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

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.