Table 2. Average air-pollution reduction (NO2 and PM2.5) for all ground-level monitoring stations as well as urban-background stations separately (in parentheses) for the entire year 2020 as well as for two lockdown periods for the four cities.
| City | Period | Dates | Air Pollution Reduction (%) | |
|---|---|---|---|---|
| NO2 (Urban Background) | PM2.5 (Urban Background) | |||
| Greater London | Year | 13 January–30 December | –42% (–38%) | –31% (–28%) |
| First lockdown | 23 March–10 May | –47% (–39%) | –13% (–8%) | |
| Second lockdown | 5 November–2 December | –35% (–29%) | 0% (0%) | |
| Cardiff | Year | 13 January–30 December | –32% (–41%) | –35% (–30%) |
| First lockdown | 23 March–10 May | –36% (–50%) | –5% (–4%) | |
| Second lockdown | 23 October–9 November | –43% (–53%) | –10% (–10%) | |
| Edinburgh | Year | 13 January–30 December | –27% (–49%) | –42% (–42%) |
| First lockdown | 23 March–10 May | –54% (–53%) | –35% (–37%) | |
| Second lockdown | 20 November–11 December | –18% (–38%) | –24% (–24%) | |
| Belfast | Year | 13 January–30 December | –23% (–24%) | –33% (–33%) |
| First lockdown | 23 March–10 May | –43% (–35%) | –33% (–32%) | |
| Second lockdown | 27 November–11 December | –23% (–21%) | –14% (–14%) | |