Indoor environmental quality in school buildings, and the health and wellbeing of students.

Poor indoor environmental quality (IEQ) in classrooms may be a risk for health symptoms and cause absence from school. We conducted a comprehensive study in order to assess the connection between IEQ in Finnish elementary school buildings and the health and academic performance of sixth grade students. The specific aim of the present paper was to study the school- or grade-level prevalence of symptoms in relation to IEQ. The school- or grade-level (i.e. group level) prevalence of self-reported symptoms and perceived IEQ was studied using data collected by a health questionnaire comprising 37 questions. The health questionnaire was sent to all 6th grade students in a stratified random sample of 355 elementary schools in Finland. Indoor environmental conditions were assessed with measurements of ventilation rate and thermal conditions of classrooms in a subsample of 56 schools. Altogether 297 elementary schools participated in the health questionnaire study and a total of 4248 questionnaires were returned (estimated response rate 62.6%). The most common weekly symptoms in the spring semester were fatigue (7.7%), stuffy nose (7.3%), and headache (5.5%). However, both mean prevalence values for different symptoms among all 6th grade students and group-level prevalence values for specific symptoms varied considerably. On the group level, the prevalence values most frequently found above 95% CI (calculated for N=15) were wheezing, cough with wheezing, and fever over 37°C. The most frequently reported IEQ factors causing daily inconvenience in classrooms were noise (11.0%) and stuffy air/poor indoor air quality (IAQ) (7.0%), which were also found most frequently above 95% CI on the group level (calculated for N=15), together with self-reported high indoor temperature and dust or dirtiness. Self-reported daily stuffiness/poor IAQ was significantly correlated with measured mean temperatures and ventilation rates in classrooms. High prevalence of students' self-reported stuffiness/poor IAQ may indicate high indoor temperature or low ventilation rate in classrooms. Also high group level prevalence of other IEQ factors and certain symptoms may be indicative of IEQ problems that should be further studied. The results of this study can be used as a reference for assessing the questionnaire-based prevalence of self-reported symptoms among 6th graders, and their association with IEQ in classrooms. For such assessment, the number of students responding to the questionnaire must be carefully considered, also bearing in mind that prevalence values are symptom specific.