Lockdowns during the COVID-19 pandemic in China led to a significant decrease in air pollution levels in 174 cities. A study analyzed the impact of reduced human activities on air pollutants like NO2, SO2, PM2.5, and PM10. The findings showed that the short-term control effect of emissions ranged from 53.0% to 98.3% in all cities, with southern cities having a stronger effect than northern cities. Small-medium cities had a similar impact on NO2 and SO2 but a greater effect on PM2.5 and PM10 compared to megacities.