Characterization of indoor air quality in primary schools in Antwerp, Belgium

The indoor air quality of 27 primary schools located in the city centre and suburbs of Antwerp, Belgium, was assessed. The primary aim was to obtain correlations between the various pollutant levels. Indoor:outdoor ratios and the building and classroom characteristics of each school were investigated. This paper presents results on indoor and local outdoor PM(2.5) mass concentrations, its elemental composition in terms of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Al, Si, S, and Cl, and its black smoke content. In addition, indoor and local outdoor levels of the gases NO(2), SO(2), O(3), and BTEX (benzene, toluene, ethyl benzene, and xylene isomers) were determined. Black smoke, NO(2), SO(2) and O(3), occurred at indoor:outdoor ratios below unity, indicating their significant outdoor sources. No linear correlation was established between indoor and outdoor levels for PM(2.5) mass concentrations and BTEX; their indoor:outdoor ratios exceeded unity except for benzene. Classroom PM(2.5) occurred with a different elemental composition than local outdoor PM(2.5). The re-suspension of dust because of room occupation is probably the main contributor for the I/O ratios higher than 1 reported for elements typically constituting dust particles. Finally, increased benzene concentrations were reported for classrooms located at the lower levels.The elevated indoor PM(2.5), and BTEX concentrations in primary school classrooms, exceeding the ambient concentrations, raise concerns about possible adverse health effects on susceptible children. This is aggravated by the presence of carpets and in the case of classrooms at lower levels. Analysis of PM(2.5)'s elemental composition indicated a considerable contribution of soil dust to indoor PM(2.5) mass. In order to set adequate threshold values and guidelines, detailed information on the health impact of specific PM(2.5) composites is needed. The results suggest that local outdoor air concentrations measurements do not provide an accurate estimation of children's personal exposures to the identified air pollutants inside classrooms.