Daily use of public transit might cause hearing loss.

It’s a conclusion anyone who’s taken Toronto rail transit might reach after one ride, but researchers from the University of Toronto now have data to suggest it may be true.

A recent study suggests people who take the subway, the bus or ride a bike in city traffic on a daily basis are routinely exposed to bursts of noise that can contribute to hearing loss.This constant noise exposure has been linked to a number of chronic conditions including depression and heart disease, although the exact nature of the relationship has not yet been determined.

The study was conducted in Toronto, using noise dosimeters attached to people’s shirt collars while they used private and public transportation. Researchers used guidelines from the U.S. Environmental Protection Agency to determine exposure to harmful noise thresholds, which are measured in weighted decibels.

“Peak noise levels in (decibels) across both public and personal transport exceeded the EPA recommended thresholds,” Dr. Vincent Lin, an associate professor in U of T’s department of otolaryngology, said in a news release.

“The average noise level is actually quite acceptable, but the concern is the peaks that people are exposed to,” Lin added in an interview with CTV News Channel on Thursday. He cited such occasional noises as screeching wheels and crowd noises as the main culprits.

Data collected from 210 measurements suggests people are exposed to higher-than-recommended noise levels nine per cent of the time on the subway, 12 per cent of the time on the bus and 14 per cent of the time while cycling. It also found people are exposed to brief bursts of excessive noise on the streetcar, in a car or walking, but noise levels did not exceed those recommended by the EPA.

“We were surprised at the overall average noise exposure commuters experience on a daily basis, especially the peak noise intensity not only on trains but also on buses,” Lin said. “Short, intense noise exposure has been demonstrated to be as injurious as longer, less intense noise exposure.”

Previous research suggests exposure to excessive noise over a long period of time can cause gradual hearing loss, as cells in the ears die off bit by bit. “Once those cells are lost it’s permanent,” Lin said.

“You can lose quite a bit before you notice the hearing loss, but every cells counts,” he added.

Lin and his fellow researchers published their findings in the open access Journal of Otolaryngology – Head and Neck Surgery. They say the data is not yet expansive enough to reach conclusions about cause and effect, but that their findings do highlight problematic elements that can contribute to hearing loss.

Lin recommends city planners pay more attention to noise reduction on public transit.

He also suggests individual riders wear ear protection when taking transit, even if it’s just a pair of foam earplugs or some earbuds with the music off.

“This is a potentially preventable type of risk factor,” he said.