ON ENVIRONMENTAL HEALTH
SCHOOLS, MOULD AND HEALTH -
AN INTERVENTION STUDY
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 firstname.lastname@example.org
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
Financing SYTTY organization:The Academy of Finland, The Finnish Work
Funding from SYTTY / Total funding of project (€): 183627 / 379667
Person-months of work funded by SYTTY / Total person-months of work: 62,5 /
KEY WORDS: moisture, mould,
health, repair, intervention
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
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
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))
3 Results and discussion
Moisture damage in school
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
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 .
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
Symptoms and infections of
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
Repairs of moisture and mold
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
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.
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.
 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.
 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.
 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.
 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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