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Quijingue, Bahia, Brazil, occupies a strategic position within the semi-arid Sertão region of northeastern Brazil. Located at approximately -10.7525° latitude and -39.2092° longitude, the city’s geography is dominated by undulating plains characteristic of the Brazilian Highlands, with an average elevation of around 500 meters above sea level. This relatively low elevation, combined with the region’s climate, influences local air circulation patterns. The surrounding landscape is primarily a mosaic of *caatinga* vegetation – a thorny, drought-resistant biome – interspersed with agricultural lands and scattered settlements. While Quijingue itself is a small urban center with a population of roughly 27,626, it sits within a broader agricultural zone, with subsistence farming and livestock rearing being common practices in the immediate vicinity. This proximity to agricultural activities introduces potential sources of particulate matter, particularly during periods of land clearing or burning. The city’s distance from major industrial belts minimizes direct industrial pollution, but the regional reliance on charcoal production for cooking and heating, a traditional practice, can contribute to localized air quality issues. The lack of significant bodies of water nearby limits natural air purification processes, and the prevailing wind patterns, often influenced by the seasonal shifts in the Intertropical Convergence Zone, play a crucial role in dispersing or concentrating pollutants within the region. The urban–rural gradient around Quijingue is gradual, with agricultural land seamlessly blending into the urban fabric, impacting air quality through diffuse sources.

Quijingue’s tropical climate dictates a distinct wet and dry season pattern, profoundly impacting its air quality. The dry season, typically spanning from April to September, is characterized by intense heat, low humidity, and infrequent rainfall. This period often witnesses a build-up of particulate matter due to reduced precipitation to wash pollutants from the atmosphere and increased dust from agricultural activities and unpaved roads. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, exacerbating localized air quality concerns. The months of July and August are generally considered periods to exercise caution for individuals with respiratory sensitivities. Conversely, the wet season, from October to March, brings increased rainfall and higher humidity, naturally cleansing the air and dispersing pollutants. The monsoon-like rains flush particulate matter from the atmosphere, leading to improved air quality. However, heavy rainfall can also temporarily increase humidity, which may affect individuals with asthma or allergies. Fog, though infrequent, can occur during the transition periods between seasons, trapping pollutants and reducing visibility. During the wet season, outdoor activities are generally more favorable, although sudden downpours can disrupt plans. Sensitive groups, including children, the elderly, and those with pre-existing respiratory conditions, should remain vigilant during the dry season, minimizing prolonged outdoor exposure and taking precautions such as wearing masks when necessary. The interplay of these meteorological factors creates a dynamic air quality profile throughout the year, demanding adaptive strategies for public health.