Yves Lavoie didn't know he had asthma until two years ago, when dust coming from the reconstruction of the Turcot Interchange left him feeling ill.

"I'm not a scientist. I don't know if it's the cause, but I've been sick since the work started," said the Saint-Henri resident, who lives near the construction site.

"It was so bad that I wanted to leave the area, to move," Lavoie said.

Lavoie's symptoms have eased as the amount of dust in the air decreased, but data obtained by CBC News shows that on some days over the past two years, the dust has been 13 times above government-recommended limits.

The chart below shows the daily average concentration of dust captured by an air quality sensor close to the site, on Notre-Dame Street near Gadbois Park.

Each square represents one day since Jan. 8, 2016.

(Duk Lee / CBC News Graphics)

The concentration of dust in the area has fallen from all-time highs in the spring of 2016, when the data shows that nearly every day the dust in the air was thick enough to taste and to coat parked cars.

But there are still days when dust levels surpass the government-recommended limits of 0.15 mg of particles per cubic metre over 24 hours.

Residents of Saint-Henri say it's been a common occurrence to find their parked cars covered in a thick layer of dust from the Turcot Interchange construction project. (CBC)

Residents near the construction site have complained about noise and dust since the project began in 2015, prompting public health officials to press Transports Québec to act.

That's when the ministry installed four pollution sensors around the construction site and alerted residents when levels surpassed government-recommended limits.

CBC News found that between all the sensors, dust levels have exceeded those norms on 460 days since the start of 2016.

The dust was heaviest in the immediate area of the construction site.

Another sensor on Richelieu Street (number 101 on the map below) only registered excessive dust on 137 days since 2016.

The locations of the air quality sensors near the Turcot Interchange. Sensor 102, near Gadbois Park, registered dust levels nearly 13 times higher the ideal limits. (CBC News)

"There's days you can see the dust everywhere you walk," said resident Jill Prescesky, who is a member of a committee that tracks the Turcot project's effects on the neighbourhood.

"Once it's in your lungs, it's there. There's nothing you can do."

Few long-term health risks

Construction dust is usually made of particles too large to infiltrate the lungs, which are usually filtered by the nose and throat. The health effects are mostly temporary, said Dr. Geoffroy Denis, head of occupational health at the the CIUSSS Centre-Sud,the regional health agency serving the most affected area.

People might experience irritation of the eyes and throat, and the dust could aggravate seasonal allergies or asthma, Denis said.

"These symptoms tend to disappear as soon as the dust lowers," he said.

Dust levels tend to be highest during the spring, for several reasons, said Transports Québec spokesperson Martin Girard.

Construction activity usually picks up when the weather gets warmer, and winds tend to be stronger in the spring, which sends dust further afield.

"When there's a lot of wind, it's hard to control the dust, even with mitigating measures," Girard said.

Demolition of the old Turcot Interchange can create a lot of dust. Watering keeps the dust down, but weather conditions can still carry it far and wide. (CBC)

Certain jobs, like the demolition of tall structures and the transportation of dirt, are tricky for dust control, he said.

Among its control measures, the ministry deployed dust-trapping water cannons around the site and swept the streets and sidewalks after major work. It also lowered the speed limit around the site.

Girard couldn't say to what extent such measures had an impact on dust levels, but on average, the number of days of excessive dust have waned since 2016, and residents contacted by CBC News say the dust is more tolerable now than it's been in the past.

A barrier along St-Jacques Street in Notre-Dame-de-Grâce shields buildings from dust and noise coming from the Turcot Interchange construction site. (submitted by Jill Prescesky)

Summer was worse, "probably because the windows are open," said Malaka Ackaoui, who sits on a neighbourhood committee that exchanges information with Transports Québec on the construction's progress.

"The house would get very dirty when you have the windows open and there's construction outside. There's more dust in the air."

- With files from CBC's Kate McKenna