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Leanja, a small city within the Boeny region of Madagascar, sits approximately 16 kilometers inland from the Mozambique Channel, near the larger urban centre of Mahajanga. Its coordinates (-15.5430, 47.9186) place it in a relatively low-lying coastal plain, with an elevation generally under 50 meters. The surrounding landscape is characterised by a mix of savanna, mangrove forests closer to the coast, and increasingly, agricultural land dedicated to rice paddies and vanilla cultivation. This proximity to both the ocean and agricultural activity significantly influences Leanja’s air quality. The prevailing winds, generally from the southeast during the cooler months, carry moisture inland, while during the hotter, wetter season, winds shift and can bring dust from the inland plateaus. The urban-rural gradient is quite sharp; Leanja itself is a relatively small settlement, quickly transitioning to rural agricultural areas. Limited industrial activity within Leanja itself means that much of the pollution stems from domestic sources – wood and charcoal burning for cooking – and agricultural practices like slash-and-burn farming, particularly during land preparation. The coastal location also means potential for salt spray and marine aerosols to contribute to particulate matter in the air, impacting respiratory health. The terrain offers little natural dispersion of pollutants, increasing localised concentrations.

Leanja experiences a distinct wet and dry season, rather than traditional four seasons. Air quality is generally better during the wet season (November to April) due to rainfall effectively washing particulate matter from the atmosphere. However, increased humidity can also foster mould growth, impacting indoor air quality. The peak of the dry season (May to October) brings the poorest air quality. This is driven by increased reliance on wood and charcoal for cooking and heating, coupled with drier conditions that allow dust and smoke to linger. August and September are typically the worst months, with reduced rainfall and stronger winds stirring up dust from agricultural lands. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near ground level. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during these months. The transition periods, November and April, offer the most favourable conditions. Monitoring wind direction is crucial; winds from inland can bring smoke from agricultural burning, while coastal breezes may carry salt spray. Simple measures like using well-ventilated cooking areas and avoiding outdoor exercise during peak pollution times can significantly reduce exposure.