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December 2025 Air Quality Shows Record Low Pollution Levels
Published: January 1, 2026 · Period: 2025-12-01 – 2025-12-31In December 2025, air quality was notably improved with 27 days of minimal pollution and no exceedances in pollutant concentrations, marking a significant reduction in pollution levels compared to previous years like 2018, 2019, and 2023. The mean concentrations for O3, NO2, and PM10 were lower or comparable to past years, contributing to the overall better air quality.
In December 2025, the air quality was predominantly characterized by very low pollution levels, with 27 days having a KBI value of 1, indicating minimal air pollution. There were 4 days with a KBI value of 2, and no days with KBI values of 3 or higher. The mean concentrations for pollutants were 15.6 µg/m³ for O3, 22.5 µg/m³ for NO2, and 13.9 µg/m³ for PM10, with no exceedances recorded for any of these pollutants.
When comparing December 2025 to previous years, the data indicates that air pollution levels were generally lower. The number of days with very low pollution (KBI 1) was higher than in previous years, such as 2018, 2019, and 2023, which had fewer days with KBI 1. Additionally, the mean O3 concentration was significantly lower in 2025 compared to other years, such as 2018 and 2023. The NO2 and PM10 concentrations were comparable to previous years, with no exceedances noted. Overall, December 2025 experienced better air quality than the same month in prior years.
Table 1: Monthly Summary for December 2025
| metric | December 2025 | Avg since 2019 |
|---|---|---|
| Days with KBI = 1 | 27 | 18 |
| Days with KBI = 2 | 4 | 13 |
| Days with KBI = 3 | 0 | 0 |
| Days with KBI ≥ 4 | 0 | 0 |
| Max NO₂ [µg/m³] | 53 | 60 |
| Max O₃ [µg/m³] | 76 | 86 |
| Max PM₁₀ [µg/m³] | 83 | 40 |
| Mean NO₂ [µg/m³] | 22 | 22 |
| Mean O₃ [µg/m³] | 16 | 29 |
| Mean PM₁₀ [µg/m³] | 14 | 12 |
| NO₂ exceedances | 0 | 0 |
| O₃ exceedances | 0 | 0 |
| PM₁₀ exceedances | 0 | 0 |
Figure 1: Maximum and Average Ozone (O₃, µg/m³) Concentrations in December
Figure 2: Maximum and Average NO₂ Concentrations (µg/m³) in December
Figure 3: Maximum and Average Fine Particles (PM₁₀, µg/m³) in December
Additional resources: Luftqualität in den Kantonen AG. BE, BL, BS, JU, SO, Topic Air, Federal Office for the Environment, Switzerland, World's Air Pollution: Real-time Air Quality Index
🤖 This text was generated with the assistance of AI. All quantitative statements are derived directly from the dataset listed under Data Source.