Hearing Loss is Preventable

Technology advances worker ability to fit protection properly

By Theresa Y. Schulz, PhD., LtCol USAF (ret)

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Noise-induced hearing loss is an often neglected occupational illness. According to the National Institute for Occupational Safety and Health (NIOSH), noise-induced hearing loss (NIHL) is the most common occupational injury in the United States, with more than 22 million American workers exposed to hazardous noise on a daily basis and approximately 8 million who suffer from occupational hearing loss. Workers’ compensation for hearing loss varies widely by jurisdiction. In the United States, maximum awards for occupational hearing loss range from less than $10,000 to as much as $150,000 over and above replacement of lost wages.

Despite its prevalence and potential cost, occupational hearing loss is a silent illness (no pun intended). Hearing loss is usually not obvious to an individual until it has progressed to a handicapping level. Ringing in the ears, known as tinnitus, is an earlier symptom but is often ignored. Although noise-induced hearing loss is progressive, cumulative and can be permanent, the good news is that it is also preventable.

Strategies to Stop Hearing Loss
Hearing loss prevention's best strategy is to reduce noise exposure: minimize the hazard through engineering controls; limit worker exposure time in and around the hazard; and use hearing protectors (earplugs and earmuffs) when exposed to loud noise.

Engineering controls can be as simple as equipment maintenance to decrease “rattling parts” or can involve expensive modifications to the environment or equipment. In some cases, even successful noise controls cannot achieve safe exposure levels. Limiting worker exposure time (called administrative controls) is sometimes difficult due to productivity demands.

Hearing Protectors and NRR
The burden often falls to personal protective equipment (hearing protectors) to manage the hazardous exposure. For years, we've known that many workers in the "real world" do not achieve the same amount of attenuation (reduction of noise) from hearing protectors as shown on the noise reduction rating (NRR) label required by the Environmental Protection Agency (EPA). The EPA is planning a major change in the required labeling and method of testing of hearing protection devices (HPD).

Under the EPA's proposed change, the new label will still show a NRR, but the "rating" will be a two-number range rather than a single number. The range will give some indication of how much attenuation most minimally trained users (the lower number) and highly motivated, trained users (the higher number) might be expected to achieve.

Although the new label for hearing protectors proposes more realistic information, if employers rely solely on the NRR to determine whether a worker is protected, how confident will they be that each worker is really protected from the hazardous noise? What's needed is a way to truly know whether employees are protected from hazardous noise.

Training Offers Better Fit and Measurement
There are two new innovations in hearing conservation technology that can provide answers: individual earplug fit-testing and in-ear dosimetry.

There are now several commercially available ways to determine individual attenuation or "personal attenuation rating” (PAR). The OSHA/National Hearing Conservation Association/NIOSH Alliance has provided a summary of this emerging technology, and suggests several ways to use fit-testing in an effective hearing conservation program (www.hearingconservation.org).

Earplug fit-testing can help determine the actual attenuation workers receive from their earplugs, taking much of the guesswork out of the hearing protector selection process. Fit testing provides both safety managers and workers the information they need to select hearing protection based on a PAR for the worker using his or her actual earplugs in their actual work environment. This information helps safety managers determine whether workers are receiving optimal protection, require additional training on how to fit their earplugs, or need to try a different model.

Not only does the PAR document the amount of attenuation provided for a particular earplug for each worker, studies have shown that one-on-one training (as opposed to group instruction) is the most effective method for teaching proper fit of hearing protection. One of the main values of fit-testing hearing protectors is to train the user and provide feedback as to the level of attenuation they get with a given hearing protector. By using a fit-testing system, end users see a number associated with the amount of attenuation provided in each ear. That gives the worker immediate feedback about the fit. After some training (about 2 minutes) and a fit test (about 3 minutes) workers can tell whether they have a good fit or not.

Worker efficacy in predicting the attenuation level of a given fit after a short training session.

In a study of 17 construction workers, the volunteers were allowed to fit their own earplugs and then complete checks with the fit-testing system about two to four times until they felt confident in estimating the attenuation provided by a given fit. As a final step, they again fit their own plugs and performed their final check and were asked to report the level of attenuation they thought they were getting by 5-dB categories. Categories were “less then 10 dB,” “10-15 dB,” “15-20 dB,” “20-25 dB,” “more than 25 dB.” Figure 1 shows that for 19 of the 34 ears, the user predicted their attenuation in the correct 5-dB category. Only four individuals (in one ear) were off by more than one category in their self assessment of the amount of attenuation and three of those were consistently achieving adequate attenuation. With improved self-efficacy in fitting hearing protection, it is possible that workers will be better protected.

Traditional personal dosimetry measures a worker's ambient noise exposure level, but does not provide any information on individual noise dose or exposure levels when wearing HPDs. However, recent advances now make it feasible to measure the protected noise exposure level provided by earplugs or earmuffs. This new style of in-ear dosimetry records daily noise exposure levels for the wearer under their hearing protectors to provide an accurate, complete measurement of personal noise dose.

By measuring and recording a worker's actual noise dose, with and without protection during a work shift, in-ear dosimetry provides real-time monitoring and alerts users when their individual noise dose approaches or exceeds safe limits. This not only helps workers to better identify when and where they must wear hearing protection, it also allows safety managers to more efficiently deploy workers, especially in extreme noise where dual protection is often required. At-risk or workers with a documented hearing loss also benefit from the real-time monitoring; through continuous monitoring, workers can become more aware of their noise exposures and take actions on their own to prevent further noise exposure. In one case, a facility with a significant number of noise-exposed workers was able to stop further progression of NIHL through continuous monitoring with in-ear dosimetry.

Conclusion
Whether covered by OSHA or other regulatory statute, hearing protection is part of an effective hearing loss prevention program, so it makes sense (and cents) to ensure that hearing protection is effective.

WP

Dr. Theresa Y. Schulz, LtCol, USAF (ret), recently joined Sperian Hearing Protection, LLC, as Hearing Conservation Manager. She began her career as an audiologist in the military and since her retirement in 2004, has worked in a number of positions, including team leader of the Hearing Loss Prevention Branch at NIOSH. She is a Certified Professional Supervisor for Audiometric Monitoring (CPS/A), a past president of the National Hearing Conservation Association, a certified member of the American Speech-Language-Hearing Association, and a fellow in the American Academy of Audiology.

Useful link related to this article:
The Silent Hazard: Stop the Creeping Threat of Hearing Loss
http://workplacetrainingcenter.com/Prod-1516.aspx