Five years of national airborne pollen monitoring in South Africa: biome-specific calendars to inform allergy diagnosis and prevention

Abstract

Pollen monitoring is crucial for understanding seasonal patterns, supporting allergy diagnosis and informing early warning tools to mitigate allergic diseases. The Southern Hemisphere lacks long-term pollen seasonal data, with extremely few records from Africa. We present pollen calendars based on five years of data from South Africa. Airborne pollen from 2019 to 2024 across South African biomes was collected in seven cities using Hirst-type volumetric spore traps and standard protocols. Daily concentrations were analysed by light microscopy. The five-year mean annual pollen integral (APIn) were calculated for each site. The five-year mean APIn was highest in the Grassland Biome (Bloemfontein) and lowest in the Albany Thicket Biome (Gqeberha). The Grassland Biome (Johannesburg) had the highest average tree pollen integral, while the Savanna Biome (Kimberley) had the highest average annual grass pollen integral. The grass family (Poaceae ) was the most common pollen type across all biomes. Other common taxa were exotic trees Cupressaceae, Platanus , Morus and Betula . Tree seasons were July to September, while grass and weed pollen seasons varied across the biomes. These five-year pollen calendars provide the first biome-specific national reference for airborne pollen exposure in South Africa. The findings provide baseline data for the clinical management of allergic disease.

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