Basel Ozone Hits 158 µg/m³, 12th Highest in Past Year
August 12, 2026On August 11, 2026, Basel experienced a significant ozone event with a maximum concentration of 158.0 µg/m³ that exceeded the regulatory threshold, while nitrogen dioxide and particulate matter remained well within their limits. The elevated ozone levels ranked among the highest in recent history and were notably above seasonal averages, likely driven by strong sunlight and stagnant summer conditions.
On August 11, 2026, air quality in Basel was marked by elevated ozone levels. The maximum ozone concentration reached 158.0 µg/m³, which exceeded the regulatory threshold of 120.0 µg/m³ for the maximum hourly average. This value ranked as the 12th highest daily maximum ozone concentration recorded in the past 365 days. In contrast, nitrogen dioxide and particulate matter remained well within their respective limits. The maximum nitrogen dioxide concentration was 13.6 µg/m³, far below the 80.0 µg/m³ daily average standard, and the maximum PM10 concentration was 31.8 µg/m³, below the 50.0 µg/m³ daily average threshold. The average concentrations for the day were 113.1 µg/m³ for ozone, 8.0 µg/m³ for nitrogen dioxide, and 25.7 µg/m³ for PM10.
Comparing the day’s measurements to historical data since 2018, the ozone maximum of 158.0 µg/m³ was notably high, ranking 48th out of 2990 days on record. The all-time maximum ozone value of 206.3 µg/m³ occurred on June 27, 2019. The nitrogen dioxide maximum was unremarkable, ranking 2484th historically, with the record maximum of 83.2 µg/m³ set on February 15, 2019. The PM10 maximum ranked 394th, with its historical peak of 165.1 µg/m³ recorded on August 24, 2023. Relative to recent seasonal and 30-day averages, the day’s ozone levels were elevated. The average ozone concentration of 113.1 µg/m³ was above the seasonal average of 89.2 µg/m³ and the 30-day average of 98.9 µg/m³. The PM10 average of 25.7 µg/m³ was also higher than both the seasonal average of 14.3 µg/m³ and the 30-day average of 15.5 µg/m³. Nitrogen dioxide values were consistent with recent norms.
Overall, the air quality on August 11, 2026, was characterized by a significant ozone event, while other pollutants remained at typical levels. The elevated ozone concentrations were the primary driver of the day’s considerable air quality rating. Such high ozone levels are typically associated with strong sunlight and stagnant atmospheric conditions that promote photochemical production, which is consistent with a summer day.
Table 1: Statistics for Air Quality Parameters on 2026-08-11
| Constituent | Average µg/m³ | Maximum µg/m³ | Standard | Comments |
|---|---|---|---|---|
| NO2 | 7.6 | 25.4 | 80.0 | daily average may not exceed standard |
| Ozone | 97.0 | 158.0 | 120.0 | maximum hourly average may exceed standard only one time per year |
| PM10 | 16.0 | 32.1 | 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 | 71.3 | 192.4 | 93 |
| PM10 | 11.9 | 165.1 | 0 |
Figure 1: NO2 Concentrations in Basel, last 90 Days
Figure 2: Ozone Concentrations in Basel in the last 90 Days
Figure 3: PM10 Concentrations of last 90 Days at Binningen/Basel
Additional resources: Umweltbericht beider Basel, Luftqualität Nordwestschweiz, Luftreinhalte-Verordnung (LRV)
🤖 This text was generated with the assistance of AI. All quantitative statements are derived directly from the dataset listed under Data Source.