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Andriba, nestled within the Mahajanga Province of Madagascar, occupies a geographically significant position on the Mozambique Channel coastline. Located at approximately -17.5977° latitude and 46.9308° longitude, the town’s terrain is characterized by a gently undulating landscape transitioning from coastal plains to low hills inland. The proximity to the Mozambique Channel exerts a powerful influence, moderating temperatures and contributing to a humid, tropical climate. The surrounding landscape is a mosaic of coastal scrub, mangrove forests fringing the shoreline, and extensive agricultural zones dedicated primarily to vanilla, rice, and cashew cultivation. This agricultural activity, while vital to the local economy, introduces potential sources of particulate matter, particularly during harvesting and processing seasons. Andriba’s urban character is that of a developing market town, with a relatively low population density of around 32,000. The urban–rural gradient is gradual, with small villages and agricultural fields seamlessly blending into the town’s periphery. There are no major industrial belts immediately adjacent to Andriba; however, the port of Mahajanga, approximately 150km north, represents a potential source of shipping-related emissions that could, under specific meteorological conditions, impact air quality. Elevation is relatively low, rarely exceeding 30 meters above sea level, which can exacerbate the trapping of pollutants during temperature inversions. The prevailing winds generally blow from the east, bringing moisture from the Mozambique Channel, but their strength and direction can vary significantly, influencing the dispersion of any localized pollution.

Andriba’s tropical climate dictates a distinct wet and dry season pattern, profoundly influencing its air quality. The wet season, typically spanning from November to April, brings frequent rainfall and high humidity. While the rain naturally helps to cleanse the atmosphere, reducing particulate matter concentrations, the increased humidity can trap gaseous pollutants, particularly during periods of reduced wind. The dry season, from May to October, is characterized by lower rainfall and generally clearer skies. However, this period often sees a rise in dust and smoke pollution. Agricultural burning, a common practice for land clearing and crop residue disposal, significantly contributes to particulate matter during this time, especially in September and October. Fog, a relatively frequent occurrence during the cooler months (June-August), can trap pollutants near the ground, leading to localized episodes of reduced visibility and potentially impacting respiratory health. Temperature inversions, where a layer of warm air sits above cooler air, are less common but can occur, preventing vertical mixing and trapping pollutants. The months of September and October should be approached with caution for individuals with respiratory sensitivities, as agricultural burning is at its peak. During the wet season, while overall pollution may be lower, the high humidity can exacerbate existing respiratory conditions. Children, the elderly, and individuals with pre-existing respiratory illnesses are particularly vulnerable and should limit prolonged outdoor exposure during periods of agricultural burning or dense fog.