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

Long-term exposure to high surface ozone (O-3) concentrations, a complex oxidative atmospheric pollutant, can adversely impact human health. Based on O-3 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 O-3 concentration, exposure risk, and dominant meteorological factors. Results indicated that over 40% of the cities worldwide were exposed to harmful O-3 concentration ranges (4060 mu g/m(3)), with most cities distributed in China and India. Moreover, significant seasonal variations in global O-3 concentrations were observed, presenting as summer (45.6 mu g/m3) > spring (47.3 mu g/m(3)) > autumn (38.0 mu g/m3) > winter (33.6 mu g/m(3)). Exposure analysis revealed that approximately 12.2% of the population in 261 cities were exposed to an environment with high O-3 concentrations (80-160 mu g/m(3)), with about 36.32 million people in major countries. Thus, the persistent increase in high O-3 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 O-3 variability. The synergy of meteorological factors is critical for understanding O-3 changes. Our findings are important for enforcing robust air quality policies and mitigating public risk.