Abstract
Air pollution epidemiological studies often use outdoor concentrations from central-site monitors as exposure surrogates, which can induce measurement error. The goal of this study was to improve exposure assessments of ambient fine particulate matter (PM2.5), elemental carbon (EC), nitrogen oxides (NOx), and carbon monoxide (CO) for a repeated measurements study with 15 individuals with coronary artery disease in central North Carolina called the Coronary Artery Disease and Environmental Exposure (CADEE) Study. We developed a fine-scale exposure modeling approach to determine five tiers of individual-level exposure metrics for PM2.5, EC, NOx, CO using outdoor concentrations, on-road vehicle emissions, weather, home building characteristics, time-locations, and time-activities. We linked an urban-scale air quality model, residential air exchange rate model, building infiltration model, global positioning system (GPS)-based microenvironment model, and accelerometer-based inhaled ventilation model to determine residential outdoor concentrations (Cout_home, Tier 1), residential indoor concentrations (Cin_home, Tier 2), personal outdoor concentrations (Cout_personal, Tier 3), exposures (E, Tier 4), and inhaled doses (D, Tier 5). We applied the fine-scale exposure model to determine daily 24-h average PM2.5, EC, NOx, CO exposure metrics (Tiers 1–5) for 720 participant-days across the 25 months of CADEE. Daily modeled metrics showed considerable temporal and home-to-home variability of Cout_home and Cin_home (Tiers 1–2) and person-to-person variability of Cout_personal, E, and D (Tiers 3–5). Our study demonstrates the ability to apply an urban-scale air quality model with an individual-level exposure model to determine multiple tiers of exposure metrics for an epidemiological study, in support of improving health risk assessments.
Highlights
Epidemiological studies have found associations between exposure to ambient fine particulate matter (PM2.5, particulate matter ≤2.5μm in aerodynamic diameter) and its component elemental carbon (EC), nitrogen oxides (NOx ), and carbon monoxide (CO) and indices of acute respiratory and cardiovascular morbidity and mortality [1,2,3,4]
This study describes the application of Exposure Model for Individuals (EMI) for ambient PM2.5, EC, NOx, and CO in the Coronary Artery Disease and Environmental Exposure (CADEE) study [16]
To apply the fine-scale exposure model for the CADEE study, we modeled five tiers of daily exposure metrics for all 15 study participants and their homes
Summary
Epidemiological studies have found associations between exposure to ambient (i.e., outdoor-generated) fine particulate matter (PM2.5 , particulate matter ≤2.5μm in aerodynamic diameter) and its component elemental carbon (EC), nitrogen oxides (NOx ), and carbon monoxide (CO) and indices of acute respiratory and cardiovascular morbidity and mortality [1,2,3,4]. Most of these studies used central-site measurements of these air pollutants as exposure surrogates due to cost and participant burden of using indoor or personal air pollution monitoring devices. Depending on the epidemiological study design, these errors can add bias or uncertainty in health effect estimates [5,6]
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