Analysing allergen-environment interactions to identify drivers of asthma presentations in Metropolitan Melbourne,...

Although associations between airborne allergens, weather conditions and respiratory health have been established, the precise mechanisms that contribute to the onset and severity of epidemic thunderstorm asthma (ETSA) events remain poorly understood. One critical area of this research lies in understanding the role of fungal spores, which have not been extensively studied for their impact on asthma exacerbations compared to pollen, as well as the influence of certain pollutants like ozone on airborne allergens, which is not well documented. This study aimed to identify the environmental parameters that influence the dispersal & distribution of airborne allergens and how these factors are associated with asthma presentations. Analysis was conducted on 475 days of data collected over a 6-year period between October-December. Using eight global negative binomial generalised linear mixed model formulations combined with a model selection approach, we analysed airborne levels of grass pollen, Alternaria spp., and Cladosporium spp. from Metropolitan Melbourne, along with weather values from the Bureau of Meteorology (precipitation, temperature, humidity, dew point, wind direction, wind speed, air pressure) and pollution values from the Environmental Protection Authority (CO, NO₂, O₃, SO₂) to identify effects on asthma presentations from five emergency departments. Rainfall and O₃ levels had significant positive relationships with number of asthma presentations, with Incidence Response Ratios of 1.074-1.088 and 1.05-1.06, respectively. High allergen levels (allergenPC1, representing overall levels of grass pollen and fungal spores) had an interactive effect with high rainfall creating positive association with asthma cases. On days of low rainfall, allergen levels had minimal impact on asthma presentations, but on days of high rainfall, there were substantially greater numbers of presentations when allergen levels were also high (e.g. a predicted four-fold increase on days with 45 mm of rain). This impact of overall allergen count highlights the role of several prominent allergens in seasonal asthma, as well as potential cross reactivity between pollen and spores. The results of this study will inform researchers of several environmental monitoring parameters that should be included in risk forecasts for ETSA to allow for a more robust and accurate detection system and help improve public health responses across Australia.