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Bonou is situated within the fertile Ouémé Department of Benin, nestled in a low-lying coastal plain characterized by its proximity to the winding Ouémé River. This strategic location defines its urban character as a rural-agricultural hub rather than an industrial center. The terrain is predominantly flat, with minimal elevation, which allows for the easy movement of air masses but also makes the region susceptible to humidity and seasonal flooding. Surrounding the settlement are vast agricultural zones dominated by subsistence farming and livestock grazing, creating a distinct urban-rural gradient where the built environment blends seamlessly into the verdant landscape. The air quality in Bonou is heavily influenced by this geographic setting; while it lacks the heavy industrial belts found in Cotonou, the prevalence of biomass burning for land clearing and domestic cooking introduces significant particulate matter into the local atmosphere. The river acts as a thermal regulator, modulating local temperatures, yet the lack of significant topographical barriers means that regional pollutants and transboundary dust can settle easily over the town. Because the settlement is dispersed, the concentration of pollutants is generally lower than in Benin's larger cities, but the reliance on traditional fuel sources creates localized pockets of poor air quality. The interaction between the humid riverine environment and the surrounding vegetation helps filter some pollutants, yet the flat topography ensures that during periods of atmospheric stability, smoke from agricultural fires can linger near the surface.

Bonou’s air quality follows a rhythmic cycle dictated by the tropical wet and dry climate of southern Benin. During the dry season, specifically from November to February, the region is dominated by the Harmattan, a northeasterly trade wind that transports vast quantities of mineral dust from the Sahara Desert. This period marks the peak of particulate pollution, as the air becomes hazy and dry, often leading to respiratory irritation for sensitive groups. Conversely, the rainy seasons, which typically occur from April to June and September to October, provide a natural scrubbing mechanism. Frequent precipitation washes airborne pollutants and dust from the sky, leading to the cleanest air of the year. However, the transition periods are critical; during the onset of the dry season, agricultural burning peaks as farmers clear land, creating thick plumes of smoke that can trigger asthma or bronchitis. Temperature inversions during cool dry mornings can trap these pollutants close to the ground, intensifying the smog. For those with chronic respiratory conditions, the Harmattan months are the most challenging, and limiting outdoor exertion during peak dust events is highly recommended. Outdoor activities are best enjoyed during the peak of the rainy season when the atmosphere is freshest. Health guidance for the elderly and children emphasizes hydration and the use of face coverings during dust storms to mitigate the inhalation of fine mineral particles, ensuring that the seasonal swings in air quality do not compromise long-term pulmonary health.