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Sahasoa, nestled within the Fianarantsoa Province of Madagascar, occupies a geographically significant position within the island’s central highlands. Located at approximately -21.9480 latitude and 45.9891 longitude, the city’s elevation contributes to its unique microclimate and influences air quality dynamics. The surrounding landscape is dominated by rolling hills and terraced rice paddies, characteristic of the Betsileo region, a major agricultural zone. This proximity to intensive farming practices, particularly the burning of agricultural waste after harvest, represents a key source of particulate matter pollution. Sahasoa itself is a small, relatively low-density urban settlement, exhibiting a clear urban-rural gradient as it transitions into the surrounding agricultural lands. The terrain is gently sloping, which can exacerbate the accumulation of pollutants, particularly during periods of low wind. While not directly adjacent to a major river, the region receives significant rainfall, contributing to humidity levels that can trap pollutants close to the ground. The absence of large-scale industrial belts within immediate proximity is a mitigating factor, however, the city’s reliance on wood-fired stoves for cooking and heating, a common practice in Madagascar, introduces significant levels of carbon monoxide and fine particulate matter. The regional position, far from major coastal shipping lanes, minimizes marine-borne pollutants, but the prevailing winds from the east can carry dust and aerosols from the surrounding highlands.

Sahasoa’s air quality is intrinsically linked to its tropical highland climate, exhibiting a distinct wet and dry season pattern. The dry season, typically spanning from May to October, often sees a noticeable increase in air pollution. Reduced rainfall means less atmospheric cleansing, and the prevailing winds, frequently light during this period, struggle to disperse pollutants. Agricultural burning, a common practice to clear fields for the next planting season, peaks during the transition from the dry to the wet season (September-November), resulting in elevated particulate matter concentrations. The wet season, from November to April, brings increased rainfall, which naturally washes pollutants from the atmosphere, leading to improved air quality. However, periods of prolonged fog, common during the wet season, can trap pollutants near the ground, creating localized pockets of poor air quality. Temperature inversions, though less frequent than in colder climates, can occasionally occur during the cooler months (June-August), further hindering pollutant dispersion. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season and periods of fog, limiting prolonged outdoor exposure. The months of September and October, coinciding with peak agricultural burning, are particularly challenging for air quality. While the wet season generally offers respite, awareness of localized fog events remains crucial for protecting vulnerable populations. The reliance on wood-fired stoves throughout the year contributes to a baseline level of indoor and outdoor air pollution, regardless of the season.