Reducing hazards, improving safety culture among solutions
More and more attention has been focused in recent years on the effects of noise in public spaces. When Woodstock General Hospital in Ontario opened a new facility in 2011, it built in design features — including soundabsorbing ceiling tiles and smaller nursing stations — to reduce patients’ exposure to noise. Organizations provide lists of quiet restaurants free of charge. Recently, one frustrated diner developed an app with a sound meter that will let restaurant patrons measure actual noise levels when they’re out for dinner.
For patients and diners, excessive noise causes annoyance, stress and the inability to communicate. But too much noise can also affect workers. In fact, while hearing loss has long been considered a major hazard for workers in heavy industry, manufacturing and mining, it is proving to pose a hazard in occupations not generally associated with a high risk of hearing loss.
A 2018 study by the National Institute for Occupational Safety and Health (NIOSH) in the United States looked at workers in the health-care and social assistance sector and concluded that hearing loss rates were higher than expected, given that these occupations have long been assumed to present low exposure to noise. The study found the overall prevalence of hearing loss among noise-exposed workers in the sector was 19 per cent, while it was 31 per cent in the medical and diagnostic laboratories subsector. Other high-risk sectors included: child day care services; ambulatory and health-care services; offices of some health practitioners; community food and housing services; and emergency and other relief services.
A 2015 study published in the International Archives of Otorhinolaryngology said that noise levels in a hospital emergency room reached peak levels in excess of 85 dBA occurring at least once per minute from monitor alarms, overhead speakers and slamming doors. High noise levels were also reported in operating rooms, hospital kitchens, intensive care units, hospital laundry facilities and around helicopter emergency medical crews.
WorkSafeBC recently issued a safety bulletin to draw attention to the risk of hearing loss for bartenders, servers and other workers in the service industry. Despite the hazard, caused largely by the use of amplified music, noise levels in pubs and nightclubs across Vancouver and Victoria routinely exceed safe limits during workers’ regular shift hours.
Exposure to hazardous noise can cause permanent hearing loss, as well as tinnitus (ringing or buzzing in the ears). Noise-induced hearing loss limits a person’s ability to hear high-frequency sounds and understand speech. Lower noise levels, while they may not damage hearing, can still lead to such nonauditory health effects as annoyance, lack of sleep, stress, interference with speech communication, performance and behaviour, reading, memory acquisition and mental health. Though not well documented, excessive noise has been associated with increased risk of cardiovascular disease, especially among workers who are already predisposed to heart problems.
Determining hazardous noise levels
To determine whether any amount of noise is safe, the safety manager requires two numbers: the noise level and worker exposure duration, says Alberto Behar, a professional engineer and researcher at Ryerson University in Toronto. The level is expressed in decibels, which is usually abbreviated to dB(A). (The “A” indicates the sound is measured using a special filter, called “A,” which cuts low frequencies.)
Generally, noise is hazardous to a worker if the noise level during an eight-hour work shift is at or above the time-weighted average of 85 dB(A), about the same as a leaf blower or a motorcycle. Exposure to this noise level over many years will result in hearing loss.
“The noise level has to be within 85 decibels, and the worker has to be exposed no more than eight hours a day, or 40 hours a week, to be safe from hearing loss. That means, over the person’s working life, they won’t suffer hearing loss,” Behar says. “What is safe also depends on anatomy. Some people can be exposed to higher noise than 85 decibels without any problem, and some people will be exposed to less noise and they will have hearing damage.”
Most Canadian jurisdictions set the occupational exposure limit (OEL) for eight hours at 85 dB(A). Federal legislation sets the limit at 87 dB(A), while the limit in Quebec is 90 dB(A).
When a noise level is higher than 85 decibels in a workplace, noise levels and exposure time should be reduced. Determining the revised maximum exposure time for a worker is calculated using an “exchange rate”: As the sound level goes up by the amount of an exchange rate, exposure time must be halved.
In Canada, the most commonly used exchange rate is three. This is largely because, based on how noise is measured, whenever a noise level rises by three decibels, the sound pressure doubles. For example, using an exchange rate of three, an employer would calculate that if the workplace sound level is 88 decibels and a worker has an eight-hour shift, then the worker’s exposure time must be decreased to four hours.
To determine whether there is a workplace noise hazard, safety managers should identify sources and levels of noise, the workers who are affected and exposure duration. This information will help managers determine what hearing protection they should provide to workers. If the noise level is at or above 85 decibels, employers should establish a hearing conservation program.
Reducing noise hazards
The first step in a hearing conservation program is to reduce the noise, says Anna Van Maanen, audiologist at WorkSafeBC.
“Ideally, you do not start off with hearing protection; the first step in hearing conservation is reducing the noise at its source,” she says.
Bars and nightclubs often have design features — high ceilings and hard floors and surfaces — that reflect sound around the room and magnify noise. To dampen the sound, employers can cover walls and ceilings with sound-absorbing materials. They can install carpeting or use soft, sound-absorbing ceiling tiles to muffle noise coming from hard floors. Curtains will absorb sound bouncing off glass windows.
In hospitals and other health-care facilities, noise can be reduced by using floor mats and lowering the volume on alerting bells and phones. Loud equipment can sometimes be modified to produce less noise; otherwise, managers can isolate the equipment, or put sound walls or curtains between the equipment and workers. Additionally, when well maintained, machinery and equipment work more quietly.
But loud noise is not the only potential contributor to hearing loss in the health-care sector. Some drugs — including anticancer, antiinflammatory, antithrombotic, antimalarial and antirheumatic drugs — are classified as ototoxic, meaning exposure to them can elevate workers' risk for hearing damage. Occupational health professionals should seek to reduce worker exposure to these drugs.
Effective administrative controls may be implemented as well. For example, employers can provide quiet areas for workers or modify work shifts to limit individual workers’ exposure to noise.
Protecting workers’ hearing
If engineering and administrative controls cannot be used, then personal hearing protectors should be used. Ear plugs work by stopping the passage of noise energy to the inner ear, Behar says. While they are an effective way to block out noise, hearing protectors can also create problems for workers.
“First, people are not comfortable wearing them, and comfort is number 1 with plugs or muffs. Muffs are hot because they enclose your outer ear and it’s uncomfortable. The plug is something you put into your ear, and now there’s a pressure there, so it’s also uncomfortable,” he says.
According to the WorkSafeBC bulletin, bartenders, servers and other industry workers are often reluctant to use hearing protection because they believe it will make it difficult to communicate with customers. However, hearing protection devices protect workers while still allowing them to hear clearly, usually even better than without them, the agency says.
“Studies show that when noise levels reach 90 decibels or higher, hearing protection actually improves your ability to hear speech,” said Dan Strand, director of prevention services at WorkSafeBC, in the bulletin. “We need to change how we think about hearing protection in the service industry.”
When selecting plugs, there are many variables to consider: What attenuation level is needed for an area? How comfortable are they to wear? Do some workers already have some hearing loss and so need a different attenuation level? What are the workers’ communication and listening needs during the job?
One effective ear plug used by people who work in bars and nightclubs is called a flat-attenuation plug. These devices are generally affordable and comfortable. They come in flange rubber plugs and custom-moulded plugs, typically made of silicone or vinyl materials.
“Most hearing protectors don’t attenuate all pitches the same. You may get more attenuation in the high pitches than in the low pitches, so the sound is muffled and distorted, as well as being attenuated,” Van Maanen says. “But with flat attenuation plugs, the sound is attenuated equally or close to equally across the pitch, or frequency, spectrum. The sound is just dampened, and the pitch and everything else doesn’t change. There’s not the distortion there.”
These types of earplugs are designed to allow the hertz levels of voices to come through while protecting against other hazardous noise.
“They’re really popular among musicians. They want to hear their vocal tones, but they don’t want the drums and guitar coming through as loud. That’s the nub of it: Filter out hazardous noise, but allow pleasant noise like a human voice to come through,” says Marc Kirsch, product marketing manager for the United States and Canada at Charlotte, N.C.-based Honeywell.
Ear plugs reduce noise by various amounts, and it’s important to select plugs with the attenuation amount that is appropriate for the workplace noise level. The attenuation amount should just reduce noise to a safe level, one below 85 decibels. Reject the urge to choose plugs that provide more protection than workers need.
“People tend to think that more attenuation is better. But that, in fact, can lead to safety risks if you can’t hear something. You have to bring it down to a safe level, but it doesn’t have to be way beyond that,” Van Maanen says.
Ear plugs are classified to indicate the amount of attenuation they provide. In Canada, noise attenuation is indicated by three classes: Class A (greatest reduction), Class B and Class C. Ear plugs available in Canada may also carry the American classification called noise reduction rating (NRR). The higher the rating, the greater the protection provided. These rating numbers must be used with caution because they indicate the potential, not the actual, amount of attenuation of a given ear plug. The rating numbers tend to be artificially high; most users obtain less attenuation than the NRR label indicates.
It is very important for ear plugs to be comfortable and fit into the ear properly, Behar says. Workers should be trained on how to insert them into the ear canal so they create a complete seal. An inadequate insertion can result in discomfort or inadequate attenuation.
“If it’s not properly inserted, the noise energy goes around the plug and gets to the inner ear anyway. What I recommend in any workplace is to have a training program where managers can convey, first, the dangers of noise and, then, how to properly insert the plugs,” Behar says.
Workers in environments that might not be traditionally associated with high risks of hearing loss — such as health care — or that don’t typically have a strong safety culture — such as bars and restaurants — need specific training on the negative effects of noise exposure. They need to understand how excessive noise can not only impact their work but their overall quality of life as well.
The reality is the risk of hearing loss at work is often overlooked, and it’s a problem that is likely to become more urgent as today’s young people start their careers, says Kirsch.
“Young people always have something in their ear. And if they don’t, they’re in clubs or bars or at concerts where the noise is overly loud. This exposure will pose an additional hazard to those young adults as they get into the workforce,” he says. “The workforce is changing. People are coming into the job with existing hearing loss. So, it’s definitely something for us, as an overall hearing industry, to watch out for and plan for. It’s something to think about.”
This article originally appeared in the March/April 2020 issue of COS.”
MAXIMUM UNPROTECTED EXPOSURE TIME
The risk of hearing loss depends on the noise level and duration of exposure. This table shows how long unprotected workers can be exposed to certain levels of noise without harm.
COMMON NOISE PRODUCERS AND DECIBEL LEVELS
- 150dB Rock concert
- 130 dB Jackhammer
- 100 dB Chainsaw
- 90 dB Lawnmower
- 70dB Vacuum cleaner
- 40dB Quiet room
- 30dB Whisper