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Merimandroso, a small urban centre within the greater Antananarivo region of Madagascar, occupies a challenging geographical position. Situated at approximately -18.7517 latitude and 47.5162 longitude, the town is nestled amongst the highlands of central Madagascar. The terrain is characterised by rolling hills and valleys, a landscape heavily sculpted by erosion over millennia. Its elevation, around 1,200-1,400 meters above sea level, contributes to cooler temperatures than the coastal regions, but also fosters temperature inversions that can trap pollutants. The surrounding landscape is a mosaic of rice paddies, small-scale agriculture, and increasingly, peri-urban development encroaching on formerly rural areas. While not directly adjacent to a major body of water, Merimandroso is within the watershed of several rivers that feed into larger systems. Antananarivo itself, a significant industrial and commercial hub, exerts a strong influence on Merimandroso’s air quality due to prevailing wind patterns and the urban-rural gradient. The increasing use of charcoal for cooking and heating in both cities is a major contributor to particulate matter. The relatively limited infrastructure for waste management further exacerbates the issue, with open burning common, especially during the dry season. This combination of factors creates a localised air pollution ‘bowl’ effect, particularly pronounced in lower-lying areas of Merimandroso.

Merimandroso experiences a distinct wet and dry season, profoundly impacting air quality. The wet season, roughly November to April, brings relief from particulate matter as rainfall effectively washes pollutants from the atmosphere. However, increased humidity can also foster mould growth, impacting respiratory health. The heaviest rainfall typically occurs in January and February, offering the cleanest air of the year. Conversely, the dry season, from May to October, sees a significant deterioration in air quality. This is driven by increased dust from agricultural activities, widespread charcoal burning for cooking and heating, and a greater propensity for open waste burning. August and September are typically the worst months, with dry winds carrying pollutants across the region. Temperature inversions, common during the cooler dry season nights, trap pollutants near ground level. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit outdoor activity during these peak pollution periods. During the transition months (April/November), air quality is variable, requiring increased vigilance. Monitoring local conditions and avoiding strenuous activity on visibly hazy days is advisable. The prevailing winds, generally from the east, also play a role in transporting pollutants from Antananarivo towards Merimandroso.