Time series comparison of pre- and post-lockdown for sample cities show that the lockdown impact on NO2 concentrations varies

Cities worldwide have been imposing lockdowns due to coronavirus, leading to traffic reductions and related to that, less NO2 pollution. The strength of the effect is not the same everywhere, being dependent on a number of variables, such as pollution levels and amount of traffic before the lockdown at the particular location, fleet composition, weather conditions and topography and urban architecture. Furthermore, the measures defining the “lockdown” were not the same everywhere and were also implemented with different levels of rigour. Without analyzing in-depth the factors at play at different places across the world, here just a few examples of what the change in NO2 pollution looked like in a few cities:

• Wuhan
• Paris
• London
• Fresno
• Dehli
• Boston