Characterization of multi-pollutant air quality in China using health-centric air pollution indices

Epidemiological studies have consistently demonstrated a strong association between air pollution and human health. However, the current Air Quality Index (AQI) methodology used in China has been criticized for relying solely on the maximum concentration of a single pollutant, thereby failing to reflect the cumulative health impact of multiple pollutants. This study evaluated the effectiveness of three alternative indices-the Health Risk-Based Air Quality Index (HAQI), the Air Quality Health Index, and the Air Pollution Index (API)-in characterizing multi-pollutant air quality across China from 2014 to 2023. Our analysis indicates that the AQI underestimates health risks in regions with simultaneous exceedances of multiple pollutants, particularly in the North China Plain. Moreover, pollutants such as SO₂ and CO contributed minimally to the overall AQI, whereas the excess risk (ER) value offered a more comprehensive representation of the health risks posed by all pollutants. The findings also show that HAQI and API more effectively captured seasonal variation in pollution levels and outperformed AQI in assessing the severity of health risks during episodes of severe air pollution. In conclusion, the study underscores the need for more stringent measures during high pollution events, beyond those currently recommended under the AQI framework.