• Aucun résultat trouvé

Detection of mold damaged buildings by airborne mold spores: evaluation of the method

N/A
N/A
Protected

Academic year: 2021

Partager "Detection of mold damaged buildings by airborne mold spores: evaluation of the method"

Copied!
7
0
0

Texte intégral

(1)

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

10th International Conference on Indoor Air Quality and Climate [Proceedings],

pp. 2479-2483, 2005-09-04

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=cdecf88d-7866-4277-9095-99e9c40d5551 https://publications-cnrc.canada.ca/fra/voir/objet/?id=cdecf88d-7866-4277-9095-99e9c40d5551

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Detection of mold damaged buildings by airborne mold spores:

evaluation of the method

(2)

D e t e c t i o n o f m o l d d a m a g e d b u i l d i n g s b y

a i r b o r n e m o l d s p o r e s : e v a l u a t i o n o f t h e

m e t h o d

N R C C - 4 9 2 4 7

S c h l e i b i n g e r , H . ; L a u s s m a n n , D . ; E i s , D . ;

R ü d e n , H .

A version of this document is published in / Une version de ce document se trouve dans: Proceedings of Indoor Air 2005, Lisbon, Portugal, June 4-8, 2006, pp. 2479-2483

The material in this document is covered by the provisions of the Copyright Act, by Canadian laws, policies, regulations and international agreements. Such provisions serve to identify the information source and, in specific instances, to prohibit reproduction of materials without written permission. For more information visit http://laws.justice.gc.ca/en/showtdm/cs/C-42

Les renseignements dans ce document sont protégés par la Loi sur le droit d'auteur, par les lois, les politiques et les règlements du Canada et des accords internationaux. Ces dispositions permettent d'identifier la source de l'information et, dans certains cas, d'interdire la copie de documents sans permission écrite. Pour obtenir de plus amples renseignements : http://lois.justice.gc.ca/fr/showtdm/cs/C-42

(3)

Proceedings: Indoor Air 2005

2479

DETECTION OF MOLD DAMAGED BUILDINGS BY AIRBORNE MOLD SPORES:

EVALUATION OF THE METHOD

H Schleibinger1,2∗, D Laußmann3, D Eis3 and H Rüden2

1 National Research Council, Institute for Research in Construction, Ottawa, Canada

2 Institute of Hygiene and Environmental Medicine, Charité, University Medicine Berlin, Free University and Humboldt University Berlin, Germany

3 Robert Koch-Institute, Department Epidemiology and Health Reporting, Division Non-Communicable Diseases, Epidemiology, Environmental Health, Berlin, Germany

ABSTRACT

In order to validate microbial methods for the detection of mold infestations in indoor areas in a first step the sampling of airborne fungal spores with an impaction method was checked. When the group ”moldy apartments” was compared with the group ”non-moldy apartments”, only the genera Aspergillus and Penicillium were in significantly higher concentrations in the infested rooms (nutrient: malt extract agar). As these two genera appeared complementarily in moldy homes as a rule, a sum score was calculated by the logistic regression model. With this sum score cutoff50 values were calculated: 110 cfu/m³ for airborne fungal spores (Σ A + P) without

correction for the outdoor situation and 80 cfu/m³ (Σ A + P) with correction for the outdoor air concentration. With these cutoff50 values a very good classification (high sensitivity and high specificity) concerning moldy and

non-moldy apartments was achieved.

INDEX TERMS

Moldy buildings, airborne mold spores, sedimentation, house dust, cutoff values

INTRODUCTION

There are different methods for the assessment of the microbial situation in indoor air. All methods used for investigations should fulfill certain quality demands, i.e. they should be validated. The quality of such tests can be assessed e.g. with data concerning specificity and sensitivity. Preference should be given to methods with only few false-positive results (high specificity) and few false-negative results (high sensitivity). Unfortunately, although there is a demand for them, these quality criteria have not yet been given enough consideration in environmental hygiene (Pasanen 2001). The specificity and sensitivity of the respective methods can be determined then from the percentage of correct classifications.

The aim of this study was therefore to validate the sampling of airborne fungal spores by the impaction method regarding its ability to predict a mold infestation in indoor areas. We also wanted to examine which mold genus or combination of genera can differentiate the two apartment categories ”moldy homes” and ”non-moldy homes” as clearly as possible. It was also intended to create cutoff values concerning these mold genera in order to classify the apartments concerning their mold infestation to determine the sensitivity and specificity of the methods used.

RESEARCH METHODS Study design

The study was performed as a single-blinded observation study examining 43 apartments with and 47 without mold infestation (Schleibinger et al. 2004a). Apartments with a broad range of mold-infested areas were included in the study. Of the 43 mold-infested apartments, 12 had mold areas of up to 0.5 m2, 10 between 0.5 and 1 m2, and 21 with more than 1 m2. Apartments without mold infestation were selected from an ongoing indoor study and an environmental field study carried out by the Robert Koch-Institute, Berlin, Germany. All apartments were carefully inspected before sampling to check the presence or absence of mold infestation (Schleibinger et al. 2004b).

Sampling and mycological evaluation

(4)

w Indoor and outdoor air sampling was done with 2-stage Andersen cascade impactors. Sampling time was 2.0 and 3.5 minutes at 28.3 l min-1 respectively.

w Malt extract agar (1% glucose, MEA, results given here) and dichloran 18% glycerol agar (DG 18, results to be published elsewhere) served as culture medium. The mesophilic molds were incubated at 24±1°C, and counted and differentiated after 3 - 7 days. The quality of the differentiation was assured by participating regularly in inter-laboratory experiments.

Statistical analysis

All statistical tests were based on a double-sided hypothesis. A probability of error of p = 0.05 was considered significant. SPSS® for Windows®, version 11.5, was used.

Logistic regression analysis for the derivation of cutoff50 values

Logistic regression analyses were performed to check statistical correlations between the dichotomously coded characteristic "mold infestation in the apartment" (yes/no) and the concentration of airborne fungal spores. The resulting cutoff50 values were used as discriminating values. A decision threshold of 0.5 (cutoff50) was selected that

corresponded to a 50% infestation probability. Concentrations above the cutoff value are associated with an infestation probability of more than 50% and thus lead to classification into the group of mold-infested apartments and vice-versa.

RESULTS

Genus patterns in apartments with mold infestation

Airborne mold spores of the genera Aspergillus and Penicillium were significantly more predominant in mold-infested apartments compared to non-moldy apartments (see table 1). In the group of the mold infested apartments an often complementary occurrence of the two genera Aspergillus and Penicillium was observed (see fig. 1). For this reason the sum of both genera was generated.

Seasonal influence on the sum value "Aspergillus + Penicillium"

The results concerning this sum score were subdivided into winter, spring, summer and autumn periods and depicted graphically in relation to the mold status in the examined apartments (see fig. 2). This figure shows that the distribution of values measured in apartments with and without mold infestation hardly overlap in the four subgroups. There is no recognizable seasonal trend, and even the total annual values of the four seasons examined show only slight overlapping between the groups ”moldy apartments” and ”non-moldy apartments”.

Table 1. Airborne mold genera (cfu/m³) in moldy and non-moldy apartments

N = number of valid measurements; P = percentile; AM = arithmetical mean value Nutrient: malt extract agar. Significant values are printed bold.

Mold genus Mold damage

N Min 5th P 10th P 50th P AM 90th P 95th P Max P value (cfu/m3) yes 43 < < < < < < 20 50 Alternaria no 47 < < < < < 10 20 30 0.030 yes 43 < < < 80 760 3760 4300 4820 Aspergillus no 47 < < < < 10 30 40 40 2.8E-07 yes 43 < < < < < 20 20 20 Botrytis no 47 < < < < < 10 10 30 0.632 yes 43 < < < < < 260 470 500 Cladosporium no 47 < < < 20 120 200 660 2290 0.029 yes 43 < < < < < < 10 20 Eurotium no 47 < < < < < < < < 0.225 Yeasts yes 43 < < < < 30 30 150 870 0.134

(5)

Proceedings: Indoor Air 2005 2481 no 47 < < < < 10 20 30 40 yes 43 < 20 60 210 2330 10260 11990 21770 Penicillium no 47 < < < 10 20 40 80 170 3.6E-18 yes 43 < < < < < < 20 20 Ulocladium no 47 < < < < < < < < 0.105 yes 43 < < < < < < < < Wallemia no 47 < < < < < < < < yes 43 < < < < 10 60 90 150 Sterile Mycelia/ unknown no 47 < < < 20 20 40 50 90 0.011 yes 43 170 190 220 1000 3200 10710 12360 21770 Total cfu no 47 < 10 40 100 180 300 740 2340 5.5E-18

Logistic regression for the derivation of cutoff50 values

According to these results a seasonally independent value was calculated using the univariate logistic regression method, which separated the two examined groups in ”moldy apartments” and ”non-moldy” apartments. These cutoff50 values are given in table 2).

Table 2. Cutoff50 values and classification results from the univariate logistic regression method concerning the

sum parameter Aspergillus + Penicillium

Impaction method

Cutoff50

value [cfu/m³]

non moldy homes: # of classifications moldy homes: # of classifications specificity (%) (95% confidence interval) sensitivity (%) (95% confidence interval) false positive true negative false negative true positive

indoor air only 110 1 46 3 40 97.9 (88.9 – 99.7) 93.0 (80.9 – 98.5) indoor air minus outdoor air 80 1 46 3 40 97.9 (88.9 – 99.7) 93,0 (80.9 – 98.5) Sampling method: impaction with the 2-stage Andersen impactor

Nutrient: malt extract agar

0 1000 2000 3000 4000 5000 6000 0 5000 10000 15000 20000 25000

Indoor air concentration of Penicillium [cfu/m3]

In d o o r a ir c o n c e n tr a tio n o f A s p e rg il lu s [ c fu /m 3] yes no

mold infested rooms malt extract agar

(6)

Results obtained with the Andersen 2-stage impactor in moldy and non-moldy apartments. Nutrient: malt extract agar Sep - Nov June - Aug March - May Dec - Feb overall A s p e rg il lu s + P e n ic il li u m [ c fu /m 3 ], l o g1 0 5 4 3 2 1 0 outdoor air no mold infestation mold infestation

malt extract agar

Figure 2. Seasonal and overall distributions of the sum parameter ”Aspergillus + Penicillium” in moldy and

non-moldy apartments and in the outdoor air.

The logistic regression model also provides the results for the classification quality (= number of correctly classified samples). With the evaluation of the sum parameter Aspergillus + Penicillium a very high percentage of the samples were correctly classified. The specificity of the impaction method was 98%, the sensitivity was 93%. Astonishingly the classification results were not improved, when the indoor air concentrations were corrected by subtraction for the outdoor air concentration, i.e. the specificity and the sensitivity of this method was equal, but not better, when the outdoor air situation was considered.

DISCUSSION

Selection of mold genera as indicator organisms

Statistical evaluation of the samples showed, that only Aspergillus and Penicillium had significantly higher concentrations in apartments with mold infestation than in those without mold damage. This was not the case in all the other differentiated genera. A dominance of Aspergillus and Penicillium in humidity-damaged and mold-infested buildings was also reported by Flannigan and Miller (1994), Dales et al. (1997), Bex et al. (2002) and Morey et al. (2003). According to Grant et al. (1998), Aspergillus and Penicillium are primary colonizers of damp materials like wallpaper, pressboard, plasterboard and noise insulation material, making these genera also particularly suitable and sensitive indicators for very recent mold infestations. Therefore these two genera seem to be very suitable markers for mold contamination. As it was found in this study, that these genera often appear in a complementary way, a sum-score of them is obviously even more indicative.

When using the sum-score of Aspergillus + Penicillium as an indicator it could be shown by means of the univariate logistic regression method that the often-recommended parallel evaluation of the outdoor air does not lead to better classification results. According to the results of this study the outdoor sample can be omitted, if only the decision moldy/non-moldy apartment has to be made. This would facilitate many inspections, especially as it is often very difficult to get a timely and locally corresponding outdoor air sample.

(7)

Proceedings: Indoor Air 2005

2483

Comparison with the sedimentation and the house dust method

Our results obtained with the impaction method showed that measuring airborne mold spores leads to very good classification results concerning moldy and non-moldy apartments, if the sum parameter Aspergillus + Penicillium is used. Comparably good classification results were obtained with the sedimentation (= open Petri dish) method (see table 3). Here Petri dishes with a diameter of 90 mm were exposed over a period of 8 and 24 h respectively, and a maximum of one window airing was allowed during the collection period. Classifications with the collection of 7 days´ house dust also lead to comparable results (see table 3). Here the ALK-sampler was used. An area of 1 m² was marked and carefully vacuumed 7 days prior to the dust sampling. On the sampling day this area was vacuumed again for 4 minutes, and the dust was collected on a fiberglass filter. According to the results received in this study all three compared methods (impaction, open Petri dish, house dust) can be used alternatively. The specificity concerning all three methods ranged from 98 – 100 %, the sensitivity from 93 – 98 %. In spite of the good classifications results we recommend the use of at least 2 independent methods for the detection of mold damage.

Table 3. Specificity and sensitivity of three microbiological methods

Method Cutoff50 value

Speci-ficity (%) 95% confidence interval Sensitivity (%) 95% confidence interval

Sedimentation 10 cfu/petri dish

and day 97.8 88.4 – 99.6 97.7 87.1 – 99.6 House dust

(unsieved) 60.000 cfu/g 100.0 92.4 – 100 95.2 83.8 – 99.3 Impaction method

(indoor only) 110 cfu/m

3

97.9 88.9 – 99.7 93.0 80.9 – 98.5

REFERENCES

Bex V., Mouilleseaux A., Bordenave L. and Squinazi F. (2002): Indoor fungal exposure in some French homes. Proceedings of the 9th international conference on indoor air and climate, Monterey, California 4, 770-775 CAAIA. (2000): Committee on the assessment of asthma and indoor air. Indoor biologic exposures. In: Clearing

the air. Asthma and indoor exposures. Committee on the assessment of asthma and indoor air. Division of health promotion and disease prevention. Institute of medicine. National Academic Press, Washington, D.C. 105-222

Flannigan B. and Miller JD. (1994): Health implications of fungi in inoor environments - an overview. In: Samson RA, Flannigan B, Flannigan ME, Verhoeff AP, Adan OCG, Hoekstra ES, Eds: Health implications of fungi in inoor environments. Air Quality Monographs, 2. Elsevier, Amsterdam, 3-28

GMDS. (1989): Memorandum for the evaluation of diagnostic means. Köbberling J, Trampisch HJ, Windeler J (Hrsg.), Schriftenreihe der Deutschen Gesellschaft für Medizinische Dokumentaton, Informatik und Statistik e.V., Heft 10, Schattauer, Stuttgart - New York, 1989

Grant C., Hunter CA., Flannigan B. and Bravery AF. (1989): The moisture requirements of molds isolated from domestic dwellings. Int. Biodeter 25, 259-284

Lichtnecker H., Obeloer M. and Beyer A. (2001): Biologic influencing parameters. Part 3: Molds: Health risks, prophylaxis, diagnostics and therapy. In: Beyer A, Eis D (Hrsg). Praktische Umweltmedizin Sektion 09.04, Springer Verlag Berlin-Heidelberg-New York, 1-38

Pasanen AL. (2001): A review: fungal exposure assessment in indoor environments. Indoor Air 11, 87-98 Schleibinger H., Laußmann D., Samwer H., Nickelmann A., Eis D. and Rüden H. (2004a): Discrimination of

moldy and non-moldy apartments by airborne mold spores. Results of a field study in Greater Berlin. Umweltmed Forsch Prax, submitted January 2004

Schleibinger H., Laußmann D., Samwer H., Eis D. and Rüden H. (2004b): Are MVOC suitable indicators for concealed mold damage? Umweltmed Forsch Prax, 9, 151-162.

Dales RE., Miller D. and McMullen E. (1997) Indoor air quality and health: validity and determinants of reported home dampness and moulds. Int J Epidemiol 26: 120-125

Morey PR., Hull MC. and Andrew M. (2003) El Niňo water leaks identify rooms with concealed mould growth and degraded indoor air quality. Intern Biodeterior and Biodegrad 52: 197-202

Figure

Table 1. Airborne mold genera (cfu/m ³ ) in moldy and non-moldy apartments    N = number of valid measurements; P = percentile; AM = arithmetical mean value
Table 2. Cutoff 50  values and classification results from the univariate logistic regression method concerning the  sum parameter Aspergillus + Penicillium
Figure 2. Seasonal and overall distributions of the sum parameter  ” Aspergillus + Penicillium ”  in moldy and  non-moldy apartments and in the outdoor air
Table 3. Specificity and sensitivity of three microbiological methods  Method  Cutoff 50  value

Références

Documents relatifs

Fin mars 2019, 17,6 % des salariés du privé tra- vaillent à temps partiel et 82,4 % travaillent à temps complet dans les entreprises de 10 salariés ou plus, hors

Abstract: The principal function of a continuous casting mold is to receive the liquid steel, and ensure its cooling in order to permit the formation of a solidified skin,

En introduisant ceci comme mod`ele de comportement local dans l’algorithme 4.4, on restitue bien la premi`ere partie du comportement d’une ´eprouvette d’AMF en

Content of total phenolic compounds, flavonoids, and antioxidant activity of Ericaceae species..

 Le Firewall se Le Firewall se situe entre le situe entre le réseau interne et réseau interne et le réseau externe le réseau externe ATM TCP/UDP IP Packet Filter

To explore meta- bolic profile changes induced by artesunate in allergic airway inflammation, we analysed bronchoalveolar lavage fluid (BALF) and serum from naı¨ve and

Our experiments on two reference datasets with very different com- binations of the parameters governing runtimes (number of taxa and alignment length) show that, on real data,

• Energy distinguishable low-energy structures (Mercier &amp; Le Page 2008) • No layer rotation upon solid state transformation (Dera et al. 2003)..