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Pahou, a commune in the Atlantique Department of Benin, occupies a relatively flat coastal plain situated approximately 30km east of Cotonou, the country’s largest city and economic hub. Located at 6.3833°N latitude and 2.2167°E longitude, Pahou’s terrain is characterised by low-lying land, typical of the Benin coastal region. The city’s proximity to the Atlantic Ocean – roughly 5km to the south – exerts a significant influence on its climate and, consequently, its air quality. The surrounding landscape is a mix of coconut plantations, small-scale agriculture (primarily maize, cassava, and vegetables), and increasingly, residential development as Cotonou expands. While not heavily industrialised itself, Pahou experiences air quality impacts from industrial activity and port operations in Cotonou, transported by prevailing winds. The urban-rural gradient is becoming blurred as Pahou grows, with increasing vehicle traffic and domestic fuel burning contributing to localised pollution. Drainage can be poor in the wet season, exacerbating dust resuspension when the land dries. The lack of significant topographical features means pollutants are not readily dispersed, leading to potential concentration issues, particularly during periods of calm weather. This flat terrain and coastal location create a unique set of challenges for maintaining clean air.

Pahou experiences a tropical climate with distinct wet and dry seasons, profoundly impacting air quality. The dry season, spanning November to March, is typically associated with poorer air quality. Harmattan winds, originating from the Sahara, carry substantial amounts of dust and particulate matter, significantly increasing PM10 and PM2.5 levels. These dust events are most frequent in December and January, making outdoor activity less advisable for those with respiratory conditions. The transition periods – October/November and March/April – see fluctuating conditions, with localised burning of vegetation for agricultural purposes adding to particulate pollution. The wet season, from April to October, generally brings improved air quality due to rainfall scavenging pollutants from the atmosphere. However, increased humidity can also foster mould growth, impacting indoor air quality. August and September, the peak of the rainy season, offer the most favourable conditions for outdoor activities. Temperature inversions, though less common than in temperate climates, can occur during the cooler, drier nights, trapping pollutants near ground level. Sensitive groups – children, the elderly, and those with pre-existing respiratory illnesses – should take extra precautions during the Harmattan season and periods of agricultural burning.