The Léonard-De-Vinci elementary school in Saint-Michel is throwing distance away from the Metropolitan Highway, where 144,000 cars pass daily and choke the air with pollutants.

The school's 650 students, aged 4 to 12, are exposed daily to fumes that are known to cause respiratory problems, in addition to the noise from the busy and congested road.

It's one of 127 elementary and secondary schools in the greater Montreal region that are within 150 metres of busy roads, a zone that health authorities in Quebec and elsewhere have deemed hazardous to sensitive people.

"We know that air pollution from transport related to cars and trucks can contribute to asthma. We know that it can contribute to heart disease and lung disease and also, over the long term, to lung cancers in adults," said David Kaiser, an environmental specialist with Montreal's public health department.

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In 2014, health authorities in Quebec, following the example of other jurisdictions, recommended that no new schools, day cares and hospitals be built within 150 metres of busy roads. For those that already exist, the Direction de santé publique recommended installing better ventilation systems and barriers between roads and buildings frequented by children.

To date, no changes to zoning laws have been made to prevent new construction along busy arteries, Kaiser said.

"In Montreal in 2019, you can drive along Highway 40 and see that there are developments along there. Some are seniors' residences. So those are elderly people who are going to be living right on the highway," he said.

On the island of Montreal alone, 103 out of 640 schools — 16 per cent — are within 150 metres of roads that have an average daily traffic of 20,000 or more vehicles.

Lester B. Pearson was the only school board contacted by CBC that said it has addressed the issue. After receiving a provincial grant in 2015, it upgraded ventilation systems in all schools. Three of its schools in the West Island are beside busy roads, including Beaconsfield High School.

"Even something as simple as hairspray will be caught inside the filter so it's actually not going into the school," said Carol Heffernan, the Lester B. Pearson School Board's assistant director general.

The English Montreal School Board, which has 13 schools in the 150-metre zone, said roadside pollution has never been flagged as a problem.

"From school admins to senior staff, these issues have not been raised by any of these schools," EMSB spokesperson Michael J. Cohen wrote in an email.

There is a small barrier between the schoolyard at Léonard-de-Vinci school in Montreal and the busiest highway in Quebec, Highway 40. (Sudha Krishnan/CBC)

Marguerite-Bourgeoys School Board, which has six of its 113 elementary and secondary schools near busy roads, including Beaconsfield elementary, responded similarly.

The Commission scolaire de Montréal, which has the most schools in the 150-metre zone — 46 in all — did not return repeated requests for comment.

Ultra-fine particles concentrated near roads

The area immediately next to busy roads has been found to have high concentrations of ultra-fine particles (UFPs), pollutants too small to be filtered by the nose and trachea that often make it inside the lungs.

A study by McGill University researcher Scott Weichenthal estimated UFP concentrations on the island of Montreal by attaching air quality sensors to bicycles and having cyclists bike around the city. The busier the road, the higher the concentration of UFPs.

These UFP levels are long-term estimates and can change on any day. Generally, higher traffic areas have higher UFP levels. (CBC News Graphics)

By the Décarie Expressway, Highway 40, and along railroads, the concentration of UFPs were found to be up to five times higher than in quiet residential areas.

However, UFP concentrations drop significantly after 150 metres, which is why public health authorities recommend this buffer zone around roads.

Although there's no law preventing new construction within this zone, the City of Montreal collaborates with school boards and the Quebec Ministry of Education when planning the locations of new schools.

"If a terrain is deemed inadequate for a new school, like being in an industrial area or close to a highway, we recommend to the school boards to consider other options," Montreal city spokesperson Karla Duval told CBC News.

Barriers can reduce pollutants

It may not be feasible to move schools away from highways as governments try to balance urban development with public health. But placing structures between schools and roads has been found to greatly reduce the pollutants that get through.

Sound barriers and dense vegetation can keep particles on the road or trap them in leaves. The U.S. Environment Protection Agency tested different kinds of barriers and found that a combination of sound wall and dense vegetation can reduce pollution by up to 60 per cent.

Dense vegetation barriers or a combination of sound wall and vegetation have been found to reduce roadside pollution in nearby buildings. (CBC News Graphics)

There is no information on barriers that have been built between busy roads and the schools near them in the greater Montreal region. Transports Québec says it works with municipalities to install sound barriers near roads but has no specific policy for structures that reduce pollutants.

Methodology

CBC used geospatial software (GIS) to find schools that are within 150 metres of busy roads. The locations of schools came from the Quebec Ministry of Education. Only public schools that serve preschool, elementary and secondary students were analyzed. For private schools, all were analyzed.

CBC used the National Road Network data to map the roads and isolated those with an average daily traffic of 20,000 vehicles or more. For highways, traffic counts came from Transports Québec . For local roads, the data came from the City of Montreal .

A 150-metre buffer was added to the selected roads and the schools within that buffer were detected with a spatial join.