The State of Occupational Hearing Conservation

New technologies make the goal of OSHA's Hearing Conservation Amendment, the elimination of noise-induced hearing loss, very feasible.

• By Brad Witt
• Mar 01, 2011

When OSHA enacted its new Hearing Conservation Amendment in 1983, evidence at the time suggested it would be a strong force in eliminating noise-induced hearing loss (NIHL) from the workplace. But nearly 30 years later, reality has shown the high hopes to be unfounded. Occupational hearing loss continues to be called "the most common permanent and preventable occupational injury."¹ And the Bureau of Labor Statistics reports that, despite decades of legislation and intervention by employers, the average number of cases of recordable NIHL in industry has been about 25,000 per year for the past five years.²

The noise hazard remains the same in 2011, but now the landscape for hearing conservation is much different. Technology has fundamentally changed the way we measure the effectiveness of hearing protectors, and several long-awaited changes in regulations appear to be making headway toward enactment. Here is an update of issues and changes that have a major effect on hearing conservation efforts for your noise-exposed workers.

OSHA Rulemaking
At the core of OSHA's Hearing Conservation Amendment are two numbers: the 90 dB Permissible Exposure Limit (PEL) and the 5 dB Exchange Rate (ER). The PEL is OSHA's definition of maximum safe noise; any 8-hour exposure exceeding this level requires hearing protection for noise-exposed workers. The Exchange Rate describes the rate at which allowable exposure time is halved; a "5 dB exchange rate" means allowable exposure time is halved for every 5 dB increase in noise levels.

These numbers have their roots in the Walsh-Healey noise regulation of 1969. But the preponderance of scientific evidence since then suggests these levels are far too lax in their protective value. The 90 dB PEL and 5 dB ER still allow a substantial percentage of noise-exposed workers (23 to 32 percent, by NIOSH estimates) to suffer NIHL. This makes workers in the United States far less protected than their counterparts in Europe, Australia, or most other parts of the world.

Reducing the PEL by just 5 decibels (from 90 to 85 dB) would put OSHA in good company. Nearly every country in the world except the United States uses the more-protective 85 dB limit value, and even NIOSH and the U.S. Department of Defense define the 85 dB PEL and 3 dB ER as best practice. Professional organizations including the National Hearing Conservation Association and American Industrial Hygiene Association called upon OSHA last year to reduce the PEL from 90 to 85 dB and adjust the ER from 5 to 3 dB. Most noise dosimeters now allow users to select either 3 or 5 dB exchange rates.

While OSHA has resisted efforts to reopen or update its Hearing Conservation Amendment since its enactment in 1983, there is a growing expectation for a change to be made soon. This is due in part to the fact OSHA may be obligated to update its hearing conservation standard to accommodate a change in the way hearing protectors are rated by the Environmental Protection Agency.

EPA Rating
Although not directly related to the OSHA regulation, a second government agency --- EPA -- makes regulations significantly affecting hearing conservation. EPA oversees the labeling of hearing protectors and is responsible for defining the Noise Reduction Rating (NRR) that must appear on the packaging of all protectors sold in the United States.

In a long-awaited Notice of Proposed Rulemaking in 2009, EPA proposed a number of significant changes to the 30-year-old NRR. Foremost among these is replacing the old, single-number NRR with a two-number range defining the expected protection level for the 20th/80th percentiles of populations of wearers. Workers who are well trained in fitting their protectors would be expected to achieve the higher rating in the two-number range, while poorly trained users or those who have a poor fit would be expected to achieve the lower protection value.

A new NRR range is not the only change in EPA's proposal, which was working its way through public comment and review at the time of this writing. Other changes include new methods of rating active (electronic) hearing protectors, required periodic retesting, and additional information on the package to assist purchasers in their selection of appropriate ear plugs or ear muffs.

When will a final regulation be issued and the new rating numbers appear on packaging? It may be a few years. Knowing that regulatory change for hearing protection moves slowly (the last regulation endured 30 years), EPA is carefully building a consensus among manufacturers and end users. Changes to hearing protector packaging would likely appear during a phase-in period lasting two to five years.

Technology
In contrast to the drawn-out pace of regulatory changes such as those being considered by OSHA and EPA, the fast pace of technology has brought some valuable tools to hearing conservation programs. Foremost among these in 2011 are three technologies: fit testing, in-ear dosimetry, and intelligent protection devices.

Fit testing. All safety professionals are familiar with the concept of fit-testing for respirators, but most are not aware that fit testing of hearing protectors is also now available. Why fit test an ear plug? It has long been known that many workers in the "real world" do not achieve the same level of attenuation from hearing protectors as indicated on the EPA label. This problem is so widely accepted that OSHA recommends de-rating an NRR by 50 percent in certain situations. Merely having an ear plug in the ear is no guarantee of protection; in fact, many ear plugs worn by workers offer little or no protection due to poor fit or wrong selection of plug for that worker's ear.

Several fit-testing systems are now available, allowing employers to measure the attenuation of any ear plug. The result is a number called the Personal Attenuation Rating (PAR), which is the protection level of that particular ear plug worn by that particular worker. Fit testing provides immediate feedback whether a worker has a correct fit and can assist in immediately identifying and retraining workers with a poor fit. Fit testing also can be used to assist employers in selecting the right hearing protector for each employee from a variety of suitable choices.

Benefits of fit testing of hearing protectors were recently highlighted in a Best Practices Bulletin published by an alliance of OSHA, NIOSH, and National Hearing Conservation Association. The document³ endorses fit testing as a best practice in a hearing conservation program and cites the major benefits, including employee training, refitting of workers with a threshold shift, and as a helpful tool in selecting the best hearing protector for each worker.

In-Ear Dosimetry. For decades, dosimetry has been a valuable tool for safety professionals in measuring hazardous noise. Recent technology has literally brought dosimetry to a new level -- inside the ear.

Most conventional dosimetry measurements are taken with the microphone placed near the worker's ear, clipped to the collar or hard hat brim. This microphone placement monitors ambient noise but cannot tell us how much noise is reaching the eardrum of a worker when wearing hearing protectors.

Using in-ear dosimetry, the microphone pick-up of the dosimeter is placed under the ear plug (via a thru-hole) or under the ear muff (wired to the inside of the earcup). This in-ear microphone placement monitors the noise levels actually reaching the eardrum, under the protectors. At the end of the work shift, a poorly fitted ear plug generates a high noise dose on the dosimeter, while a properly fitted plug generates a very safe noise dose (under 50 percent of the criterion level).

An added benefit of in-ear dosimetry is its ability to monitor wear time. Noise-exposed workers frequently "cheat" in their use of hearing protectors for job-critical reasons: to communicate with co-workers, talk on their communication radios, or listen for maintenance sounds emanating from machinery. They remove the ear plugs for just a few minutes, thinking no harm is done. But the logarithmic decibel scale creates some devastating effects for workers who remove their hearing protectors in loud noise, even for just a few minutes. By removing a well-fitted ear plug offering 30 dB of protection, for example, noise levels reaching the eardrum increase by 1,000 times. In noise exposures, small intervals of no protection quickly negate large intervals of good protection.

In-ear dosimetry captures all of this information as it monitors the noise level at the eardrum, whether the ear plugs are fitted well, poorly, or not at all.

Intelligent Protection Devices. In a NIOSH study designed to find out why workers do not use their ear plugs more consistently,⁴ researchers reported that the predominant reasons are inability to communicate ("I can't hear my co-workers talking to me") and interference with job performance ("I can't hear the maintenance sounds from my machine or warning signals"). The ideal hearing protector should not block all sound (overprotection), but rather reduce hazardous noise levels while still allowing a worker to hear the sounds that are job-critical (two-way radio communications, signals, alarms).

New intelligent protection devices bridge the gap between total hearing protection and communication. Intelligent protection devices greatly improve the crucial stages of communication in noisy surroundings while protecting -- but not overprotecting -- workers from complex and damaging noise. They "enhance" workers' hearing where and when needed through Active Noise Cancellation (ANC), while adaptive talk-through technology significantly improves situational awareness without exposing workers to additional noise. Connected to two-way communication radios, intelligent protection devices now provide increased capability to workers in extreme environments.

Conclusion
Among occupational hazards, noise is an old and well-known adversary. While the hazard has not changed much in 30 years of regulation and intervention, 2011 now brings some powerful tools to aid in hearing conservation efforts. Pending regulatory updates, both at OSHA and EPA, are intended to reduce the damage risk of noise-exposed workers in the United States by more than 50 percent, and new technologies including fit testing, in-ear dosimetry, and intelligent protection now make the goal of OSHA's Hearing Conservation Amendment very feasible: the elimination of noise-induced hearing loss.

This article originally appeared in the March 2011 issue of Occupational Health & Safety.