Leatherhead Air Quality Index (AQI)

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Leatherhead, nestled in the heart of Surrey, occupies a strategic position within the North Downs, approximately 20 miles south-west of London. The town’s geography is defined by a gently undulating landscape, rising to higher ground on the fringes of the Downs, influencing local wind patterns and pollutant dispersion. Situated in the Mole Valley, the River Mole meanders through Leatherhead, contributing to localised humidity and potential for temperature inversions, particularly during calmer weather. Historically a market town, Leatherhead’s urban character is a blend of historic buildings and modern development, reflecting its commuter belt status. The surrounding area is predominantly agricultural, with farmland to the south and east, and woodland covering the slopes of the Downs. This mix creates a complex air quality scenario. While the rural buffer offers some natural filtration, proximity to the M25 motorway and the A243 creates significant road traffic emissions. The urban-rural gradient is relatively sharp, with air quality generally deteriorating closer to major roads and the town centre. The prevailing winds, often from the south-west, can carry pollutants from London and the south coast, impacting Leatherhead’s air quality, especially during stagnant high-pressure systems. The town’s elevation, around 72 metres above sea level, is low enough to experience localised pollutant build-up.

Leatherhead’s air quality follows a distinct seasonal pattern. Winter, from November to February, often sees the poorest air quality. Reduced daylight hours, coupled with increased wood burning for heating, contribute to higher particulate matter concentrations. Temperature inversions, common in the Mole Valley during these months, trap pollutants near ground level, exacerbating the issue. Fog, a frequent occurrence, further reduces dispersion. Spring (March-May) brings improvement as temperatures rise and winds become more frequent, diluting pollutants. However, agricultural activities, such as fertiliser application, can introduce ammonia into the atmosphere. Summer (June-August) generally offers the cleanest air, with strong winds and ample sunshine promoting dispersion. However, high ozone levels can form during prolonged periods of hot, sunny weather, impacting sensitive individuals. Autumn (September-October) sees a return to poorer conditions as heating demand increases and the atmosphere becomes more stable. October is often a peak month for particulate matter due to leaf fall and increased wood burning. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during winter and periods of high ozone in summer. Monitoring local forecasts is crucial for informed decision-making.