Temporal variability in the allergenicity of airborne Alternaria spores

The concentration of fungal spores in the air is traditionally considered as a proxy of allergen exposure. However, in vitro experiments have shown that the allergenicity of Alternaria spores varies depending on ecophysiological and developmental factors. Despite the potential clinical significance of these findings, it has never been verified in outdoor environments. This study, therefore, aims to investigate variability in the amount of the major allergen (Alt a 1) released from Alternaria spores in outdoor air. During the 3-year monitoring study (2014–2016), the median seasonal allergenicity of Alternaria spores exceeded 8.6 × 10−3 pg Alt a 1/spore. The most allergenic spores were collected during the driest and the most polluted season (with respect to seasonal concentrations of ozone, sulphur dioxide, and particulate matter). Within the season, daily spore allergenicity ranged from 2.4 to 34.7 × 10−3 pg Alt a 1/spore (5th-95th percentile). No repeatable effects of weather and pollution on short-term variations in Alternaria spore allergenicity were found. However, during the episodes when high-potency spores were recorded, the air masses arrived from eastern directions. Contrary, the spores with the lowest allergenicity were related to western winds. This suggests that factors such as source area (habitat types) and species diversity could be responsible for the varying exposure to Alternaria allergens. Our findings show that high and low-potency spores are recorded in the air; therefore, the airborne concentrations of fungal spores alone may not be sufficient to provide allergy sufferers and healthcare professionals with information about allergen exposure.