Behavioral and environmental determinants of personal exposures to PM2.5 in EXPOLIS – Helsinki, Finland

Behavioral and environmental determinants of PM2.5 personal exposures were analyzed for 201 randomly selected adult participants (25–55 years old) of the EXPOLIS study in Helsinki, Finland. Personal exposure concentrations were higher than respective residential outdoor, residential indoor and workplace indoor concentrations for both smokers and non-smokers. Mean personal exposure concentrations of active smokers (31.0±31.4 μg m−3) were almost double those of participants exposed to environmental tobacco smoke (ETS) (16.6±11.8 μg m−3) and three times those of participants not exposed to tobacco smoke (9.9±6.2 μg m−3). Mean indoor concentrations of PM2.5 when a member of the household smoked indoors (20.8±23.9 μg m−3) were approximately 2.5 times the concentrations of PM2.5 when no smoking was reported (8.2±5.2 μg m−3). Interestingly, however, both mean (8.2 μg m−3) and median (6.9 μg m−3) residential indoor concentrations for non-ETS exposed participants were lower than residential outdoor concentrations (9.5 and 7.3 μg m−3, respectively). In simple linear regression models residential indoor concentrations were the best predictors of personal exposure concentrations. Correlations (r2) between PM2.5 personal exposure concentrations of all participants, both smoking and non-smoking, and residential indoor, workplace indoor, residential outdoor and ambient fixed site concentrations were 0.53, 0.38, 0.17 and 0.16, respectively. Predictors for personal exposure concentrations of non-ETS exposed participants identified in multiple regression were residential indoor concentrations, workplace concentrations and traffic density in the nearest street from home, which accounted for 77% of the variance. Subsequently, step-wise regression not including residential and workplace indoor concentrations as input (as these are frequently not available), identified ambient PM2.5 concentration and home location, as predictors of personal exposure, accounting for 47% of the variance. Ambient fixed site PM2.5 concentrations were closely related to residential outdoor concentrations (r2=0.9, p=0.000) and PM2.5 personal exposure concentrations were higher in summer than during other seasons. Personal exposure concentrations were significantly (p=0.040) higher for individuals living downtown compared with individuals in suburban family homes. Further analysis will focus on comparisons of determinants between Helsinki and other EXPOLIS centers.