## 2 Materials and Methods
### Airborne Pollen Data  
The daily data of \"airborne pollen grain concentration\" come from 2 sampling stations in the municipality of Madrid, out of the total of 11 available to the Palinocam Network in the CAM. Daily data are converted to monthly data using the mean values.  
The six selected pollen types, all of them with allergenic capacity, as described below, correspond to mainly arboreal taxa, with a significant representation in Madrid's parks, gardens, and streets, and produce pollinosis in different degrees.  
Cupressaceae pollen is the most abundant in the winter months and is almost the only allergenic pollen with a high atmospheric incidence during this period. The pollen season of Cupressaceae usually begins in November and lasts until late March or early April. Perhaps _Hesperocyparis arizonica_ is the primary source of pollen, given its great abundance and the coincidence of its flowering season with the time of highest incidence. _Platanus_'s pollination period is short since it usually begins in the second half of March and lasts only 2 to 4 weeks. Its allergenic capacity is classified as moderate. It reaches the highest concentrations in Madrid [29], one of the Spanish cities with the highest atmospheric incidence of _Platanus_ pollen, as shown in a study carried out in 14 Spanish cities with different biogeographical and climatic characteristics [30].  
_Olea_ pollen shows the highest allergenicity, and in Madrid, it is the most frequent cause of PCP (positive skin tests) among patients with pollinosis and the second most important cause of rhinitis and/or asthma of pollen origin in Spain [30]. However, it is much less critical than Gramineae pollen. Its pollination period usually begins in April and lasts until June [29].  
_Pinus_ pollen is considered to have a low allergenic capacity. It usually remains in the atmosphere of the CAM from March to July [29]. _Populus_ pollen, of deficient allergenic capacity, begins to concentrate in the atmosphere from February to March, while _Ullmus_pollen, considered of low allergenic capacity, has a pollination period that extends from January to March [29].  
At this time, the system adopted by the International Association of Aerobiology, of which the Spanish Aerobiology Network is a part, and by the PALINOCAM network of the Community of Madrid is the volumetric system, with a Hirst-type capture device marketed by the Burkard house that allows daily samples to be obtained. These collectors have a sampling coverage of about 20 km under normal orographic and settlement conditions and a potentiometrically controlled suction flow rate of 10 L/min. All its components are enameled or anodized to prevent corrosion, and they have a built-in suction pump and turbine, with a work selector with 220 V alternating current or with a 12 V battery, and a clock timer for taking samples continuously for seven days [29; 31].  
The technique followed for the mounting and analysis of the samples, obtained by the Burkard collector, consisted of using fluid silicone as an adhesive substance and glycerogelatin dyed with fuchsin as a mounting medium for the preparations. Several bands were read on the same slide and an arithmetic mean of the results was made, because due to the turbulence and inequalities of the shock of the wind, some areas of the slide were different from others. For a reading of the preparations at 400\(\times\) magnification, on four longitudinal bands, the surface examined corresponds to approximately 10% of the total surface of the sample. The data obtained express the average daily concentrations in number of pollen grains per m\({}^{3}\) of air. The data were subsequently analyzed in the laboratory by expert personnel [29; 31].