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Porthcawl, a coastal town within the Bridgend County Borough of South Wales, occupies a unique geographic position that significantly influences its air quality. Situated on the eastern side of the Bristol Channel, it faces prevailing westerly winds, a crucial factor in its atmospheric dynamics. The town’s terrain is gently undulating, sloping towards the shoreline, with elevations rarely exceeding 50 meters above sea level. This low elevation, combined with its coastal location, often leads to the formation of sea fogs, particularly during autumn and winter, which can trap pollutants close to the ground. The surrounding landscape is a blend of urban and rural elements. To the north and east lie agricultural fields, primarily used for grazing and arable farming, which can contribute to particulate matter through dust and ammonia emissions, though these are generally localised. Further inland, the Vale of Glamorgan rises gradually, providing some barrier to pollutants travelling from larger industrial areas to the east. The Bristol Channel itself acts as a significant dispersal mechanism, facilitating the movement of air masses and, consequently, pollutants, both inshore and offshore. Porthcawl’s proximity to the M4 motorway, a major transport artery, introduces road traffic emissions, a persistent source of nitrogen oxides and particulate matter. The urban–rural gradient is relatively sharp, with the town transitioning quickly to agricultural land, limiting the build-up of urban pollution plumes. The town’s character is primarily residential and tourist-oriented, with a smaller industrial presence compared to larger Welsh cities, mitigating some industrial pollution risks.

Porthcawl’s air quality experiences a distinct seasonal pattern dictated by meteorological conditions. Winter months (November to February) often present the greatest challenges. Cold, stable air masses frequently lead to temperature inversions, where a layer of warm air sits above cooler air near the ground, effectively trapping pollutants. Sea fogs, common during this period, exacerbate this issue by further restricting vertical mixing. While prevailing westerly winds generally disperse pollutants, their strength can diminish during winter, allowing for localised accumulation. Spring (March to May) sees a gradual improvement as temperatures rise and wind speeds increase, promoting better ventilation. Agricultural activities, however, can contribute to ammonia emissions during this period, particularly after periods of rainfall. Summer (June to August) typically offers the best air quality, with consistent winds and higher temperatures facilitating pollutant dispersal. However, occasional heatwaves can lead to stagnant air conditions and increased ozone formation. Autumn (September to October) marks a transition period, with increasing frequency of fog and decreasing wind speeds, mirroring the winter pattern. The combination of cooler temperatures and reduced ventilation can lead to a gradual decline in air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should be particularly cautious during winter and autumn, limiting prolonged outdoor exposure on foggy days. During periods of agricultural activity in spring, minimising exposure near fields is advisable. Overall, the coastal location and prevailing winds generally mitigate severe pollution events, but localised conditions can significantly impact air quality at different times of the year.