Modeling of Residential Indoor Concentrations of Ambient PM2.5, Ozone for the Catheterization Genetics (CATHGEN) Study

Abstract

Air pollution epidemiological studies of ambient fine particulate matter (PM2.5) and ozone (O3) often use outdoor concentrations from central-site monitors as exposure surrogates, which can add bias or uncertainty in health effect estimates. The goal of this study was to improve exposure assessments of ambient PM2.5 and O3 for a 10-year epidemiological study with 2,271 participants with coronary artery disease in central North Carolina called the Catheterization Genetics (CATHGEN) study. We developed an exposure modeling approach to estimate three tiers of individual-level exposure metrics for ambient PM2.5 and O3. We used a hybrid outdoor air quality model (based on satellite- and ground-based air pollution measurements, chemical transport and land-use models) linked to a residential air exchange rate model (based on building characteristics, indoor-outdoor temperatures, wind speed) and mass-balance infiltration model to determine residential air exchange rates (AER, Tier 1), infiltration factors (Finf, Tier 2), and indoor concentrations (Cin, Tier 3). For each of the 2,271 participant homes, we applied the exposure model to determine daily house-specific PM2.5 and O3 exposure metrics (Tiers 1-3) for the 365 days before each participant’s cardiac catheterization date. The daily modeled exposure metrics for all 828,915 participant days showed considerable temporal and house-to-house variability of AER, Finf and Cout (Tiers 1-3). Our study demonstrates the ability to apply an outdoor air quality model linked to a residential infiltration model to determine individual-level ambient PM2.5 and O3 exposure metrics for a large, long-term epidemiological study, in support of improving risk estimation.