Average monthly roadside NO2 concentrations in the UK 2017-2021

In December of 2021, the concentration of nitrogen dioxide (NO2) at roadside monitoring sites in the UK fell nearly 31 percent compared to the average value between 2017 and 2019. In April 2020, concentrations of NO2 at roadside monitoring sites in the UK fell 44 percent compared to that of the previous 3 years. On March 23, 2020 the UK entered its first national lockdown to curb the spread of COVID-19. These restrictions caused traffic to plummet around the country, and it is probable that these restrictions are responsible for the lower NO2 concentrations. Overall, average roadside concentrations of NO2 fell 26 percent compared to 2019 levels in 2021.