The researchers studied a sample of 53,000 workers. "More than 60 percent were exposed to noises exceeding the norm of 90 decibels (dB) per day, which is equivalent to the sounds that emanate when a subway enters a station," says Michel Picard, a professor at the Universit de Montral's School of Speech Therapy and Audiology, who conducted the study along with his colleague Tony Leroux.

When a worker is exposed to noise exceeding 90 dB during a day's work, that worker is 6.2 percent more likely to have a work accident than colleagues working in the same environment with less noise. If the worker suffers hearing loss, his risk of injury is 7 percent greater.

Out of 43,250 reported work accidents, 5,287 were associated to noise. "What is particularly worrying is the young age of the workers," says Picard. The average individual was a 36-year-old male exposed to the noise for 13 years. And these hearing losses are permanent.