Coping with the NRR Change

How will the new EPA labeling changes for hearing protectors affect your Hearing Conservation Program?

For years, we’ve known many workers in the “real world” do not achieve the same amount of attenuation from hearing protectors as indicated on the EPA required Noise Reduction Rating (NRR) label. Numerous studies show the NRR greatly overestimates the amount of attenuation that workers get in the field. This problem is so widely accepted that OSHA recommends de-rating the NRR by 50 percent. However, studies also show that a one-size-fits-all de-rating is also inaccurate when compared to individual measures of attenuation. EPA will soon make an announcement proposing a major change in the required labeling and method of testing of hearing protection devices (HPDs).

Under EPA’s expected change, the new label will still show an NRR, but the “Rating” will be a two-number range rather than a single number. The proposed test protocol will continue to use standardized and controlled laboratory testing to indicate the capability of a given hearing protector for comparison. However, 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.

While EPA has not yet made an official announcement about the proposed change to the NRR, information about the change has been made public in a variety of public meetings, conferences, papers, and articles. Still, a recent Howard Leight poll of personal protective equipment distributors and industrial safety end users—including safety managers, industrial hygienists, and consultants—revealed only 26 percent of distributors and 32 percent of end users were aware of the pending change.

Now What?
Now that you’re aware of the change, how will it affect your Hearing Conservation Program? I’ve asked several safety managers who are aware of the new rating scheme,“ How will you determine which hearing protection to use?” The initial response is to use the lower number to ensure workers are protected. Use of the lower number, however, may underestimate the amount of attenuation provided to some workers and eliminate several hearing protectors with enough attenuation for workers exposed at the highest levels. You may create new safety hazards by overprotecting some workers so that they can’t hear important communications, warning signals, or other essential sounds. Use the higher number, and you may overestimate the attenuation for many workers, just as we currently do with the single-number NRR.

While the new rating system is expected to provide more information, it still does not predict the attenuation your workers achieve. For that, you need individual ear plug fit testing. There are now several methods available to do just that.

Ear plug fit testing can help to determine the actual attenuation workers receive from their ear plugs, 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 Personal Attenuation Rating (PAR) for the worker using his or her actual ear plugs in the actual work environment. This information helps safety managers determine whether workers are receiving optimal protection, require additional training on how to fit their ear plugs, or need to try a different model.

Just as one ear plug may not be appropriate for all workers, providing a variety of hearing loss prevention strategies can improve the overall efficacy of a Hearing Conservation Program. Individual and group analysis of PAR data can improve your program with more information and provide a route to a more personalized approach for each worker.

Variability in One Worker, One Ear Plug
Let’s look at a couple of examples of how varied the attenuation of one ear plug can be for a single worker. Figure 1 displays the PARs achieved by an individual subject with varied effectiveness over multiple fits of the same ear plug. These fit tests were accomplished over several months.

Several factors can affect the fit of an ear plug. These include, but are not limited to, ear anatomy, fitting method, and condition of the ear plug. By ear anatomy, I don’t mean that the ear changes shape; rather, each ear has its own unique shape, and it’s easier to fit an ear plug in some than in others. Fitting method actually covers many issues of fitting, such as whether the plug was prepared appropriately (roll down), whether the ear canal was opened adequately (reach over and pull), and whether the ear plug was placed at the appropriate depth in the canal.

Looking at the same data shown in Figure 1 another way, Figure 2 shows this same subject obtains very consistent protection for the right ear but more variable protection in the left ear. An alternative ear plug might be more consistent, but because the subject is now aware that the fit in the left ear is more variable, retraining that worker to simply pay more attention to the insertion and fit in that ear may be all that is required to ensure appropriate attenuation.

Variability of Many Users, One Ear Plug
Among many users, the variability is even greater. Figures 3 and 4 show data for two different foam ear plugs used and tested by multiple users. Each dot represents an individual PAR. Blue diamonds and red circles in a vertical line are left and right ear results for a single subject.

Notice that all of the subjects (Figure 3) using a foam ear plug with an NRR 33 obtained 10 dB or higher attenuation in both ears, and 85 percent of ears (46 of 54) achieved 20 dB or higher attenuation. The eight ears that achieved less than 20 dB of attenuation belong to six people. If more attenuation is required for this group of underachieving workers, additional fit training or an alternative ear plug, band, or ear muff should be provided.

The value of individual fit testing is obvious for documenting the level of noise reduction that a worker can achieve in the real world. The expected NRR labeling change brings attention to the variability of fit while still providing information about the capability of a given hearing protection device. Fit testing is also useful for one-on-one training in how to fit a hearing protector.

Additionally, simple analysis of all of the individual fit test results documents the need to offer a selection of ear plugs to workers. Comfort is the most important personal variable in selecting ear plugs. No matter how much attenuation an individual worker can achieve with a given ear plug, if he doesn’t wear it in hazardous noise, it provides 0 dB of attenuation.

Let’s look back at Figure 4 as group data for workers in a particular group. If the Time-Weighted Average (TWA) for these workers is 95 dBA and we’d like them to be protected down to 80 dBA, they will need to achieve at least 15 dB of attenuation. Nineteen of the 62 ears (30 percent) do not achieve adequate attenuation. Further one-on-one training should be conducted if these workers really like that ear plug, but because 14 workers of the 31 (45 percent) are not getting adequate attenuation for their high noise exposure, a different ear plug or double protection might be considered.

NIOSH reports that 76 percent of noise-exposed workers in the United States need no more than 10 dB of real attenuation, and 90 percent of U.S. workers need no more than 15 dB of attenuation.

Figure 5 shows subjects using a flanged ear plug. Individual results range from 0 dB to 54 dB of attenuation. Notice that only two subjects (three ears) have attenuation less than 10 dB, and only four subjects (six ears) have attenuation less than 15 dB.

Moving Forward
How will the change in NRR labels affect your company’s Hearing Conservation Program? It should provide an opportunity to look closely at the protection workers are getting from hazardous noise and to devise personalized protection strategies. Using the proposed change to implement individual fit testing will give you confidence you have an effective hearing loss prevention program.

References
1. “NRRs for Hearing Protectors: A Change is Coming,” by Brian Myers, Occupational Health & Safety, (June 01, 2008). www.ohsonline.com/Articles/2008/06/NRRs-for-Hearing-Protectors-AChange- is-Coming.aspx

2. “ANSI Standard for Measuring Attenuation Revised Ahead of Labeling Change,” Occupational Health & Safety, (Oct. 22, 2008). www. ohsonline.com/Articles/2008/10/22-ANSI-Standard-for- Measuring-Attenuation-Revised.aspx

3. “Fit Testing of Hearing Protectors,” by Brad Witt, Occupational Health & Safety, (Oct. 2, 2007. www.ohsonline.com/articles/ 2007/10/fit-testing-of-hearing-protectors.aspx

4. “Fit Testing Ear Plugs,” by Lee D. Hager, Occupational Health & Safety, (June 1, 2006). www.ohsonline.com/Articles/2006/06/Fit- Testing-Ear-Plugs.aspx

Additional Resources
1. “Inside the EPA’s Proposed Change to the Noise Reduction Rating” Brochure from Howard Leight. www.howardleight.com/best practices

2. “Hearing Protection-Emerging Trends: Individual Fit Testing,” OSHA/NHCA/NIOSH Alliance. www.hearingconservation.org/docs/ AllianceRecommendationForFitTesting_Final.pdf

This article originally appeared in the March 2009 issue of Occupational Health & Safety.

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