Comment on egusphere-2022-1412

Abstract

To curb the spread of COVID-19 pandemic, many countries around the world imposed an unprecedented lockdown producing reductions in pollutant emissions. Unfortunately, the lockdown-driven global ambient benzene changes still remained unknown. The ensemble machine-learning model coupled with the chemical transport models (CTMs) was applied to estimate global high-resolution ambient benzene levels. Afterwards, the XGBoost algorithm was employed to decouple the contributions of meteorology and emission reduction to ambient benzene. The change ratio (Pdew) of deweathered benzene concentration from pre-lockdown to lockdown period was in the order of India (−23.6 %) > Europe (−21.9 %) > United States (−16.2 %) > China (−15.6 %). The detrended change (P*) of deweathered benzene level (change ratio in 2020 – change ratio in 2019) followed the order of India (P* = −16.2 %) > Europe (P* = −13.9 %) > China (P* = −13.3 %) > United States (P* = −6.00 %). Substantial decreases of atmospheric benzene levels saved sufficient health benefits. The global average lifetime carcinogenic risks (LCR) and hazard index (HI) decreased from 4.89 × 10−7 and 5.90 × 10−3 and 4.51 × 10−7 and 5.40 × 10−3, respectively.