Personal exposure to fine particulate matter in elderly subjects: Relationbetween personal, indoor, and outdoor concentrations

The time-series correlation between ambient levels, indoor levels, and pers onal exposure to PM2.5 was assessed in panels of elderly subjects with card iovascular disease in Amsterdam, the Netherlands, and Helsinki, Finland. Su bjects were followed for 6 months with biweekly clinical visits. Each subje ct's indoor and personal exposure to PM2.5 was measured biweekly, during th e 24-hr period preceding the clinical visits. Outdoor PM2.5 concentrations were measured at fixed sites. The absorption coefficients of all PM2.5 filt ers were measured as a marker for elemental carbon (EC). Regression analyse s were conducted for each subject separately, and the distribution of the i ndividual regression and correlation coefficients was investigated. Persona l, indoor, and ambient concentrations were highly correlated within subject s over time. Median Pearson's R between personal and outdoor PM2.5 was 0.79 in Amsterdam and 0.76 in Helsinki. For absorption, these values were 0.93 and 0.81 for Amsterdam and Helsinki, respectively. The findings of this stu dy provide further support for using fixed-site measurements as a measure o f exposure to PM2.5 in epidemiological time-series studies.