Basel Ozone Levels Spike, Exceeding Seasonal and Recent Averages

August 15, 2025

On August 14, 2025, Basel experienced unusually high ozone levels, significantly exceeding typical concentrations for the time of year, while other pollutants like nitrogen dioxide, PM2.5, particle count, elemental carbon, and sulfur dioxide remained within normal historical ranges. The elevated ozone levels were the primary air quality concern, potentially due to specific meteorological conditions or increased emissions.

On August 14, 2025, the air quality in Basel was notably impacted by elevated ozone (O₃) levels. The maximum concentration of ozone reached 149.6 µg/m³, which is significant as it ranks within the top 10 highest values recorded over the past year. The average ozone level for the day was 99.5 µg/m³. These values are considerably above both the recent 30-day average of 67.4 µg/m³ and the seasonal average of 74.96 µg/m³. Historically, since 2018, the maximum recorded ozone level was 206.3 µg/m³ on June 27, 2019. The current levels, while not record-breaking, are unusually high compared to typical historical data.

For nitrogen dioxide (NO₂), the maximum concentration was 30.4 µg/m³, with an average of 8.9 µg/m³. These figures are within normal ranges, as the 30-day average was 7.05 µg/m³ and the seasonal average was 7.29 µg/m³. The historical maximum for NO₂ was 83.2 µg/m³ on February 15, 2019, indicating that the current levels are not exceptional.

PM2.5 concentrations were measured at a maximum of 17.6 µg/m³ and an average of 14.4 µg/m³. These values are slightly above the recent averages of 7.04 µg/m³ for the past 30 days and 8.4 µg/m³ for the season. However, they remain well below the historical maximum of 82.6 µg/m³ recorded on January 1, 2022.

The particle count (CPC) reached a maximum of 12,937.8 particles/cm³, with an average of 6,502.8 particles/cm³. These values are consistent with the seasonal average of 6,407.52 particles/cm³, though they are below the 30-day maximum of 24,894.8 particles/cm³.

Elemental carbon (EC) levels were low, with a maximum of 0.6 µg/m³ and an average of 0.35 µg/m³, aligning with historical norms. Sulfur dioxide (SO₂) concentrations were also low, peaking at 2.8 µg/m³ with an average of 0.72 µg/m³, which is typical for the region.

Overall, the air quality on August 14, 2025, was characterized by unusually high ozone levels, which were significantly above typical concentrations for this time of year. This could be due to specific meteorological conditions or increased emissions. Other pollutants remained within normal historical ranges, indicating that the primary concern for this period was elevated ozone levels.


Table 1: Statistics for Air Quality Parameters on 2025-08-14
Constituent Average µg/m³ Maximum µg/m³ Standard Comments
NO2 8.5 31.2 80.0 daily average may not exceed standard
Ozone 73.7 171.1 120.0 maximum hourly average may exceed standard only one time per year
PM10 14.4 46.8 50.0 daily average may not exceed standard


Table 2: Statistics for Air Quality Parameters for the Month of August, since 2018
Constituent Average µg/m³ Max µg/m³ Exceedances
NO2 8.7 49.6 0
Ozone 70.2 192.4 84
PM10 11.4 162.7 0

Figure 2: Ozone Concentrations in Basel in the last 90 Days

Figure 3: PM2.5 Concentrations of last 90 Days at Binningen/Basel

Data source: Luftqualität Station Basel-Binningen
Additional resources: Umweltbericht beider Basel, Luftqualität Nordwestschweiz

🤖 This text was generated with the assistance of AI. All quantitative statements are derived directly from the dataset listed under Data Source.