Sound can be transformed into the unsound when excessive: too much noise, too much vibration, even too much exposure to solvents can lead to hearing loss that no amount of second-guessing will restore.
A whole host of controls should be considered to protect workers from noise-induced hearing loss (NIHL), but the two main categories of personal protective equipment (PPE) to achieve this are earplugs and earmuffs.
Perhaps the strangest thing about protective gear is that the ultimate goal is that it be rendered unnecessary. Until that time, however, it may be best to take the conservative approach to hearing conservation.
Bev Borst, a technical specialist with 3M Canada in London, Ontario, says that a hearing protection program has a number of essential elements: noise exposure assessment/monitoring; education/training/motivation; engineering and administrative controls; hearing protector devices; audiometric testing; record keeping; and program evaluation.
Conservation has long been a song sung by the choir. “If prescriptions for eyewear are important for workers to see properly to preserve their vision, then it makes sense for workers to take care of their hearing the same way,” Brad Davidson, president of HearSafe Canada in Mississauga, Ontario, noted in a statement in the summer of 2009.
But is this buy-in resulting in on-the-floor protection? Borst says her view is that “most employers today explore engineering and administrative control options first and elect hearing protection if those options don’t lower the noise to below hazardous levels.”
Theresa Schulz, Ph.D., hearing conservation manager for Howard Leight/Sperian Hearing Protection, based in San Diego, notes that peer-reviewed studies and research data show that workers are more motivated to use PPE consistently when noises are louder than 90 to 95 decibels (dB).
At lower levels, Dr. Schulz says, “the noise is still hazardous, but not as annoying, and workers can be lulled into thinking they don’t have to use PPE.”
That false security is of concern since workers exposed to noise in the 80 to 90 dB range can develop NIHL.
“It can be tempting to gloss over engineering and administrative controls and see PPE as the answer,” she cautions.
If protective gear is needed, working conditions will certainly have some influence on product selection. But choices — particularly as they relate to comfort, fit and practicality — can get downright personal, notes information from the Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton, Ontario.
Earmuffs and earplugs each offer their own level of attenuation and protection, says Borst. Some things to bear in mind when determining which option is best for a workplace include the following:
– workers generally prefer earplugs in hot environments;
– banded earplugs are a good choice for intermittent, low-noise environments; and,
– communications headsets offer protection while allowing workers to communicate in high-noise environments.
Compliance is a healthy sign of a conservation approach, but compliance without proper fit can nullify benefits.
FIT TO PROTECT
Through 3M Canada’s validation fit testing for earplugs, it was found “that workers do wear hearing protection, but may not have chosen a product that fits properly or they may require additional instruction on proper insertion techniques,” says Borst. “Through instruction, workers can learn proper fitting techniques, such as insertion, fit checks and visual inspection,” she suggests.
Dr. Schulz says that “a poorly fit hearing protector can be uncomfortable, can let in too much hazardous noise or can overprotect, blocking too much noise and creating other safety issues.” To fit earmuffs, the main considerations are correct size and donning method, while earplug fitting may be trickier. “Earplug fitting is much more variable between workers, between different earplugs and even one worker fitting and refitting the same earplug repeatedly,” she cautions.
3M Canada offers a service to quantitatively fit test earplugs, which “uses proprietary algorithms to quickly analyze real-ear data to provide personal attenuation rating (PAR) and fit variability for a given pair of earplugs for the individual,” Borst says.
Gear must be worn at all times during noisy work; otherwise, protection drops off dramatically. Australian-based ProChoice Safety Gear notes “a hearing protector that gives an average of 30 dB of noise reduction if worn continuously during an eight-hour workday becomes equivalent to only nine dB of protection if taken off for one hour in that noise.”
The CCOHS also offers some examples of the maximum protection provided for the percentage of time used: 50 per cent, three dB; 60 per cent, four dB; 70 per cent, five dB; 80 per cent, seven dB; 90 per cent, 10 dB; 95 per cent, 13 dB; 99 per cent, 20 dB; and 99.9 per cent, 30 dB.
Whatever part of the body equipment is meant to protect — eyes, feet, hands or ears — comfort is a critical part of the equation. HearSafe Canada reports that a lack of comfort and difficulty with properly inserting an earplug can bring with it a lack of compliance. And equipment that is not used cannot protect.
The company cautions that disposable earplugs may come with a risk that they will either over- or under-protect. While the work-related hazards around under-protection are clear, it notes, over-protection can result in gear being removed repeatedly.
For maximum comfort and protection, HearSafe Canada notes there is no better option than custom-made gear. By taking an impression of the ear canal, the plug will be custom contoured. Fit tests and proper filtration must also be part of the mix, Davidson says.
Sometimes comfort and associated compliance issues are more a matter of big and small. In July, Chicago-based Magid Glove & Safety Manufacturing Company introduced jumbo disposable earplugs for industrial workers who have larger, deeper ear canals.
The earplugs come in corded and uncorded styles, are made from hypoallergenic polyurethane foam, feature a tapered design and offer a noise reduction rating (NRR) of 32 dB. The fluorescent orange earplugs with bright red cord make compliance checks easier.
Kimberly-Clark Professional, located in Roswell, Georgia, also sees colour as a compliance tool for work in food and pharmaceutical processing. In November, the company announced the availability of metal detectable, disposable and reuseable earplugs specifically designed for use in the sectors.
The earplugs, which have embedded metal that can be easily detected through scanning, come in a distinctive blue colour for easy monitoring and are available in universal sizes.
SHAPE OF THINGS
At first glance, shape may be regarded as a feast for the eyes, but it can be equally beneficial to the ears.
In 2009, Dentec Safety Specialists in Newmarket, Ontario released a new pre-molded earplug with a spherically curved flange design that was about far more than looks. It can conform to the shape of the ear canal and its attached triangular stem “assures better control when workers insert the plug into their ear canal. They get better fit and it doesn’t work itself loose as easily,” Claudio Dente, president of Dentec Safety Specialists, said of the earplugs at the time.
And unlike foam plugs, it “needs no rolling to insert and it can be washed for better hygiene,” the company notes.
The need to keep it clean cannot be overstated, particularly since this can directly influence product performance and the protection provided.
“Hearing protectors do their job by creating a seal so that acoustic energy is blocked, to varying degrees,” Dr. Schulz explains. Dirt or grime on the protector will compromise its ability to obtain and maintain that seal, she notes.
RATE IT TOPS
When a worker remains in one noisy location for much of his day, the need for hearing protection is an easy call. But what if noise exposure is intermittent and levels are varied?
Last January, Magid Glove & Safety introduced a banded hearing protector made from black polyurethane. The lightweight and flexible head band stretches to fit a wide range of head sizes, rests around the neck when not in use and is easy to put on and take off, the company reports. The protector comes with a pair of soft, hypoallergenic, cone-shaped foam earplugs that provide an NRR of 24.
Any information can be helpful, although one proviso is that users must understand what the information means.
Borst points out that “all products sold into Canada have a CSA [Canadian Standards Association] class as well as an NRR identified, and customers do select hearing protection based on these ratings.”
Noise ratings are not a measure of the protection received by the user, Dr. Schulz explains. “Noise ratings are measured to show what that protector can provide, not what it does provide,” she advises.
The CCOHS cites information from the National Institute for Occupational Safety and Health in the United States. If fit data are not available, NIOSH recommends derating hearing protectors by a factor that corresponds to the available real-world data. For earmuffs, subtract 25 per cent from the manufacturer’s labelled NRR; for formable earplugs, subtract 50 per cent; and for all other earplugs, subtract 70 per cent, the agency notes.
Carefully weighing factors when selecting equipment, clearly, is the smart thing to do. But some equipment itself is getting downright intelligent.
Intelligent hearing protection includes electronic earmuffs, which amplify quiet sounds, but still protect against impulsive noise, says Dr. Schulz.
Nacre, a brand offered by Sperian Hearing Protection, has teamed up with the international energy company, Statoil, and SINTEF, Scandinavia’s largest independent research organization. The partners are working to create the next generation of intelligent hearing protection and communication technologies for use in the offshore oil and gas industry, notes a joint statement issued last July.
“Workers on offshore oil platforms and other extreme environments face the risk of not only permanent hearing loss from exposures to high levels of hazardous noise over extended periods of time, but also challenges in maintaining adequate levels of speech communication and situational awareness, which are essential to maintaining safety,” it adds.
Dr. Schulz points to a number of innovations in hearing protection. For hearing-impaired workers, electronic earmuffs will amplify ambient sounds. When a hazardous level is reached, she says, “the amplification cuts off and the muff is now a passive earmuff.”
3M Company offers products that combine the high performance of a passive earmuff with advanced electronics. Workers are able to clearly hear low-level sounds, but should dangerous noises occur, the electronics limit the noise. These tactical products provide protection in high-noise environments, and models are also available to interface with two-way radios.
Guarding against potentially dangerous levels is also the goal of 3M’s noise indicator, says Borst. The small, lightweight device “clips to a wearer’s shirt or can be worn on a lanyard and flashes green when below 85 dB and red when above 85 dB.”
Active noise reduction could provide a solution for workers whose exposures are fairly constant, low-frequency hazardous noise. Available with both earmuffs and earplugs, Dr. Schulz explains that the technology includes “a microphone that analyzes the incoming noise, turns it 180 degrees out of phase and rebroadcasts it into the ear canal so that the sound waves are acoustically cancelled.”
BKK Enterprises in Dryden, Ontario distributes ZEM hearing protection, which uses a patented technology for sound cancellation. The technology is well-suited for damaging noise environments, such as manufacturing, utility work, construction, landscaping, airlines and woodworking.
Sonically sealed chambers form a vacuum that pulls harmful sounds away from the sensitive ear anatomy, the company notes. It reduces low-frequency noise, the noise that masks speech and important sounds or alerts, the information adds.
“Because noise reduction is even and highly effective, speech communication is neither masked nor distorted.”
There is also a trend to offer products that appeal to workers who will make up the work force of tomorrow. For example, 3M Canada has released headsets for people who want hearing protection while listening to the radio or an MP3 player. These limit the audio output to 82 dB plus offer a CSA Class A rating or an NRR of 26 dB.
Also with a view to the future, Moldex in Culver City, California is offering what it says is the only line of hearing products and packaging that are PVC-free. “Toxic chemicals associated with [polyvinyl chloride] disposal in landfills and incinerators have been linked to a wide range of health hazards,” notes information from the company.
The CCOHS recommends that employers provide workers a choice of gear — as long as it can do the job — to ensure hearing is protected and worker acceptance maximized.
Angela Stelmakowich is editor of OHS CANADA.
Hard on the Heart
Beyond the potentially devastating and debilitating effects of permanent hearing loss, a new cross-sectional study out of British Columbia hints at a link between chronic exposure to occupational noise and heart disease. Researchers note the exposure was strongly associated with prevalence of coronary heart disease (CHD), especially for young, male current smokers. “This study suggests that excess noise exposure in the workplace is an important occupational health issue and deserves special attention,” notes the abstract, published online in October in Occupational and Environmental Medicine. Noise exposure assessments for the 6,307 participants of the National Health and Nutrition Examination Survey 1999-2004 were based on self-reported exposure to loud noise on the job. All participants were 20 years of age or older. Compared with never-exposed participants, subjects chronically exposed to occupational noise had a two- to three-fold increased prevalence of angina pectoris, myocardial infarction, CHD and isolated diastolic hypertension.
Care and maintenance are critical to ensuring that a hearing protector protects as intended. The Canadian Centre for Occupational Health and Safety in Hamilton, Ontario offers the following tips:
– Follow the manufacturer’s instructions.
– Check hearing protection regularly for wear.
– Replace ear cushions or earplugs if they are found to be no longer pliable.
– Replace a unit when head bands are so stretched they do not keep ear cushions snugly against the head.
– Disassemble earmuffs to clean.
– Wash earmuffs with a mild liquid detergent in warm water, and then rinse them in clean warm water. Ensure that the sound-attenuating material inside the ear cushions does not get wet.
– Use a soft brush to remove skin oil and dirt that can harden ear cushions.
– Squeeze excess moisture from earplugs or cushions, placing them on a clean surface to air dry.