Basel Ozone and PM10 Spike Among Year’s Highest
July 31, 2026On July 30, 2026, Basel experienced notably poor air quality driven by a top-10 ozone event and a top-5 PM10 event over the past year, while nitrogen dioxide remained unremarkable. The elevated ozone is consistent with summertime photochemical smog, and the PM10 peak may reflect local sources like construction or traffic.
On July 30, 2026, air quality in Basel was notably impacted by elevated ozone and particulate matter levels. The maximum ozone concentration reached 166.3 µg/m³, which ranked as the 6th highest daily maximum in the past 365 days. The maximum PM10 concentration was 63.2 µg/m³, ranking 4th over the same period. In contrast, nitrogen dioxide remained low, with a maximum of 22.1 µg/m³, ranking 196th.
The daily average ozone concentration was 113.5 µg/m³, approaching the regulatory threshold of 120 µg/m³ for the maximum hourly average. The maximum value of 166.3 µg/m³ clearly exceeded this threshold, triggering an exceedance. The average PM10 concentration was 28.6 µg/m³, which is below the daily average limit of 50 µg/m³, but the maximum hourly value of 63.2 µg/m³ indicates a significant short-term peak. Nitrogen dioxide levels were unremarkable, with an average of 9.5 µg/m³, far below the 80 µg/m³ daily average limit.
Compared to the last 30 days, the ozone maximum was slightly below the period’s peak of 175.3 µg/m³, but the daily average was higher than the 30-day average of 96.0 µg/m³. The PM10 maximum of 63.2 µg/m³ was the highest recorded in the last 30 days and matched the seasonal maximum. The ozone maximum was also close to the seasonal peak of 175.8 µg/m³. Looking at the historical record since 2018, the ozone maximum ranked 28th out of 2978 days, placing it within the top percentile but below the all-time high of 206.3 µg/m³ from June 27, 2019. The PM10 maximum ranked 26th, well below the record of 165.1 µg/m³ from August 24, 2023.
Overall, the air quality on this day was characterized by a considerable pollution rating, driven by unusually high ozone and PM10 concentrations. While nitrogen dioxide was within normal ranges, the simultaneous occurrence of a top-10 ozone event and a top-5 PM10 event over the past year represents a notable deviation from typical conditions. The elevated ozone is consistent with summertime photochemical smog formation, while the PM10 peak may reflect local or regional sources such as construction, traffic, or long-range dust transport.
Table 1: Statistics for Air Quality Parameters on 2026-07-30
| Constituent | Average µg/m³ | Maximum µg/m³ | Standard | Comments |
|---|---|---|---|---|
| NO2 | 7.4 | 26.4 | 80.0 | daily average may not exceed standard |
| Ozone | 95.8 | 175.3 | 120.0 | maximum hourly average may exceed standard only one time per year |
| PM10 | 13.6 | 63.2 | 50.0 | daily average may not exceed standard |
Table 2: Statistics for Air Quality Parameters for the Month of July, since 2018
| Constituent | Average µg/m³ | Max µg/m³ | Exceedances |
|---|---|---|---|
| NO2 | 7.8 | 56.2 | 0 |
| Ozone | 77.9 | 181.9 | 107 |
| PM10 | 11.6 | 63.2 | 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.