[Concentration of ragweed pollen and prevalence of allergic rhinitis in 2 municipalities in the Laurentides].

In the province of Quebec, ragweed pollen is the principal allergen causing allergic rhinitis. The present study examines the relationship between the concentration of ragweed pollen and the prevalence of allergic rhinitis in August in the populations of two municipalities in the Laurentide area, a region on the northern limit of distribution of ragweed. The concentration of ragweed pollen was measured with a Burkhard sampler. The prevalence of allergic rhinitis was simultaneously measured by a telephone survey which was addressed to a random sample of 500 households in the two municipalities. The results showed a significant difference in the prevalence rate of allergic rhinitis in the population of the two municipalities (3,77% and 7,22%) exposed to significantly different pollen levels. Interventions aimed at lowering the pollen concentrations could lower the prevalence rate of allergic rhinitis in August.