Project leader: Aino Nevalainen, National Public Health Institute (KTL), Laboratory of Environmental Microbiology, P.O.Box 95, FIN-70701 Kuopio, Finland, tel. +358-17-210 342, e-mail:

Teija Meklin,  KTL, tel. +358-17-201 364, first
Tuula Husman, KTL, tel. +358-17-201 325
Jari Koivisto KTL, tel. +358-17-201 381
Juho Halla-aho KTL, tel. +358-17-201 381
Anne Hyvärinen KTL, tel. +358-17-201 364
Ulla Haverinen KTL, tel. +358-17-201 154
Maija-Riitta Hirvonen, KTL, tel. +358-17-201 303
Johanna Immonen KTL, tel. +358-17-201 180
Taina Taskinen, Kiuruvesi Health Care Center, tel.+358-17-76851,

Consortium: Moisture, mould and health
Financing SYTTY organization:The Academy of Finland, The Finnish Work Environment Fund
Funding from SYTTY / Total funding of project (€): 183627 / 379667
Person-months of work funded by SYTTY / Total person-months of work: 62,5 / 155,5

KEY WORDS: moisture, mould, health, repair, intervention


1 Introduction

In moisture damaged schools, higher prevalence of respiratory symptoms and infections as well as general symptoms like headache, tiredness and nausea have been reported  [1,2,3,4]. The problem has also an economical consequences due to costs of sick leaves and health care, and because considerable resources are put on the renovations. It is essential to know how the repairs of moisture damage in school environment affect the exposure and health of schoolchildren and personnel, and thus assess the achieved benefits of the renovation.

The aim of the intervention study was to find out whether the moisture and mould repairs of the school buildings have an effect on the exposure to indoor air pollutants, on the respiratory health of the school children, studied with both questionnaire and clinical methods. This intervention study had a core design around which several connected studies were carried out, and a basic characterisation of moisture damage and associated microbial growth in school buildings were performed. As a part of the clinical study the association between serum mold-specific IgG levels of schoolchildren and the microbial exposure in their school environment was measured.

2 Material and methods

A total of 30 schools, consisting of 41 school buildings, were technically investigated according to a standardized protocol by trained surveyors, and moisture damage status of each building was assessed. A total of 32 school buildings were studied to determine whether the microbial indoor air quality and associated health status of children in schools with visible moisture and mold problems differed from those in non-damaged schools. The following questions were set: What are the distributions of fungal concentrations in school buildings, and how does a moisture damage alter the concentrations? Is the moisture damage of school building associated with symptoms i.e., are the exposure times sufficient to cause symptoms to schoolchildren? Also the effect of the building frame (concrete/brick or wood) and the moisture damage on the microbial quality of school buildings was analyzed in a more accurate characterization of indoor air microbes of school buildings. The size distributions of airborne microorganisms in school buildings were considered. Special focus was paid on effects of moisture and mold damage repairs in the schools. Four school buildings were selected to study the effect of repair measures on microbial exposure and health effects of schoolchildren.

The microbial levels and flora in buildings were characterized by sampling indoor air with a six-stage impactor (Andersen 10-800) and materials from damaged structures. An epidemiological symptom survey of students was done with a previously developed questionnaire that consists of 32 questions on personal characteristics, home environment, perceived indoor air quality characteristics and occurrence of respiratory and other symptoms and infections.

As a background characterization of building mycoflora, the diversity of the mycobiota and concentration distributions of fungi and bacteria were analyzed in a database of building material samples (n=1140) taken from various buildings. The occurrence of microbes was analyzed in seven different moisture damaged building materials, grouped according to the major constituent or use.

In the intervention study, the sampling of indoor air microbes and health questionnaire of children were performed before any dismantling and repair work in the two schools. After the repairs were completed, the measurements on the exposure and health status of the school students were repeated. Part of the follow-up was done during the renovation. Changes in the prevalence of the symptoms and diseases in different buildings were analyzed. Two non-damaged schools served as control schools.

Follow-up of children included clinical measurements: heart and lung auscultation, checking of infection focuses, skin prick tests (SPT) to 11 common allergens and to mold antigens and also lung function measurements including exercise challenge test. In addition, serum samples were drawn for analysis of mould specific immunoglobulin G (IgG) determination to 24 antigens and mold-spesific immunoglobulin E (IgE) determination to 10 antigens.

One aim was to develop a method to monitor the toxicity and biological activity of the indoor particulate material. As a part of this work filter samples from indoor air of a school building before and after renovation were taken. The mouse macrophage cell line RAW264.7 (American Type Culture Collection, Rockville, MD, USA) was used in the cell exposure study. The effects of indoor air particles on cell viability and production of inflammatory mediators (nitrite, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFalpha)) were analyzed.

3 Results and discussion

Moisture damage in school buildings
Moisture and mold damage was common in school buildings. Only 10% of the buildings were assessed to be non-damaged. Out of the damaged buildings, 19 % had minor damage and 71% had evident damage. Evident odor of mold in 24% of the schools, weak mold odor was recorded in 2% of the studied schools. About 23% of the damage were located in classrooms, and most of the damage was less than 4 m2 of size. A total of 930 individual damage observations in the 18 buildings with concrete/brick frame and 157 observations in the 23 buildings with wooden frame were recorded, but the number of damage / building size [m2] was slightly greater in the buildings with wooden frame.

Indoor air microbes in school buildings
The frame material was a determinant of airborne microflora in school buildings. In wooden school buildings the concentrations and composition of the microbes differed clearly from concrete schools. Mean concentrations of viable airborne fungi were significantly and systematically higher in wooden schools than in concrete schools. Evidently, a wooden frame acts as a microbial source and creates its specific microbial conditions that differ from indoor environment of a concrete building. The material of the building frame should also be taken into account when matching buildings for exposure assessment in epidemiological studies.

Associations between mean fungal concentrations and moisture damage was seen only in concrete schools. The geometric mean concentration in the index schools (GM=19 cfu/m3) was significantly higher (p=0.001) than in the reference schools (GM=9 cfu/m3). Distributions of fungal spore concentrations can be regarded as characteristic to the two types of studied schools. Typical to the school buildings with concrete frame and moisture damage were frequent occurrence (>10%) of samples with concentration between 50 and 200 cfu/m3, and low frequency (<6%) of samples with value under detection limit. This applies to wintertime sampling in a cold climate. Temporal variation of fungal concentrations in indoor air even within short period is evident [9]. Therefore, several air samples, from 5 to 20 depending on the size of the building are needed to ensure accurate assessment of microbial concentrations. The most common fungal genera or groups were similar in both frame types of buildings, i.e., Penicillium, yeasts, Cladosporium and Aspergillus. Occurrence of Aspergillus versicolor and Stachybotrys indicated moisture damage in both school types. Elevated concentrations of Cladosporium and actinobacteria associated with moisture damage in concrete/brick schools.

Symptoms and infections of schoolchildren
Moisture damage in a school building was a risk factor for respiratory symptoms i.e. nocturnal cough, dry cough and cough with phlegm among schoolchildren. There were significant differences in the prevalence of respiratory symptoms between the schoolchildren occupying damaged and non-damaged schools. Differences in symptom prevalence during the spring season were more often significant than during fall season, which may suggest the effect of longer exposure period. The association between moisture damage and respiratory symptoms was also significant in concrete/brick school buildings alone, while the trend in wooden schools was similar with no statistical significance.

An association between occurrence of common colds and moisture damage in all school buildings was found. In addition, sinusitis, tonsillitis and bronchitis were more common in concrete/brick buildings than in buildings with wooden frame irrespective with moisture observations. Occurrence of respiratory infection was also strongly correlated with background factors such as age, female gender, smoking, atopy and moisture damage in home environment.

Microbial diversity in damaged building materials
Microbial analysis of 1140 visibly damaged samples of building material, viz. wood, paper, non-wooden building boards, ceramic products, mineral insulation materials, paints and glues, and plastics confirmed that microbial growth occurs in many different building materials and showed associations between fungal genera and type of material. The range of fungi and bacteria numbers was between 100-108 cfu g-1 in all materials, but significant differences in counts were observed between materials. Highest median concentrations of fungi were observed in wooden and paper materials, and lowest in mineral insulation, ceramic products, and paints and glues. A rich variety of fungi was found in wooden materials, with Penicillium and yeasts occurring most frequently. In paper materials, a clear difference from wood was the more frequent occurrence of Cladosporium and Stachybotrys. In gypsum boards, Stachybotrys was common, occurring in 30% of the samples. Ceramic products and paints and glues seemed to favour Acremonium and Aspergillus versicolor. Yeasts and members of the Sphaeropsidales occurred often in parallel in most materials.

Cell viability and production of inflammatory mediators
The particle material collected from the indoor air of the renovated school was less cytotoxic in raw264.7 macrophages than that collected before the renovation. Moreover, a similar change in the biological activity of the airborne particle sample before and after renovation was observed as production of nitrite and proinflammatory cytokines il-6 and tnf-alpha in the macrophages.

Repairs of moisture and mold damage
After a thorough renovation in the intervention school, a significant decrease in mean concentrations of viable airborne fungi (p=0.002) was seen. GMs of total concentration of airborne fungi decreased after renovation from 22.6 cfu/m3 to 6.3 cfu/m3, and there was no difference compared to the reference school. Successful effects of the renovation were also seen as lower number of different microbial genera or species or groups and higher frequency of samples with low levels (<20 cfu/m3) of viable fungi. In the other intervention school with only partial repair of moisture damage, no decrease in microbial levels was observed.

In the intervention study, differences in symptom prevalence between the damaged school and its reference school were significant for 10 symptoms out of 12 before the renovation of the damaged school. After the thorough renovation, a significant decrease in all other symptoms but general symptoms was seen (Figure 1). The differences in prevalence between the intervention and reference school disappeared.


Figure 1. The proportions of schoolchildren with respiratory and other symptoms in the intervention school before and after thorough repairs.

In the intervention school with minor, uncompleted repairs, the prevalence of hoarseness and general symptoms i.e. fatigue, headache and difficulties in concentration was significantly higher than in its reference school at the beginning of the study, and no changes in these prevalences were seen after the repair measures in the index school. Only the prevalence of rhinitis (spring term), sore throat (spring term) and cough with phlegm (spring term) were lower than before preliminary repairs.

Clinical measurements in schoolchildren
Mold allergy diagnosed by skin prick tests to moulds was relatively rare, in 4% of the school children. No tendency from mild to positive reactions was seen during the three-year follow-up period. Most reactions to molds were in children with multiple skin test reactions to common allergens. No association with exposure to moulds was seen any more although that was the case at the time preceding the repair. A fairly good agreement was seen between SPT and IgE responses to molds. Mold-specific IgE was mostly present in atopic children, showing no association with dampness or mold exposure in the school. Only a few associations were found between IgG antibodies to molds and exposure to moisture or molds in schools.

4 Conclusions

Decrease in symptom prevalence after renovation of moisture and mold damage confirms the association between the symptoms and damage of school building. The majority of adverse health consequences is obviously due to irritation or non-specific inflammation and not type I allergy, and is therefore reversible. Moisture and mold damage was common in studied school buildings. The monitoring of viable microbes in the indoor air as markers of the microbial status of large buildings like schools needs effort to be put on sampling, sample size and analyzing and thus is not recommended as a first routine method in daily work of health inspectors and authorities. The clear difference in microbial levels between the wooden and concrete buildings and the association between damage observations and microbial findings only in buildings of concrete construction shows that building frame has impact for indoor air quality. Knowledge about association between certain microbes and building materials gives fundamental information on behavior of microbes in built environments.

5 References

[1] Haverinen U., Husman T., Toivola M., Suonketo J., Pentti M., Lindberg R., Leinonen J., Hyvärinen A., Meklin T. and Nevalainen A. 1999. An approach to management of critical indoor air problems in school buildings. Environmental Health Perspectives, 107, 509-514.
[2] Taskinen, T., Hyvärinen, A., Meklin, T., Husman, T., Nevalainen, A., and Korppi, M. (1999). “Asthma and respiratory infections in school children with special reference to moisture and mold problems in the school”, Acta Pediatr, 88, 1373-1379.
[3] Sigsgaard, T., Jensen, H.L.C., Nichum, E., Gravesen, S., Larsen, L. and Hansen, M.Ø. (1999) “Symptoms associated to work in a water damaged school building”. In: Bioaerosols, Fungi and Mycotoxins: Health effects, Assessment, Prevention and Control. Ed. Johanning, Albany: Eastern New York Occupational and Environmental Health Center. pp. 99 – 105.
[4] Meklin, T., Husman, T., Vepsäläinen, A., Vahteristo, M., Koivisto, J., Halla-aho, J., Hyvärinen, A., Moschandreas, D., and Nevalainen, A. (2002). Indoor Air Microbes and Respiratory Symptoms of Children in Moisture Damaged and Reference Schools. Accepted in Indoor Air.

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