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 data on pollen seasons, with extremely few from Africa. We present pollen calendars based on five-year data from the South African Pollen Monitoring Network (SAPNET). Airborne pollen from 2019 to 2024 in biomes across South Africa was collected using Hirst-type volumetric spore traps and standard protocols. Daily concentrations were analysed by light microscopy. The five-year mean annual pollen integral (APIn, pollen grains/m³ per year) was calculated for each site. The five-year mean APIn was highest in the Grassland Biome (Bloemfontein, 11654 pg/m³; range 8515 to 14454 pg/m³) and lowest in the Albany Thicket Biome (Gqeberha, 1372; range 853 to 2010 pg/m³). The Grassland Biome (Johannesburg) had the highest averaged tree pollen concentration (7558; range 6575 to 8803 pg/m³). The Savanna Biome (Kimberley) had the highest average grass pollen concentration (3150; 1826 to 3785 pg/m³). The grass family (Poaceae ) was the most common pollen type across all biomes. Other common contributing taxa were exotic trees Cupressaceae, Platanus , Morus and Betula . Tree seasons were July to September, whilst grass and weed pollen seasons varied across the different 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.