Sensitizing effect of mould and mites during building redevelopment

Status:

completed 12/2009

Aims:

Mites and moulds favour similar habitats in terms of moisture, temperature, and in to some degree nutrients. These conditions are frequently found in buildings requiring redevelopment. Employees involved in building redevelopment work may therefore be exposed to dusts with a sensitizing action which contain both fungus and mite allergens. Studies conducted to date have particularly addressed the level of the fungi concentrations and the methods for reducing exposure. In a measurement campaign launched by BG BAU, the German accident insurance institution responsible for the construction sector, a study was therefore to be conducted into whether, in buildings undergoing redevelopment, various species of mite and fungi are present at the same time, and thus whether mite allergens may also contribute to a sensitizing action on the part of dusts containing fungi. The study was further to identify the fungi primarily occurring in buildings requiring redevelopment, since these could be species the allergens of which are not detected by conventional tests. Should this be the case, suitable new detection methods must be developed. Finally, the overall project was to include a study of relevant sera in order to determine whether elevated concentrations of fungi which may arise during building redevelopment measures can be shown to cause allergies among employees. Sampling and all further studies were conducted in conjunction with private contractors (Dr. W. Lorenz-Institut für Innenraumdiagnostik, Düsseldorf, and Dr. J. T. Franz, Paderborn) and with the Institute for Hygiene and Public Health at the University of Bonn and the Institute for Prevention and Occupational Medicine (IPA) of the German Social Accident Insurance at the Ruhr University, Bochum.
The task of the BGIA - Institute for Occupational Safety and Health of the German Social Accident Insurance within this project was that of determining the concentration of fungi in the material samples in terms of colony-forming units (CFUs) per g of material, and of producing isolates of the predominant mesophilic fungi in each case. The isolates were then forwarded to the Institute for Hygiene and Public Health at the University of Bonn for identification of the fungi species.

Activities/Methods:

In order for the total colony-forming units of the fungi to be quantified, the samples were ground and, depending upon the material (e.g. wallpaper, plaster, paint, expanded polystyrene, wood), agitated at room temperature in a suspension solution (0.9% NaCl solution with the addition of Tween 80). Serial tenfold dilution of this suspension was then performed and the dilution steps plated on DG18 agar (with chloramphenicol). The culture media were incubated for up to seven days at 25 °C. For quantification of the total colony-forming units, the most readily assessible dilution step was considered (5 to 150 colonies per dish). For production of the isolates, all fungi dishes were inspected visually and the five to ten most frequently occurring species from each inoculated on new nutrient media and dispatched refrigerated to the Institute for Hygiene and Public Health in Bonn for further cultivation and identification. Cryocultures were also created for use as stock cultures, and the appearance of the subcultured colonies described and documented by photographs. The IPA received the same isolates, which were identified at the Institute for Hygiene and Public Health at the University of Bonn, in the form of cryocultures, and also sterile DG18 culture dishes for cultivation of the isolates.

Results:

During the course of the project, 53 material samples obtained from buildings undergoing redevelopment were studied with regard to their contamination by fungi. The material most frequently examined, accounting for 30% of all samples, was wallpaper, followed by plaster/wall material (16%). Conversely, other construction materials such as paint, wood (particle board/panels), expanded polystyrene or carpet were less relevant, accounting for 1% to 3% of all samples.
The total concentration of fungi in the various materials ranged from 30 CFU/g to 16 billion CFU/g of material. Wallpaper samples, which were those most frequently studied, exhibited fungi concentrations of on average several hundred million CFU/g of material. The reason for this is that together with the paste adhering to it, the material, which contains cellulose, constitutes an ideal source of nutrients for these organisms. The wallpaper samples also exhibited not only the highest fungi concentrations, but also the greatest variety in species. Altogether, 140 fungal isolates were produced by the BGIA and identified by the Institute for Hygiene and Public Health at the University of Bonn. The eight most frequently occurring species included both numerous dampness indicators such as Aspergillus versicolor, Cladosporium cladosporoides and Acremonium strictum, and mycologically and allergologically very similar penicillium species such as P. chrysogenum and P. griseofulvum, which are not primarily described as dampness indicators. The two dominant species in the material samples, Aspergillus versicolor and Penicillium chrysogenum, were selected for the development of new immunoassays for the detection of specific allergens of these two fungi. The cryocultures produced at the BGIA yielded the isolates required for production of the extracts containing allergens. Culture and harvesting of the fungal biomass was performed by the BMA (biological measurement and analysis) laboratory in Bochum. The fungal immunoassays themselves were developed and tested in a sub-project conducted by the IPA.

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