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Roanne, nestled in the Loire Valley of the Auvergne-Rhône-Alpes region of France, occupies a strategic position at the confluence of the Loire and Sornin rivers. Its coordinates (46.0367, 4.0689) place it within a gently undulating terrain, characterized by fertile plains gradually rising towards the foothills of the Massif Central to the west. The Loire River, a significant geographical feature, moderates local temperatures and contributes to a generally humid climate. Historically, Roanne’s location facilitated trade and industry, leading to the development of textile mills and later, metalworking industries along the riverbanks. The surrounding landscape is predominantly agricultural, with extensive fields of wheat, corn, and rapeseed stretching outwards, creating a distinct urban–rural gradient. While the city itself is relatively compact, it’s surrounded by smaller villages and hamlets, contributing to a dispersed population density in the wider Roanne area. The proximity to the industrial belt of Saint-Étienne, approximately 60km to the southeast, introduces a potential source of regional air pollution, impacting Roanne’s air quality. Elevation plays a minor role, with the city situated at an average altitude of around 180 meters, but the valley setting can sometimes trap pollutants, particularly during periods of meteorological stability. The Sornin River, smaller than the Loire, contributes to the local microclimate and drainage patterns, influencing localized air circulation.

Roanne’s air quality experiences a distinct seasonal cycle heavily influenced by meteorological conditions. Spring (March-May) often brings a gradual improvement as temperatures rise and wind speeds increase, dispersing accumulated pollutants. However, this period can also be punctuated by episodes of stagnant air, particularly during periods of high pressure, leading to localized pollution events. Summer (June-August) generally sees the best air quality, with consistent winds and higher temperatures promoting good ventilation. The dry conditions, however, can exacerbate particulate matter pollution from agricultural activities and occasional wildfires in the surrounding areas. Autumn (September-November) marks a shift, with decreasing temperatures and calmer winds. Temperature inversions, common during this season, trap pollutants near the ground, leading to periods of reduced visibility and potentially elevated pollution levels. November, in particular, can be problematic. Winter (December-February) typically presents the most challenging air quality conditions. Cold, stable air masses, frequent fog, and reduced wind speeds contribute to pollutant accumulation. Residential heating, primarily reliant on wood and other biomass fuels in some areas, further exacerbates the problem. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor exertion during periods of fog or stagnant air, especially in the mornings. Maintaining indoor air quality through ventilation and air purification can also be beneficial during these periods. The agricultural landscape surrounding Roanne contributes to seasonal pollen levels, impacting those with allergies.