Air pollutants in Montreal | Increasingly poor air quality

Air quality has been increasingly poor in Montreal since the post-pandemic recovery, a situation attributable mainly to the increase in the number of cars on the roads and… the return of the big La Ronde fireworks.

With 33 days of poor air quality in 2022, including 4 of smog, the metropolis has returned to the average of the years preceding the COVID-19 pandemic, shows the annual report of the environment department of the City of Montreal, which will be made public on Thursday.

This is three times more than the 11-day low recorded in 2020, the year of major confinements.

“The increase in the use of the car alone for the movement of workers, [liée à] the resumption of economic and social activities, has greatly contributed to this increase, ”says the document.

It is for this reason in particular that the central districts had experienced more days when the air quality index was good, rather than acceptable or bad, observes Fabrice Godefroy, section head at the air quality (RSQA) of the City of Montreal. “The air quality is worse near motorway junctions,” adds Mr. Godefroy.

Fireworks

The return in 2022 of the International des Feux Loto-Québec, after a break forced by the pandemic, contributed to blacken the balance sheet.

These large pyrotechnic shows alone are responsible for 5 of the 33 days of poor air quality, or 15% of the total, the report indicates.

During the fireworks on August 3, the level of fine particles in the air of the Hochelaga-Maisonneuve district reached 379 μg/m^⁠3a concentration above the rate of 303 μg/m^⁠3 recorded in New York under the smoke of the forest fires, on June 7th.

“At these concentrations, there is a very serious risk to the health of the population, [surtout chez] the most vulnerable,” says Alexandre Barris, toxicologist at the Montreal Regional Public Health Department.

In the Anjou district, about 8.6 km from the site of the fireworks, the hourly concentration of fine particles reached 157 μg/m that evening.^⁠3.

Many chemicals, especially metal salts, are used in pyrotechnics to produce bright colors and visual effects, the report explains.

“Some of these compounds are released during their explosion and can have harmful effects on the environment and on human health”, indicates the document, specifying that the ephemeral aspect of the event reduces the time of exposure to emissions. .

The administration of Mayor Valérie Plante does not plan to put an end to the famous fireworks competition, which is a source of occasional contamination, underlines Marie-Andrée Mauger, responsible for the ecological transition and the Environment to the Executive Committee and Mayor of the Borough of Verdun.

Fireworks had been responsible for just one poor air quality day in 2019, five in 2018 and none in 2017.

More days, but fewer contaminants

Even if the number of days where the air quality is poor is on the rise, the concentration of fine particles, it, “has been falling for several years”, indicates the report.

The annual average of all Montreal sampling stations for fine particles was 7.1 μg/m³in 2022 – the report does not specify the rates for the previous years individually, but indicates that the three-year average from 2020 to 2022 was 7.2 μg/m³.

“There are still health effects, and potentially premature deaths,” said toxicologist Alexandre Barris.

The short-term effects, during pollution peaks, can be respiratory problems, such as asthma attacks or inflammation of the airways, itchy eyes or cardiovascular problems, he lists.

In the long term, air pollution can contribute to the onset of asthma, especially in children, cancer, cardiovascular problems or dementia, continues Mr. Barris.

Among the other causes of poor air quality, the 2022 report points to industries in eastern Montreal, road yards in Montreal North, the Port of Montreal, wood heating and building fires.

All these factors are also influenced by weather conditions, underlines Fabrice Godefroy, of the RSQA.

“Even if we have the same sources of pollution, depending on the weather, whether it’s raining or whether it’s sunny or windy, it will dilute the pollution,” he says. That’s really random. »