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Iguape, nestled along the southern coast of São Paulo state in Brazil, occupies a geographically significant position within the broader Atlantic Forest biome. Located at approximately -24.7081° latitude and -47.5553° longitude, the city’s terrain is characterized by low-lying coastal plains, gently sloping towards the Atlantic Ocean. This proximity to the sea significantly influences local weather patterns and, consequently, air quality. The surrounding landscape is a mosaic of coastal forests, mangrove swamps, and agricultural lands, primarily dedicated to sugarcane cultivation – a key economic driver for the region. Iguape sits within the wider Baixada Santista metropolitan area, a historically industrial belt stretching along the coast, though Iguape itself retains a more rural character compared to the larger cities like Santos and Guarujá. The urban–rural gradient is noticeable, with denser urban areas concentrated closer to the city center gradually transitioning into agricultural fields and forested areas further inland. Elevation is minimal, rarely exceeding 30 meters above sea level, which can exacerbate the trapping of pollutants, particularly during periods of atmospheric stability. The Ribeira de Iguape river, flowing through the city, also plays a role in local microclimates and potential pollutant dispersal. The prevailing winds, often influenced by coastal breezes, generally blow from the southeast, carrying maritime air inland, but can also transport pollutants from nearby industrial zones or agricultural burning events. The city’s location within a humid subtropical climate zone contributes to high humidity levels, which can affect the dispersion of particulate matter.

Iguape experiences a tropical wet and dry climate, dictating a distinct seasonal pattern in air quality. The dry season, typically from April to September, often sees a noticeable increase in particulate matter concentrations. This is largely attributable to agricultural practices, specifically controlled burns of sugarcane fields to prepare for planting. While regulated, these burns can release significant amounts of smoke and particulate matter into the atmosphere, particularly when wind speeds are low. The dry air also contributes to the persistence of these pollutants, as there is less rainfall to wash them out. Conversely, the wet season (October to March) brings increased rainfall and higher humidity, generally leading to improved air quality as pollutants are scavenged from the atmosphere. However, periods of intense rainfall can also lead to localized flooding, potentially releasing contaminants from soil and runoff into the air. Temperature inversions, though less frequent than in colder climates, can occasionally occur during the dry season, trapping pollutants near the ground, especially in the mornings. Fog, common during the cooler months, can also reduce visibility and concentrate pollutants. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with visible smoke or haze. Outdoor activities are generally more favorable during the wet season, although vigilance regarding potential flood-related air quality issues is still advised. The interplay of wind patterns, agricultural practices, and rainfall creates a dynamic air quality profile throughout the year in Iguape.