Investigating the interplay between air pollutants, bioaerosols, and meteorological factors in Badajoz, a low-pollution southwestern Spanish city

Pollen grains cause negative effects on human health, especially for allergy sufferers. During the last years, allergenicity has increased due to air pollution. The present study analyzes the interactions between pollen concentrations of different pollen types, meteorological variables and air pollutants present in the atmosphere of a city. For this study, a ten-year pollen data series from the city of Badajoz (southwestern Spain) was used to analyze the correlations between pollutants (NO, NO₂, SO₂, CO, O₃) and particulate matter (PM₁, PM_2.5 and PM₁₀), benzene, toluene and xylene and the concentrations of pollen types (Poaceae, Olea, Fraxinus, Urticaceae, Amaranthaceae, Plantago, Rumex, Platanus, Cupressaceae, Myrtaceae, Alnus, Anthemideae, Castanea, Echium, Lactuceae, Pinus and Quercus). The analysis was performed using daily Spearman correlations, as well as with cumulative pollution values and with time lags between both variables. The correlation with atmospheric pollutants revealed that NO_x could be negatively associated pollen concentrations of all pollen types studied except for Alnus, Fraxinus and Urticaceae, for which positive r values were obtained. Benzene, toluene, and xylene also have negative r values except for the associations between Alnus and Urticaceae pollen and benzene and toluene. On the other hand, O₃ was positively correlated pollen concentrations of most pollen types except for Alnus, Cupressaceae, Fraxinus and Urticaceae. The strongest correlations (r values) between air pollutants and various pollen types, such as Olea and Poaceae, occur with a three-day lag. These results highlight the role that air pollution has on pollen concentrations, thus providing information on the behaviour of pollen in urban environments.