Basel ozone exceeded 120 µg/m³ threshold on July 12, 2026.
July 13, 2026On July 12, 2026, Basel experienced elevated ozone levels that exceeded the regulatory threshold, with a maximum concentration of 139.4 µg/m³, while nitrogen dioxide and PM10 levels remained low and within limits. This ozone exceedance was significantly above seasonal and recent averages, likely driven by strong photochemical activity from high temperatures and sunlight rather than local emissions.
On 2026-07-12, the most notable air quality issue in Basel was elevated ozone levels. The maximum ozone concentration reached 139.4 µg/m³, which exceeded the regulatory threshold of 120.0 µg/m³ for the maximum hourly average. This concentration ranked 18th highest among the last 365 days, placing it in the top 5 percent of recent daily maximums. The average ozone concentration for the day was 98.5 µg/m³, which is above the seasonal average of 81.2 µg/m³ and the 30-day average of 87.8 µg/m³, indicating a significant increase.
Nitrogen dioxide and PM10 levels remained low. The maximum NO₂ concentration was 18.0 µg/m³, well below the daily average limit of 80.0 µg/m³, and the average was 8.1 µg/m³. The maximum PM10 concentration was 18.5 µg/m³, also far below the daily average limit of 50.0 µg/m³, with an average of 14.4 µg/m³. Neither pollutant exceeded regulatory standards.
Compared to historical data since 2018, the maximum ozone concentration of 139.4 µg/m³ is well below the all-time maximum of 206.3 µg/m³ recorded on June 27, 2019. However, it is notably higher than the typical seasonal and 30-day averages, suggesting that this day was part of a period with above-average ozone formation. The maximum NO₂ and PM10 concentrations were very low in a historical context, ranking 236th and 167th respectively out of the last 362 days, and far below their all-time maximums of 83.2 µg/m³ (February 15, 2019) and 165.1 µg/m³ (August 24, 2023).
Overall, the air quality on 2026-07-12 was unusual due to the elevated ozone levels, which were significantly higher than recent and seasonal averages and exceeded the regulatory threshold. This is characteristic of strong photochemical activity, likely driven by high temperatures and abundant sunlight, which promote the formation of ground-level ozone from precursor pollutants. The low NO₂ and PM10 concentrations suggest that local emissions from traffic or combustion were not unusually high, reinforcing that the ozone exceedance was primarily a meteorological and regional phenomenon.
Table 1: Statistics for Air Quality Parameters on 2026-07-12
| Constituent | Average µg/m³ | Maximum µg/m³ | Standard | Comments |
|---|---|---|---|---|
| NO2 | 7.0 | 26.4 | 80.0 | daily average may not exceed standard |
| Ozone | 89.1 | 159.8 | 120.0 | maximum hourly average may exceed standard only one time per year |
| PM10 | 11.6 | 27.0 | 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 | 76.4 | 181.9 | 93 |
| PM10 | 11.4 | 43.3 | 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.