Pollen Counts in Four Canadian Cities: Geographical Variation between 2008 and 2012

摘要

Pollen grains from anemophilous plants represent an important class of aeroallergens in ambient air. High concentrations of aeroallergens, including tree and grass pollen are associated with increased asthma-related emergency department visits and hospitalizations across Canada. The geographical distribution of species of plants is dependent on multiple factors, including precipitation, soil composition and moisture and average high and low temperatures. Five 'floristic zones' that support the growth of different aeroallergen-producing plants have been defined across Canada. Here we examine the differences among four Canadian cities (Vancouver, Edmonton, Winnipeg and Toronto) situated in four of the Canadian floristic zones. We describe pollen counts with respect to: start and end dates of the pollen seasons; season length; and annual pollen counts between 2008 and 2012. These cities and years were chosen to cover the antenatal and perinatal windows of sensitization for the participants in the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Pollen season was defined considering the dates when the 5% and 95% of the annual total was recorded for each pollen. The following table presents the 5-year average for pollen count and season duration for trees and grasses. With these data and estimates of traffic-related-air-pollution exposure we will present the combined effects in the development of early-life asthma. Trees Grasses City Average pollen (grains/m3) Average season duration (days) Average pollen Average season duration Participants Vancouver/42926.2/92.6/1497.8/74.6/992 Edmonton/7368.4/71.2/1522.3/54.4/774 Winnipeg/16904.1/50.8/1564.3/70.6/738 Toronto/16915.5/71.2/991.8/107/770 The geographical differences may suggest the particular needs of atopy prone and sensitized individuals in each city, and the potential need to account for local contexts when designing public health initiatives related to aeroallergen information and to green space.