Monitoring Olea europaea L. pollen in Malta

Abstract

The aim of this aerobiological study was to monitor airborne Olea europaea L. (olive tree) pollen in Malta, and investigate its correlation with meteorological factors, and implications for public health, particularly in relation to pollen-induced allergies. Using a Burkard 7-day recording volumetric spore trap, the atmosphere at the University of Malta’s Msida campus was monitored from March to June, 2024. The Main Pollen Season (MPS) of this species was identified from March 29 to May 26, lasting 59 days. The highest pollen concentrations were recorded in April, with the highest peak reaching 48.6 grains/m3. This study addressed a significant gap in local aerobiological research by creating an olive pollen calendar for Spring 2024. The temporal period of the pollen season was found to compare well with lower latitude categories of the Mediterranean. Statistical analyses using Spearman’s correlation showed that accumulated temperature, mean temperature, wind speed and wind direction are the parameters most closely correlated with variations in daily pollen counts. The division of the pollen season into pre- and post-peak phases provided stronger correlations between pollen concentrations and weather parameters and enabled a better understanding of the pollen season. Through linear regressions performed by using daily pollen concentrations or five-day mean pollen concentrations as a dependent variable and the daily values of meteorological parameters as independent variables, the most accurate predictive model obtained was for the five-day running mean pollen concentrations during the pre-peak period using cumulative temperature (y = -38.51 + 0.032Tcum). The study also highlights the health risks associated with Olea europaea pollen, which is highly allergenic and can cause pollinosis in sensitive individuals. The pollen levels of this species were relatively low at the UM campus compared to thresholds known to trigger severe allergic reactions. The findings emphasise the importance of ongoing aerobiological monitoring in Malta, especially given the increasing cultivation of olive trees. Continued research and data collection are required for refining predictive models that can assist in public health planning and agricultural management. This study lays the groundwork for future aerobiological studies in Malta, with promising applications in early-season crop yield estimates and allergy forecasting.