Personal PM_2.5 Exposure Using Time-Weighted Average Scenarios in the Seoul Metropolitan Area

Personal exposure assessment is essential in environmental and epidemiological studies. However, conventional methods often do not adequately reflect individuals' spatiotemporal activity characteristics. This study evaluates the suitability of personal exposure assessment methods using PM_2.5 as a case study, comparing measured personal exposure concentrations with three exposure estimation scenarios (S1-S3). S1 relies on fixed-site monitoring data, S2 incorporates location-based outdoor concentrations and a single indoor measurement, and S3 integrates individual location with microenvironment-specific concentrations. Using personal PM_2.5 measurements and time-activity data (TAD) from adults in the Seoul metropolitan area, exposure levels showed substantial variation depending on activity patterns and time spent in different microenvironments. Time-weighted average (TWA)-based estimates differed across scenarios; among them, the one integrating microenvironmental concentrations and TAD showed the closest agreement with measured exposure. In contrast, S1 and S2 generally overestimated exposure. Although S3 slightly underestimated short-term high-concentration events, it showed high correlation (r = 0.78) and low errors (RMSE = 4.79, MAE = 3.70), effectively capturing relative variability in personal exposure. These results suggest that integrating time-activity patterns with microenvironmental concentrations improves the accuracy and reliability of personal exposure assessment and is expected to further enhance the reliability of personal exposure assessment.