The smoke of the Canadian fires reached the Italian Alps: the Aosta Valley is under the transatlantic haze

An unusual haze wrapped the skies of the Valle d’Aosta from June 8, 2025. It is not a normal meteorological phenomenon, but of smoke coming from forest fires who are hitting the Canadawhere over two million hectares have already been reduced to ashes since the beginning of the year.

The fine dust generated by these bonfires made a thousands of kilometers a journey, crossing theAtlantic Ocean transported by high altitude atmospheric currents, up to reaching the Italian Alpine regions. A phenomenon that highlights how the atmosphere does not know boundaries and as extreme climatic events in a part of the world can have global repercussions.

The data of the ARPA Valle d’Aosta control units

The air quality monitoring stations recorded a quick increase in fine dust concentrations on the morning of June 8. According to the surveys of ARPA Valle d’Aostathe values ​​of atmospheric particulate PM10 and PM2.5 showed an initial peak around 8 in the morning, and then decreased in relation to variations in atmospheric circulation.

On June 9, the situation worsened: in the Aosta and Donnas stations, the hourly values ​​of PM10 were observed between 70 and 90 µg/m³ in the early hours of the day. In Piazza Plouves, in Aosta, the concentrations of PM2.5 jumped to 49 micrograms per cubic meter from 6 in the previous evening, while those of PM10 reached 54 micrograms from the 11 of the previous hours.

Although the legislation provides for a limit value for the PM10 of 50 µg/m³ as a daily average on the 24 hours – limit not exceeded on June 8 – the scheduled peaks recorded the next day have raised attention. The concentrations remained on levels similar to those typically observed during the winter days with heated heating and stoves.

The scientific confirmation of the Canadian origin

How can you be sure that it is actually powders from Canada? Arpa Valle d’Aosta has used several analysis tools to confirm the transatlantic origin of particulates. The atmospheric models have made it possible to calculate, backwards in time, the trajectories followed by the winds, precisely determining the area of ​​origin of the powders.

The satellite images clearly show the path of the air masses from Canada to Europe, highlighting the concentrations of carbon monoxide – a key indicator of the fires – along the entire transatlantic journey. The higher layers detection systems of the atmosphere also allowed to detect the arrival of dust at altitude, around 4000 meters above sea level, before their descent to the ground.

A particularly significant element emerged from the analysis of the composition of particulates through the advanced instrumentation present in the Aosta-Plouves station. Experts identified the presence of particles with characteristics apparently similar to those typical of winter, but rare in summer. This is interpretable as the distinctive sign of powders who have traveled in the atmosphere for a long time, “aging” and loading other materials during transatlantic transport.

According to some studies, these powders aged in the atmosphere and subjected to the action of sunlight and other substances could be more toxic than those raised in the immediate vicinity of the fires.

The fire situation in Canada

The scope of the phenomenon becomes more understandable by observing the numbers of Canadian fires. I am currently More than 200 active bonfiresover 100 of which are still out of control. The firefighters, supported by the army, are unable to contain the flames that are devastating the forests of the North American country.

According to the Canadian authorities, most fires are of human origin, although not necessarily malicious. Often the flames accidentally flare up, for example for high -speed trains passages in extremely arid places. There lack of rainfall and the Exceptional heat waves They represent the elements that most contribute to the development of the bonfires.

The closest areas of Canada and the United States have been surrounded by a dense smoke composed of carbon monoxide, water vapor and particulates, with reduced visibility and alarms for the population. TO Detroit The air quality was “very unhealthy”, while the Canadian government issued notices for the bad air quality, with a dense smoke that also enveloped Montreal.

A growing phenomenon linked to climate change

This does not represent an isolated episode. Already in 2024 similar events had occurred, with the smoke of the Canadian fires that had reached the Aosta Valley on August 21st. However, forest fires in Canada are becoming increasingly frequent and intense, probably due to climate change.

The long distance transport of atmospheric pollutants highlights the global dimension of the consequences of forest fires. As pointed out by the climatic monitoring service Copernicuswhich had already reported the arrival of Canadian fumes in Europe on June 3, these episodes represent an alarm bell on the global scope of forest fires.

The weather forecast indicates that in the next few days the trajectories of the winds from Canada could continue to be favorable to transport to Europe, with the phenomenon that could persist. A further smoking plume is expected in the next 48-72 hours, which could give particularly colorful sunsets due to the spread of red wavelengths and oranges by the suspension smoke particles.

Arpa Valle d’Aosta continues to monitor in real time the concentrations of fine dust in all stations of the regional territory, providing constant updates through its website to inform the population about the evolution of the situation.