The declining effectiveness of air quality index in China: A perspective of air pollution alert system.

Since 2013, the air quality in China has improved dramatically. However, the regulatory standard as defined in air quality index (AQI) is still the one introduced in 2012. To evaluate the gap between reality and regulation, we study the effectiveness of China's AQI from the perspective of air pollution alert, a system that reflects AQI standard directly. Specifically, based on the respiratory hospitalization data in Chengdu and three models for potential nonlinearity between air pollution and hospitalization, we assess the percentages of hospitalization that can get alerted by the different categories of AQI. We find that while the total hospitalization due to air pollution declined fast due to reduced air pollution, the percentages of hospitalization that can get alerted by different categories of AQI declined faster, resulting in an AQI system that is progressively less binding and effective. Further, we show that a counterfactual tighter standard will bring China's AQI standard closer to international ones, and reverse AQI's declining effectiveness.