A weather phenomenon where sand from the Sahara Desert in north Africa drifts over the Mediterranean Sea, turning the sky orange in Southern France, including the Alps, as featured in this photo. Screenshot from YouTube.
This June, southern France is choking under an intense bout of air pollution with unusually far-reaching origins, as the skies have turned into a global highway where haze from Canada’s aggressive wildfires crosses the Atlantic and mingles with Saharan dust storms drifting up from North Africa. During the worst days in mid-June, Marseille's Air Quality Index (AQI) reached levels between 130 and 150 — considered unhealthy for sensitive groups — compared to typical summer levels, which usually range between 40 and 60.
Beginning in May, a cluster of aggressive wildfires ignited in Central Canada, particularly in Manitoba, Saskatchewan, and Alberta. In Manitoba alone, 27 wildfires remain active, including a massive blaze near Flin Flon and Sherridon, which burned over 300,000 hectares in early June alone. In recent days, the fires have crept north, raising concerns the individual blazes could merge into what experts call a “Giga-fire” — a rare event where a single blaze engulfs over 400,000 hectares.
Screenshot of Canada's wildfire map by the Canadian Interagency Forest Fire Centre on June 12, 2025. Much of Northern Canada is facing “out of control” wildfires. Image via Situation Report.
Marseillais, the city residents, are inhaling a rare mix of wildfire smoke, Saharan dust, and ozone. The impact of this transcontinental pollution phenomenon has intensified throughout June. What began as elevated fine particle levels from Canada’s wildfires has morphed into what local authorities are calling a “multi-source pollution episode” — a perfect storm of pollutants. While Marseille regularly experiences short-lived Saharan dust events, this episode stands out due to the added layer of wildfire smoke carried across the Atlantic — a combination rarely seen in such concentration. According to AtmoSud, multi-source episodes like this are becoming more frequent and more intense as climate patterns shift and fire seasons grow longer.
Here is a video in French detailing the issue of Saharan dust storms in the Mediterranean region.
The Prefecture of Bouches-du-Rhône, the regional state authority overseeing public safety, activated pollution alert level 2 on June 13, the highest possible, as air quality monitors recorded dangerous concentrations of fine particles, ozone, and additional desert dust particles arriving from North Africa.
A screenshot of OpenAir pollution map in Bouche du Rhöne, the department where Marseille is located. The map shows that much of Southern France is facing a “bad” air quality rating.
A two-millennium-old city, Marseille is no stranger to Saharan dust. Several times a year, warm winds carry fine desert particles north across the Mediterranean, blanketing the city with an orange haze and contributing to temporary spikes in pollution, especially when combined with heat, sunlight, and stagnant air — the perfect conditions for ozone formation. What makes this episode different is the additional layer of Canadian wildfire smoke, stacking one source of pollution on top of another.
A screenshot of a video depicting the pollution levels in Marseille on June 12, 2025. Screenshot from YouTube.
AtmoSud, the regional air quality observatory, reported that for four days in a row, pollution levels in Marseille had exceeded official health safety standards Ozone — helpful high in the atmosphere but harmful near the ground — added to the health risks, aggravating respiratory conditions. Exposure to these high levels of fine particles (PM2.5 and PM10) and ozone can worsen asthma, trigger respiratory infections, strain the cardiovascular system, particularly among children, the elderly, and people with existing health conditions, and increasing the risk of hospital saturation.
With prolonged exposure worsening, local authorities have imposed traffic restrictions within Marseille’s Low Emission Zone (ZFE), limiting circulation to only the least-polluting vehicles. Speed limits were lowered by 20 kilometers per hour on major roads due to low visibility, and outdoor physical activities were officially discouraged.
As global temperatures rise, these overlapping events are turning local air pollution into transcontinental threats. For coastal cities like Marseille, which are already exposed to heat waves, drought, and rising sea levels, even distant disasters are now carried directly into the air people breathe.
