Bioclimatologie et Allergie

The pollinic data base of the RNSA makes it possible to follow the influence on pollination that weather modifications in France may have had over a period of more than 15 years. The climate of a particular place can be characterized by its latitude, its distance from the ocean and its topography. Climate can have number of actions on pollination: Direct action of CO2 on the growth of plants; a mild winter can lead to early flowering of trees; precipitation and relative humidity can influence the sedimentation of pollen; air pollution can modify the allergenic potential of pollen; and modification of the sensitivity of allergic individuals. Using RNSA data going back to 1987, it was possible to establish curves on the evolution of the starting date of pollination of the principal allergenic taxa, of the duration of this pollination, and of the number of days with significant allergic risk in a number of French cities. In the majority of the sites studied, it was observed that the beginning of tree pollination is becoming progressively earlier, going from just a few days in 1987 to more than 20 days earlier in 2003. Furthermore, the duration of tree pollination is in general becoming longer in all the sites studied, from just a few to more than 20 days. The evolution of the number of days that the allergic risk related to pollens is judged to be average, high or very high was found to vary considerably over the period studied, going from just a few days longer to a doubling of the number of days between 1987 and 2003. For grass pollen and ambrosia pollen, the onset of pollination was not significantly different over this period. On the other hand, the number of days with an average allergic risk level going to a higher risk level was found to have increased between 1987 and 2004.