Key Factors Determining Indoor Air PM(10) Concentrations in Naturally Ventilated Primary Schools in Belgrade, Serbia

INTRODUCTION: Indoor air quality (IAQ) is rated as a serious public health issue. Knowing children are accounted as more vulnerable to environmental health hazards, data are needed on air quality in schools. METHODS: A project was conducted from 2007 until 2009 (SEARCH, School Environment and Respiratory Health of Children), aiming to verify links between IAQ and children’s respiratory health. Study was conducted in ten primary schools on 735 children, in 44 classrooms. Children were randomly selected. Research tools and indicators used for children’s exposure to school environment were indoor and outdoor pollutants, two standardized questionnaires for school and classroom characteristics. In both classroom air and ambient air in front of them we measured, during a 5-day exposure period for continuous 24h measuring: carbon monoxide, carbon dioxide, indoor air temperature, relative humidity, and PM(10) during classes. RESULTS: PM(10) concentrations were significantly most frequent in an interval of ≥80.1μg/m(3), that is, in the interval above 50μg/m(3). Mean PM(10) value was 82.24±42.43 μg/m(3), ranging from 32.00μg/m(3) to of 197.00μg/m(3). CONCLUSION: The increase of outdoor PM(10) concentration significantly affects the increase of indoor PM(10). A statistically significant difference exists for average IAQ PM(10) concentrations vs. indicators of indoor thermal comfort zone (p<0.0001); they are lower in the classrooms with indicators within the comfort zone. Moreover, dominant factors for the increase of PM(10) are: high occupancy rate in the classroom (<2m(2) of space per child), high relative humidity (>75%), and indoor temperature beyond 23°C, as well as bad ventilation habits (keeping windows shut most of the time).