Forecasts Assist Allergy Sufferers

Nothing is more joyful, after a long cold winter, than the sight of lush green grass, and fields and forests bursting into bloom. What is a sight for sore eyes for some, however, simply means sore eyes and other nasty symptoms for those who suffer from pollen and spore allergies.

In Nova Scotia, an area prone to elevated levels of airborne pollutants due to the direction of prevailing winds, about one third of the population is sensitive to fungal and mould spores or pollen from trees, weeds and grasses. To enable sufferers to avoid outdoor exposure when a heavy pollen or spore load is expected, Environment Canada's Meteorological Service of Canada (MSC)—Atlantic Region, Saint Mary's University, and the Lung Association of Nova Scotia conducted an experimental pollen and spore forecast research program for the Halifax area from May 1 to August 31, 2000.

The Weather Network has broadcast summer pollen forecasts for Halifax, Moncton, Saint John, Charlottetown and St. John's since 1997 using a forecast methodology based on a statistical model. The experimental forecast program, however, incorporated daily pollen and spore counts using a special device mounted on the rooftop at Saint Mary's University to trap airborne allergens. The trapped allergens were analyzed and quantified in the lab, and correlations were made with weather and climatic conditions for the same time period.

Using this information, scientists were able to combine 24-hour weather forecasts provided by MSC's Maritimes Weather Centre with the most recent pollen and spore counts to produce a daily forecast of pollen released from trees, weeds and grasses and of fungal and mould spores. The forecasts took into consideration such factors as variations in pollen release by time in the growing season, recent and expected moisture input, temperature, sunshine, and wind speed and direction. Temperature and sun are significant triggers for pollination, while high winds can lower concentrations and spread them over a larger area. Rain can trigger the dispersal of mould spores and wash pollen out of the air.

Conditions were deemed low, medium or high, depending on concentrations of grains or spores in the air, and values for suburban and rural areas were estimated by multiplying urban values by two and four, respectively. The forecast in the summer of 2000 proved most accurate in the low category, which also occurred the most often, with diminished accuracy in the higher categories. This trend is also very common in weather forecasting, in that rare events are more difficult to predict. Environment Canada assisted with the public distribution of the forecasts via an Internet Web site and the Maritimes Weather Centre's automated telephone answering system.

In addition to providing weather forecasts for the research project again this allergy season, Environment Canada is expanding its involvement to include an international literature search on other pollen and spore forecasting methods for potential use in North America. It has also purchased two new pollen and spore traps that are being set up in a suburban area of Halifax and a rural region of the Annapolis Valley to more accurately reflect grass-pollen levels along highway margins, fields and farmlands—and to determine the validity of past estimates. Comparisons in the ratio of pollen reported from the two traps and the urban site may be used later to extrapolate real-time detailed Halifax pollen counts to suburban and rural areas.

MSC is investigating the possibility of conducting a focus group study to determine how people respond to the forecasts, and whether or not they use them. With concerns growing over possible correlations between allergy symptoms and co-factors related to pollution, this and other research projects dealing with aero-allergens will be of increasing importance.

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