MONTREAL -- There’s been a sharp drop in gas emission levels in Montreal and other Canadian cities throughout the pandemic, according to researchers at Concordia University.

A study, published in the journal Science of the Total Environment on Dec. 24, found carbon dioxide emissions fell sharply — by half in Montreal — when lockdown measures were first imposed in March.

The study, the first of its kind in Canada, was led by second-year Concordia civil engineering master’s student Xuelin Tian.

With millions of Canadians no longer commuting to work, vehicle traffic across Canada plummeted, and it’s had a significant impact on air quality in all major Canadian cities

The most noticeable drop-off was the week of March 15, when national lockdown measures were first implemented.

Traffic congestion levels decreased by as much as 75 per cent in Montreal.

Motor gasoline consumption fell by almost half during the pandemic’s early weeks, with a corresponding drop seen in carbon dioxide emissions.

Nitrogen dioxide levels, another toxic gas emitted from vehicles, also dropped significantly.

The paper looked at downtown air quality monitoring station data from Vancouver, Edmonton, Saskatoon, Winnipeg, Toronto, Montreal, Halifax and St. John’s., and found similar results throughout the country.

It looked at the cities’ concentration levels of carbon dioxide and nitrogen dioxide, but also sulphur dioxide, a gas emitted from power plants and other industrial facilities. Researchers compared this year’s levels to figures recorded over the previous two years.

Researchers also used satellite imagery and urban transportation fuel consumption figures.

“I hope to find something which can help better understand the impact of the pandemic and support the future decision making of the governments,” said Tian, the paper’s lead author.

“Governments everywhere are trying to reduce their use of carbon-based fuels,” said Chunjiang An, assistant professor in building, civil and environmental engineering at Concordia, and the project’s supervisor.

“Now we have some data that shows what happens when we reduce the number of gasoline-powered vehicles and the effect that has on emissions.”

Emissions began to grow again over the summer, but researchers have not yet had a chance to examine data from the second lockdown that began in the fall.