Parameters of ragweed pollination in the Lyon’s area (France) from 14 years of pollen counts

Abstract

This study analyzes the pollen counts obtained from the air of the greater Lyon (corresponding to the urban area of Lyon) an area which has been overrun by ragweed in the last 40 years. Two periods are investigated, 1982–1989 and 1990–1995. The year 1995 deserves specific attention because for the first time a campaign of ragweed eradication was launched in greater Lyon. From the data of the 14 pollination seasons it was possible to define some parameters: subpathological risk period, pathological risk period and the position and level of the pollen peak. Our study indicates the progression of the weed in the infested area over the two periods. In 1995 a slight decrease in the pollen count was observed but this was followed by a second peak probably related to later growth of some plants which had been cut. In this connection, 4 weeks weeding campaign is not long enough and in the future a 6-week campaign without the use of weedkillers should be planned. Determining the parameters of ragweed pollination every year will be useful both to patients and physicians concerned by allergy to ragweed pollen. According to the level of the ragweed pollen in the air, the patients may take appropriate medication. This study emphasizes the necessity to record air pollen concentrations over many years. In particular, the actual impact of cutting ragweed before pollination on ragweed pollen counts can only be evaluated after several years of eradication.