This study was conducted in a school center that had been the focus of intense public concern over 2 years because of suspected mold and health problems. Because several attempts to find solutions to the problem within the community were not satisfactory, outside specialists were needed for support in solving the problem. The study group consisted of experts in civil engineering, indoor mycology, and epidemiology. The studies were conducted in close cooperation with the city administration. Structures at risk were opened, moisture and temperature were measured, and the causes of damage were analyzed. Microbial samples were taken from the air, surfaces, and materials. Health questionnaires were sent to the schoolchildren and personnel. Information on the measurements and their results was released regularly to school employees, students and their parents, and to the media. Repairs were designed on the basis of this information. Moisture damage was caused mainly by difficult moisture conditions at the building site, poor ventilation, and water leaks. Fungal genera (concentrations <200 colony-forming units (cfu)/m3, <3000 cfu/cm2) typical to buildings with mold problems (e.g., Aspergillus versicolor, Eurotium) were collected from the indoor air and surfaces of the school buildings. Where moisture-prone structures were identified and visible signs of damage or elevated moisture content were recorded, the numbers of microbes also were high; thus microbial results from material samples supported the conclusions made in the structural studies. Several irritative and recurrent symptoms were common among the upper secondary and high school students. The prevalence of asthma was high (13%) among the upper secondary school students. During the last 4 years, the incidence of asthma was 3-fold that of the previous 4-year period.

The association between moisture-related microbial growth (mesophilic fungi and bacteria) within insulated exterior walls and microbial concentrations in the indoor air was studied. The studied apartment buildings with precast concrete external walls were situated in a subarctic zone. Actinomycetes in the insulation layer were found to have increased concentrations in the indoor air. The moisture content of the indoor air significantly affected all measurable airborne concentrations.Concrete sandwich facade panels have been commonly used in building frameworks in northern Europe since the 1960s. These panels consist of two reinforced concrete panels enclosing a layer of mineral wool thermal insulation (rock or fiberglass wool), essential in the subarctic climate. Mold growth has been reported on the internal concrete core, initiated by the condensation of indoor humidity due to serious panel cracks (3). In a previous study (16) it was shown that microbial growth is found infrequently in the insulation layer in structures of this type in Finland, but such growth is increased if the external wall is in poor condition. Microbial growth within the exterior walls has seldom been considered a risk factor for indoor air quality (10). Compared to microbial growth on internal structures, the envelope does not necessarily have similar direct contact with the indoor air. However, if the supply airflow drifts through a contaminated wall structure, it may affect the quality of the indoor air. In the present study, we evaluated whether indoor air quality may be influenced by microbial contamination in the insulation layer of precast concrete external walls.Test buildings and insulation samples. We studied 50 inhabited apartment buildings, 2 to 38 years in age, with precast concrete sandwich panels as their framework structure. The buildings were situated in the southern coastal area of Finland, in the Turku region (60°50ЈN, 22°05ЈE to 60°39ЈN 22°40ЈE) and in Salo (60°39ЈN, 23°12ЈE). Prior to sampling, the condition of the exterior walls was monitored visually by using five parameters (Table 1) with a three-step scale (bad, moderate, good). Insulation samples from the external wall were taken from the whole depth of the insulation layer through boreholes from the outside. The sampled sites of the panel were (i) the central upper edge, (ii) the upper corner, (iii) the side edge of the panel, (iv) below the window, (v) the lower edge, and (vi) the central area. A total of 364 concrete panels were sampled. For the microbiological analysis, a subsample of the insulation sample was suspended in peptone water (1.0 g of peptone, 0.85 g of NaCl, and 0.02% Tween 80 detergent in 1 liter of deionized water), and the concentrations were determined by dilution plating (14) . Fungal colonies were counted after 7 days, and bacteria were counted after 10 days of incubation (at 25°C). The results are expressed as CFU per gram of insulation material. The fungal genera were identified microscopically, and bacteria were classified as actinomycet...

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