2.2 | Assessment of PM exposure and other environments
To assess the long-term exposure to ambient PM with an aerodynamic diameter ≤ 10μm (PM10) from birthday through the age of 3, we utilized a fusion model combining monitoring data from the air quality monitoring sites (AQMSs) and Community Multiscale Air Quality (CMAQ) modeling data. This fusion technique can improve air pollution exposure estimation in a large and complex urban area like the Seoul Metropolitan Area where spatial heterogeneity of air pollution is significant and monitoring data are limited in space.
The CMAQ model (version 5.0.2)18,19 was run for one year in 2018 to capture local gradient of PM10concentrations in the Seoul Metropolitan Area in a nested mode at 27, 9, and 3 km horizontal grid dimensions; The fine-scale innermost domain (D3 in Figure 1) is the target area of the study that covers the Seoul Metropolitan Area. Detailed CMAQ-ready meteorological and emission inputs, initial and boundary conditions, and physical and chemical options used in our CMAQ modeling were described previously by Oh et al.20 Hourly gridded concentrations predicted by the CMAQ model were averaged on a monthly basis to blend ambient monitored data. Monitored concentrations of PM10 and other air pollutants were obtained from 141 AQMS (Figure 1b) in the study area. Neighbor AQMS surrounding each patient’s residential locations (updated monthly for three years) within a 5 km radius were first identified. An inverse-distance weighted (IDW) average of observed values was obtained. Fused concentrations were then calculated by multiplying IDW average concentrations with the ratio of CMAQ modeling data for the destination grid-cell containing the patient’s residence to those containing the neighbor monitor. These fused concentrations were calculated on a monthly basis and averaged throughout the exposure assessment period of 3 years. Monthly exposure to PM was assessed by checking subjects’ addresses whenever they moved during the study period from January 2007 to June 2020.