The Department of Land has published the report “Air Quality in Ticino” for 2025, a document that captures the evolution of the air quality in the Canton through data collected by the monitoring network. The full report, along with appendices containing detailed data for each monitoring point, is available on the Office for Air Safety and Soil website: www.ti.ch/aria.
The analysis confirms a now consolidated trend: emissions of the main pollutants continue to decrease, and 2025 will be among the years with the lowest values since systematic measurements began almost forty years ago.
An improvement that continues over time
According to the report, air quality in Ticino continues to benefit from technological advances introduced in recent decades. The evolution of vehicles, industrial processes, and household systems has led to a steady reduction in emissions, largely offsetting the increase in human activity.
Added to these factors, during 2025, were meteorological conditions generally favorable to the dispersion of pollutants, limiting the accumulation episodes in the atmosphere that can occur in the presence of highly stable situations.
The result is a further step forward in a positive trend that has characterized the cantonal territory for years now.
Nitrogen dioxide at lowest levels
Among the most significant indicators is the continuous decline in nitrogen dioxide (NO₂), a substance closely linked above all to vehicular traffic.
Annual averages decreased in all areas of the Canton, continuing an almost uninterrupted series of new historical lows recorded in recent years.
Not only was the progressive reduction in emissions beneficial, but also a particularly mild winter, which limited the formation of persistent temperature inversions. During the rest of the year, good mixing of the lower atmosphere further favored the dispersion of pollutants.
Ozone increases during an exceptionally warm June
The picture is different for ozone, whose behavior continues to be strongly influenced by meteorological conditions.
In 2025, the number of hours during which the legal limit was exceeded increased significantly compared to 2024, a year that had recorded particularly low values.
The main cause was the exceptional heat wave recorded in June, the second warmest since meteorological observations began in 1864. The high temperatures, combined with the strong solar radiation and the greater number of daylight hours typical of early summer, favored the formation of ozone.
Spring, characterised by temperatures above the climatic average and greater sunshine, also contributed to the increase in hourly exceedances.
Fine dust levels below the limits at all stations
The report also highlights particularly positive results on the PM10 fine dust front.
For the first time in the context of the multi-year improvement trend, all stations in the cantonal network respected the annual limit value required by law.
PM10 concentrations depend not only on human activities, but also on natural phenomena, such as Saharan dust transport. In 2025, however, the near-absence of prolonged periods of atmospheric stability during the winter months helped keep particulate matter levels low.
Even the abundant rainfall in January, combined with overall mild temperatures, favored the dispersion of pollutants, ensuring that daily concentrations almost always remained below legal limits.
Technology and weather favor improvement
The picture outlined by the report confirms that improved air quality is the result of a combination of structural interventions and favorable atmospheric conditions.
The reduction in emissions achieved thanks to technological innovation continues to represent the main driver of progress, while meteorological variability can cause annual fluctuations, especially for substances such as ozone and fine particles.
Overall, 2025 consolidates the improvement path recorded in Ticino over the past decades, while remembering that some pollutants remain closely linked to climate conditions and can still cause temporary episodes of exceeding the limits established by the legislation.
To consult the complete report and detailed data for individual measuring stations, you can visit the website of the Office of Safety, Air and Soil: www.ti.ch/aria.
