Loading air quality context...

Saint-Louis, Senegal, occupies a unique geographic position at the mouth of the Senegal River, where it meets the Atlantic Ocean. Founded on the sandy island of Ndar, the city’s urban fabric is tightly constrained by this natural boundary, creating a linear urban form stretching along the coast. The surrounding landscape is characterized by a flat, low-lying coastal plain, transitioning into the Ferlo desert further inland. Elevation is minimal, rarely exceeding 10 meters above sea level, making the city vulnerable to sea-level rise and coastal erosion. Historically, Saint-Louis thrived as a major trading post, and remnants of this past are visible in its colonial architecture. While not heavily industrialized, the city’s port activity and associated transport contribute to localized pollution. Surrounding the island are extensive tidal flats and mangrove ecosystems. The urban-rural gradient is relatively sharp, with agricultural lands dominating the river valley and the arid Ferlo providing a stark contrast. This coastal location significantly impacts air quality; sea breezes can disperse pollutants, but also carry salt spray and, during Harmattan winds, Saharan dust, impacting respiratory health. The river itself can act as a conduit for pollutants from upstream sources, influencing local air composition.

Saint-Louis experiences a distinct tropical climate with a pronounced wet and dry season, heavily influencing air quality. The dry season, roughly November to May, is characterized by the Harmattan wind, bringing significant amounts of Saharan dust. This dust dramatically increases particulate matter concentrations, leading to reduced visibility and respiratory irritation. January and February are typically the months with the poorest air quality due to this influx. The transition to the wet season, around June, brings a temporary improvement as rainfall washes away accumulated dust. However, increased humidity can also foster mold growth, impacting indoor air quality. The wet season, lasting from June to October, generally offers the best air quality, with frequent rainfall cleansing the atmosphere. However, stagnant air masses can develop during periods of reduced rainfall, leading to localized pollution build-up from vehicle emissions and port activity. August and September, while wet, can experience these periods of stagnation. Sensitive groups, including children and the elderly, should limit strenuous outdoor activity during Harmattan season and periods of stagnant air. Monitoring wind patterns and rainfall is crucial for predicting air quality fluctuations.