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Ianantsony, nestled within the Toliara region of Madagascar, presents a unique geographic context influencing its air quality. Situated at coordinates -23.5523, 43.7603, the city occupies a relatively flat terrain close to the Onilahy River, a significant waterway in the southwest. The surrounding landscape is dominated by dry deciduous forests and spiny forests, characteristic of the southern Madagascar ecoregion. This proximity to vegetation, while offering some natural filtration, is increasingly impacted by deforestation for agriculture, primarily subsistence farming and the cultivation of sisal. Ianantsony’s position isn’t near major industrial belts, but the prevalence of small-scale charcoal production for cooking and heating contributes to localised particulate matter. The urban-rural gradient is quite sharp; the city itself is compact with a population of approximately 15,000, quickly transitioning to rural agricultural lands. Dust from unpaved roads and agricultural activities is a constant factor. The coastal influence brings sea breezes, but these can also carry salt spray and, occasionally, dust from further afield. The elevation is low, minimizing the potential for significant atmospheric mixing and trapping pollutants near the ground, particularly during calm weather conditions. This combination of factors creates a localized air quality profile heavily influenced by human activity and natural processes.

Ianantsony experiences a distinct wet and dry season, profoundly impacting air quality. The dry season, roughly from April to November, is characterised by consistently high temperatures and minimal rainfall. This period sees a peak in dust resuspension from unpaved roads and agricultural lands, exacerbated by strong winds. Charcoal production also increases as households prepare for cooler evenings. November and December often bring the highest levels of particulate matter. The wet season, from December to March, offers a temporary reprieve. Rainfall effectively washes away dust and suppresses agricultural burning, leading to improved air quality. However, increased humidity can promote mold growth, potentially impacting respiratory health. January and February are generally the most favourable months for outdoor activity. Temperature inversions, where cooler air is trapped beneath warmer air, can occur during the transition periods (March/April and November/December), trapping pollutants near ground level. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during the dry season, particularly in November and December. Monitoring local conditions and staying indoors during dusty periods is crucial for protecting health.