Effects of mould remediation on school teachers health

Transcription

1 International Journal of Environmental Health Research 14(6), (December 2004) Effects of mould remediation on school teachers health RIITTA-LIISA PATOVIRTA, TEIJA MEKLIN, AINO NEVALAINEN and TUULA HUSMAN National Public Health Institute, P.O.B. 95, Kuopio, Finland The follow-up study of the health of teachers (n = 56) of three mould damage schools were done with selfadministered symptom questionnaire before and 1 year after the remediation of school buildings. Technical and microbiological investigations were done parallel at the same time. In the beginning of the study symptoms of allergic rhinitis, sinusitis, conjunctivitis and fatigue were high compared to normal population and 1 year after the intervention a decrease in fatigue (OR = 0.4) and headache (OR = 0.2) was observed. An association between female gender and sinusitis was found before the remediation (OR = 8.1). Age over 40 years was a risk factor for voice problems and more than 10 working years at the same school were associated with increased risk for conjunctivitis (OR = 8.5) and headache (OR = 5.4). Other exposure situations such as mould problems at home and mould exposure during leisure time also have an effect on teachers health. Significant reduction was found in symptoms of fatigue and headache after the cessation of exposure, while respiratory symptoms need much longer time to relieve after the remediation. Age, female gender, atopy, long-term exposure time and other exposure situations might be the risk factors for prolonged symptoms among mould exposed teachers. Keywords: Moisture; mould; remediation; health; follow-up; adults. Introduction Health effects of indoor air pollutants, especially dampness and moisture problems have been under public interest during the last decade. A number of studies have shown a connection between exposure to indoor dampness, moisture or mould and diseases like sinusitis, allergy and asthma among the occupants. The association has been found as well in homes (Pirhonen et al. 1996; Peat et al. 1998; Koskinen et al. 1999; Kilpeläinen et al. 2001; Bornehag et al., 2001; Zock et al. 2002) as in working places such as offices (Menzies et al. 1998), hospitals (Seuri et al. 2000) and day-care centres (Ruotsalainen et al. 1995). However, the main body of evidence concerning the adverse health effects of biological particles comes from occupational medicine where the effects of exposure to organic dust have long been known e.g. in farming, saw mills and biotechnical industry (Halpin et al. 1994; Erkinjuntti-Pekkanen et al. 1999; Thorn et al. 2002). In spite of existing evidence, detailed understanding about the causal agents and pathophysiology of the indoor moisture and mould-related symptoms and even diseases are still unrevealed. Correspondence: Riitta-Liisa Patovirta, National Public Health Instute, P.O. BOX 95, FIN Kuopio, Finland. Tel.: ; Fax: ; riitta.patovirta@ktl.fi ISSN print/issn online/04/ # 2004 Taylor & Francis Ltd DOI: /

2 416 Patovirta et al. The indoor air quality of schools is a concern since the schools are a daily working environment of children and teachers. Moisture and mould damages are common in Finnish school buildings (Kurnitski et al. 1996; Koivisto et al. 2002), and these problems are associated with respiratory symptoms and infections among the school children (Savilahti et al. 2000; Meklin 2002). As for teachers, the few studies available report respiratory symptoms but also observations about increased prevalence of fatigue, eye irritation, nausea, dry throat and hoarseness (Tho rn et al. 1996; Cooley et al. 1998; Sigsgaard et al. 2000; Åhman et al. 2000). Based on this documentation, it is evident that not all the teachers exposed to moisture and mould develop health problems, and hence the risk groups and factors contributing to the risk of illness should be identified. While the relationships between exposing agents and effects are still unclear, intervention studies where the changes in the health status resulting from the elimination of exposure, i.e., the remediation of the building damage, are monitored, may provide further evidence about causal connection between the exposure and effects. Intervention studies of mould damaged buildings may be difficult to cover large populations since the decision making about the timing, financing and technical planning of the intervention, i.e. the technical remediation of the school building is often beyond the influence of the researchers. Futhermore, the number of teachers in a typical school is too low, to fulfil the criteria of a population study, and hence the strength of the study design must be obtained by pairwise observations of the same individuals before and after the intervention. As a summary of the studies published so far, the decrease of the occupants subjective symptoms following a remediation has been notable but not a simple nor quick consequence of the remediation measures (A hman et al. 2000; Ebbehoj et al. 2002). According to objective indicators like nasal hyperreactivity, the responses among mould-exposed teachers decreased slowly taking several years to normalize (Rudblad et al. 2002). A similar trend in slow recovery from the symptoms after remediation was observed among school children, but the effect of remediation was more evident among new pupils attending the school, since they did not develop symptoms (Meklin 2002). Microbial measurements of the indoor air are a surrogate of the exposure estimating the true exposure to pollutants originating from microbial growth in the building structures. The absolute levels of fungi in the indoor air have usually not correlated well with observed health effects (Strachan et al. 1990; Etzel et al. 1998; Garrett et al. 1998; Klanova 2000; Su et al. 2001) but they are rather more linked to the building condition (Hyvärinen 2002). Evidence on whether the fungal counts in indoor air can be used to verify the success of the remediation is scarce, but such tools to evaluate the cost effectiveness of the repair measures are urgently needed. The aim of this study was to document the effects of the building remediation on teachers health and on the microbial status of the indoor environment of the schools. Monitoring the health status and microbial exposure in a parallel time frame together with the remediation allowed the analysis of the possible causal connections between the phenomena. Identifying the risk factors among the teachers that may contribute to the onset of symptoms was also considered relevant. In this study the health of teachers was followed in three mould-damaged schools before and after mould remediation. The health data was collected by self-administered questionnaires. The three school buildings were verified as moisture or mould damaged buildings using technical investigation criteria developed earlier (Nevalainen et al. 1998). Two of the schools underwent a thorough renovation, while the third school was only partly renovated. The exposure assessment was performed with microbial indoor sampling prior to the renovation.

3 Effects of mould on teachers health The same study protocol was repeated in each school 1 year after the remediation process had been completed. 417 Material and methods The three schools under the study are situated in central part of Finland. There were no differences in climatic conditions or sosioeconomic status of the schools. Health data was collected with self-administered questionnaires from the teachers (n = 163) working in those three schools. The questionnaire was based on O rebro-questionnaire (MM4O) (Andersson 1998) and the Tuohilampi questionnaire (Susitaival and Husman 1996) and it included 70 questions on irritation, respiratory and general symptoms, acute respiratory and chronic diseases and allergic diseases. Also demographic data and information on living habits and other exposure situations such as mould exposure at home or hobbies connected to exposure to biological dust (e.g., horseback riding or gardening) were included. The first questionnaire was sent before technical investigations were started. The response rate was 75%. One year after the completion of the repairs a similar questionnaire was sent to the teachers as a follow-up. The time period between the two questionnaires differed from 3 6 years depending on the timetables of the repairs. Both questionnaires were identical to each other. Out of the 123 teachers who answered the first questionnaire, 56 were still working at the same school and answered the second questionnaire. Among the rest of the teachers, 29 had changed their job, 27 had retired and 11 did not return the second questionnaire. To focus on the effects of the intervention only the 56 teachers who answered both questionnaires were included in this study. Among the study participants 16 (29%) were males, mean age of the participants was 45 years, seven (13%) were smokers, 29 (52%) had worked more than 10 years in the studied schools, 13 (23%) reported mould problems at home and 10 (18%) reported exposure to biological dust under their leisure time. The status of moisture and mould damage in the studied school buildings were technically investigated by a trained civil engineer according to a standardized protocol developed and described earlier (Nevalainen et al. 1998). During the investigations various types of visible moisture signs were recorded using a checklist and surface moisture recorders (Doser BD-2) were used to assess the moisture level of surface materials. The extent of the damage and the obvious reasons for the damage were recorded when possible. Detailed technical information regarding the buildings is presented in Table 1. The schools A and B were totally remediated for all known damage, while school C underwent only partial remediation due to economical restraints in the local community. Exposure to indoor air microbes was characterized with environmental sampling using a sixstage impactor (Andersen ). Two different general-purpose media for detecting moulds from indoor environments were used; 2% malt extract agar (MEA) and dichloran 18% glycerol agar (DG18) (Samson et al. 1994), and samples for bacteria were taken on tryptone glucose yeast agar (TGY). Samples were taken mainly from the classrooms, hail facilities, teacher s offices and gyms in different parts of the buildings during their occupancy. Sampling was performed during winter months, when the ground was covered by snow, to minimize the effect of fungi from outdoor air. The total numbers of samples taken were 18, 12 and 17 for the schools A, B and C, respectively. The sampling was repeated in an identical way after the moisture and mould damage remediation works in the schools in the same season of the year. Sampling times were from 7 15 min and detection limits varied from 2 to 5 cfu m 7 3 depending on the sampling time. Incubation times were 7 days at 258C and up to 14 days at

4 Table 1. The geometric means (GM) and the ranges of total concentrations of viable airborne fungi and bacteria and the total numbers of different microbial groups detected before and after the moisture and mould remediation in the studied schools School A School B School C (partially remediated) Building time: 1952 main frame material: concrete/brick area/volume: 5520 m 2 /23552 m 3 five floors Building time: main frame material: concrete/brick area/volume: m 2 /28000 m 3 from one to three floors Building time: 1950, earlier renovated in 1965 main frame material: concrete/brick area/volume: 5644 m 2 /25707 m 3 four floors 1st sampling 2nd sampling 1st sampling 2nd sampling* 1st sampling 2nd sampling Gm Range Gm Range P Gm Range Gm Range P Gm Range Gm Range P Total fungi 23 ND ND ND Total bacteria ND *microbes detected only with MEA. P refers to statistical significance of differences. ND not detected. 418 Patovirta et al.

5 Effects of mould on teachers health room temperature (about 208C) for fungi and bacteria, respectively. Microbial colonies were counted as colony forming units (cfu m 7 3 ) using positive hole correction (Andersen 1958) and fungi were identified morphologically by genus using a light microscope with magnification. Aspergillus versicolor, Aspergillus fumigatus and Aspergillus penicillioides, being regarded as indicators of moisture problems (Samson et al. 1994; Flannigan and Morey 1996), were identified to species level. The procedure of sampling and microbial quantification and identification is described in more detail by Meklin (2002). Statistical analysis Total concentrations of viable airborne fungi and bacteria and concentrations of the most common fungi within a school before and after intervention were compared using the Wilcoxon rank-sum test. Differences in frequencies of certain concentration categories between the schools as well as frequencies of different microbial groups were tested using the w 2 -test. McNemar s test was used to test differences in the occurrence of microbial groups before and after intervention within school. The change in symptom frequencies among the teachers in the follow-up was examined with logistic regression using generalized estimating equations approach to account for the withinteachers dependence (Zeger and Liang 1986). The differences in the occurrence of the dichotomous symptoms and infection variables between different groups were tested with multiple logistic regression and w 2 -tests. The SPSS statistical package, version 10, was used for the analyses (SPSS Inc.,1988). 419 Results The total concentrations of viable airborne microbes in the samples taken before and after repair measures in the studied school buildings are presented in Table 1. All microbial genera found in indoor air in the studied schools before and after the remediation of the school buildings are shown in Table 2. The most frequently found fungi were Penicillium, Cladosporium, Aspergillus and yeasts in all the studied buildings. The total numbers of the different genera, species or groups of fungi were 23, 14 and 19 for the schools A, B and C, respectively. After the remediation, significantly lower mean concentrations of fungi and bacteria were found in indoor air of two school buildings (schools A and B) that went through a total remediation for all the identified moisture and mould damage (Table 1). The reduction was mainly due to reduction in Penicillium concentration but also the occurrence of Aspergillus and Gladosporium was reduced. The overall diversity of the fungal flora was reduced in these two schools. Instead, in the partially remediated school (school C), the concentrations of fungi and bacteria were higher after the repair measures than detected in the initial sampling (Table 1). Only actinomycetes that were frequently found in the school C before the repairs were not found after the repair measures (Table 2). Self-reported allergic symptoms, infections, respiratory symptoms, skin symptoms, medication and general symptoms of the teachers working in mould damaged schools in the initial survey and in the follow-up after the remediation are shown in Table 3. At the beginning of the study, the prevalence of sinusitis was 27%, that of conjunctivitis 25%, allergic rhinitis 30% and fatigue 39%. In the follow-up, after the remediation work in the studied schools, a clear decrease in the risk of fatigue (OR = 0.4, CI ) and headache (OR = 0.2, CI ) was observed. Similar trend was found also in conjunctivitis. The risk for symptoms of allergic rhinitis increased (OR = 1.5, CI ).

6 420 Patovirta et al. Table 2. The occurrence of microbes in indoor-air samples taken in school buildings before and after repair measures School A School B School C (partially remediated) Microbe Before repairs After repairs Before repairs After repairs* Before repairs After repairs Acremonium Aspergillus spp A. fumigatus + + A. niger + A. penicillioides + + A. terreus + A. versicolor Aureobasidium Basidiomycetes + Botrytis + + Cladosporium Chrysosporium + + Doratomyces + Eurotium Exophiala + Geomyces Hyalodendron + + Monocillium + Mucor + + non-sporing isolates Ochroconis + Oidiodendron + + Olpitrichum + Paecilomyces Penicillium Rhizopus Scopulariopsis + + Sphaeropsidales-group Stachybotrys + Trichoderma Trichotechium + Tritirachium + + Ulocladium + yeasts Wallemia actinomycetes Total number of genera observed *only MEA-agar used in fungal analysis. The risk factors contributing to symptoms were considered at the beginning of the study. The results of health status of teachers working in the mould damaged schools in relation to gender, age, working years in that school, exposure to biological dust under leisure time, atopy and

7 Effects of mould on teachers health Table 3. Self-reported health status of the teachers working in the mould damaged schools at the beginning of the study and in the follow up 421 Initial Survey Final Survey n = 56 n = 56 n (%) n (%) OR CI 95% Infection diseases and medication Laryngitis 9 (16) 4 (7) 0.5 ( ) Sinusitis 15 (27) 14 (25) 0.9 ( ) Bronchitis 8 (14) 7 (13) 0.9 ( ) Conjunctivitis 14 (25) 8 (14) 0.4 ( ) Regular medication 17 (30) 22 (39) 1.5 ( ) Irregular medication 19 (34) 16 (29) 0.9 ( ) Respiratory, allergic and skin symptoms Cough with phlegm 12 (21) 8 (14) 0.6 ( ) Rhinitis 18 (32) 14 (25) 0.8 ( ) Allergic rhinitis 17 (30) 22 (39) 1.5 ( ) Hoarseness 8 (14) 7 (13) 1.1 ( ) Facial eczema 10 (18) 7 (13) 0.7 ( ) Hand eczema 10 (18) 8 (14) 0.7 ( ) General symptoms Headache 8 (14) 2 (4) 0.2 ( ) Fatigue 22 (39) 11 (20) 0.4 ( ) mould problems at home at the beginning of the study are shown in Tables 4 and 5. The female teachers had more sinusitis (OR = 8.l, CI ) and fatigue (OR = 4.0, CI ) and they used more irregular medication (OR = 5.1, CI ) compared to male teachers. In addition, while none of the male teachers reported hoarseness and sore throat, 20% and 18% out of female teachers reported these symptoms. Among teachers 40 years of age and below, the risk of allergic rhinitis was significantly higher (OR = 3.7, CI ), whereas the use of regular medication was increased among older teachers. Seven out of eight teachers who had bronchitis or hoarseness were more than 40-years old at the beginning of the study. Extended exposure time (more than 10 years in the same school) clearly associated with conjunctivitis (OR = 8.5, CI ), regular medication (OR = 7.2, CI ), irregular medication (OR = 3.9, CI ) and headache (OR = 5.4, CI ) (Table 4). As shown in Table 5 teachers reporting exposure to organic dust, such as gardening, under leisure time had more frequently sinusitis (OR = 6.0, CI ) and conjunctivitis (OR = 4.0, CI ) and they also often used more irregular medication (OR = 6.4, CI ) than teachers with no such activities. Similarly, hand eczema and face eczema were associated with gardening. Atopic individuals had an increased risk for allergic rhinitis (OR = 7.9, CI ) and ordinary rhinitis (OR = 4.4, CI ) and a similar trend was also found in sinusitis and facial and hand eczema. Mould problems at home was a risk factor for sore throat (OR = 5.9, CI ) and as a trend for headache.

8 Table 4. Effect of gender, age, and exposure years at school on the self-reported health status of the teachers working in the mould damaged school at the beginning of the study Gender Age Years at school male female 5 40 years 4 40 years 5 10 years 4 10 years n (%) n (%) OR 95% CI n (%) n (%) OR 95% CI n (%) n (%) OR 95% CI Allergic diseases Allergic rhinitis 4 (25) 13 (33) 1.4 ( ) 11 (46) 6 (19) 3.7 ( ) 9 (35) 7 (24) 0.6 ( ) Atopic eczema 5 (31) 11 (28) 0.8 ( ) 7 (29) 9 (28) 1.0 ( ) 6 (23) 9 (31) 1.5 ( ) Respiratory infections Sinusitis 1 (6) 14 (35) 8.1 ( ) 6 (25) 9 (28) 0.9 ( ) 6 (23) 9 (31) 1.5 ( ) Bronchitis 1 (6) 7 (18) 3.2 ( ) 1 (4) 7 (22) 0.2 ( ) 3 (12) 5 (17) 1.6 ( ) Conjunctivitis 3 (19) 11 (28) 1.6 ( ) 4 (17) 10 (31) 0.4 ( ) 2 (8) 12 (41) 8.5 ( ) Regular medication 4 (25) 13 (33) 1.4 ( ) 3 (13) 14 (44) 0.2 ( ) 3 (12) 14 (48) 7.2 ( ) Irregular medication 2 (13) 17 (43) 5.2 ( ) 8 (33) 11 (34) 1.0 ( ) 5 (19) 14 (48) 3.9 ( ) Respiratory and skin symptoms Cough with phlegm 2 (13) 10 (25) 2.3 ( ) 4 (17) 8 (25) 0.6 ( ) 5 (19) 7 (24) 1.3 ( ) Rhinitis 3 (19) 15 (38) 2.6 ( ) 6 (25) 12 (38) 0.6 ( ) 8 (31) 9 (31) 1.0 ( ) Sore throat 0 7 (18) * 2 (8) 5 (16) 0.5 ( ) 1 (4) 6 (21) 6.5 ( ) Hoarseness 0 8 (20) ** 1 (4) 7 (22) 0.2 ( ) 2 (8) 6 (21) 3.1 ( ) Facial eczema 3 (19) 7 (18) 0.9 ( ) 5 (21) 5 (16) 1.4 ( ) 4 (15) 5 (17) 1.1 ( ) Hand eczema 2 (13) 8 (20) 1.8 ( ) 4 (17) 6 (19) 0.9 ( ) 6 (21) 3 (12) 2.0 ( ) General symptoms Fatigue 3 (19) 19 (48) 3.9*** ( ) 8 (33) 14 (44) 0.6 ( ) 8 (31) 14 (48) 2.1 ( ) Headache 1 (6) 10 (25) 5.0 ( ) 2 (8) 9 (28) 0.2 ( ) 2 (8) 9 (31) 5.4 ( ) *P = 0.074, **P = 0.053, ***P = Patovirta et al.

9 Table 5. Effect of exposure to gardening, atopy and mould problems at home on the self-reported health status of the teachers working in the mould damaged schools at the beginning of the study Gardening Atopy Mould at home yes no yes no yes no n (%) n (%) OR 95% CI n (%) n (%) OR 95% CI n (%) n (%) OR 95% CI Allergic diseases Allergic rhinitis 4 (40) 13 (29) 1.6 ( ) 10 (63) 7 (18) 7.9 ( ) 5 (39) 12 (28) 1.6 ( ) Atopic eczema 5 (50) 11 (25) 3.1 ( ) 16 (100) 0 **** 6 (46) 10 (23) 2.8 ( ) Respiratory infections Sinusitis 6 (60) 9 (20) 6.0 ( ) 7 (44) 8 (20) 3.1 ( ) 4 (31) 11 (26) 1.3 ( ) Bronchitis 1 (10) 7 (16) 0.6 ( ) 2 (13) 6 (15) 0.8 ( ) 2 (15) 6 (14) 1.1 ( ) Conjunctivitis 5 (50) 9 (20) 4.0* ( ) 5 (31) 9 (23) 1.6 ( ) 3 (23) 11 (26) 0.9 ( ) Regular medication 1 (10) 16 (36) 0.2 ( ) 7 (44) 10 (25) 2.3 ( ) 5 (39) 12 (28) 1.6 ( ) Irregular medication 7 (70) 12 (27) 6.4 ( ) 8 (50) 11 (28) 2.6 ( ) 6 (46) 13 (30) 2.0 ( ) Respiratory and skin symptoms Cough with phlegm 0 12 (27) ** 5 (31) 7 (18) 2.1 ( ) 3 (23) 9 (21) 1.1 ( ) Rhinitis 2 (20) 16 (36) 0.5 ( ) 9 (56) 9 (23) 4.4 ( ) 6 (46) 12 (28) 2.2 ( ) Sore throat 2 (20) 5 (11) 2.00 ( ) 2 (13) 5 (13) 1.00 ( ) 4 (31) 3 (7) 5.9 ( ) Hoarseness 3 (30) 5 (11) 3.4 ( ) 2 (13) 6 (15) 0.8 ( ) 2 (15) 6 (14) 1.1 ( ) Facial eczema 4 (40) 6 (13) 4.3*** ( ) 5 (31) 5 (13) 3.2 ( ) 4 (31) 6 (14) 2.7 ( ) Hand eczema 4 (40) 6 (13) 4.3*** ( ) 5 (31) 5 (13) 3.2 ( ) 3 (23) 7 (16) 1.5 ( ) General symptoms Fatigue 5 (50) 17 (38) 1.6 ( ) 6 (38) 16 (40) 0.9 ( ) 6 (46) 16 (37) 1.4 ( ) Headache 2 (20) 9 (20) 1.00 ( ) 3 (19) 8 (20) 0.9 ( ) 5 (39) 6 (14) 3.9***** ( ) Effects of mould on teachers health *P = 0.049, **P = 0.065, ***P = 0.048, ****P = 0.000, *****P =

10 424 Patovirta et al. Discussion In this intervention study the same group of the teachers of the school were followed before and after the remediation of the school buildings. This was done to study the effect of elimination of moisture and mould exposure on teachers health. The buildings were investigated before and after remediation process by a protocol used in earlier studies (Nevalainen et al. 1998). Two of the schools were repaired completely, one partly. The improvement in the microbial status of the buildings after moisture and mould remediation was clearly seen in two of the studied schools. Both the airborne and concentrations and diversity of microbes decreased. In the partially remediated building, the improvement was not as evident and seen in single microbial groups rather than in total concentration. The results support the conclusion that the microbial status of building reflects its condition in the sense of dampness and moisture conditions, but the connection of microbial counts and diversity to occupants health is more complicated. The symptom profiles of the teachers did not differ between different schools, thus, the teachers were considered as one group in the follow-up. In the beginning of this study, symptoms of allergic rhinitis, sinusitis, conjunctivitis and fatigue were increased compared to randomly selected population (Pirhonen et al. 1996). Otherwise the frequencies of the self-reported symptoms and diseases among moisture and mould exposed teachers were not exceptionally high compared to general population (Pirhonen et al. 1996). After the remediation, the symptom rate of allergic rhinitis was 39%, which is an even higher prevalence than before. As for sinusitis and conjunctivitis, no significant change as a result of intervention was observed. This suggests that the development of such symptoms and diseases is a slow process, which does not necessarily stop immediately after the exposure has ceased. It has been previously observed that the recovery of the symptoms may also be slow and last for years, like decrease of acquired hyper-reactivity of the upper airways as reported among a group of mould exposed teachers in Sweden (Rudblad et al. 2002). Out of non-specific symptoms, fatigue was exceptionally often reported. As a result of intervention fatigue and another non-specific symptom, headache, were significantly reduced. Fatigue and headache have often been connected to moisture and mould exposure in indoor environments (Pirhonen et al. 1996; Koskinen et al. 1999; Bornehag et al. 2001), however, any causal relationship to a specific exposing agent is not known. In this intervention study, a significant reduction in the prevalence of these symptoms speaks for a causal connection. Contrary to the respiratory symptoms discussed above, these symptoms appear to be more closely related to existing exposure and to decrease after elimination of exposure. Female gender turned out to be a risk factor for sinusitis as well as symptoms of sore throat, hoarseness and fatigue at the beginning of the study. It has been shown in previous studies that females tend to report symptoms more often (Pirhonen et al. 1996). To the knowledge of the authors this is the first study where an association between female gender and sinusitis has been found in moisture and mould exposed teachers. Sinusitis, which is a doctor-diagnosed disease, confirms the previous differences in symptom reporting between females and males. Those differences may have hormonal and immunological background (Paavonen et al. 1981; Evangelatou and Farrant 1994), although the phenomenon is still poorly understood. Age was another significant risk factor since the teachers over 40 years old reported more voice problems than younger ones. All the individuals reporting problems with voice were females, but the proportion of male teachers was so small that their risk could not be assessed. In earlier studies among female teachers voice problems were reported twice as often as male teachers (Russell et

11 Effects of mould on teachers health al. 1998), but the aetiology of this phenomenon is still open. It is not possible to distinguish which risk factor is more important but both female gender and age seemed to be involved. Atopy increased the risk of allergic diseases like allergic rhinitis and atopic eczema and as a trend more sinusitis, facial and hand eczema was found among atopic than non-atopic teachers. Working years at school, i.e. duration of exposure seemed to have an influence on teachers health. At the beginning of the study, conjunctivitis and headache were connected with work history exceeding 10 years at the same school. In long-term exposures, also low exposure levels may finally lead to health consequences (Bernstein et al. 1983; Kateman et al. 1990). Adverse health effects of occupational exposure to indoor mould are complicated to assess because microbial exposure occur not only at the work place but also at home and during leisure activities. This study found a significant association between exposure to biological dust in garden work under leisure time and sinusitis, conjunctivitis, facial- and hand eczema. This interesting finding is in accordance with previous findings for example in farming (Erkinjuntti- Pekkanen et al. 1999) and green house work (Larese et al. 1998). Although the microbial concentrations under leisure time activities like gardening are probably lower than in farm work, the exposing agents are partly the same in these environments. Also, mould problems at home had an effect on teachers health in moisture and mould damaged schools. Sore throat and headache were more common in teachers living in a house with mould problems. Thus in spite of repair, continuing exposure in other environments than the work place may have a role in continuing irritation symptoms among the previously exposed teachers. 425 Conclusion Fatigue and headache seem to be symptoms that timewise connect to indoor exposure to mould, while many respiratory symptoms need a much longer time to relieve after the remediation. Mould problem is a complicated phenomenon and in evaluation of beneficial effects of remediation, other factors influencing general health and exposure in other surroundings also have an effect. Based on results obtained in this study, risk factors for continuing symptoms among teachers can be age, female gender, atopy, extended exposure time and other exposure situations. This is a challenge to occupational health care system. Acknowledgements The authors thank Mr Pekka Tiittanen MSc. for his advice in statistical analyses. We are also grateful to the teachers and town administration for making this research possible. References Andersen, A.A. (1958) New sampler for collection, sizing and enumeration of viable airborne particles. J. Bacteriol. 76, Andersson, K. (1998) Epidemiological approach to indoor air problems. Indoor Air 4(suppl.), Ahman, M., Lundin, A., Musabasic, V. and So derman, E. (2000) Improved health after intervention in a school with moisture problems. Indoor Air 19,

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