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São Miguel, nestled in the coastal state of Rio Grande do Norte, Brazil, occupies a geographically significant position within the Ponta do Mel region. Located at approximately -6.2119 latitude and -38.4969 longitude, the city’s terrain is characterized by a gently undulating landscape transitioning from the coastal plains to low hills. Its proximity to the Atlantic Ocean, roughly 10 kilometers inland, exerts a considerable influence on local climate and, consequently, air quality. The surrounding landscape is a mosaic of small-scale agriculture, primarily focused on fruits and vegetables, interspersed with patches of native Caatinga vegetation – a semi-arid biome adapted to seasonal drought. This agricultural activity, while vital to the local economy, can contribute to particulate matter emissions, particularly during harvesting and soil preparation. The urban–rural gradient is relatively gradual, with small settlements and agricultural fields blending seamlessly into the city’s periphery. São Miguel’s elevation is relatively low, averaging around 20 meters above sea level, which can exacerbate the trapping of pollutants under certain meteorological conditions. There are no major industrial belts directly adjacent to São Miguel; however, larger industrial centers are located further south along the coast, and prevailing winds can occasionally transport pollutants from these areas. The city’s coastal location also means it is susceptible to sea breezes, which can both disperse and concentrate pollutants depending on the time of day and atmospheric stability. The Caatinga biome, while drought-resistant, can contribute to dust events, particularly during the dry season, impacting air quality.

São Miguel’s tropical climate dictates a distinct wet and dry season pattern, profoundly influencing its air quality profile. The dry season, typically spanning from August to December, is characterized by reduced rainfall and increased temperatures. This period often sees a rise in particulate matter concentrations due to the prevalence of dust storms originating from the Caatinga vegetation and agricultural lands. The lack of rainfall means there's less natural scrubbing of the atmosphere, allowing dust and other pollutants to linger. During this time, temperature inversions are more frequent, trapping pollutants closer to the ground, especially during calmer nights. The wet season, from January to July, brings increased rainfall and higher humidity, which generally improves air quality by washing away particulate matter and diluting gaseous pollutants. However, periods of intense rainfall can lead to localized flooding, potentially releasing pollutants from contaminated sites. Wind patterns are crucial; consistent sea breezes during the wet season help disperse pollutants, while weaker winds during the dry season can lead to stagnation. Months like September and October, coinciding with the peak of the dry season and agricultural activity, are generally periods to exercise caution for individuals with respiratory sensitivities. Conversely, March and April, during the transition to the wet season, often offer the most favorable air quality conditions. Sensitive groups, including children, the elderly, and those with pre-existing respiratory conditions, should monitor local conditions and limit outdoor exertion during periods of elevated dust or stagnant air.