Has Air Pollution Concentration Increased over the Past 17 Years in Seoul, South Korea?: The Gap between Public Perception and Measurement Data

Abstract

While there have been growing public concerns on increased particulate matter (PM) air pollution in South Korea, published summaries based on regulatory monitoring data showed decreasing patterns over years. Aiming to identify the pollution features aligned with public concerns, we developed diverse statistics that represent daily PM with a diameter ≤10 µm (PM10) and explored temporal patterns for 2001~2017 in Seoul, Korea. We obtained PM10 hourly measurements at 25 urban background regulatory monitoring sites in Seoul for 2001~2017. In addition to daily averages commonly used in previous studies, we computed 15 additional daily statistics for three features: 1) within-day concentration level, 2) between-days difference, and 3) within-day hourly categorization. For the within-day concentration level, we used four statistics: 24-hour mean, 5th percentile, 95th percentile, and interquartile range. The between-days difference statistics were computed as the difference in the mean, minimum, or maximum concentrations on the concurrent day from that on the past one or three days. The within-day hourly categorization includes the number of hours for daytime and 24 hours in each of the three categories based on the Comprehensive Air-quality Index (“Good”, “Moderate”, and “Unhealthy” for <30, 31~80, and 81~150 µm/m3, respectively). To assess the temporal patterns of PM10 concentrations, we created year-specific time-series boxplots for each of the 16 statistics over 17 years. Using within-day concentration level statistics, PM10 concentrations generally decreased over 17 years with stable or slightly increasing patterns for the recent six years since 2012. The within-day hourly categorization statistics also showed overall increases in “Good” hours over 17 years and recent decreases. Our results suggest that public concerns on PM are possibly related to stable concentrations for the recent 6 years despite an overall decrease for 17 years. Future studies should confirm our findings by expanding our investigation to different areas.