefore, measurements of fungi and Actinobacteria are often used to reveal mould problems in buildings. There are very few data available on the range of microbe levels in normal office environments in Europe. This study presents the wintertime concentrations of fungi and bacteria, as well as fungal flora in moulddamaged and control office buildings in a subarctic climate. These findings can be used as reference values when abnormal indoor microbe sources are assessed for such a climate. 2. Materials and methods 2.1. Buildings and moisture investigation This study included a total of 77 office buildings in Southern Finland. All of the buildings were selected from the database of the Finnish Institute of Occupational Health (FIOH), Helsinki. Experienced construction engineers carried out inspections of the buildings for damage caused by moisture and mould. An inspection included an interview of building maintenance and management personnel and workers, a survey of the construction drawings, an inspection for signs of moisture and mould, and the opening of structures if needed. Microbe growth in the structures was primarily verified with microbe analyses. A surface moisture indicator (Tramex Moisture Enco 11860 ME 5970165, Tramex Moisture Encounter Plus 31262 MEP 9057587) and a humidity and temperature indicator (HM141 (ID), serial no. X4440092) with a measurement sensor (HMP42, X5040003) were used to detect moisture. The inspection revealed dampness or visible mould damage in 34 of the 77 office buildings. These 34 buildings were selected as ‘mould-damaged buildings’ in this study. The 43 buildings without any dampness or visible mould damage were selected as ‘control buildings’. Environmental samples were taken to clarify hazard identification when the results of a walk-through inspection revealed no significant moisture or mould construction damage (damaged area p1 m2) in the moulddamaged buildings. Settled dust samples were collected from all of the control buildings, and indoor air samples were collected from 20 of the buildings. The office buildings represented the typical Finnish urban style, and most of them had a concrete framework, flat roof and several floors.
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Altogether 86% of the buildings were equipped with supply and exhaust air ventilation systems; the rest had only an exhaust air system or natural ventilation. Samples of indoor air (34 buildings), settled dust (55 buildings) and building material (33 buildings) were collected from the buildings during the winter (November–March) within a period of 5 years. 2.2. Airborne fungi samples Indoor air samples of airborne fungi were collected from 14 of the 34 mould-damaged buildings (46 samples) and from 20 of the 43 control buildings (56 samples) with the use of an Andersen six-stage cascade impactor and a volume flow rate of 28.3 l min1 (Andersen, 1958). All of the samples were taken at a height of about 1.5 m, and the sampling time was 15 min. The samples were collected on 2% malt extract agar (MEA) and 18dichloran glycerol agar (DG18) for fungi and tryptone glucose yeast agar (TYG) for bacteria. The plates were incubated at 25 1C for 7 days (14 days for Actinobacteria). Fungi were identified at the genus/species/type level with the use of a light microscope. The air concentrations of fungi and bacteria were expressed as colony-forming units (cfu) m3. No outdoor air samples were taken because outdoor air levels of fungi and Actinobacteria are very low in subarctic climates during winter, and thus outdoor air has a negligible impact on the micro-organism levels of indoor air (Reponen et al., 1992). 2.3. Settled dust samples Dust samples from 55 buildings (47 settled dust samples from 15 mould-damaged buildings and 126 samples from 40 control buildings) were collected from horizontal surfaces (e.g., book shelves), at a height of about 1.5 m, over a 2-week period during normal office activities. The settled dust samples indicated somewhat cumulated air samples. Samples were taken with a sterile moisture swab from a sampling area of 100 cm2 and directly cultivated on MEA and DG18 for fungi and on TYG for Actinobacteria. The samples were incubated at 25 1C for 7 days (14 days for Actinobacteria), after which the fungi were identified according to the previously described method. The results were expressed according to the following semi-quantitative scale:
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+ ¼ 1–9 cfu 100 cm2; ++ ¼ 10–49 cfu 100 cm2; and +++ ¼ 449 cfu 100 cm2. 2.4. Material samples For the microbe analyses, the material samples were collected from different types of building materials (wood, gypsum boards, mineral insulation materials, paints, glues, etc.) in 23 mould-damaged buildings (70 samples). The micro-organisms were extracted from the material samples (weight about 10 g) into sterile Tween buffer solution with dilutions of 101–105. Fungi were determined on MEA and DG18 agar plates, and TYG agar plates were used for bacteria. The samples were incubated at 25 1C for 7 days (14 days for Actinobacteria); the fungi were identified according to the previously described method. The concentrations of fungi and bacteria in the material samples were expressed as colony-forming units (cfu) g1. 2.5. Statistical analysis Statistical tests were carried out using the SAS program package (version 9.1, SAS Inc., Cary, NC, USA). The Kolmogorov–Smirnov test was applied to check the normality of the concentration distributions (three agar plate types: MEA, DG18 and TYG). The distribution of the bacteria concentrations was lognormal, but the fungi concentrations were not. Therefore, upper limits based on a lognormal distribution were not used. Instead, the distributions were illustrated using the Box and Whisker plot diagram and the percentiles of the distributions. The differences in the distributions between the concentrations of Penicillium in the settled dust samples were tested with the chi-square test. The differences in the distributions between the mould-damaged and control buildings were tested with the Wilcoxon rank-sum test (Fig. 1). The statistical significance of the differences in the different fungal genera groups were calculated between the mould-damaged and control buildings (Figs. 2 and 3). 3. Results 3.1. Indoor air samples The indoor air concentrations of fungi spores and bacteria in the mould-damaged and control buildings are presented in Fig. 1. The median fungi
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6800
10000
cfu/m3
1000
100
10
1 DG-18
DG-18
MEA
MEA
moulddamaged buildings
control buildings
moulddamaged buildings
control buildings
Bacteria (TYG)
Bacteria (TYG)
moulddamaged buildings
control buildings
Fig. 1. Median spore concentrations of fungi and bacteria for the indoor air of mould-damaged (46 samples) and control (56 samples) buildings. The figure also shows the minimum, maximum and quartiles of the distributions.
% 0
20
40
60
80
100
*** Penicillium * Yeasts Cladosporium * Sterile ** Aspergillus versicolor Aspergillus penicillioides Engyodontium Aspergillus sydowii Wallemia sebig * Paecilomyces variotii * Rhizopus stolonifer Aspergillus fumigatus Eurotium herbariorum * Aspergillus niger Aspergillus ochraceus Other fungi (13 species) <5 %
Mould-damaged buildings Control buildings
Fig. 2. Prevalence of 29 different fungal genera or groups found in the indoor air of the mould-damaged and control buildings (cultivated on DG18 agar): *po0.05, **po0.01, ***po0.001.
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% 0
20
40
60
80
100
** Penicillium Sterile Yeasts Cladosporium ** Aspergillus versicolor * Aspergillus fumigatus Arthrographis Engyodontium * Acremonium Aspergillus sydowii Aspergillus ochraceus Other fungi (22 species) <5 %
Mould-damaged buildings Control buildings
Fig. 3. Prevalence of 32 different fungal genera or groups found in the air samples from the mould-damaged and control buildings (cultivated on MEA agar): *po0.05, **po0.01, ***po0.001.
concentrations were statistically significantly higher (DG18: po0.001; MEA: po0.001) in the moulddamaged buildings than in the control buildings. Such a clear difference was not detected for the bacteria concentrations because the concentration range was greater for the mould-damaged buildings than for the control buildings. Actinobacteria were detected in only 34% of the indoor air samples. The median concentration range was clearly greater (po0.001) for Actinobacteria in the moulddamaged buildings than for Actinobacteria in the control buildings, the average values being 16 and 3 cfu m3, respectively. The results are presented in more detail in Table 1. They show that 90% of the fungi concentrations in the control buildings were o15 cfu m3, whereas, in the mould-damaged buildings, 90% of the concentrations were o210 cfu m3 and 70% were o55 cfu m3. The geometric mean of the fungi counts was about six-fold higher in the moulddamaged buildings than in the control buildings. The fungi concentration of 100 cfu m3 was exceeded in only about 20% of the air samples from the mould-damaged buildings. The bacteria concentrations were higher in all of the buildings than
the fungi concentrations were. Altogether 90% of the bacteria concentrations were o309 cfu m3 in the control buildings and o584 cfu m3 in the mould-damaged buildings. The maximum bacteria concentration in the mould-damaged buildings was about 2.9-fold greater than that of the control buildings. The prevalence of fungal genera or groups in comparison with the total viable spore count is shown in Figs. 2 and 3 for the mould-damaged and control buildings. The commonest fungi in both the mould-damaged and control buildings were Penicillium, yeasts, Cladosporium, non-sporing isolates and Aspergillus versicolor. The occurrence of airborne fungal spores in the mould-damaged and control buildings differed significantly (po0.05) for seven species on DG18 agar and five species on MEA agar. The concentrations of Penicillium, A. versicolor and yeasts indicated the presence of mould damage in the buildings studied (po0.001). The median concentration (arithmetic average for the DG18 and MEA samples, respectively) of A. versicolor was 61–66 cfu m3 for the moulddamaged buildings and 2–5 cfu m3 for the control buildings. Several fungal genera were detected in
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Table 1 Basic statistics and percentiles for the fungal and bacterial concentrations in the mould-damaged (n ¼ 46) and control buildings (n ¼ 56) Fungi (DG18) Mould-damaged buildings
Control buildings
Mould-damaged buildings
Bacteria (TYG) Control buildings
Mould-damaged buildings
Control buildings
22
4
20
3
122
62
6
3
6
3
4
5
24 33 43 73 208 2468
5 5 7 12 15 45
21 31 54 94 199 2431
2 5 7 9 14 26
114 209 264 348 582 1551
80 118 156 207 309 536
Geometric mean (cfu m3) Geometric S.D. (cfu m3) Percentiles (cfu m3) Median P60 P70 P80 P90 Maximum
Fungi (MEA)
S.D.: standard deviation.
both the damaged and control buildings, but the concentrations were significantly higher in the mould-damaged buildings. These genera included Aspercillus penicillioides, Engyodontium, Aspergillus sydowii, Wallemia sebi, Aspergillus fumigatus, Eurotium herbariorum, Aspergillus nidulans, Phoma, Arthrographis, Aspergillus ustus, Aureobasidium and Geomyces pannorus. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in the mould-damaged buildings.
of indicator fungi (Samson, 1994) were detected: A. versicolor, Trichoderma, Exophiala, Phialophora, Ulocladium, Stachybotrys, Fusarium, A. fumigatus and yeasts. A. versicolor occurred in more than 25% of the samples. Other fungi that were detected in greater concentrations in damaged materials were A. sydowii, Cladosporium, yeasts, Acremoniun and sterile. The other identified fungi were detected in o15% of the material samples. 4. Discussion
3.2. Settled dust samples The prevalence of fungi in the settled dust samples is indicated in Tables 2 (DG18 agar) and 3 (MEA agar). The tables show that the predominant fungi in the settled dust samples were Penicillium, yeasts, sterile and Cladosporium in both the mould-damaged and control buildings. The semi-quantitative amount of Penicillium was higher (po0.001) in the mould-damaged buildings than in the control buildings. A. versicolor, Aureobasidium, Phialophora and Trichoderma viride occurred more often in the samples collected from the moulddamaged buildings than in those from the control buildings. A. ochraceus was found only in settled dust samples from the mould-damaged buildings. 3.3. Material samples Penicillium species were the predominant fungi in the material samples (on both MEA and DG18). The following nine fungal genera or groups
Because fungi concentrations vary over a wide range, threshold values are difficult to determine (Gots et al., 2003). Much data on fungi concentrations and flora have been published with respect to home environments. For example, Miller et al. (1988) suggested that fungi concentrations should be below 150 cfu m3 in home environments. According to Finnish guidelines for urban or suburban residences (Reponen et al., 1992), spore concentrations exceeding 500 cfu m3 in the indoor air during subarctic winter, and bacteria concentrations of over 5000 cfu m3, indicate abnormal microbe sources indoors. The concentrations of viable fungal spores, especially in the indoor air of moisture-damaged offices, and also in schools and day-care centres, have been reported as being fairly low in comparison with the suggested guidelines (Reponen et al., 1994; Koskinen et al., 1995; Meklin et al., 1996; Lindroos et al., 1998; Lappalainen et al., 2001). In our study, special attention was paid to the differences in bacteria and fungi
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Table 2 Prevalence of fungi in the settled dust samples (DG18 agar) taken from the mould-damaged and control buildings
Penicillium Yeasts Sterile Cladosporium Aspergillus versicolor Rhizopus stolonifer Eurotium herbariorum Aspergillus sydowii Aureobasidium Phialophora Ulocladium Other fungi (6 species)
% of samples
% of samples
Mould-damaged buildings (47 samples)
Control buildings (126 samples)
+
++
+++
+
++
+++
34.0 38.3 23.4 21.3 12.8 8.5 8.5 4.3 4.3 4.3 4.3 o2.1
19.1 – – – – 2.1 – – – – – o2.1
2.1 – – – – – – – – – – –
23.0 15.1 13.5 13.5 4.8 3.2 2.4 1.6 1.6 1.6 1.6 o0.8
– 1.6 – – – – – – – – –
– – – – – – – – – – –
Penicillium Cladosporium Sterile Yeasts Alternaria Aspergillus versicolor Aureobasidium Rhizopus stolonifer Aspergillus sydowii Acremonium Chrysonilia sitophila Other fungi (4 species)
Incidence: + ¼ 1–9 cfu 100 cm2, ++ ¼ 10–49 cfu 100 cm2, +++ ¼ 449 cfu 100 cm2. po0.001 (chi-square test).
Table 3 Prevalence of fungi in the settled dust samples (MEA agar) taken from the mould-damaged and control buildings
Penicillium Yeasts Sterile Cladosporium Aspergillus versicolor Rhizopus stolonifer Exophiala Trichoderma viride Chaetomium globosum Aspergillus ochraceus Aspergillus sydowii Aureobasidium Other fungi (8 species)
% of samples
% of samples
Mould-damaged buildings (47 samples)
Control buildings (126 samples)
+
++
+++
+
++
+++
29.8 38.3 19.1 8.5 10.6 10.6 8.5 8.5 6.4 4.3 4.3 4.3 o2.1
17.0 – – 6.4 2.1 – – – – – – – –
2.1 – – – – – – – – – – – –
20.6 17.5 15.1 4.8 3.2 1.6 1.6 1.6 o0.8
– – – – – – – – –
– – – – – – – – –
Yeasts Penicillium Cladosporium Aspergillus versicolor Aureobasidium Chaetomium globosum Alternaria Chrysonilia sitophila Other fungi (16 species)
Incidence: + ¼ 1–9 cfu 100 cm2, ++ ¼ 10–49 cfu 100 cm2, +++ ¼ 449 cfu 100 cm2 (see Table 2). po0.001 (chi-square test).
concentrations between office work environments with and without mould damage. An abnormal range of microbe concentrations and mycoflora that can be associated with mould damage in office buildings were detected. According to the results, airborne fungi concentrations above 50 cfu m3 indicated abnormal microbe sources in modern office environments (i.e., those with efficient ventilation). In control offices, about 90% of the fungi
concentrations measured were below 15 cfu m3, the highest level being 45 cfu m3. Thus this normal maximum fungi concentration (50 cfu m3) is applicable to urban office buildings in subarctic climates when the measurements are performed with a six-stage impactor during winter. It has been recognised that the qualitative determination of microbes provides more information about possible abnormal microbe sources than
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merely concentrations of viable fungi. The following list of fungi and bacteria associated with water damage has been published by Samson (1994): Trichoderma, Exophiala, Phialophora, Ulocladium, Stachybotrys, Fusarium, Wallemia, A. versicolor, A. fumigatus, Actinobacteria, Gram-negative bacteria and yeasts (e.g., Rhodotorula and Sporobolomyces). Our study shows, however, that low concentrations of many indicator micro-organisms could also be found in the control buildings. In the study of Hyva¨rinen et al. (2001a), the total concentrations of viable fungi and the concentrations of Penicillium, Aspergillus, and A. versicolor were significantly higher in the residences with moisture problems than in the reference buildings. In another study, these authors found that yeasts and Penicillium were the most frequently detected fungi types in moist building materials (Hyva¨rinen et al., 2001b). Penicillium has been reported to be associated with moisture damage also in other studies (Li and Kendrick, 1995; Mahooti-Brooks et al., 2004). The findings agree with the results of this study (i.e., increased concentrations or occurrences of the Penicillium species were the commonest indicators of abnormal indoor sources of microbes, according to air, settled dust and material samples). Higher airborne concentrations of Aspergillus, Cladosporium, Penicillium, non-sporing fungi (including basidiomycetes) or yeasts have previously been observed in buildings with moisture damage or visible mould growth than in control buildings (Pasanen, 1992; Pasanen et al., 1992a; DeKoster and Thorne, 1995; Garrett et al., 1998). In our study, Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in indoor air and in settled dust in both the mould-damaged and control buildings. The airborne concentrations of Penicillium and yeasts were statistically significantly higher in the moulddamaged buildings than in the control buildings. Apart from these common fungi, A. versicolor, A. sydowii and Acremonium were the most predominant fungi in the material samples collected from the mould-damaged buildings. Penicillium is a typical indoor air fungus that may originate from building materials (e.g., Pasanen et al., 1992b). Thus substantial amounts of Penicillium can easily grow in wet materials. Of the non-sporing isolates, in addition to the Penicillium species, Aureobasidium, Acremonium and Sphaeropsidales are the commonest fungi found in damaged material samples (Hyva¨rinen et al., 2002).
The bacteria levels reported for residences have varied between 10 and 104 cfu m3 (Macher et al., 1991; Nevalainen et al., 1991; Reponen et al., 1992; DeKoster and Thorne, 1995; Rautiala et al., 1996; Ross et al., 2000; Pessi et al., 2002). In our study, the highest concentration of airborne bacteria measured in the control buildings was 540 cfu m3. Most of the buildings were equipped with a modern ventilation system with a design value for the outdoor airflow of 1.5 dm3 s1 m2 (Finnish Ministry of the Environment, 2003). On the basis of these findings, we agree that the highest normal level of bacteria in offices is 600 cfu m3. If this level is exceeded, the building conditions need to be evaluated. The result may indicate insufficient ventilation or abnormal sources of micro-organisms. Moreover, additional assessments may be necessary in cases when a concentration of 300 cfu m3 (90 percentile level) is exceeded. Thus far, the occurrence of Actinobacteria in indoor air has been found to be associated with the presence of water damage (Nevalainen et al., 1991). The airborne concentrations of viable Actinobacteria are usually low (o4–154 cfu m3) even in moulddamaged buildings in winter (Nevalainen et al., 1991; Rautiala et al., 1996; Lappalainen et al., 2001), and they have rarely been found in reference buildings (Nevalainen et al., 1991). In our study, very low concentrations of Actinobacteria (geometric mean (GM) 3 cfu m3) were detected in the control buildings, but the concentrations in the mould-damaged buildings were about five times higher (GM 16 cfu m3). The sampling of settled dust has proved to be useful in characterising the microbial status of buildings (Gravesen, 1978). Chao et al. (2003) reported that viable fungal propagules accumulate in dust and are likely to have fewer variables than airborne fungi. In addition, Hyva¨rinen et al. (1993) and Niemeier et al. (2006) reported that more fungi species were identified by air sampling than by swab sampling. In our study, we found similar fungi in the air samples, swab samples from settled dust, and material samples. All of these methods complement each other and may be useful in specific cases. The advantage of cultivation methods is that they enable the identification of major fungi species, the equipment for analyses is simple, and there is a great deal of reference data. However, cultivation methods also have some weaknesses. They are slow and always selective, and therefore lead to underestimates of total fungi counts and overestimates of the
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most tolerant species. It has been reported that airborne culturable fungi comprise only 0.002–25% of total spore concentrations, and therefore the use of viable measurements may lead to significant error in calculations of total exposure (Pasanen, 2001). Another important error is variation in fungi concentrations over time (and space). As for other error sources, the error range of samplers and pumps, the transport of samples and human errors with the sampling and analyses should be mentioned. The presence of spore aggregates increases the variation of the counting processes, although, in our study, the correction table for multiple impaction was used. The total error is a sum of systematic and random errors (Lappalainen, 2002). New DNA techniques may revolutionise the environmental assessment of micro-organisms in the future (Pasanen, 2001), but thus far, viable spore methods are widely used for indoor air environments. The Finnish guidelines for the microbial quality of indoor air in residences are based on the concentrations of viable spores. The guidelines are also used for identifying abnormal indoor sources of fungi in office buildings and, therefore, may be misleading in many cases. This study offers some reference values for indoor office environments in subarctic climates. On the basis of our results, we suggest that additional investigations are needed if the bacteria levels exceed 600 cfu m3 or the fungal spore levels exceed 50 cfu m3 in the indoor air of office buildings during winter. Elevated fungi concentrations may indicate hidden mould damage in structures, while bacteria concentrations may be associated with insufficient ventilation or abnormal indoor air sources of micro-organisms in office buildings. The recommended levels should not be used for evaluating health risks. Acknowledgements The authors warmly thank Mr. Henri Riuttala for his skilful statistical advice, the indoor air researchers of FIOH Uusimaa for their excellent field investigations and Professor Anna-Liisa Pasanen for her valuable comments and advice.
References Andersen, A.A., 1958. New sampler for the collection, sizing and enumeration of viable inhaled particles. Journal of Bacteriology 76, 471–484.
6805
Bornehag, C.-G., Blomquist, G., Gyntelberg, F., Ja¨rvholm, B., Malmberg, P., Nordvall, L., Nielsen, A., Pershagen, G., Sundell, J., 2001. Dampness in buildings and health. Indoor Air 11, 72–86. Brunekreef, B., Dockery, D.W., Speizer, F.E., Ware, J.H., Spengler, J.D., Ferris, B.G., 1989. Home dampness and respiratory morbidity in children. American Review of Respiratory Disease 140, 1363–1367. Chao, H.J., Schwartz, J., Milton, D.K., Burge, H.A., 2003. The work environment and workers’ health in four large office buildings. Environmental Health Perspectives 111, 1242–1248. DeKoster, J.A., Thorne, P.S., 1995. Bioaerosol concentrations in noncomplaint, complaint and intervention homes in the Midwest. American Industrial Hygiene Association Journal 56, 573–580. Finnish Ministry of the Environment (YM, Ympa¨risto¨ministerio¨), 2003. Suomen rakentamisma¨a¨ra¨yskokoelma, Rakennusten sisa¨ilmasto ja ilmanvaihto, ma¨a¨ra¨ykset ja ohjeet (National Building Code of Finland, D2. Indoor climate and ventilation in buildings, regulations and guidelines). Finnish Ministry of the Environment, Helsinki (in Finnish). Garrett, M.H., Rayment, P.R., Hooper, M.A., Abramson, M.J., Hooper, B.M., 1998. Indoor airborne fungal spores, house dampness and associations with environmental factors and respiratory health in children. Clinical and Experimental Allergy 28 (4), 459–467. Gots, R.E., Layton, N.J., Pirages, S.W., 2003. Indoor health: background levels of fungi. American Industrial Hygiene Association Journal 64, 427–438. Gravesen, S., 1978. Identification and prevalence of culturable mesophilic microfungi in house dust from 100 Danish homes. Allergy 33, 268–272. Haahtela, T., Reijula, K., 1997. Sisa¨ilman terveyshaitat ja ehdotukset niiden va¨henta¨miseksi. AT-Julkaisutoimisto Oy, Helsinki (in Finnish). Hodgson, M.J., Morey, P., Leung, W.Y., Morrow, L., Miller, D., Jarvis, B.B., Robbins, H., Halsey, J.F., Storey, E., 1998. Building-associated pulmonary disease from exposure to Stachybotrys chartarum and Aspergillus versicolor. Journal of Occupational Environmental Medicine 40, 241–249. Horner, E.W., Worthan, A.G., Morey, P.R., 2004. Air- and dustborne mycoflora in houses free of water damage and fungal growth. Applied and Environmental Microbiology 70 (11), 6394–6400. Hyva¨rinen, A., Reponen, T., Husman, T., Ruuskanen, J., Nevalainen, A., 1993. Characterizing mould problem buildings-concentrations and flora of viable fungi. Indoor Air 3, 337–343. Hyva¨rinen, A., Vahteristo, M., Meklin, T., Jantunen, M., Nevalainen, A., Moschandreas, D., 2001a. Temporal and spatial variation of fungal concentrations in indoor air. Aerosol Science and Technology 35, 688–695. Hyva¨rinen, A., Reponen, T., Husman, T., Nevalainen, A., 2001b. Comparison of the indoor air quality in mould damaged and reference buildings in a subarctic climate. European Journal of Public Health 9 (3), 133–139. Hyva¨rinen, A., Meklin, T., Vepsa¨la¨inen, A., Nevalainen, A., 2002. Fungi and Actinobacteria in moisture-damaged building materials-concentrations and diversity. International Biodeterioration and Biodegradation 49, 27–37.
ARTICLE IN PRESS 6806
H. Salonen et al. / Atmospheric Environment 41 (2007) 6797–6807
Koivisto, J., Ja¨a¨skela¨inen, E., Nevalainen, A., 1996. Asuinkerrostalojen kosteusvauriot-yleisyyden ja korjauskustannusten selvitta¨minen (in Finnish). Kuopio: Kansanterveyslaitoksen julkaisuja B9/1996. Koskinen, O., Husman, T., Hyva¨rinen, A., Reponen, T., 1995. Respiratory symptoms and infections among children in day care center with mould problems. Indoor Air 5, 3–9. Lappalainen, S., 2002. Occupational exposure to fungi and methods to assess the exposure. Doctoral dissertation, Kuopio University Publications C. Natural End Environmental Sciences, vol. 141. University of Kuopio, Kuopio, Finland. Lappalainen, S., Ka¨hko¨nen, E., Loikkanen, P., Paloma¨ki, E., Lindroos, O., Reijula, K., 2001. Evaluation of priorities for repairing in moisture-damaged school buildings in Finland. Building and Environment 36, 981–986. Lehtonen, M., Reponen, T., Nevalainen, A., 1993. Everyday activities and variation of fungal spore concentrations in indoor air. International Biodeterioration and Biodegradation 31, 25–39. Li, D., Kendrick, B., 1995. Indoor aeromycota in relation to residential characteristics and allergic symptoms. Mycopathologia 131, 149–157. Lindroos, O., Lappalainen, S., Reijula, K., 1998. Concentrations of viable spores of fungi and a ventilation channels. In: Proceedings of Third International Conference on Bioaerosols, Fungi and Mycotoxins, 23–25 September 1998, Saratoga Springs, New York, USA. Macher, J.M., Huang, F.-Y., Flores, M., 1991. A two-year study of microbiological indoor air quality in a new apartment. Archives of Environmental Health 46, 25–29. Mahmoudi, M., Gershwin, M.E., 2000. Sick building syndrome. III. Stachybotrys chartarum. Journal of Asthma 37, 191–198. Mahooti-Brooks, N., Storey, E., Yang, C., Simcox, N.J., Turner, W., Hodgson, M., 2004. Characterization of mold and moisture indicators in the home. Journal of Occupational and Environmental Hygiene 1, 826–839. Meklin, T., Taskinen, T., Nevalainen, A., 1996. Microbial characterization of four school buildings. In: Proceedings of Indoor Air’96. The Seventh International Conference on Indoor Air Quality and Climate, vol. 2. Nagoya, Japan, pp. 1083–1088. Miller, J.D., Laflamme, A.M., Sobol, Y., Lafontaine, P., Greenhalg, R., 1988. Fungi and fungal products in some Canadian houses. International Biodeterioration 24, 103–120. Nevalainen, A., Seuri, M., 2005. Of microbes and men. Indoor Air 15 (9), 58–64. Nevalainen, A., Pasanen, A.-L., Niininen, M., Reponen, T., Kalliokoski, P., Jantunen, M.J., 1991. The indoor air quality in Finnish homes with mould problems. Environment International 17, 299–302. Nevalainen, A., Partanen, P., Ja¨a¨skela¨inen, E., Hyva¨rinen, A., Koskinen, O., Meklin, T., Vaahteristo, M., Koivisto, J., Husman, T., 1998. Prevalence of moisture problems in Finnish houses. Indoor Air 4, 45–49. Niemeier, R.T., Satheesh, K., Sivasubramani, K., Reponen, T., Grinshpun, S.A., 2006. Assessment of fungal contamination in mouldy homes: comparison of different methods. Journal of Occupational and Environmental Hygiene 3, 262–273. Pasanen, A.-L., 1992. Airborne mesophilic fungal spores in various residential environments. Atmospheric Environment 26A (16), 2861–2868.
Pasanen, A.-L., 2001. A review: fungal exposure assessment in indoor environments. Indoor Air 11, 87–98. Pasanen, A.-L., Niininen, M., Kalliokoski, P., Nevalainen, A., Jantunen, M.J., 1992a. Airborne Cladosporium and other fungi in damp versus reference residences. Atmospheric Environment 26B (1), 117–120. Pasanen, A.-L., Juutinen, T., Jantunen, M.J., Kalliokoski, P., 1992b. Occurrence and moisture requirements of microbial growth in building materials. International Biodeterioration and Biodegradation 30, 273–283. Peat, J.K., Dickerson, J., Li, J., 1998. Effects of damp and mould in the home on respiratory health: a review of the literature. Allergy 53, 120–128. Pessi, A.-M., Suonketo, J., Pentti, M., Kurkilahti, M., Peltola, K., Rantio-Lehtima¨ki, A., 2002. Microbial growth inside insulated external walls as an indoor air biocontamination source. Applied and Environmental Microbiology 68 (2), 963–967. Platt, S.D., Martin, C.D., Hunt, S.M., Lewis, C.W., 1989. Damp housing, mould growth, and symptomatic health state. British Medical Journal 298, 1673–1678. Rao, C.Y., Burge, H.A., Chang, J.C., 1996. Review of quantitative standards and guidelines for fungi in indoor air. Journal of the Air and Waste Management Association 46, 899–908. Rautiala, S., Reponen, T., Hyva¨rinen, A., Nevalainen, A., Husman, T., Vehvila¨inen, A., Kalliokoski, P., 1996. Exposure to airborne microbes during the repair of moldy buildings. American Industrial Hygiene Association Journal 57, 279–284. Reponen, T., Nevalainen, A., Jantunen, M., Pellikka, M., Kalliokoski, P., 1992. Normal range criteria for indoor air bacteria and fungal spores in a subarctic climate. Indoor Air 2, 26–31. Reponen, T., Hyva¨rinen, A., Ruuskanen, J., Raunemaa, T., Nevalainen, A., 1994. Comparison of concentrations and size distributions of fungal spores in buildings with and without mould problems. Journal of Aerosol Science 25, 1595–1603. Ross, M.A., Curtis, L., Scheff, P.A., 2000. Association of asthma symptoms and severity with indoor bioaerosols. Allergy 55, 705–711. Ruotsalainen, R., Jaakkola, N., Jaakkola, J.J., 1995. Dampness and moulds in day-care centers as an occupational health problem. International Archives of Occupational and Environmental Health 66 (6), 369–374. Samson, R.A., 1994. Recommendations. In: Samson, R.A., Flannigan, B., Flannigan, M.E., Verhoeff, A.P., Adan, O., Hoekstra, E.S. (Eds.), Health Implications of Fungi in Indoor Environments. Elsevier, Amsterdam, The Netherlands, pp. 529–538. Seuri, M., Paldanius, M., Leinonen, M., Roponen, M., Hirvonen, M.-R., Saikku, P., 2005. Chlamydophila pneumoniae antibodies in office workers with and without inflammatory rheumatic diseases in a moisture-damaged building. European Journal of Clinical and Microbiological Infectious Diseases 24, 236–237. Spengler, J., Neas, L., Nakai, S., et al., 1994. Respiratory symptoms and housing characteristics. Indoor Air 4, 72–82. Statistics Finland, 2006. Tyo¨voimatilasto 2005: vuosikatsaus, ennakkotietoja. Tyo¨markkinat. Statistics Finland, Helsinki. Taskinen, T., Hyva¨rinen, A., Meklin, T., 1999. Asthma and respiratory infections in school children with special reference
ARTICLE IN PRESS H. Salonen et al. / Atmospheric Environment 41 (2007) 6797–6807 to moisture and mould problems in the school. Acta Paediatria 88, 1373–1379. Teijonsalo, J., Kurnitski, J., Miettinen, P., Ruotsalainen, R., 1991. Luokkahuoneiden ilmanlaatu-alustava kartoitus (in Finnish). Paper presented at the Sisa¨ilmasto-ja ilmastointiseminaari, Espoo. Trout, D., Bernstein, J., Martinez, K., Biagini, R., Wallingford, K., 2001. Bioaerosol lung damage in a worker with repeated exposure to fungi in a water-damaged building. Environmental Health Perspectives 109, 641–644.
6807
Tuomisto, J., 2000. SYTTY Sytyke Suomen ympa¨risto¨terveyden tutkimukselle. In: Va¨likyla¨, T. (Ed.), Ympa¨risto¨ ja terveys, vol. 6, pp. 5–9. Wieslander, G., Norback, D., Nordstrom, K., Walinder, R., Venge, P., 1999. Nasal and ocular symptoms, tear film stability and biomarkers in nasal lavage, in relation to building-dampness and building design in hospitals. International Archives of Occupational and Environmental Health 72, 451–461.