Researchers have not yet identified all the elements involved in the increase in pollen in the air… And they lack the tools to get there.
Pollinic trends suggest that seasonal allergies may s worsen in the coming decades due to the increase in temperature.
Polen wanders in the air earlier and earlier, stays there later and later and is found there in greater and greater quantities. People with allergies have been seeing this in the nose, and scientists, with concrete observations for a few years now.
In 2021, an exhaustive study published in the PNAS showed that climate change is indeed worsening pollen seasons in North America:
- They start about 20 days earlier;
- They last in average eight days longer;
- They contain 21% more pollen.
In addition, the pollen trends they observe suggest that the phenomenon is likely to worsen in the coming decades due to the increase in temperature.
Quebec is no exception to the continental phenomenon. The season can now start there at the end of March (with pollen from trees and shrubs), continue during spring and summer (pollen from grasses) and end in October (pollen from ragweed).< /p>
This reality worries public health experts, since exposure to allergenic pollens represents a significant risk of respiratory problems.
Pollen concentration is highest in the morning and when the weather is hot, dry and windy. Conversely, the rain deposits the pollen grains on the ground, thus giving respite to people sensitive to this allergen.
Exposure to pollens can exacerbate asthma symptoms and lead to attacks that require visits to the emergency room. But in most cases, it causes allergic rhinitis, which results in inflammation of the nasal mucosa (sneezing, discharge) and tingling in the throat and eyes.
Dr. Marie-Jo Ouimet, of the National Institute of Public Health of Quebec (INSPQ), believes that allergic rhinitis is not a benign problem.
“It has a lot of impact on a person's quality of life. There are surveys that show that 50% of allergy sufferers have severe symptoms that impact their day-to-day life. »
— Dr. Marie-Jo Ouimet, National Institute of Public Health of Quebec (INSPQ)
This is an important issue. We must not forget the impacts on mental health, sleep, depression and anxiety, adds Dr. Ouimet.
Since the 1990s, people with allergies have relied on pollen cues to manage their symptoms. These predictions are made from sampling stations that measure pollen concentrations in the air.
However, there are only 32 sampling stations in Canada, including three in Quebec: Montreal, Quebec, and Sherbrooke. These three stations (in service since 1997-1998) provide the data that feed the pollen indices of several media, notably MétéoMédia. This information is also useful for pharmaceutical companies in the context of certain clinical trials or for private companies who use it for marketing purposes.
A station used by Aerobiology Research Laboratories.
These stations are the property of Aerobiology Research Laboratories, a private Ottawa company that does not receive any government funding to carry out this important work of collecting pollen data, assures Daniel Oates, the laboratory's spokesperson.
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“We would like to cover more territory, serve more cities, but making accurate forecasts costs a lot of money. We need other sponsors to create more stations. »
— Daniel Oates, Aerobiology Research Laboratories
Mr. Oates adds that currently, the priority of his company is to improve the collection of data to allow real-time sharing of information with his customers. The only way to do that right now is to use current equipment, he explains.
Dr. Marie-Jo Ouimet of the INSPQ believes that the fact that there are only three sensors in Quebec does not give an accurate picture that can properly guide government decision-making. We are faced with a great lack of knowledge, she concedes.
But there is also a general lack of information concerning pollens.
This situation prevents us from helping people who are victims of allergies, explains Professor Alain Paquette, from the Department of Biological Sciences at UQAM.
“People think we know the allergens, how much they are found and when, but we don't know! »
— Alain Paquette, professor in the Department of Biological Sciences at UQAM
We do not know enough about all the species that produce pollen, their location, their concentration or even their spatial coverage, notes Dr. Ouimet.
And the interactions of pollens with air pollutants, insecticides and pesticides are also not very well understood.
Currently, the most popular technique for calculating the amount of pollen in air – and the one used by Aerobiology Research Laboratories – relies on harvesting pollen grains using pollen sensors. These grains are then counted and visually identified by an analyst during a microscope examination.
While Daniel Oates assures that his company's measurements are 80% accurate within a radius of 50 km around the sampling station, he acknowledges that the forecasts are more on the macro scale than the micro one.
But the island of Montreal stretches over 483 km2.
“It is a very large island in which the presence of tree species varies greatly from one district to another. There are also the winds which are not the same from place to place due to the effects of buildings or the absence or presence of trees. »
— Alain Paquette, professor at UQAM
Can we extrapolate for everyone in Montreal from a single station? I don't think so, points out Alain Paquette.
Professor Paquette's laboratory has received funds from the Quebec Ministry of Health with the aim of developing a truly effective and relevant pollen monitoring.
Her team created easy-to-build, inexpensive sampling stations that she placed at 25 locations on the island of Montreal and a few other locations across the province.
The sampling stations are located at 25 locations on the island of Montreal.
“The idea is to eventually get the most accurate information possible about the variability of pollen concentrations, data that will be useful allergy sufferers who know that taking antihistamines a few days before symptoms makes them much more effective. »
— Alain Paquette, professor at UQAM
Beyond medication, people can also change their schedule and decide to move up or delay an activity depending on the presence of this or that pollen. But to do so, we need to have precise information, continues the professor.
One of the sampling stations of Professor Paquette's project
The stations developed by Professor Paquette's group each cost around $4 to make.
“It's basically an assembly of ABS tubing that you find in hardware stores into which you put a container like the ones you use for urine samples. A layer of a liquid or gel that retains the pollen is placed in the bottom and collected every two weeks for analysis. »
— Alain Paquette, professor at UQAM
The stations developed by the Professor Paquette's group each cost around $4 to make.
Professor Paquette's group is also developing molecular tools in collaboration with researcher Isabelle Laforest-Lapointe from the University of Sherbrooke.
The DNA of pollens is directly analyzed to identify their origin . These molecular analyzes make it possible to go beyond the genus, to identify the types of pollen of trees, grasses and herbs at the species level, adds the professor.
“When we give forecasts for maple, it means nothing to botanists. For a city like Montreal, it is extremely important to know which of the three maple species it is, since their phenology is not the same. »
— Alain Paquette, professor at UQAM
Phenology is the rate of occurrence of important events in a plant's cycle. Thus, the flowering phenology of silver and Norway maples, the two most abundant species, varies by one month.
“It is believed that the pollens of some species are smaller or of particular shapes, and that they are transported over long distances, while others are transported over shorter distances. »
— Alain Paquette, professor at UQAM
If these molecular analyzes make it possible to specify the species present, they do not however give any information concerning their relative quantity, an essential data.
For this reason, the researchers are also developing a method based on flow cytometry, which is used for the analysis of urine or blood samples.
The technique allows to establish how many grains there are pollen of each species in the sample.
Paired with artificial intelligence, it will make it possible to evaluate the proportions of different pollens in a given location.
It is artificial intelligence that will recognize which are the characteristics that differentiate pollens.
“Obviously, when a sample comes from a field or a city, it doesn't just contain pollens. There's a bunch of other stuff in there, like dust and bits of bugs. This is an additional level of difficulty for the artificial intelligence, which must discern what is a pollen and what is not. »
— Alain Paquette, professor at UQAM
Professor Paquette's laboratory is simultaneously carrying out a large survey of people with allergies that will make it possible to note where they go. found on the island of Montreal and what their symptoms are.
“This will provide a better understanding of the spatial distribution of pollens. For example, how far away from a particular tree or group of trees are people affected? »
— Alain Paquette, professor at UQAM
Using the postal codes of the people recruited, particularly those located in the immediate vicinity of our 25 stations, Professor Paquette and his colleagues hope to be able to establish a link between allergic symptoms and the presence and the absence and abundance of certain species in their immediate environment, where they live.
If all this information collected through these initiatives is useful for people allergic, they will also be for the cities which will be able to use them to better plan their urban forests.
In the past, cities have mainly chosen male trees because they do not produce fruit, which was appreciated for the maintenance of streets and sidewalks, notes Marie-Jo Ouimet of the INSPQ. However, the main consequence of this choice was the increase in the pollen emitted by the males in circulation in the air, she adds.
For Professor Paquette, several cities are now showing goodwill and acting on their urban forest to minimize the amount of allergenic pollen in circulation.
The problem is that the cities consult several guides that do not agree with each other, points out Mr. Paquette, who notes that they all indicate, with supporting scores (often from 1 to 10), species allergenicity. Two guides can say exactly the opposite about the same species. These guides seem to us based on legends, the professor is surprised.
“It's really dramatic. The city of Montreal goes from green to red from one guide to another. In one, it is considered populated by low allergenic species, and in the other, by highly allergenic species. »
— Alain Paquette, professor at UQAM
However, these guides are created from the same inventory of trees. The UQAM team published an article in the journal Scientific reports (in English) in 2021 on the subject.
Well-meaning municipal decision-makers rely on these guides to decide what to plant to improve the health of citizens, believing that they are done right, if at all. indignant Professor Paquette, who hopes that the knowledge acquired through his work will help cities to diversify tree species and reduce the relative proportions of each of them.
