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Humberto de Campos, nestled in the southeastern Maranhão state of Brazil, occupies a geographically significant position within the Cerrado biome. Located at approximately -2.5983° latitude and -43.4611° longitude, the city’s terrain is characterized by undulating plains and gently sloping hills, typical of the transition zone between the Amazon rainforest and the drier Cerrado savanna. The surrounding landscape is dominated by expansive grasslands interspersed with gallery forests along seasonal streams and rivers, a defining feature of the Cerrado. While not directly adjacent to a major river, Humberto de Campos benefits from proximity to smaller tributaries that feed into larger river systems, influencing local humidity and microclimates. The urban–rural gradient shifts rapidly, with agricultural lands – primarily soybean and maize cultivation – extending outwards from the city limits. This agricultural activity, coupled with potential livestock farming, contributes to diffuse sources of air pollution. The city’s elevation, relatively low, means it is susceptible to temperature inversions, particularly during the drier months, which can trap pollutants near the ground. The regional position, far from major industrial belts, suggests that industrial emissions are likely a less significant factor compared to agricultural practices and residential wood burning. The prevailing winds, generally easterly, play a crucial role in dispersing or concentrating pollutants, impacting air quality across the municipality. The Cerrado’s characteristic vegetation, while generally beneficial for carbon sequestration, can also release volatile organic compounds (VOCs), influencing ozone formation under specific meteorological conditions.

Humberto de Campos experiences a tropical savanna climate, defined by distinct wet and dry seasons, profoundly influencing its air quality. The dry season, typically spanning from May to September, is characterized by reduced rainfall, higher temperatures, and increased frequency of temperature inversions. These inversions trap pollutants, leading to periods of stagnant air and potentially elevated concentrations of particulate matter from agricultural burning and residential wood use for cooking and heating. The months of July and August often see the most pronounced effects, with reduced wind speeds exacerbating the issue. During the wet season (October to April), increased rainfall effectively ‘washes’ pollutants from the atmosphere, leading to improved air quality. However, heavy rainfall events can also mobilize dust and soil particles, temporarily degrading air quality. The increased humidity during the wet season can also influence the formation of ground-level ozone, although this is generally less significant than particulate matter concerns. Fog, though infrequent, can occur during cooler periods, further reducing air dispersion. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of agricultural burning. Limiting outdoor exertion and avoiding areas with visible smoke are advisable. The transition months (April/May and September/October) often present a mixed picture, with fluctuating conditions requiring vigilance and awareness of local air quality conditions. Maintaining indoor air quality through proper ventilation and air filtration can provide additional protection.