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.