Allergy season is growing longer in parts of Canada, and changing in others.
The culprit? Climate change, according to experts.
Data from Aerobiology Research, a company that measures pollen and provides forecasts to the Weather Network and others, shows that for certain allergens, the season has grown longer over the last 11 years.
Birch pollen season in Toronto increased by 60 days between 2006 and 2017, according to their numbers. Montreal’s pine pollen season increased by 36.3 days.
Grass pollen season in Saint John, N.B. increased by 24 days. And cedar pollen season in Prince Albert, Sask. increased by 81.1 days over that period.
This isn’t the case everywhere or for every pollen type, said Dawn Jurgens, director of operations of Aerobiology Research Laboratories, but “definite increases” can be seen.
“It’s changing, let’s say from the way that it used to be. Quite a bit sometimes, and other times not so much,” she said.
“In some locations the pollen seasons are lasting a lot longer. And in some locations the amount of pollen being released is dramatically higher as well.”
Experts estimate that about 25 or 30 per cent of Canadians suffer from seasonal allergies. So any changes could make lots of people miserable.
Health Canada is currently studying the link between climate change and allergies in Canada and plans to release its findings in 2019.
Pollen is significantly affected by the weather and, as such, can vary considerably from year to year.
A cold or late spring, like Ontario is experiencing this year, means that trees might release pollen later.
Last year’s cold, wet summer in the region might also mean less pollen this year.
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But the overall trend is for pollen seasons to be longer, said Dr. David Fischer, president of the Canadian Society of Allergy and Clinical Immunology.
“The warmer it gets, the longer the seasons are, and the more likely people are to suffer,” he said.
“The evidence shows especially in Canada we’re seeing maybe a one month longer allergy season on average than 15 years ago,” said Michael Brauer, a professor at UBC’s School of Population and Public Health.
Similar trends have been observed in the United States, according to a recent report by Vox. The ragweed pollen season has been longer in many locations – especially the further north you go.
It’s not just that the season is becoming longer, it might even be growing worse, Fischer said.
Extra CO2 can even make ragweed produce more pollen, according to some studies, he said.
“It becomes a more powerful producer of pollen in certain hot, humid conditions,” he said.
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But is this year, and every year after, the worst allergy season ever? Not according to Susan Waserman.
“I hear this every year: worst season ever. At this point in time, these kind of things are quite unpredictable and it varies from year to year,” said the professor in the division of clinical immunology and allergy at McMaster University’s School of Medicine.
“The amount of pollen that we see is extremely weather-dependent,” she said.
However, she thinks that global warming may cause certain changes over time.
“I think what we can say is that with global warming, it seems that species of plants that never would have grown in certain areas can now find more favourable conditions. Or that the growing seasons may be longer.”
There’s evidence from Europe that some new tree species are showing up in areas where they didn’t used to grow, said Brauer. And so, people might discover that they’re allergic to those too.
Predicting pollen is complicated, he said, but he’s not optimistic.
“The future doesn’t look great for people who suffer from seasonal allergies.”