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Sahanaty, nestled within the Toamasina Province of Madagascar at coordinates -17.4514, 48.9984, presents a unique geographic profile significantly influencing its air quality. Situated on the eastern coast, the city benefits from proximity to the Indian Ocean, a factor that generally promotes sea breezes and ventilation, potentially mitigating some pollution. However, this coastal location also introduces the risk of salt spray and marine aerosols impacting air composition. The surrounding landscape is characterized by a gradual transition from coastal plains to rolling hills and eventually, the highlands of the Betsimisaraka Plateau. This terrain creates localized microclimates and can trap pollutants under certain meteorological conditions. Sahanaty’s relatively small population of 16,334 suggests a primarily rural or small-town character, likely with a significant agricultural presence in the immediate vicinity. The urban–rural gradient is likely quite sharp, with agricultural lands and small villages dominating the surrounding areas. While large-scale industrial belts are not immediately apparent, localized agricultural processing or small-scale industries could contribute to air emissions. The elevation is relatively low, contributing to a warmer, more humid climate. Prevailing winds, often influenced by monsoon patterns, play a crucial role in dispersing or concentrating pollutants. The presence of the Pangalanes Canal, a series of interconnected lakes and waterways, further influences local wind patterns and humidity levels, impacting the behaviour of airborne particles. Understanding this interplay between coastal influence, terrain, and surrounding land use is vital for assessing Sahanaty’s air quality challenges.

Sahanaty’s tropical climate dictates a distinct wet and dry season cycle, profoundly impacting its air quality. The wet season, typically spanning from November to April, brings frequent rainfall and high humidity. While rainfall naturally helps to cleanse the atmosphere by removing particulate matter, the increased humidity can exacerbate respiratory issues for sensitive individuals. The frequent cloud cover reduces solar radiation, potentially impacting photochemical smog formation, a common issue in urban areas. The dry season, from May to October, is characterized by lower rainfall and increased sunshine. This period often sees a build-up of pollutants due to reduced precipitation and increased evaporation, leading to higher concentrations of ground-level ozone and particulate matter. During the dry season, temperature inversions – where a layer of warm air traps cooler air below – can occur, particularly in the evenings, further concentrating pollutants near the ground. Wind patterns shift seasonally; the monsoon winds are strongest during the wet season, providing some ventilation, while the dry season often experiences calmer conditions, allowing pollutants to accumulate. Outdoor activities are generally more favourable during the wet season, although the humidity can be uncomfortable. Sensitive groups, including children, the elderly, and those with respiratory conditions, should exercise caution during the dry season, particularly during periods of stagnant air or when haze is observed. Agricultural burning, a common practice in the surrounding areas, can significantly worsen air quality during the transition periods between seasons, releasing smoke and particulate matter into the atmosphere.