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Abertawe, known as Swansea in English, occupies a distinctive coastal position in South Wales, United Kingdom, nestled at the mouth of the River Tawe where it meets Swansea Bay. This urban centre, with a population of approximately 246,700, lies within the historic county of Glamorgan, positioned roughly 45 miles west of Cardiff. The city's geography is characterised by a dramatic interplay between coastal lowlands and surrounding uplands. To the north, the urban area transitions into the foothills of the Welsh mountains, including areas like Clyne Common, while to the east lies the Gower Peninsula, an Area of Outstanding Natural Beauty. Swansea's terrain slopes gently from these higher grounds down to the coastal plain, with elevations ranging from sea level to about 150 metres in northern suburbs. This coastal setting profoundly influences air quality: prevailing south-westerly winds from the Atlantic Ocean typically disperse pollutants, but the city's position in a sheltered bay can occasionally trap emissions, especially under stable atmospheric conditions. The urban-rural gradient is sharp, with dense urban cores giving way to semi-rural valleys and protected coastline. Historically part of an industrial belt known for copper smelting and steel production, modern Swansea retains some industrial activity in its eastern zones near Port Talbot, while the western areas are more residential and commercial. The River Tawe corridor and Swansea Bay create microclimates that can affect pollution dispersion, with sea breezes moderating temperatures but sometimes recirculating local emissions when wind patterns are weak.

In Swansea, air quality follows a distinct seasonal rhythm shaped by its temperate maritime climate. During winter, from December to February, pollution levels often peak due to increased domestic heating emissions, particularly from wood-burning stoves in residential areas, combined with frequent temperature inversions that trap pollutants in the cold, stagnant air of the Tawe Valley. These inversions are exacerbated by calm conditions and radiation fog, common in low-lying parts of the city, making early mornings particularly problematic for sensitive groups like asthmatics or the elderly. Spring, from March to May, brings gradual improvement as Atlantic weather systems increase, with stronger westerly winds dispersing pollutants and frequent rainfall cleansing the atmosphere—April and May are generally favourable for outdoor activities. Summer, from June to August, sees the lowest pollution levels overall, thanks to vigorous sea breezes and reduced heating needs, though occasional high-pressure systems can lead to ozone formation on warm, sunny days, especially in July and August, affecting those with respiratory conditions. Autumn, from September to November, marks a transition, with pollution beginning to rise as temperatures drop and atmospheric stability increases, compounded by agricultural burning in surrounding rural areas. Sensitive individuals should monitor local air quality forecasts year-round, avoiding strenuous outdoor exercise during winter inversion episodes and summer ozone peaks, while generally finding the cleanest air during spring and early autumn.