This report on air quality in Basel for July 31, 2025, is published because the daily maximum of one of the air quality parameters exceeded the 95th percentile of all values measured in July. On this day, the air quality showed varied concentrations of pollutants. The maximum ozone (O₃) concentration recorded was 81.3 µg/m³, with an average of 53.9 µg/m³. Nitrogen dioxide (NO₂) reached a maximum of 17.9 µg/m³, averaging 5.7 µg/m³. Particulate matter (PM₂.₅) had a peak of 15.0 µg/m³, with an average of 5.45 µg/m³. The particle count (CPC) peaked at 10,149.1 particles/cm³, averaging 4,147.7 particles/cm³. Elemental carbon (EC) had a maximum of 0.3 µg/m³ and an average of 0.17 µg/m³. The maximum solar radiation was 751.5 W/m², with an average of 217.7 W/m². Sulfur dioxide (SO₂) reached a maximum of 1.0 µg/m³, averaging 0.23 µg/m³. Nitrogen oxides (NOx) peaked at 19.0 µg/m³, with an average of 6.88 µg/m³.

Comparing these values to historical data since 2018, the ozone levels were below the average of 73.3 µg/m³ observed over the last 30 days and the seasonal average of 73.13 µg/m³. NO₂ levels were also below the recent 30-day average of 6.28 µg/m³ and the seasonal average of 7.07 µg/m³. PM₂.₅ concentrations were slightly below the 30-day average of 6.09 µg/m³ and the seasonal average of 7.87 µg/m³. The particle count was significantly lower than the 30-day average of 5,856.84 particles/cm³ and the seasonal average of 6,346.34 particles/cm³. EC levels were within the typical range, slightly above the 30-day average of 0.16 µg/m³ but below the seasonal average of 0.21 µg/m³. Solar radiation was below both the 30-day and seasonal averages. SO₂ levels were below the 30-day average of 0.33 µg/m³ and the seasonal average of 0.48 µg/m³. NOx concentrations were below the 30-day average of 7.54 µg/m³ and the seasonal average of 8.25 µg/m³.

Overall, the air quality on July 31, 2025, was within historical norms, with most pollutants showing concentrations below their typical averages. No specific pollutant stood out as significantly higher than usual, indicating that the air quality conditions were generally stable and consistent with historical patterns.