Solving the Noise Induced Hearing Loss Problem by Asking the Right Questions: Part One of a Two Part Series
By Jeffrey Goldberg
As former U.S. Surgeon General William Stuart once said, “Calling noise a nuisance is like calling smog an inconvenience. Noise must be considered a hazard to the health of people everywhere.”
People have known this about noise and its effects on hearing for decades and yet noise-induced hearing loss (NIHL) remains epidemic in the workplaces of America. Why? Maybe as Bertrand Russell once noted, “In all affairs, it’s a healthy thing now and then to hang a question mark on the things you have long taken for granted.”
Noise Induced Hearing Loss Problem: Regulating Noise
Let’s examine why we haven’t made more progress eliminating NIHL. It starts with the history of noise as an industrial hazard. The history of hazardous noise is well defined. As early as the beginning of the last century, noise was recognized as an industrial hazard.
Though the measure of the noise was difficult to achieve at that time, because it wasn’t accurately measurable, NIHL was recognized but not quantified nor were any limits on exposure set. After a series of studies by the military and military sponsorship of civilian laboratories after World War II through the mid-1960s, 90 A-weighted decibels (dBA) was determined to definitely be a level above which actions to limit exposures were necessary. Therefore, 90 dBA was written into the U.S. Occupational Noise Standard in 1969 as part of the legislation as the permissible exposure limit (PEL). The Occupational Safety and Health Administration (OSHA) was directed to develop the rest of the regulation to define the steps necessary to form an effective hearing conservation program.
It is recognized that approximately 25 percent of workers whose daily exposure level (LEX,8h) is above 90 dBA will develop NIHL. Although the National Institute for Occupational Safety and Health (NIOSH) revised its own recommended exposure limit down from 90 to 85 dBA and further recommended a 3-dB exchange rate instead of the earlier 5-dB exchange rate in the legislation, today the 90 dBA PEL remains in the U.S. OSHA regulation.
OSHA set an action level of 85 dBA that includes exposed workers in a hearing conservation program and the use of hearing protection devices (HPDs) for those workers who had shown a change in hearing that could be attributed to noise exposure.
Noise Induced Hearing Loss Problem: Hearing Protection Devices Enter
There is more to the history of NIHL regulation in North America. In 1979 the U.S. Environmental Protection Agency issued a regulation that required HPD attenuation value be placed on the packaging of all HPDs sold in the United States. The same information appears in Canada, as the products sold in Canada are generally the same as the U.S. products. This “required HPD attenuation” is the noise reduction rating (NRR) that was to be used by audiologists and industrial hygienists to determine if the HPDs noise reduction would be adequate to reduce protected exposure levels to below the PEL.
The problem was that although audiologists and industrial hygienists now had this new NRR for selecting HPDs matched to noise exposures, workers still continued to lose their hearing. Study after study-comparing NRRs to attenuation actually achieved by those wearing the protection yielded considerable discrepancies. Finally, in 1994, a study published by Berger (Aearo, now 3M), Franks (NIOSH ret) and Lindgren (GN Netcom) compiled the data from 22 previous studies from the prior 20 years and conclusively showed that there was minimal relation between the NRR and the protection workers actually received(1). Further, studies of the HPD-using noise-exposed workers found that they continued to get NIHL. OSHA directed programs were merely documenting the development of NIHL, not preventing it. One union official referred to this as “audiometric voyeurism.”
There was a wide discrepancy between what laboratories determined for the NRR as the attenuation potential of a hearing protector and what users were achieving in practice. Why?
Noise Induced Hearing Loss Problem: Too Much Focus on Fit Tests
Set aside the consideration of whether the PEL/exchange-rate should be 90-dBA/5 dB or 85-dBA/3 dB and let’s look at other issues. For years the most prevalent thinking concerning the ineffectiveness of HPDs has been the problem of matching earplugs and earmuffs with a particular wearer’s ears. Once the best match HPDs had been selected, a wearer needed to be taught how to fit them properly. The industry began fit testing with the development of Fit Check in 1995(2). Three decades of pursuing this course has had relatively little effect on the problem. In fact Dr. Peter Rabinowitz, an associate professor in the Department of Environment and Occupational Health at the University of Washington, has studied one of the leading users of Fit Testing systems, Alcoa, for years. Dr. Rabinowitz saw no change in outcomes of Alcoa’s hearing conservation program as a result of fit testing. Maybe fitting the protector is not the entire problem.
Recent unpublished research conducted by a branch of the U.S. military has shown an inability to trigger preliminary hearing loss with even a minuscule amount of hearing protection. What does that mean? It might mean the weight we have been placing on matching attenuation to noise exposure is less important than we thought in preventing NIHL. Is it possible we’ve been asking ourselves the wrong question?
Instead of asking ourselves, “How do we get people to wear their hearing protection?” we should be asking, “Why aren’t people using their hearing protection to greatest effect?” Sadly, a panel of experts at the recent National Hearing Conservation Association conference observed that they were not aware of any research into the topic of the causes of NIHL either on going or planned.
In the next article, I’ll suggest some solutions to the NIHL conundrum. Look for the July issue of Workplace Safety for some innovative if scientifically unsupported ideas about solving the NIHL problem.
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