Reversal in China’s Air Quality Gains

Abstract

China’s air quality has improved rapidly since the early 2010s, when the government launched an action plan focussed on reducing fine particulate matter (PM2.5) pollution, the pollutant species associated with the largest negative health impact. Measurements from China’s monitoring network, now consisting of >2000 surface stations, have shown a rapid fall in PM2.5 concentrations consistently over the period 2014–2019, while sulphur dioxide (SO2), carbon monoxide (CO) and nitrogen dioxide (NO2) concentrations have also significantly decreased. Concurrently there has been a rapid increase in ozone concentrations, which has been partly attributed to falling particulate matter concentrations. However, air quality data from China remains difficult to access, and recent changes in China’s economic outlook mean that the future trajectory of China’s air quality continues to be highly uncertain. Here we analyse 10 years of air quality monitoring data from May 2014 to April 2024 to assess whether China’s air quality has continued to improve in recent years, in the wake of the COVID-19 lockdowns and other economic challenges. After using an improved data cleaning algorithm to remove outliers from the dataset, we use a non-linear trend fitting technique to extract underlying trends and their uncertainties. We find that the steep negative trend in PM2.5 that was observed during 2014–2019 has now reversed, and since June 2022 there has been a significant (>95% confident) positive trend at over half of China’s air quality monitoring stations. This is mirrored by the average trend of ozone, which was positive during 2014–2019, but since December 2022 there has been a significant negative trend at almost half of monitoring stations. The increase in PM2.5 exposure has the potential to worsen air quality health impacts in China, particularly given its ageing population.