Surface ozone in global cities: A synthesis of basic features, exposure risk, and leading meteorological driving factors

Long-term exposure to high surface ozone (O₃) concentrations, a complex oxidative atmospheric pollutant, can adversely impact human health. Based on O₃ monitoring data from 261 cities worldwide in 2020, generalized additive model (GAM) and spatial data analysis (SDA) methods were applied in this study to quantitatively evaluate the spatiotemporal distribution of O₃ concentration, exposure risk, and dominant meteorological factors. Results indicated that over 40% of the cities worldwide were exposed to harmful O₃ concentration ranges (40–60 µg/m³), with most cities distributed in China and India. Moreover, significant seasonal variations in global O₃ concentrations were observed, presenting as summer (45.6 µg/m³) > spring (47.3 µg/m³) > autumn (38.0 µg/m³) > winter (33.6 µg/m³). Exposure analysis revealed that approximately 12.2% of the population in 261 cities were exposed to an environment with high O₃ concentrations (80–160 µg/m³), with about 36.32 million people in major countries. Thus, the persistent increase in high O₃ levels worldwide is a critical factor contributing to threats to human health. Furthermore, GAM results indicated temperature, relative humidity, and wind speed as primary determinants of O₃ variability. The synergy of meteorological factors is critical for understanding O₃ changes. Our findings are important for enforcing robust air quality policies and mitigating public risk.