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Nandi Hills, nestled within the Nandi County of Kenya, occupies a unique geographic position in the western highlands. Situated at coordinates 0.1037, 35.1843, the town benefits from a relatively high elevation, contributing to a cooler climate compared to the surrounding lowlands. The terrain is characterised by rolling hills and fertile valleys, typical of the Kenyan highlands, and is part of the larger Great Rift Valley system. This landscape significantly influences air quality; the hilly topography can trap pollutants, particularly during temperature inversions. Nandi Hills is largely surrounded by agricultural zones, primarily tea plantations and small-scale farming, which contribute to particulate matter from land preparation and biomass burning. While not heavily industrialised, the increasing presence of small-scale industries and transport networks adds to localised emissions. The town’s position isn’t directly adjacent to major bodies of water, but numerous rivers and streams dissect the landscape, potentially influencing the dispersion of airborne pollutants. The urban-rural gradient is pronounced, with a clear transition from denser settlement in the town centre to more dispersed agricultural land. This gradient impacts pollution levels, with higher concentrations typically found in the built-up areas. The prevailing winds, influenced by the regional climate patterns, play a crucial role in pollutant transport and dispersion.

Air quality in Nandi Hills follows a distinct seasonal pattern largely dictated by Kenya’s bimodal rainfall regime. The ‘long rains’ from March to May generally bring improved air quality. Increased rainfall effectively washes particulate matter from the atmosphere, and higher humidity suppresses dust. However, this period can also see increased dampness leading to mould spore concentrations. The drier season, June to October, witnesses a gradual deterioration in air quality. Agricultural activities intensify, with land preparation and post-harvest burning releasing significant amounts of smoke and particulate matter. November to February, the ‘short rains’ season, offers a temporary respite, though it’s often less effective at clearing pollutants than the long rains. Temperature inversions, common during the cooler nights of the dry season, exacerbate pollution by trapping emissions near ground level. Sensitive groups – children, the elderly, and those with respiratory conditions – should exercise caution during the drier months, particularly between July and September. Outdoor activity is best planned during or immediately after rainfall. Fog, prevalent in the highlands, can also contribute to localised pollutant build-up. Monitoring wind patterns is crucial, as pollutants can be transported from surrounding agricultural areas.