Indoor Environment in University Buildings. Assessment of subjective and objective parametres and outcomes
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In 2004, symptoms, perceptions and indoor exposures were studied among 173 (86%) of the employees in four University buildings of which two were claimed to have dampness problems (problem buildings), two other buildings served as controls. In addition, physiological signs from eyes, airways and blood were examined. The main objective was to study symptoms and physiological signs in relation to the indoor environment. The buildings were inspected and characterised, including noise and lighting assessments. Indoor climate measurements of air temperature (T-air), relative humidity (RH%), carbon dioxide (CO2), air velocity, and particulate matter, assessed gravimetric as particles with less than 10 μm aerodynamic diameter (PM10), were performed in a number of representative rooms that were categorised according to location, size and function. In total, 56 logging points were covered. The logging periods were mostly set to two days (9 am to 4 pm) and one night (4 pm to 9 am) in each room. Measurements were collected every fifth minute through the monitoring period for the thermal data, CO2, air velocity and RH%. Outdoor meteorological data were also collected. The results were modelled according to building and office size in order to assign data for the work site of all participants. Microbiological assessments included viable microbiological sampling in air aiming to compare microbial flora composition between outdoor air, air intakes and indoor air. Air samples were collected from outdoors near the air inlets, inside the ventilation aggregates, between the filter and the fan, in technical rooms and in user areas including offices. A total of 191 air samples were collected. A questionnaire with standardised questions about symptoms and perception of indoor climate, demographic and life-style factors, home environment and job demands, control and social support at work were answered by the participants. A symptom score (SC) was constructed from the number of weekly symptoms. Job demands and control were combined to the factor “strain”. Multiple linear and logistic regressions were applied. A medical investigation was performed at the workplace in March 2004, after the influenza season and before the pollen season. Tear film break-up time was measured by ocular microscopy (NIBUT) and by recording the time the individual could keep their eyes open without blinking (SBUT). Nasal patency was measured by acoustic rhinometry. Nasal lavage fluid analysis (NAL) included eosinophilic cationic protein (ECP); myeloperoxidase (MPO), lysozyme and albumin. Total serum IgE and specific IgE (Phadiatop®) were analysed. The microbial airborne flora was normal in all buildings and other environmental exposures were within prevailing requirements and recommended standards. Comparing the buildings, no differences were found in psychosocial environment. Workers in the problem buildings had higher prevalence of one dermal and five general symptoms, but no increase of ocular, nasal or other respiratory symptoms, specific IgE (Phadiatop), total IgE or any physiological signs. In general, both NIBUT and SBUT were shorter at lower night temperature. Adjusted day NIBUT and SBUT increased at higher night air temperatures with B; 95% CI: 0.6; 0.04-1.2 and 1.3; -0.02-2.5, respectively. Low air temperature at 6 a.m. was associated with decreased tear film stability during work hours. This association was weaker for air temperature at 8 a.m. and no associations were found for air temperature at 10 a.m. Higher relative humidity at mean day air temperature < 22.1oC was associated with increase of adjusted NIBUT and SBUT; B; 95% CI: 0.16; 0.03- 0.29 and 0.37; -0.01-0.75, respectively. Air velocity below prevailing winter recommendations and lower relative humidity in the range of 15-30% were associated with perceiving dry air and too low temperature. 15% of the participants had a damp dwelling, and 20% had a cat or dog. Home building dampness was associated with increased NAL-lysozyme (p=0.02) and an increase of airway infections (OR=3.14: p=0.04). Pet keeping was associated with more difficulties to concentrate, feeling heavy-headed and tiredness but less airway infections. Women reported more often health symptoms than men and also more complaints on physical but not psychosocial factors at work. Men’s symptoms and complaints were more specifically associated to air velocity and humidity. For both genders, symptoms were related to both strain (P=0.02) and perceived physical environment (P=0.01). Lower relative humidity in the range of 15–35% was associated with perception of too low temperature and dry air. Perceiving “dry air”, having ocular symptoms and lower BUT were strongly associated in office environment employees. To have experienced “ever asthma” and “ever hay fever” were predictors for symptoms and perceived air quality respectively. Markers of atopy in terms of Phadiatop, Total IgE, familiar allergy and “ever eczema” were not associated to symptoms or perceived environments. Gender was associated to environmental perceptions, BUT and nasal patency. Age was associated to nasal patency. Recent airway infections were predictors for nasal lavage markers. In conclusion, workers in the problem buildings had more general and dermal symptoms, but not more objective signs than the others. However, thermal climate and ventilation in university buildings, may affect both symptoms and physiological signs. Both gender, psychosocial and physical environment factors were related to symptoms and perceived indoor climate. Reduced night time temperature might create impaired indoor environment. A combined use of questionnaires of symptoms, perceived air environmental complaints, measurements of tear film break up time, nasal patency and NAL-markers can be a useful method to study human reactions to the indoor environment. A holistic perspective is needed.
PublisherThe University of Bergen
Copyright 2008 Jan Vilhelm Bakke.