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Antsiranana, Madagascar, cradles Milanoa, a small town situated on the northeastern coast, a region characterized by a dramatic interplay of coastal plains, volcanic highlands, and lush rainforest. Located at approximately -13.5833° latitude and 49.7833° longitude, Milanoa benefits from its proximity to the Indian Ocean, a significant factor influencing local weather patterns and, consequently, air quality. The town sits on a gently sloping plain, transitioning quickly to the foothills of the Montagne d'Émeraude (Emerald Mountain), a prominent volcanic peak that dominates the skyline. This elevation gradient creates localized microclimates, with cooler, moister air descending from the highlands, often interacting with the warmer, more humid air rising from the coast. The surrounding landscape is predominantly agricultural, with small-scale farming of vanilla, cloves, and coffee being common. Further inland, dense rainforests extend, acting as a natural filter but also a potential source of biomass burning during agricultural clearing periods. The urban–rural gradient around Milanoa is relatively sharp; the town itself is compact, with a clear delineation between built-up areas and the surrounding agricultural and forested zones. The coastal location exposes Milanoa to sea breezes, which can help disperse pollutants, but also introduce salt aerosols. There are no major industrial belts immediately adjacent to Milanoa, but the port of Antsiranana, a short distance away, represents a potential source of maritime emissions and dust, impacting air quality intermittently. The terrain’s topography and the surrounding land use patterns significantly influence the local air circulation and pollutant dispersion.

Milanoa’s tropical climate dictates a distinct wet and dry season, profoundly impacting its air quality profile. The wet season, typically spanning from November to April, brings frequent rainfall and high humidity. While the rain naturally helps to cleanse the atmosphere, reducing particulate matter, the increased humidity can exacerbate respiratory issues for sensitive individuals. The dry season, from May to October, is characterized by lower rainfall and higher temperatures. During this period, biomass burning from agricultural practices intensifies, releasing significant amounts of smoke and particulate matter into the air. Stagnant air conditions, particularly during the transition months of September and October, can lead to pollutant accumulation. Temperature inversions, where a layer of warm air traps cooler air near the ground, are less frequent than in temperate climates but can occur, especially during clear, calm nights, further hindering pollutant dispersal. Sea breezes, a consistent feature of the coastal environment, generally provide ventilation, but their effectiveness diminishes during periods of calm weather. The months of August and September are often the most challenging for air quality, coinciding with peak agricultural burning and the potential for temperature inversions. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should limit outdoor activity during these periods and consider using face masks when air quality is visibly affected. The increased humidity during the wet season can also trigger mold growth, impacting indoor air quality and potentially exacerbating allergies.