New research shows that diesel exhaust is entering the ventilation systems of some GO trains, leaving riders exposed to five times more toxic particles than they would encounter while walking along University Avenue during rush hour.

Researchers with the Southern Ontario Centre for Atmospheric Aerosol Research at the University of Toronto used portable devices to measure the air on GO Transit’s Richmond Hill line for two components of diesel exhaust - ultrafine particles and black carbon.

The researchers, led by Dr. Greg Evans, found that the concentration of the components was not significantly high when the trains were in “push mode,” which is when the diesel locomotive is at the back of the GO train.

The researchers, however, found that when the train is in “pull mode” with the diesel locomotive at the front, the concentrations of ultrafine particles and black carbon were five and four times higher than the levels recorded on a busy downtown stretch of University Avenue during rush hour.

The uptick in the presence of the particle was even more pronounced in the front passenger train, where research revealed it to be nine times higher than levels recorded on downtown streets.

GO trains are in “pull mode” about half of the time, according to Metrolinx.

“Overall, these results clearly indicate that some passengers on-board pull-mode trains are being exposed to elevated level of diesel exhaust,” the research states. “Hence, it is recommended that immediate steps be taken to evaluate and where needed mitigate exposure in all diesel-powered passenger trains, both commuter and inter-city. Installations of high efficiency filters in the ventilation system of each coach may offer a relatively quick opportunity to reduce in-train exposure. In the interim, public health officials should consider advising susceptible individuals to travel near the rear of pull-mode commuter trains as a precaution.”

Concentration rises as train accelerates

The research, which will be published in the Atmospheric Environment journal, was based on measurements recorded on a total of 43 trips during morning and afternoon rush hour in the summer of 2015.

According to the study, the concentrations of the two toxic diesel components “slowly rose” as the train made its way to and from Richmond Hill, suggesting that accumulation is an issue.

The study also stated the concentrations rose “10 to 40 seconds” after the train accelerated, suggesting that speed could further exacerbate the problem.

“Before departure the background pollutant levels in the coach were low. These levels started to rise within 4 minutes from the departure,” the research states.

Metrolinx cooperated with study

Metrolinx worked with researchers throughout the study and were briefed on its results ahead of publication.

In a statement issued on Tuesday, Chief Operating Officer Greg Percy said that the transit agency is already “addressing all of the recommendations made in the report,” including the installation of improved ventilation filters and the use of locomotives with higher emission standards. Percy also pointed out that Metrolinx has plans to eventually electrify its fleet of GO trains, which would largely solve the issue.

“We don’t take these issues lightly, and we welcome any findings that can help us run a healthier, safer transit service,” he said. “As Dr. Evans points out, the study is not meant to discourage customers from using GO trains. He has been commuting on GO trains for years, and so have I - 15 years, to be exact - and I will continue to do so.”