Personal exposures to NO2 in the EXPOLIS-study: relation to residential indoor, outdoor and workplace concentrations in Basel, Helsinki and Prague

Abstract

Personal exposures, residential indoor, outdoor and workplace levels of nitrogen dioxide (NO2) were measured for 262 urban adult (25–55 years) participants in three EXPOLIS centres (Basel; Switzerland, Helsinki; Finland, and Prague; Czech Republic) using passive samplers for 48-h sampling periods during 1996–1997. The average residential outdoor and indoor NO2 levels were lowest in Helsinki (24 12 and18 11 mgm 3, respectively), highest in Prague (61 20 and43 23 mgm 3), with Basel in between (36 13 and27 13 mgm 3). Average workplace NO2 levels, however, were highest in Basel (36 24 mgm 3), lowest in Helsinki (27 15 mgm 3), with Prague in between (30 18 mgm 3). A time-weightedmicroenvironmental exposure model explained74% of the personal NO2 exposure variation in all centres and in average 88% of the exposures. Log-linear regression models, using residential outdoor measurements (fixedsite monitoring) combinedwith residential andwork characteristics (i.e. work location, using gas appliances and keeping windows open), explained48% (37%) of the personal NO2 exposure variation. Regression models based on ambient fixed site concentrations alone explained only 11–19% of personal NO2 exposure variation. Thus, ambient fixedsite monitoring alone was a poor predictor for personal NO2 exposure variation, but adding personal questionnaire information can significantly improve the predicting power.