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Limoeiro do Norte, nestled in the heart of Ceará state, Brazil, occupies a geographically significant position within the broader Northeast region. Located at approximately -5.1458° latitude and -38.0978° longitude, the city’s terrain is characterized by undulating hills and valleys, typical of the Sertão biome. Its elevation, though modest, contributes to localized microclimates and influences air circulation patterns. The surrounding landscape is predominantly semi-arid, transitioning from scrubland and cacti-dotted plains to the fringes of the Jaguaribe River basin. This river, though subject to seasonal fluctuations, provides a vital water source and influences humidity levels, impacting atmospheric stability. Limoeiro do Norte sits within a predominantly rural-agricultural zone, with small-scale farming and livestock rearing being key economic activities. While not directly adjacent to major industrial belts, the city’s proximity to larger urban centers like Fortaleza (approximately 200 km) means it can be affected by transboundary pollution events. The urban–rural gradient is relatively sharp, with the city’s built environment gradually blending into the surrounding agricultural lands. The prevailing winds, often originating from the Atlantic Ocean, play a crucial role in dispersing pollutants, though their effectiveness can be hampered by temperature inversions, particularly during drier periods. The city’s location within a region experiencing increasing desertification also impacts air quality, with dust storms becoming more frequent, contributing to particulate matter pollution. The relatively low population density (59,560) generally mitigates localized urban pollution, but agricultural practices and regional weather patterns remain key factors.

Limoeiro do Norte’s tropical climate dictates a distinct wet and dry season cycle, profoundly influencing air quality throughout the year. The dry season, typically spanning from August to November, is characterized by intense solar radiation, high temperatures, and minimal rainfall. This period often sees a build-up of pollutants due to reduced precipitation to wash them away and decreased wind speeds, which can lead to stagnant air conditions. Temperature inversions, where cooler air is trapped beneath a layer of warmer air, are more common during these months, further exacerbating pollution accumulation. Dust storms, originating from the surrounding semi-arid landscape, are also more frequent, significantly increasing particulate matter concentrations. The wet season, from February to July, brings increased rainfall and higher humidity, naturally cleansing the atmosphere and dispersing pollutants. Stronger winds associated with the monsoon-like patterns also aid in ventilation. However, heavy rainfall can occasionally lead to increased mold and fungal spores, impacting indoor air quality. During the transitional months (December-January and July-August), air quality tends to be more variable, influenced by shifting wind patterns and fluctuating temperatures. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak heat and dust storm events. Maintaining indoor air quality through proper ventilation and air filtration is particularly important during these periods. The increased humidity during the wet season can be beneficial for those with dry skin or respiratory issues, but vigilance regarding mold growth is advised.