Disentangling drivers of air pollutant and health risk changes during the COVID-19 lockdown in China

The COVID-19 restrictions in 2020 led to distinct variations in NO2 and O3 concentrations in China. Using a combined model–measurement approach, this study disentangles the drivers of anthropogenic emission changes, including Chinese New Year (CNY), China’s 2018–2020 Clean Air Plan (CAP), and the COVID-19 lockdown, and evaluates meteorological contributions via machine learning. Impacts on the multi-pollutant Health-based Air Quality Index (HAQI) are quantified. On average, CNY reduced NO2 by 26.7% annually, the COVID-lockdown led to an additional 11.6% reduction in 2020, and CAP (2018–2020) reduced NO2 by 15.7%, while meteorology during 23 Jan–7 Mar 2020 increased NO2 by 7.8%. For O3, the effects were +23.3% (CNY), +21.0% (COVID-lockdown), +4.9% (CAP), and −0.9% (meteorology). The combined drivers led to a drastic reduction in multi-pollutant-related health risk across China, though meteorology adversely affected the Northeast. CAP’s contribution highlights the effectiveness of air-quality regulations on NO2 reduction.