Across Acoustics
Across Acoustics
Quiet Down! Lowering the Recommended Occupational Noise Exposure Limit
The National Institute for Occupational Safety and Health’s (NIOSH) recommended exposure limit for occupational noise is often cited as the upper limit for loudness in all situations-- but that's not actually the case. Worse, the limit may not even fit modern ears, which face a barrage of loud sound in and out of the workplace, starting at an early age. In this episode, we talk to Daniel Fink of Quiet Coalition about how NIOSH's recommended exposure limit for occupational noise impacts even those of us in quiet workplaces, and why the limit needs to be revised downwards.
Associated paper: Daniel Fink. "The recommended exposure limit for occupational noise needs to be revised downwards." Proc. Mtgs. Acoust. 50, 040002 (2022). https://doi.org/10.1121/2.0001729.
Read more from Proceedings of Meetings on Acoustics (POMA).
Learn more about Acoustical Society of America Publications.
Music Credit: Min 2019 by minwbu from Pixabay. https://pixabay.com/?utm_source=link-attribution&utm_medium=referral&utm_campaign=music&utm_content=1022
Kat Setzer 00:06
Welcome to Across Acoustics, the official podcast of the Acoustical Society of America's publications office. On this podcast, we will highlight research from our four publications. I'm your host, Kat Setzer, editorial associate for the ASA.
Kat Setzer 00:25
Today I'm talking with Daniel Fink, whose article, "The recommended exposure limit for occupational noise needs to be revised downwards," appeared in POMA last year and is based off a presentation he gave at the 183rd ASA meeting. Thanks for taking the time to speak with me today, Dan, how are you?
Dan Fink 00:40
I'm fine.
Kat Setzer 00:42
So first, tell us a bit about your research background.
Dan Fink 00:46
Well, I don't have a research background in acoustics, or audiology or otolaryngology. It's really a background in health services research a long time ago. I spent my career, though, in medical management, not in research. And my noise research, in quotes, such that it is, is really literature research. My three secret powers, if you will, in doing my research are first that I have skin in the game; I developed tinnitus and hyperacusis after one time exposure to loud noise at a New Year's Eve dinner on December 31, 2007. So my noise activities aren't just an academic exercise, but they're really a personal quest to make the world a quieter place. The second secret power is that I was trained in school always to go back to the original source, especially if one had a question, and that has allowed me to see things that perhaps others haven't seen. The third secret power is that I am a generalist both in my clinical training- I’m trained as a general internist- and in my management training, which was a specialty in health care administration, not in finance, or accounting, or marketing, so I’ve always had to figure out what information I need to make clinical or management decisions. I’m not in any disciplinary silo- acoustics, audiology, or ENT- so I can make connections between and among information from these disciplines and others, including public health
Kat Setzer 02:24
Okay, yeah, so it sounds like you're kind of in a unique position. So what is occupational noise?
Dan Fink 02:31
Occupational noise is exactly what it sounds like: noise that is occurring at work. As an aside, not all occupational noise exposure is in factories, or from operating heavy construction equipment. In a study done in Sweden, Rick Neitzel, who is based at the University of Michigan here in the States, found that preschool teachers had higher noise exposure levels at work than aircraft maintenance workers.
Kat Setzer 03:01
Oh, my goodness. Yeah, that makes sense. Walking into my son's daycare, I would believe that.
Dan Fink 03:08
Let me expand on that a little bit. In terms of occupational noise exposure, the standard exposure measurement is for eight hours a day, 50 weeks a year for a 40-year work history. So when later on, perhaps we'll be talking about noise exposure for the public. The public is not exposed to continuous noise, eight hours a day, 50 weeks a year for 40 years. But the occupational noise exposure recommended level of 85 dB A-weighted decibels does not protect workers from hearing loss and it certainly isn't safe for the public.
Kat Setzer 03:53
Okay, got it. So let's get into that a little bit. What is the National Institute for Occupational Safety and Health recommended exposure limit for occupational noise? It sounds like you just mentioned 85 dB. And how did NIOSH decide on this limit?
Dan Fink 04:09
That is detailed in two monographs published by NIOSH, the first in 1972 and then an updated monograph in 1998. So just over 25 years ago, what they did was look at a wide variety of studies of occupational noise exposure and hearing loss. After reviewing the literature, they calculated that the safe noise exposure level for occupational noise was 85 A-weighted decibels (dBA). A-weighting, adjusts unweighted sound measurements to approximate the frequencies heard in human speech. The reason A-weighting is used in occupational health and safety is that the compensable workplace injury is the inability to hear speech as measured by pure-tone audiometry at 500 Hz, and 1, 2, 4, and optionally 6 kHz. We’ll come back to that later on. More importantly, the noise exposure level from NIOSH Recommended Exposure Limit does not prevent hearing loss in exposed workers. At 85 dBA, approximately 8% of workers are at risk of developing excess material hearing loss. The Occupational Safety and Health Administration (OSHA) permissible exposure level, limit, of 90 dBA allows a 25% risk of excess hearing loss.
Kat Setzer 05:33
Okay, so your concern is non-occupational noise. What is that? Why should it affect occupational noise limits?
Dan Fink 05:42
Now, non-occupational noise is all noise exposure occurring out of work. And only a few decades ago, noise exposure outside of work was very limited-- maybe musicians, garage band drummers, for example, or electric guitar players, hunters, woodworkers. And noise exposure really didn't begin until one started work in a noisy factory. That has changed. Non-occupational noise exposure occurs beginning early in childhood. I don't know if your child uses headphones while watching a video on an iPad or equivalent device but--
Kat Setzer 06:29
Not yet.
Dan Fink 06:30
Not yet. But he probably will. A lot of children do beginning as early at age three, if not earlier. And then beginning somewhere age nine to 11, kids start listening to music on their smartphones. By the teen years virtually all teens are listening to music or podcasts many hours a day at very high volumes. And even for workers, NIOSH assumed that workers had quiet when not at work. And that's no longer true. And we'll talk about that in a little bit.
Kat Setzer 07:13
Okay, okay. Yeah, that makes a lot of sense. On average, how much non-occupational noise does a person experience during the day?
Dan Fink 07:21
That's an impossible question to answer. Every individual’s daily and average annual average noise exposure vary widely. For example, if one goes to a sports event, on that day, the non-occupational noise exposure may be very large. If a person lives in New York City or San Francisco or internationally in London or Paris, and takes the subway in New York, BART in San Francisco, the Tube in London or the Metro in Paris, that person gets a lot of non-occupational noise exposure en route to a very quiet office job. So it really varies. but there are studies which are referenced in the article in a variety of countries using a variety of methods, including estimates and direct measurement with noise dosimeters, that pretty much show that all people living in industrialized countries get too much noise exposure every day.
Kat Setzer 08:14
Mmmmkay. So you also talk about some other reasons you think that the recommended exposure limit for occupational noise should be revised. What are those reasons? And why are they so important to consider?
Dan Fink 08:25
As I listed in the paper in Proceedings of Meetings on Acoustics, there are at least four reasons why the NIOSH recommended exposure level for occupational noise needs to be revised. The first is that, as I noted above, NIOSH assumed workers were in quiet when not at work, evenings, nights and weekends, and that appears to be quiet of about 60 A-weighted decibels. That’s something no longer true.
Dan Fink 08:56
Second, the NIOSH calculations were developed in the 1970s when noise exposure didn't begin until one started work in the noisy factory or operating heavy equipment. And children certainly weren't exposed to loud noise. Also, the average life expectancy was only 65 to 67 years. So any concern about hearing loss in really old people wasn't an issue. Lifetime noise exposure now has to be considered within occupational noise exposure calculations to prevent hearing loss in retirement years.
Dan Fink 09:38
The third reason is that NIOSH measured hearing using limited frequency pure tone audiometry from 500 Hz to 4 or 6 kHz.. More sensitive measures of auditory damage, as discussed in the article, would undoubtedly find more auditory damage much earlier. These methods would include things like extended-frequency audiometry to 12 kilohertz or even 20 kilohertz, questions about speech in noise difficulty-- the difficulty hearing one conversation among many in a noisy restaurant, for example. There are actually formal speech-in-noise testing protocols to quantify the amount of speech-in-noise difficulty. Questions about noise sensitivity or hyperacusis: Does loud noise bother you more than other people? These and some research methods would all find much more prevalent auditory damage much earlier than limited frequency pure-tone audiometry.
Dan Fink 10:38
And the final reason, the fourth reason, is that NIOSH used a 15-decibel hearing threshold level as normal. In other words, one could have a 15-decibel hearing loss as normal, but that's actually enough to cause a speech-in-noise difficulty. And the actual normal hearing is zero hearing thresholds, that is zero decibel hearing loss.
Kat Setzer 11:02
Right. Right. That would make sense. Yeah. Okay. So how would updating the guidelines for occupational noise affect the noise exposure of those of us in less noisy jobs?
Dan Fink 11:13
You know, I'm actually not sure if it would affect those in less noisy jobs. Because in the office setting, I don't think people are exposed to 85 dBA, eight hours a day, 40 hours a week, 50 weeks a year for 40 years.
Kat Setzer 11:32
Right.
Dan Fink 11:33
But I think the main impact would be on advice for the public. Despite an editorial I published, now seven years ago, in January 2017, the American Journal of Public Health, titled "What is the safe noise level for the public?" audiologists especially continue to cite the NIOSH 85 dBA recommended exposure level with or without A weighting as safe for the public, or sometimes mentioned as the noise level above which auditory damage begins. I did a Google search on this recently using the search word "audiologists 85 dB," and that yielded 8.2 million hits in 0.32 seconds.
Kat Setzer 12:23
Oh my.
Dan Fink 12:24
The president of the American Academy of Audiology Bopanna Ballachanda, PhD, was quoted in the article about noisy toys in USA Today in December, before the Christmas holiday, as having said federal guidelines acknowledge 85 decibels as the level at which noise can cause damage to a person's hearing if they're exposed to the sound for extended periods of time. And then in a direct quote in the article, which again discusses noisy toys. Bellachanda goes on to say, "If the the toys come in at five decibels or higher when holding your phone microphone near them, like a child would hold the toy near their own ear, don't buy them. It isn't work worth the risk."
Dan Fink 13:09
And so that's just not true. For starters, there are no evidence-based safe noise-exposure levels for children; those have never been calculated. One can't rationally extrapolate noise exposure studies done on healthy workers. By definition, if you're at work, you're healthier than somebody who's sick in bed or in the hospital. You can't extrapolate those to children and their delicate developing auditory systems, which don't reach full development to the late teen years or even early 20s. And the NIOSH recommended exposure level doesn't prevent hearing loss. So the main impact, I think, of lowering the NIOSH recommended exposure level wouldn't be on workers in noisy occupations, and certainly not on office workers like yourself and your colleagues at the Acoustical Society of America office, but would be on the general public, because even if it was only revised by NIOSH to 80 dBA, or better yet 75 dBA, then audiologists and others, citing the NIOSH REL as safe for the public would be citing a lower level.
Dan Fink 14:27
Let me explain a little bit more. 85 dBA isn’t a safe noise level for the public. The World Health Organization recommends only 1 hour exposure at 85 dBA to prevent hearing loss. But the real problems with 85 dBA are that it’s human nature to always want more- we want more food, more alcohol, more possessions, more money, more speed when driving a car, more noise when listening to music or going to a concert. And most members of the American public are also innumerate. They don’t understand what a logarithmic scale is, and they don’t know that the decibel scale is logarithmic. So they think, “Gee, if 85 dB is safe, 20% more is only 100 dB and that can’t be too bad.” Unfortunately, it is pretty bad. The OSHA Permissible Exposure Limit for 100 dBA noise is only 15 minutes to prevent noise-induced hearing loss, even using NIOSH’s relatively insensitive measures of hearing loss. There’s no easy conversion factor from unweighted decibels to dBA, but my experience using the NIOSH smartphone sound meter app is that dBA measurements are about 5-7 dB lower than unweighted measurements. So if the advice is for 85 dB, a 3 decibel increase indicates a doubling of sound energy, due to the logarithmic nature of the decibel scale, and 100 dB is a much greater noise exposure than 85 dBA.
Kat Setzer 16:18
Got it, got it. So at least if the public would get be guided towards a quieter existence, essentially, if NIOSH had a lower limit, right.
Dan Fink 16:28
Yes. In fact, I have a confession to make. I'm really not interested in occupational noise. At least workers have the NIOSH recommendations, the OSHA permissible exposure levels, a workers compensation system to compensate them for hearing loss suffered at work, including hearing health care visits and payment for hearing aids if it's shown that the hearing loss is connected to noise exposure at work, but the American public has nothing, not even guidelines, not even recommendations, certainly no standards for non-occupational noise exposure or noise exposure for the public. And the only protection we have is the tort law system, but proving that one suffered hearing loss or develop tinnitus, or hyperacusis after one time loud noise exposure when there is no previous record of any history of a visit to a doctor complaining of auditory health, and most doctors not asking questions about how's your hearing and documenting that in the chart In a routine office visit, it would be hard to prove in a court of law that one develop auditory difficulties after non-occupational noise exposure. So I hoped that revised lower NIOSH occupational noise exposure recommendations will lead to lower noise exposure guidance for the public. That's my real goal.
Kat Setzer 18:02
That makes a lot of sense. Do you have any closing thoughts?
Dan Fink 18:06
Yes. I'm not certain if the younger generation knows who Helen Keller was; she was born blind and deaf or develop those conditions after an infection I forget which. Anyway, she was taught to communicate and she is quoted as having said (even though she apparently didn't say it), that "Blindness separates people from things, deafness separates them from other people." Hearing has been called the social sense. When asked, "What is the worst thing that could happen to you, other than being killed?", most people say going blind. That's because people can read, they can navigate the environment on their own. I think hearing is undervalued as one of the five senses.
Dan Fink 18:51
Also, hearing loss is considered a part of normal aging, just like the need to wear reading glasses in midlife. And people don't think there's anything they can do about hearing loss. But that's not true. CDC states that noise-induced hearing loss is the only form of hearing loss that's 100% preventable. Based on studies done largely in the 1960s and isolated populationsnot exposed to noise, largely in Africa, the literature shows that without noise exposure, auditory sensitivity hearing is preserved in the old age.
Dan Fink 19:31
In the 1950s, people were advised to get a healthy tan. I certainly spent a lot of time in the sun as a boy. Now dermatologists recommend avoiding sun exposure. This line always gets a laugh at the meetings when I say it: A dermatologist once told me if you want to see what your skin should look like all your life, look at your butt. Unless you're a nudist, it hasn't been exposed to the sun! And just as deep wrinkles, age spots and skin cancers aren't part of normal aging (in fact that L'Oreal cosmetics company has actually studied this and published a paper about it in the Journal of Clinical Investigative Dermatology), hearing loss is not part of normal aging, but largely represents noise exposure.
Dan Fink 20:16
Avoid loud noise and your ears should last an entire lifetime. I like to say, if it sounds loud, it's too loud, and your auditory health is at risk. Avoid loud noise, turn down the volume, leave the noisy environment, or use hearing protection. A quieter world will be better and a healthier world for all.
Kat Setzer 20:37
Yeah, I feel like I could agree with that. You know before your article, I don't think I realized how cumulative noise exposure is and how, you know, all that loud music that I listened to as a teenager, although it wasn't necessarily on headphones, could impact my hearing today. It really does make sense that even though those of us who aren't in traditionally noisy work environments can be impacted by the NIOSH noise limits. Thank you for taking the time to speak with me today about this important issue.
Dan Fink 21:03
You're most welcome. Thank you for inviting me.
Kat Setzer 21:05
Yeah, you're welcome.
Kat Setzer 21:08
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