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Diang, nestled within the Est Region of Cameroon at approximately 4.5833° latitude and 13.3500° longitude, occupies a geographically significant position within the nation’s coastal plains. The city’s terrain is predominantly low-lying, characteristic of the region’s alluvial soils deposited by the numerous rivers that crisscross the landscape. While not directly bordering a major river, Diang benefits from proximity to smaller waterways and drainage systems, influencing local humidity and microclimates. The surrounding landscape is a mosaic of small-scale agriculture – primarily cocoa, plantains, and cassava – interspersed with patches of dense tropical forest. This agricultural activity, while vital to the local economy, contributes to potential sources of particulate matter, particularly during harvesting and burning seasons. Diang’s urban character is that of a small, developing settlement, exhibiting a gradual urban–rural gradient as one moves outwards. The city’s location, relatively isolated from major industrial belts, mitigates some industrial pollution risks. However, the reliance on biomass fuels (wood and charcoal) for cooking and heating within the community and surrounding rural areas represents a consistent source of air pollutants. The elevation is low, typically below 50 meters above sea level, which can exacerbate the trapping of pollutants during periods of stable atmospheric conditions. The coastal proximity also introduces the potential for salt spray and marine aerosols, impacting local air quality and visibility, especially during the Harmattan season.

Diang’s tropical climate dictates a distinct wet and dry season pattern, profoundly influencing its air quality. The dry season, typically spanning from November to March, presents the most significant air quality challenges. Reduced rainfall leads to lower atmospheric moisture, promoting the accumulation of particulate matter. Agricultural practices, including controlled burns for land clearing and crop residue disposal, release substantial amounts of smoke and soot into the air. Furthermore, the Harmattan wind, a dry, dusty trade wind originating from the Sahara, frequently blows across the region during this period, carrying fine particulate matter and reducing visibility. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, intensifying their impact. The wet season, from April to October, brings relief through frequent rainfall, which naturally washes pollutants from the atmosphere. However, heavy downpours can also temporarily increase particulate matter as soil is resuspended. Humidity levels are significantly higher during the wet season, which can affect the respiratory system. Outdoor activities are generally more favourable during the wet season, particularly in the months of May, June, and September. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting prolonged outdoor exposure and considering the use of face masks when air quality is visibly impacted. The prevalence of biomass burning necessitates improved cookstove technologies and sustainable agricultural practices to mitigate pollution’s impact.