Indoor and outdoor BTX levels in Barcelona City metropolitan area and Catalan rural areas

Five aromatic hydrocarbons (benzene, toluene, and three isomeric xylenes) were monitored in indoor and outdoor air of 7 public buildings and 54 private homes, located in Barcelona City metropolitan area and in several rural areas of Catalonia. The sampling was carried out over four periods: spring-summer and winter of 2000, and summer and winter of 2001. Passive ORSA 5 Draiger samplers were used for benzene, toluene, and xylenes (BTX) adsorption. BTX were extracted with carbon disulphide and analysed using a gas chromatograph coupled to a FID detector. In Barcelona metropolitan area the outdoor average concentrations of BTX were 3.5, 34.2, and 31.3 μg/m3 in urban areas, and 1.4, 9.2, and 9.2 μg/m3 in rural areas, respectively. Average indoor air concentrations of BTX were respectively 4.3, 64.8, and 47.6 μg/m3 in urban areas and 5.8, 67.0, and 51.4 μg/m3 in rural areas, respectively. A direct connection between the house and garage was one of the most influential factors for indoor BTX concentrations in rural areas. In urban areas, diffuse traffic sources were the predominant BTX source, slightly influenced by tobacco smoke in indoor air.