Dampness and Mold
Dampness and Mold in Schools
A detailed discussion of the significance of building dampness and mold in homes for health is provided in the section of this website dedicated to dampness and mold and health. Based on a large body of research, visible dampness and mold in homes and mold odor are associated with increases in respiratory and asthma symptoms, and with increases in development of the disease of asthma, although the specific agents causing the increases in health effects are not known. A smaller but significant body of research indicates that dampness and mold in homes is associated with increases in respiratory infections.
Less research is available on the health consequences of dampness and mold in schools, although the number of published studies is now substantial. Table 3 below summarizes features and findings of 23 studies published in refereed archival journals. Many of the published studies have a cross sectional design, with dampness and mold data and health data collected from numerous schools or classrooms, and statistical models employed to test for associations (correlations) of health effects with measures of dampness and mold. Typically, data on other factors that may confound the relationship of dampness and mold with health were collected and used in the statistical models to better isolate the relationships of dampness and mold with health. Some of these cross sectional studies have intentionally selected sets of buildings with and without known dampness problems. Cross sectional studies test for associations (correlations) but cannot prove causal relationships. A handful of published studies include assessments of health effects before and after remediation efforts designed to reduce or eliminate dampness and mold problems. These studies usually include reference buildings without any known dampness problems and without remediation efforts, and some of these studies also incorporate a pre-renovation cross-sectional element.
Various subsets of the studies identified in Table 3 can be considered together because of their common features. First consider the eight largest studies, each with more than 1000 subjects [1-8]. Six of these studies [1, 2, 4, 5, 7, 9] report statistically significant increases in respiratory symptoms or asthma in schools or classrooms with moisture damage or mold, or with higher airborne mold levels, or report reductions in symptoms after remediation to address water damage and mold problems. One study [3] reported a small statistically significant decrease in wheeze. Next consider the 13 studies that used visible moisture damage or mold or mold odor as a risk indicator [2, 4, 6, 7, 10-18]. Eleven of the 13 studies report statistically significant increases in one or more respiratory symptoms or school absence when water damage and/or mold is present [2, 4, 7, 10-12, 14-18]. These findings mirror the similar findings from studies in homes. Five studies in Table 3 used higher concentrations of mold in the air as the risk factor [1, 3, 8, 19, 20]. Three of five report statistically significant increases in respiratory symptoms or asthma with higher airborne mold levels [1, 8, 20], one reported a small statistically significant decrease in wheeze [3]. One study reported no significant associations of nasal symptoms with airborne molds [19] but found higher airborne mold associated with reduced nasal patency (reduced openness of the nose). Three studies from Table 3 used higher levels of mold in dust as the measure of risk [2, 21, 22]. Two of the three studies found this risk parameter associated with increases in health symptoms of various types or with asthma [21, 22]. Table 3 includes four studies that assessed whether renovations to address dampness and mold problems in schools improved health [5, 23-25]. All four report statistically significant improvements in some respiratory health outcomes after renovations. In one of these studies, a through renovation was associated with improved health but a partial renovation did not significantly improve health [5]. Finally, Table 3 includes seven studies that investigated whether dampness and mold indicators were associated with objective (measured) health outcomes such as lung function or markers of allergic or inflammatory responses [2, 10, 19-21, 24, 25]. Three of the seven studies find statistically significant associations of objective health outcomes with indicators of building dampness or mold [19, 20, 25]. Most of the studies in Table 3 included assessments of several health outcomes. When studies found worsened health with indicators of dampness and mold, often only a modest subset of the assessed health outcomes worsened. In instances with worsened health outcomes with indications of dampness and mold, the magnitude of the increase was often greater than 50% and in a few cases greater than 200%.
The relatively consistent findings of a substantial number of quality studies indicate that there is an association of dampness and mold in schools with increased respiratory health symptoms, such as reported cough or wheeze, among occupants of the schools. Visible dampness and mold or mold odor are more clearly associated with symptoms than are higher levels of measured mold in air or dust. Objective health measures are, however, less consistently associated with dampness and mold in schools. Overall, these findings mirror those available from a larger body of research on dampness and mold in homes.
A published meta-analysis [26] of eleven cross sectional studies provides a quantitative synthesis of the associations of respiratory health effects with visible dampness or mold, or mold odor, in schools. The meta-analysis yielded central estimates of associations, essentially correlations, of respiratory health effects of school occupants with dampness and mold in schools based on the results of multiple studies. The meta-analysis provided central estimates for odds ratios and their 95% confidence limits. The odds ratios indicate the direction and strength of associations. For example, an odds ratio of 1.3 with 95% confidence limits of (1.1 – 1.5) for wheeze would indicate approximately a 30% increase in wheeze when dampness and mold is present. When the 95% confidence limits exclude unity, such as in the example above, the finding is considered to be statistically significant, with a low probability that the central estimate differs from unity by chance. The central estimates of odds ratios from the meta-analysis were consistently above unity suggesting increased respiratory health effects when schools have dampness or mold. The evidence of adverse health effects of dampness and mold in schools was strongest for cough and wheeze, which had 95% confidence limits excluding unity in some or all analyses. The central estimates of odds ratios of 1.32 for cough and 1.68 for wheeze suggest moderate, 30% to 60%, increases in health risk. A report version of the published paper based on this meta analysis is available in the downloadable papers section.
Improvements in building design, construction, operation, and maintenance practices are the key to prevention of dampness and mold in schools. Also, when problems occur the sources of moisture should be addressed and contaminated materials cleaned or replaced. For more information, see the subsection on implications for good building practice in the section of this web site on dampness and mold.
Table 3. Studies of association of health outcomes with dampness and mold in schools.
|
Setting (study type codes*) |
Key findings |
Key Strengths and Weaknesses |
Ref-erence |
|
173 workers from two university buildings in Norway with, and two buildings without, history of dampness and complaints (VM, OH) |
In the problem buildings, there were statistically significant increases in general symptoms (heavy headed, headache, nausea/dizziness, difficulty concentrating) and one dermal symptom and there were non-statistically-significant increases in other dermal symptoms and mucosal symptoms. Objective signs of health including tear film stability, a measure of nasal openness, and indicators of allergy and inflammation in nasal lavage fluids were not increased in problem buildings. |
Strengths: Controlled for age and gender; inclusion of objective health measures Weaknesses: Small study size |
[10] |
|
419 children, age 6 – 12 with respiratory health conditions from Finland, Netherlands, and Spain from 15 moisture damaged and 10 reference schools (VM) |
Symptom scores were generally lower during weekends and school holidays. In students from moisture damaged Spanish schools, there were statistically significantly larger decreases in lower respiratory symptoms during holidays. In students from moisture damaged Finish schools, there were statistically significantly larger decreases in other symptoms. |
Strengths: Controlled for age, sex, day with colds, exposure to smoke Weaknesses: NA |
[11] |
|
6346 schoolchildren, age 6 to 15, from 44 schools in Taiwan (LS, AM) |
In students from classrooms with higher concentrations of certain types of fungal spores, there was a statistically significant increase in reported current asthma and in asthma with symptoms reduced during holidays. |
Strengths: Analysis controlled for age, sex, parental allergy, mother smoking during pregnancy, visible mold at home and at school; large study size Weaknesses: Short measurement period; many statistical tests increased chance of random associations |
[1] |
|
522 teachers from 15 Danish schools with range of building dampness (DM, OH) |
Objective indicators of allergy and inflammation were not associated with amounts of mold in floor dust. In female teachers, there were statistically significant associations of mucous membrane and skin symptoms and general symptoms (e.g., headache, fatigue) symptoms with higher levels of mold in floor dust. |
Strengths: Analysis controlled for personal and work related factors, and some building characteristics. Inclusion of objective measures of health Weaknesses: NA |
[21] |
|
3842 children, age 6-12, from 15 moisture damaged and 10 reference schools in Finland, Netherlands, Spain. Lung function data were from 2736 of the children (LS, VM, DM, OH) |
Respiratory symptoms were generally higher in moisture damaged schools but the increase was statistically significant only for dry cough at night. There was no associations of measured lung function with moisture damage. Symptoms and lung function were also not associated with levels of microbial markers in samples of settled dust. |
Strengths: Analysis controlled for gender, age, parental education, moisture damage at home; large study size Weaknesses: Dust samples from multiple classrooms was pooled. |
[2] |
|
500 elementary and secondary teachers in schools from New York state (VM) |
Teachers who reported visible mold, or moisture damage at school, or mold odor had statistically significant and substantial (> 50%) increases in having any symptom, and any allergic/respiratory symptom |
Strengths: Analysis controlled for age, gender, school size, school district economic need, years at school, grade level, tobacco smoke exposure, pets at home, nearby busy road Weaknesses: No measurements; Teachers reported both their symptoms and prevalence on dampness/mold problems |
[12] |
|
1014 students from 8 primary schools in Sweden, no classrooms had visible signs of dampness or mold, or mold odor (LS, AM) |
There was a very small but statistically significant decrease in wheeze with higher levels of total airborne viable mold. There were statistically significant increases in nocturnal breathlessness, but not wheeze, daytime breathlessness, or doctor diagnosed asthma with higher concentrations of microbial volatile organic compounds (VOCs that can be emitted by microorganisms but that may also have other sources) |
Strengths: Analysis controlled for age and gender Weaknesses: Measurements were made in only a sample of classrooms housing the students |
[3] |
|
In Finland, pupils of one moisture damaged elementary school before and after renovation, and pupils of one reference elementary school over same period (DR) |
Prior to the renovation there were statistically significantly higher prevalence rates of most nasal and respiratory symptoms in the damp school. After renovation, symptom prevalence rates decreased in the renovated school and became similar to, and sometimes lower than, prevalence rates in the reference school. Prior to the renovation, but not post renovation, concentrations of airborne microbial agents were higher in the damp school. |
Strengths: One of very few studies of renovation effectiveness Weaknesses: Small study, no control for potential confounders except for matching of schools by grade level and socio-economic region |
[23] |
|
4365 pupils from 26 schools in Finland, some with known moisture problems (LS, VM) |
Moisture damage was a statistically significant risk factor for increased respiratory symptoms of students in schools with concrete/brick construction but not schools constructed of wood. |
Strengths: Analysis controlled for age, gender, atopy, moisture at home Weaknesses: NA |
[4] |
|
> 1300 students from two moisture damaged and then renovated schools and two reference schools, all in Finland (LS, DR) |
In the one school with thorough moisture damage renovation, respiratory and other symptoms decreased, see [23] for an update. In the school with only partial repairs of moisture problems, there were few statistically significant decreases in symptoms. |
Strengths: One of very few studies of renovation effectiveness Weaknesses: No mention of control for potential confounding factors |
[5] |
|
942 children, age 3 to 5, in 175 daycare centers in Norway. (VM) |
Dampness problems were common but rarely severe. Dampness was not associated with any respiratory symptom, respiratory infection, or with asthma or hay fever |
Strengths: Analysis controlled for several daycare, family, and home environmental characteristics. Dampness assessment by a trained inspector Weaknesses: NA |
[13] |
|
234 staff of 12 primary schools in Sweden (AM, OH) |
Nasal symptoms were not associated with airborne total mold or airborne viable molds. There was a statistically significant decrease in nasal patency (a measure on nasal openness) with higher airborne levels of total molds and when Aspergillus spp. was present. Aspergillus spp. was also associated with allergic and inflammatory markers in nasal lavage fluids. |
Strengths: Analysis controlled for age, gender, smoking, atopy, classroom temperature Weaknesses: Small study, Measurements performed in only two classrooms per school |
[19] |
|
462 students from 32 classes of 8 secondary schools in Malaysia (DM) |
There were statistically significantly increases in daytime breathlessness with higher Aspergillis versicolor DNA in dust and increases in doctor diagnosed asthma with higher ergosterol (a fungal marker) in dust. |
Strengths: Analysis controlled for gender, race, smoking, parental allergy/asthma Weaknesses: NA |
[22] |
|
323 employees of 13 college buildings in U.S., 7 buildings had moisture damage (VM) |
There were approximately two to three fold higher rates of eight respiratory symptom in the moisture damaged buildings, and the increases were statistically significant. There were statistically significant increases in wheeze, chest tightness, shortness of breath, nasal symptoms and sinus symptoms, but not cough and throat irritation, with visible mold. An index of individual exposure to mold and water damage was associated with symptoms in a dose response manner. |
Strengths: Analysis controlled for age, gender, smoking, job status, year of hire, atopy, use of latex gloves. Dampness assessed by trained inspectors. Weaknesses: NA |
[14] |
|
31 teachers from two school buildings in Finland with moisture and mold damage, before and after remediation, and 13 teachers from a reference building at the same campus (DR, OH)
|
After remediation, among teachers in the moisture-damaged schools there were statistically significant decreases in bronchitis, conjunctivitis, allergic rhinitis, and respiratory infection episodes, but no statistically significant improvements in several other symptoms or lung function. In the teachers from the reference school, there were two symptom categories with statistically significant increases and one symptom category with statistically significant decreases. |
Strengths: One of few studies of intervention effectiveness Weaknesses: Small study size |
[24] |
|
268 female workers at 30 daycare centers in Finland (VM) |
70% of daycare centers had water damage, 17% had mold odor. In centers with water damage and mold odor, there were statistically significant increases in eye and nasal symptoms, non-significant increases in several other symptoms, and non-significant decreases in skin symptoms and difficulty concentrating |
Strengths: Analysis controlled for age, atopy, smoking, job type, building type, ventilation system type, ventilation rate, moisture at home. Building dampness verified by research team Weaknesses: Small study size |
[15] |
|
309 employees of two U.S. elementary schools with dampness and mold (VM) |
Relative to symptom rates reported by adults in a national survey, there were statistically significant increases in a variety of respiratory, eye, and skin symptoms. |
Strengths: Analysis controlled to some extent for gender, age, smoking Weaknesses: Reference population not closely matched to exposed population |
[16] |
|
1077 students of eight elementary schools in Japan (LS, VM) |
In general, health symptoms increased in schools with dampness and mold, but the increases were not statistically significant except for nasal symptoms. |
Strengths Analysis controlled for age, sex, atopy, housing type and its ventilation method, ventilation method of school, construction year of dwelling, pupils per class Weaknesses: Not clear if analysis controlled for dampness at home |
[6] |
|
397 students of two elementary schools in Finland, one with moisture damage, before and after remediation. Blood samples for IgE tests from 119 children (VM, DR, OH) |
Prior to renovation, respiratory symptoms, respiratory infections, and visits to a doctor were higher among students of the moisture damaged school and the differences were statistically significant. Also, elevated IgE levels, a measure of allergic response, were more common among students of the moisture damaged school. Students of the moisture damaged school had a higher rate of new allergic diseases after starting school, but the increases were generally not statistically significant. After renovation, there were no significant differences in these health outcomes between the two schools. |
Strengths: Groups were not different in pets at home, tobacco smoke at home, visible mold at home. Weaknesses: Analysis did not control for several potential confounders |
|
|
654 students, mean age 10, from 46 classrooms in Europe, with lung function tests of 244 students (AM, OH) |
There were statistically significant and more than two-fold increases in risks for dry cough at night, persistent cough, and rhinitis with high viable mold levels in air. Higher Aspergillis/Penicillium DNA in dust was associated with increased wheeze and higher Aspergillis versicolor DNA in dust was associated with increased wheeze, rhinitis, and cough, and the associations were statistically significant. Also, performance in lung function tests diminished with increased Aspergillis and Streptomyces DNA in dust. |
Strengths: Analysis controlled for gender, age, smoke exposure at home, asthma; inclusion of objective health measures Weaknesses: NA
|
[20] |
|
2751 grade K-12 schools in New York state (LS, VM) |
There were statistically significant increases in student absence with visible mold, and generally non-significant increases in absence with water damage |
Strengths: Analysis controlled for socio-economic status, urban school, attendance by high school students, pupil teacher ratio Weaknesses: Analysis was at the school level, not the classroom level. No control for conditions at home, such as mold at home. |
[7] |
|
Students of 100 classrooms from 39 primary and secondary schools in Sweden, with data collected in 1993 and 1997 (LS, AM) |
There was a statistically significant increase in new asthma diagnosis among children without atopy with higher mold levels in classroom air. |
Strengths: Analysis controlled for age, gender, allergic status, smoking; large study size Weaknesses: Short term (4 h) sampling for airborne mold |
[8] |
|
662 children age 7 – 13 from a moisture damaged or reference elementary school in Finland; includes 212 children with asthma, wheezing, or prolonged cough (VM) |
Children from moisture damaged school had a statistically significant increase in wheeze and cough, but not asthma. Among 212 children with asthma, wheeze, or persistent cough, rates of allergic rhinitis and atopic eczema, but not allergic conjunctivitis, were significantly increased among the students of the moisture damaged school. During the spring, there was a statistically significantly increase in emergency visits (presumably to hospital emergency room) and antibiotic use among students of the moisture damaged school. |
Strengths: Analysis controlled for age, gender, atopy Weaknesses: Only 2 schools |
[18] |
* LS = large study with > 1000 subjects VM = study used visible mold or water damage or mold odor as indicator of risk AM = study used airborne mold levels as indicator of risk DM = study used dust mold levels or level of microbial markers in dust as indicator of risk DR = study of effectiveness of dampness and mold renovation OH = study with objective (measured) health outcomes
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