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Bemanonga, nestled within the Toliara region of Madagascar, occupies a unique geographic position significantly influencing its air quality. Located at approximately -20.2920 latitude and 44.3513 longitude, the city sits on a relatively flat coastal plain, just inland from the Mozambique Channel. This proximity to the Indian Ocean introduces a constant maritime influence, generally moderating temperatures but also contributing to humidity and potential for sea salt aerosol deposition. The surrounding landscape is characterized by a transition zone between the drier, spiny forests typical of southwestern Madagascar and the more humid coastal ecosystems. To the west, the terrain gradually rises towards the interior highlands, though Bemanonga itself remains at a low elevation, rarely exceeding 50 meters above sea level. This low elevation limits vertical mixing of air pollutants. The region’s economy is largely agrarian, with significant agricultural activity focused on vanilla, cloves, and rice cultivation in the surrounding areas. While Bemanonga itself is a small town, it serves as a local market hub, and occasional transport of agricultural goods via trucks can contribute to localized dust and exhaust emissions. The urban–rural gradient is relatively sharp; the town is immediately bordered by agricultural land and sparsely populated villages, minimizing the sprawling urban footprint often associated with larger cities and their attendant pollution sources. The prevailing winds, generally easterly, tend to carry pollutants away from the coast, but localized conditions can trap them within the town itself, particularly during periods of calm weather. The lack of significant industrial zones within immediate proximity is a mitigating factor, though the reliance on wood for cooking and heating in some households remains a potential source of particulate matter.

Bemanonga’s tropical climate dictates a distinct wet and dry season pattern, profoundly impacting air quality. The dry season, typically spanning from May to October, is characterized by consistently high temperatures and reduced rainfall. During this period, the lack of precipitation allows dust generated from agricultural activities and unpaved roads to accumulate, leading to increased particulate matter concentrations. Calm wind conditions are more frequent during the dry season, hindering pollutant dispersion and fostering localized stagnation. While sea breezes offer some relief, they are often insufficient to fully clear the air. The wet season, from November to April, brings frequent rainfall and higher humidity. The rain effectively ‘washes’ the atmosphere, removing particulate matter and generally improving air quality. However, periods of intense rainfall can lead to flooding, which can temporarily release pollutants from inundated areas. Fog, a relatively common occurrence during the transition months (October/November and April/May), can trap pollutants near the ground, creating localized episodes of poor air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of prolonged calm and dust events. Outdoor activities are generally more favorable during the wet season, although heavy rainfall can still pose challenges. The use of traditional cooking methods, often relying on wood or charcoal, can contribute to indoor air pollution, particularly during the dry season when fuel wood is more readily available. Maintaining adequate ventilation is crucial to minimize exposure to these pollutants.