Impacts of COVID-19 restrictions on regional and local air quality
across selected West African cities
Abstract
The emergence of COVID-19 brought panic and a sense of urgency causing
governments to impose strict restrictions on human and vehicular
movement. With anthropogenic emissions, especially traffic and
industrial activities, said to be a significant contributor to ambient
air pollution, this study assessed the impacts of the imposed
restrictions on the atmospheric concentrations and size distribution of
atmospheric aerosols and gaseous pollutants over West African sub-region
and seven major COVID-19 epicenters in the sub-region. Satellite
retrievals and reanalysis datasets were used to study the impact of the
restrictions on Aerosol Optical Depth (AOD) and atmospheric
concentrations NO2, SO2, CO and O3. These anomalies were computed for
2020 relative to 2017-2019 (the reference years). In 2020 relative to
the reference years, there was a significant reduction of between
0.5±24.6 – 13.7±30.3% and 5.9±17.1% in area-averaged AOD levels at
the epicenters and over the sub-region, respectively. The levels of NO2
and SO2 also reduced substantially at the epicenters, especially during
the periods when the restrictions were highly enforced. However, the
atmospheric levels of CO and ozone increased slightly in 2020 compared
to the reference years. This study shows that “a one cap fits all”
policy cannot reduced the level of air pollutants and that traffic and
industrial processes are not the major sources of CO in major cities in
the sub-region. Although not available, ground-based measurements would
have given a clearer and better picture of the anomalies observed with
the dataset used in this study which are on a coarser spatial
resolution.