Seasonal allergy sufferers are in for a long summer of sniffling and sneezing, experts say.
In most regions of Canada, allergen-producing plants started growing up to a month early. Adding to many Canadians' misery, weather forecasters suggest there may be less rain than usual to wash away pollen and smog.
David Phillips, a senior climatologist with Environment Canada, notes that in provinces east of Alberta spring began in early March, with record temperatures warming the country from southeastern Alberta to Newfoundland.
British Columbia and northern Alberta were among the few regions to experience slightly below normal temperatures and an allergy season delayed by almost a month.
In most parts of Canada, however, "the number of days that allergy sufferers could experience their ailment is clearly longer this year," Mr. Phillips says.
Vegetation began to pollinate early because of "long, intense and persistent" high temperatures in much of the country from March 10 to 22, he says. While grass normally pollinates in May, "people were walking on their lawns in April," he recalls.
Meanwhile, trees were blooming. "What we saw in April was probably a merging of the two [pollen]cycles," he says.
That same month, many allergy sufferers experienced a brief reprieve from their symptoms when a "killing frost" nipped fruit trees and other vegetation in the bud.
But while April frost slowed down the growing season, "it didn't reverse it," Mr. Phillips says. The allergy season will likely continue until summer ragweed is killed by autumn frosts.
With the predicted warmer, drier forecast for June, July and August, the lack of rainfall could worsen symptoms for allergy sufferers, since "precipitation can be a great scavenger" of pollen and smog, Mr. Phillips explains.
Airborne pollution is concentrated in Ontario and Quebec – from Windsor to Quebec City – and to a lesser extent British Columbia's Lower Mainland. Depending on how the wind blows in relation to power plants south of the border, the predicted warmer and dryer weather "probably means more episodes of smog," Mr. Phillips says.
That's bad news for people with asthma and seasonal allergies, according to Christopher Carlsten, a specialist in environmental respiratory diseases at Vancouver General Hospital.
Research by Dr. Carlsten and colleagues suggests that air pollution combined with common airborne allergens have a compound effect on allergy sufferers. "The effect is much higher than adding the two separately," he explains.
Dr. Carlsten notes that global levels of pollen and other airborne allergens have increased with global warming. Because of the synergistic effect of combined exposure, he says, "we're seeing that even modest levels of traffic-related air pollution can have serious effects."
He recommends that people with allergies or asthma avoid walking or cycling through "street canyons" – major thoroughfares flanked by tall buildings, which prevent traffic pollution from dispersing. Air quality tends to improve about 300 metres (two to three blocks) away from a major roadway, he says.
Unless a person has a truly debilitating allergy, which may warrant staying indoors in an air-filtered environment, sufferers can usually manage their symptoms during outdoor activities by taking antihistamines, Dr. Carlsten says. "We generally believe that the benefits of exercise far outweigh the risks."
The best time to exercise is after a rain, when airborne pollen and particulates are dampened down, he says.