Microbial exposure and health in schools - effects of moisture damage and renovation
Meklin, T.
2002
Dissertation, University of Kuopio
Meklin, T., (2002), "Microbial exposure and health in schools - effects of moisture damage and renovation", Dissertation, University of Kuopio.
| Abstract:
A total of 32 school buildings were studied to determine whether the microbial indoor air quality and associated respiratory symptoms among children in schools with visible moisture and mold problems differed from those in non-damaged schools. Also, the effect of the building frame (concrete/brick or wood) of schools was analyzed and the size distributions of airborne microorganisms in school buildings were considered. A total of 5345 children returned the symptom questionnaire. To study the effects of moisture and mold damage repairs on microbial exposure and symptom prevalence in the schools, four school buildings were selected to the study. Samplings of indoor air microbes were performed identically before and after repair works in the damaged schools. Change in symptom prevalence caused by repairs was studied before and after repairs in the cross-sectional surveys. Comparable surveys were done in two non-damaged schools. Over 1300 schoolchildren participated the stu dy.
The type of building frame material affected the microbial content of the building; mean concentrations of fungi were significantly higher in the school buildings of wooden construction than in the schools with a concrete/brick frame. An association between concentrations of fungi and moisture damage was found in concrete schools, but not in wooden schools. Typically, in moisture-damaged school buildings of concrete construction, the geometric mean wintertime concentration was above 10 cfu/m3, there was a low frequency of samples with values under the detection limit, and the frequent occurrence of samples with concentrations above 50 cfu/m3. Elevated concentrations of Cladosporium and actinobacteria (concrete schools) and the occurrence of Aspergillus versicolr, Stachybotrys and Acremonium (both frame types of schools) were associated with moisture damage. The average geometric mean diameter of total viable fungi was smaller in the wooden schools than in the concrete schools, and smaller in the moisture-damaged than in the reference school s. Moisture damage in the school building was a risk factor for respiratory symptoms among schoolchildren. The association between moisture damage and respiratory symptoms was statistically significant only in the concrete schools. Indoor characteristics causing discomfort were also more often reported in the damaged schools than in the reference schools.
After a thorough renovation of moisture- and mold damage in a school, the levels of airborne microbes and the fungal diversity of the samples normalized to the level in the reference school. Also, a remarkable decrease in prevalence of 10 symptoms out of studied 12 symptoms among schoolchildren was achieved. After only partial repairs, an increase of contamination was detected in the air samples. An improvement in symptom prevalence was less marked than after thorough renovati on. |
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