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Central, Bahia, Brazil, a small municipality nestled within the broader Salvador metropolitan region, occupies a geographically significant position in the Recôncavo Baiano, a coastal plain characterized by low-lying terrain and a unique estuarine environment. Situated at approximately -11.1542° latitude and -42.0814° longitude, the city’s elevation rarely exceeds 20 meters above sea level, contributing to a generally flat landscape. This proximity to the Atlantic Ocean and the Baía de Todos os Santos (All Saints Bay) profoundly influences local climate and, consequently, air quality. The surrounding landscape is a mosaic of agricultural lands – primarily sugarcane and cocoa plantations – interspersed with patches of Atlantic Forest remnants. This agricultural activity, while economically vital, introduces potential sources of particulate matter and volatile organic compounds into the atmosphere. The urban–rural gradient is relatively sharp, with Central transitioning quickly from a small, densely populated core to agricultural fields and scattered rural settlements. Salvador, a major industrial and port city, lies within a reasonable distance, potentially impacting Central’s air quality through long-range transport of pollutants. The Recôncavo’s geology, composed largely of sedimentary rocks, also influences soil composition and dust generation, further impacting local air quality. The bay itself acts as a receptor for pollutants, and its shallow waters can exacerbate stagnant air conditions, particularly during periods of calm weather. The prevailing easterly trade winds, however, generally provide some degree of ventilation, though their effectiveness can be diminished by temperature inversions.

Central’s tropical climate dictates a distinct wet and dry season pattern, significantly influencing air quality dynamics. The dry season, typically spanning from September to April, is characterized by reduced rainfall and increased sunshine hours. While this might seem beneficial, the lack of precipitation allows accumulated pollutants to persist for longer periods. The lower humidity also contributes to increased dust levels, particularly from agricultural activities and unpaved roads. Temperature inversions, common during the dry season, trap pollutants near the ground, leading to periods of poorer air quality. The wet season, from May to August, brings frequent rainfall, which naturally cleanses the atmosphere by removing particulate matter and gaseous pollutants. However, heavy rainfall can also lead to increased soil erosion and runoff, carrying sediment into the air. During the transition months (April/May and September/October), the combination of changing wind patterns and fluctuating humidity can create unpredictable air quality conditions. The months of October and November often experience a surge in agricultural burning, a traditional practice for land clearing, which dramatically elevates particulate matter concentrations. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season and avoid strenuous outdoor activities on days with visible haze or dust. The increased humidity during the wet season can exacerbate allergies for some individuals. Maintaining indoor air quality through proper ventilation and air filtration is advisable year-round, but particularly during periods of elevated pollution.