Geometric mean PM2.5 and NO2 in Scotland 24 March–23 April in years 2017–2020, including both observed and normalised data
| Pollutant | 2017 period geometric mean concentration (µg/m3) | 2018 period geometric mean concentration (µg/m3) | 2019 period geometric mean concentration (µg/m3) | 2020 period geometric mean concentration (µg/m3) |
| PM2.5 (observed) | 6.7 | 7.4 | 12.8 | 6.6 |
| PM2.5 (normalised) | 6.9 | 6.4 | 7.6 | 6.1 |
| NO2 (observed) | 21.9 | 23.7 | 22.4 | 9.9 |
| NO2 (normalised) | 25.8 | 25.4 | 24.4 | 15.1 |
NO2, nitrogen dioxide; PM2.5, fine particulate matter.