Substantial changes in air pollution across China during 2015–2017

China's rapid industrialisation and urbanisation has led to poor air quality. The Chinese government have responded by introducing policies to reduce emissions and setting ambitious targets for ambient PM₂.₅, SO₂, NO₂ and O₃ concentrations. Previous satellite and modelling studies indicate that concentrations of these pollutants have begun to decline within the last decade. However, prior to 2012, air quality data from ground-based monitoring stations were difficult to obtain, limited to a few locations in major cities, and often unreliable. Since then, a comprehensive monitoring network, with over 1000 stations across China has been established by the Ministry of Ecology and Environment (MEE). We use a three-year (2015–2017) dataset consisting of hourly PM₂.₅, O₂, NO₂ and SO₂ concentrations obtained from the MEE, combined with similar data from Taiwan and Hong Kong. We find that at 53% and 59% of stations, PM₂.₅ and SO₂ concentrations have decreased significantly, with median rates across all stations of −3.4 and −1.9 μg m−³ year−¹ respectively. At 50% of stations, O₃ maximum daily 8 h mean (MDA8) concentrations have increased significantly, with median rates across all stations of 4.6 μg m−³ year−¹. It will be important to understand the relative contribution of changing anthropogenic emissions and meteorology to the changes in air pollution reported here.