Imagine driving along on Highway 401, Canada’s busiest highway, in a convertible with the top down and a large diesel truck directly in front of you the entire time. That’s how Greg Evans compares the amount of diesel exhaust a passenger travelling in a car behind the locomotive of a GO Transit train is exposed to.

Evans is a professor of chemical engineering at the University of Toronto and a co-author of a new study that found that GO train users, particularly those in the car directly behind the locomotive pulling the train, are at risk of high levels of diesel exhaust pollutants.

GO Transit services the Greater Toronto Area and several surrounding communities. The average weekday ridership on the GO trains was 215,000 in the fall of 2015.

The diesel exhaust research was conducted by The Southern Ontario Centre for Atmospheric Aerosol Research (SOCAAR) at the University of Toronto and is expected to be published later this week in the journal Atmospheric Environment. An “essentially final” copy of the study was provided to CTV News on Tuesday.

The researchers studied GO Transit trains travelling along the Richmond Hill, Ont. route to Union Station in downtown Toronto during 43 trips in 2015.

They used handheld devices to measure two components of diesel exhaust: ultrafine particles and black carbon during “pull mode” or “push mode,” when the locomotive is behind the train. The researchers also monitored the amount of diesel exposure while walking on a sidewalk in the city during rush hour.

The study found that concentrations of the diesel exhaust were higher when the locomotives were in front pulling the trains than they were during the push mode or while walking on the sidewalk.

Evans told CTV News Channel on Tuesday that there is a range of health risks associated with exposure to diesel exhaust, such as cardiovascular and respiratory problems or even lung cancer.

“I would not want to overly alarm people. We are exposed to different air pollutants throughout our day, it’s just that this particular exposure is likely the highest source of exposure for people during the day,” he explained.

The professor said that travellers with respiratory and cardiac problems as well as pregnant women should be extra careful. Evans advised them against sitting in the car directly behind the locomotive when it’s in the pull mode. For example, the study suggested that diesel exhaust concentrations in cars in the middle of the train were three or four times lower than those in the car closest to the locomotive.

Diesel pollutants aren’t always noticeable for the average passenger either, according to Evans. He said he’s been commuting on the GO train for many decades and he rarely smells the diesel fumes inside the cars.

Changes underway

Evans told CTV News Channel that he was pleasantly surprised and encouraged by the response researchers received from GO Transit’s parent company Metrolinx. He said the company has taken the research seriously since it was alerted about the issue.

Greg Percy, the chief operating officer for Metrolinx, told CTV Toronto that the company has already started installing new high-efficiency filters to reduce pollution in its train cars.

“We jumped on it right away,” Percy said. “It’s really important that we keep the ride for our customers comfortable and they need to confidence in what we do.”

In a statement released on Tuesday, Percy said Metrolinx would be conducting further tests in partnership with the University of Toronto and SNC Lavalin to “better understand the issue.”

The researchers proposed a long-term solution of electrifying commuter trains instead of using diesel locomotives as well as adopting emissions-friendly Tier 4 engines to help achieve better air quality.

Although Metrolinx already has an electrification plan for the majority of its train network, it will be years before the project is completed. And the company is not alone. The study stated that 18 out of 26 public transit agencies in Canada and the U.S. rely solely on diesel locomotives for their commuter trains.