Atmospheric Environment 37 (2003) 5563–5575 Exposure of population and microenvironmental distributions of volatile organic compound concentrations in the EXPOLIS study K. Saarela a, *, T. Tirkkonen a , J. Laine-Ylijoki b , J. Jurvelin c , M.J. Nieuwenhuijsen d , M. Jantunen e a Technical Research Centre of Finland, VTT, Building and Transport, Espoo, Finland b Technical Research Centre of Finland, VTT, Processes, Espoo, Finland c Jyv . askyl . a Polytechnic, School of Engineering and Technology, Jyv . askyl . a, Finland d Imperial College of Science, Technology, and Medicine, London, UK e Department of Environmental Hygiene, Finnish National Institute of Public Health, KTL, Kuopio, Finland Received 1 April 2003; received in revised form 21 July 2003; accepted 4 September 2003 Abstract Determination of volatile organic compounds (VOCs) formed one part of the EU-EXPOLIS project in which the exposure of European urban populations to particles and gaseous pollutants was studied. The EXPOLIS study concentrated on 30 target VOCs selected on the basis of environmental and health significance and usability of the compounds as markers of pollution sources. In the project, 201 subjects in Helsinki, 50 in Athens, 50 in Basel, 50 in Milan and, 50 in Oxford and 50 in Prague were selected for the final exposure sample. The microenvironmental and personal exposure concentrations of VOCs were the lowest in Helsinki and Basel, while the highest concentrations were measured in Athens and Milan; Oxford and Prague were in between. In all cities, home indoor air was the most significant exposure agent. Workplace indoor air concentrations measured in this study were generally lower than the home indoor concentrations and home outdoor air played a minor role as an exposure agent. When estimating the measured personal exposure concentrations using the measured concentrations and time fractions spent at home indoors,athomeoutdoors,andattheworkplace,itcouldbeconcludedthatthesethreemicroenvironmentsdonotfully explainthepersonalexposure.Otherimportantsourcesforpersonalexposuremustbeencountered,themostimportant being traffic/transportation and other indoor environments not measured in this study. r 2003 Elsevier Ltd. All rights reserved. Keywords: Volatile organic compounds; Indoor air; Occupational exposure; Environmental exposure 1. Introduction Thetotalhumanexposuretoairpollutantsisthesum of the exposures in different locations and times. Determining exposure on the population level is a very challenging task. Stationary outdoor air pollution levels cannot be used as surrogates for exposure concentra- tions. Pollution concentrations in indoor environments must also be determined. A limited number of studies have been performed where personal volatile organic compound (VOC) exposures of representative population samples have been measured. Total Exposure Assessment Methodol- ogy (TEAM) studies in the eighties (Wallace et al., 1986, Hartwell et al., 1987) and the National Human Exposure Assessment Survey (NHEXAS) in the early nineties (Robertson et al., 1999) were performed in the US. In Europe, corresponding multi-route exposure studies have only been per- formed in Germany in 1985–1986 and 1990–1992 ARTICLE IN PRESS *Corresponding author. 1352-2310/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2003.09.031