Estimating Ambient-origin PM(2.5) Exposure for Epidemiology: Observations, Prediction, and Validation using Personal Sampling in the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE: We aim to characterize the qualities of estimation approaches for individual exposure to ambient-origin fine particulate matter (PM(2.5)), for use in epidemiological studies. METHODS: The analysis incorporates personal, home indoor, and home outdoor air monitoring data and spatio-temporal model predictions for 60 participants from the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). We compared measurement-based personal PM(2.5) exposure with several measured or predicted estimates of outdoor, indoor, and personal exposures. RESULTS: The mean personal 2-week exposure was 7.6 (standard deviation 3.7) μg/m(3). Outdoor model predictions performed far better than outdoor concentrations estimated using a nearest-monitor approach (R=0.63 versus R=0.43). Incorporating infiltration indoors of ambient-derived PM(2.5) provided better estimates of the measurement-based personal exposures than outdoor concentration predictions (R=0.81 versus R=0.63) and better scaling of estimated exposure (mean difference 0.4 versus 5.4 μg/m(3) higher than measurements), suggesting there is value to collecting data regarding home infiltration. Incorporating individual-level time-location information into exposure predictions did not increase correlations with measurement-based personal exposures (R=0.80) in our sample consisting primarily of retired persons. CONCLUSIONS: This analysis demonstrates the importance of incorporating infiltration when estimating individual exposure to ambient air pollution. Spatio-temporal models provide substantial improvement in exposure estimation over a nearest monitor approach.