Hearing loss is easy to ignore. There is usually no pain, no pressure and no bleeding as hearing loss from noise exposure occurs.
Things that happen gradually, such as hearing loss, are easily ignored until it is too late. If a drop of blood came out of our ears every time we heard a noise that was loud enough to injure our hearing, we would find hearing loss difficult to ignore. But that does not happen.
Subsequently, there are an estimated 33 million people with significant hearing loss in the U.S. -- hearing loss severe enough to affect their daily activities; their ability to perform and function in vocational, professional, personal and familial areas.
Of the 33 million people who are hearing impaired, noise exposure accounts for one-third of that population. In addition, there are 36 to 37 million people who suffer from various degrees of tinnitus, which is a noise or ringing in the ear.
Employees are going to get more noise exposure where they work than in any other situation. Why? Because they may be exposed to work-related noise 8 hours a day, 40 hours a week, for a 40-year career. More workers identify noise as the most unpleasant and annoying contaminant in their work environments than any other factor. Noise compromises the character of the work environment and often leads to reduced productivity and increased worker anxiety. It also can contribute to excessive absenteeism.
In addition to its effects on quality of life, the toll on the auditory system from noise can be enormous. Millions and millions of people go to work each day and are exposed to noise levels which, over time and without proper precautions, can produce irreversible damage to their auditory systems.
Hearing Loss and Noise
The type of hearing loss associated with workplace exposure is known as sensory-neural. It is damage to a very sensitive part of the hearing system called the cochlea, which is a receptor organ for hearing in the inner ear that converts sound waves into electrical impulses that are then sent up to higher auditory centers. It also is the auditory analyzer for sound, and functions as a series of tuned resonators, somewhat similar to the keys of a piano. There are 16,500 little tiny hair cells in each cochlea which differentiate between sounds of different pitch that can be damaged by loud noise.
In general, sensory-neural hearing loss (SNHL) is not correctable or reversible by any known method of medical or surgical treatment. It does respond very, very well to all kinds of hearing aids, but the purpose of hearing conservation programs is to avoid reaching that point whenever possible.
There are hundreds of causes of sensory-neural hearing loss. The top three causes are aging and the hearing loss associated with aging, which is known as presbycusis. The second major cause is ototoxic medications. There are a number of medicines which, as a side effect, can cause damage to the hearing system. These do not have to be prescription drugs; the most common ototoxic medication is aspirin. The third factor is noise, both in industry and in a recreational environment.
Of these three major causes of hearing loss, we really have tremendous control over two of them. We can"t control the aging factor, but we can control, to a significant degree, the medications we use and our noise exposure. The general feeling is that noise in some areas in or out of the workplace accounts for more new cases of SNHL and tinnitus than all the other hundreds of factors combined. And that"s why I devoted a major part of my professional life to trying to alert people to the problem and what to do about it.
Do You Need a Program?
These are indications, in the absence of actual measurement, whether a noise problem exists in a workplace:
- Workers report tinnitus for various periods of time after they leave the workplace.
- Workers have difficulty communicating unless they scream at each other.
- When workers leave after an 8-hour day, they have difficulty hearing and understanding speech. Words like pit, kit, fit and sit all sound alike. This is known as difficulty in consonant discrimination and word recognition.
If any of those three factors exists, then there is a problem that needs to be explored and measured and a program instituted. A noise survey can document the need for an occupational hearing conservation program (OHCP).
A noise survey uses information gathered from two sources: sound level meters used to monitor the noise level in the workplace, and dosimeters worn by the workers to measure their personal exposure to workplace noise. If there"s a tremendous amount of noise in one part of the plant and there"s nobody there exposed to it, we don"t need to be too concerned.
In regulations governing workplace safety, the Occupational Safety and Health Administration (OSHA) has set what is called an "action level": the noise level at which an employer must take action to protect the hearing of his workers.
Action levels depend on the noise level and the time spent in the noisy environment. The action level which appears to impact the most workplaces is the exposure of workers to noise at a level of 85 dBA for a time-weighted average of 8 hours.
There are instances when noise levels higher than 85 dBA are allowed before an action level is reached, but as the noise level increases, the allowable exposure time decreases. That is known as a time/intensity trade-off. For example, exposures up to 115 dBA for a steady state of noise are allowed, but only for a total of 15 minutes in any 8-hour period.
Noise surveys must be conducted at least every two years, more often if a change in production, processes, equipment or controls increase action-level noise exposure to additional employees or if hearing protective devices have been rendered inadequate to meet OSHA requirements.
If an action level is reached, then OSHA requires that an employer implement an OHCP. The first step in any OHCP is to test the current hearing ability of employees.
A critical component of the OHCP is audiometric and audiological services. A company cannot force employees to take audiometric tests, but they must make them available.
Such testing tells us what the noise exposure is doing to the employee"s auditory system. It allows the people administering the OHCP, whether it"s a safety director or an occupational health professional or an audiologist, to evaluate a worker"s auditory status at the time of employment; the effect of workplace noise exposure on hearing; the effectiveness of various occupational hearing protective devices; and the status of a worker"s hearing when he or she retires or leaves employment.
There are many causes of hearing loss. In addition to noise, employees may suffer from tumors of the audiological nerves or viral or bacterial infections. Audiometric testing must be followed up by professional review and referral of workers showing significant problems to audiologists and otologists who can provide the necessary diagnostic and treatment services.
If hearing shifts are discovered among workers, or if action levels are reached, then employers must move to reduce noise levels and/or noise exposure. OSHA regulations tell employers to target three specific areas to reduce employee exposure to harmful sound levels.
Remember the Hierarchy
OSHA calls for engineering controls, administrative controls and (hearing) protective devices to prevent employee exposure to harmful noise levels.
An important step is instituting engineering controls, which can eliminate or reduce noise levels at the source. Such controls might include maintenance of machinery to eliminate excessive noise; mufflers for noisy equipment; noise baffles or equipment enclosures; placement of noisy machinery in areas of the facility which are away from employees; or "buying quiet" programs.
If engineering controls are not feasible or are considered prohibitively expensive, then administrative controls are the next step suggested by OSHA. Can scheduling changes be used to distribute noisy operations throughout the day instead of running them all at once, thereby minimizing their impact on the ambient noise level? Is it possible to limit the number of employees in the area where the loudest operations are being run?
If engineering and administrative controls together cannot control employee exposure to harmful noise levels, then employers are advised to provide hearing protection. This involves more than handing earplugs or ear- muffs to employees and telling them to wear them.
Employees should be given instructions on how to place hearing protection in or on the ears; how to care for their hearing protection and when to replace it; and how to reduce the potential for infection.
OSHA requires that employers provide workers with an education program once a year. In addition to nuts and bolts issues like care and storage of hearing protection, the program should describe all aspects of the hearing conservation program; the audiometric testing program; the dangers of exposure to noise; and describe the relationship of noise to hearing damage.
It is my experience that employees do not like wearing hearing protection. In fact, I think it is harder to convince employees to wear hearing protection than it is to get them to wear any other type of protective equipment.
A common employee complaint is that they cannot hear machine cues while wearing hearing protection and that if they use it, they won"t be able to listen for important sounds. There is an adjustment process, but if they stick with it for a couple of days, they will learn to recognize a new set of auditory cues from their machines.
It is the role of the occupational hearing conservation team, which might include an audiologist or other hearing specialist, the safety manager and or occupational health nurse, to sit down with employees and overcome the resistance to hearing protection. A thorough education program will address each issue raised by employees and convince them of the importance of hearing protection and of protecting their hearing from noise, both on the job and recreationally. If management supports the program, and employees see supervisors and managers wearing hearing protection, they are more likely to go along with it.
There are four "P"s" to remember about occupational hearing loss: It is permanent, painless, progressive and preventable. We can"t monitor what people do in their homes, but we can protect them in the workplace. The hope is that the education they receive in the workplace will be remembered once they get past the gates.
Recreational Noise Exposure
In the recreational environment, there are no controls. Nobody tells you what to do in the privacy in your home, and a lot of noise exposure occurs there.
There"s a T-shirt that says: "If it"s too loud, you"re too old," which says something about the attitude of young people toward their auditory systems. Adolescents and young people think they"re totally protected from the ravages of the rest of the world. They"ve said to me: "Who the hell are you to tell me what I can listen to or be exposed to in the privacy of my home when I"m not at work? I have the right to damage my hearing."
They do have that right. If we try to get too involved in trying to control nonworkplace noise, we are talking about an invasion of personal freedom.
That said, educating people about the dangers of noise and the importance of hearing conservation is more important than ever. A study conducted by David Lipscomb at the University of Tennessee indicated that elementary school children are already showing signs of noise-induced hearing loss.
Some 3.8 percent of sixth graders in one study failed a hearing test. That went up dramatically by the ninth grade, when 11 percent failed. Among college freshmen, 32.9 percent failed the test. These young people are entering the work force with retirement-age ears, making audiometric testing for new hires doubly important. Their hearing loss is not occupational, but their employers and safety managers need to be aware it exists.
I"ve had workers tell me: "My grandfather lost his hearing. My father lost his hearing. And I"m losing my hearing." Some treat it like a badge of honor.
These are people who, when they reach retirement age and are ready to enjoy themselves, won"t be able to hear the birds sing, their grandchildren play or the dialogue in a movie. Their ability to enjoy their lives will be severely impaired and that is nothing to brag about. But, at that point, it may be too late to reverse the process.
For information about the effects of noise on hearing; other causes of hearing loss; and the names of audiologists in your area, call the American Speech-Language-Hearing Association at (800)638-TALK.
Dr. Maurice H. Miller, Ph.D., received his doctorate from Columbia University in 1956. He is a professor of audiology and speech language pathology at New York University. He is chief audiologic consultant for the New York Department of Health and chairs the advisory committee for communicative disorders for the New York City Department of Health. He helped establish hearing conservation programs for the New York Times, Con Edison and the New York City Transit Authority; has served as a consultant for industry; and has testified as an expert witness.