A Comparative Analysis of Daily Variations in the Gramineae Pollen Counts at Córdoba, Spain and London, UK

Abstract

The features of five grass pollen seasons from two areas of contrasting climate were investigated and the relative importance of the variables controlling daily variations were determined. The records from London, UK (temperate maritime climate) and Cdrdoba, Spain (mediternnean climate) were analysed in relation to meteorological factors. The length of the seasons differs a great deal between the two locations and from year to year. However the total cumulative catches and the number of days with counts over 50 grains metreJ are similar for the two locations. Regression analysis of standardised daily avenge pollen counts shows clearly that for London, maximum and average temperatures are the most important factors influencing daily variation. In the case of C6rdoba this relationship holds true for the period from the start of the season until the peak count, but after this the relationship becomes negative. Hours of sunshine and humidity are also important. The negative effect of increased humidity on pollen release is most marked in the data for C6rdoba but it is also apparent in the case of London. The results emphasise the need for individual analysis in different climates and the application of different statistical treatments depending on the operation of the variables.

May the definition of pollen season influence aerobiological results?

“…The 98% criterion (Gala´n et al, 1995) yielded the longest Poaceae season in all cities and years, while the criteria proposed by Mullenders et al (1972) and by Spieksma et al (1995) yielded the shortest season ( Figure 2b). Major differences (over 100 days) were observed between pollenseason durations as determined by the various Table 1.…”

“…the time with 95% of the whole pollen amount. Gala´n et al (1995) The period from which the sum of daily mean pollen concentrations reaches 1% of the total sum until the time when the sum reaches 99% i.e. the time with 98% of the whole pollen amount.…”

“…One of these -widely used in the past and still found today -is the period over which a given percentage of the total annual pollen count is recorded in the atmosphere (Nilsson and Persson, 1981;Andersen 1991;Torben, 1991;Gala´n et al, 1995). Another definition refers to the period between the first and last day with pollen counts higher or lower than a specific level (Davies and Smith, 1973;Giorato et al, 2000;Clot, 2001;Sa´nchez-Mesa et al, 2003).…”

Reproducibility between counts of airborne allergenic pollen from two cities in the East Midlands, UK

“…90% (Andersen 1991;Piotrowska 2004), 95% (Andersen 1991;Rodriguez-Rajo et al 2004;Mendez et al 2005) and 98% (Galán et al 1995). The retrospective percentage technique eliminates the long tails of low values at the start and end of the seasons which could otherwise introduce bias to the results during statistical analysis (Galán et al 1995). The 98% criterion was shown to yield the longest grass season in a multi-year, multi-city study and resulted in a long tail at the end of the season (Jato et al 2006).…”

“…Sum75, (Driessen et al 1990;Emberlin et al 1999), a technique often used for forecasting purposes during the season with no defined end point, or defining the season retrospectively as the period during which a defined percentage of the annual total was counted with the remaining percentage equally divided either side of the season e.g. 90% (Andersen 1991;Piotrowska 2004), 95% (Andersen 1991;Rodriguez-Rajo et al 2004;Mendez et al 2005) and 98% (Galán et al 1995). The retrospective percentage technique eliminates the long tails of low values at the start and end of the seasons which could otherwise introduce bias to the results during statistical analysis (Galán et al 1995).…”