Veteranclaims’s Blog

October 5, 2012

Acoustic Trauma v. Noise Induced Hearing Loss, Position of American College of Occupational and Environmental Medicine

In Memorandum Decision, Study v. Shinseki, No. 11-2475, October 2012, VA relied upon the 2002-03 position of the American College of Occupational and Environmental Medicine to assert that acoustic trauma is immediate and not progressive” and that “hearing loss due to noise “does not progress beyond age-related changes once the exposure to noise is discontinued”.
see article below.

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Excerpts from American College of Occupational and Environmental Medicine Position Paper:
“Occupational acoustic trauma is a sudden change in hearing as a result of a single exposure to a sudden burst of sound, such as an explosive blast.”
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“The diagnosis of noise-induced hearing loss is made clinically by a medical professional and should include a study of the noise exposure history.”
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“Co-exposure to ototoxic agents such as solvents, heavy metals, and tobacco smoke may act in synergy with noise to cause hearing loss.9”
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“the loss of hearing due to noise is not reversible”
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“A 10 dB confirmed threshold shift from baseline in pure tone average at 2000, 3000, and 4000 Hz (OSHA standard threshold shift), while not necessarily resulting in significant impairment, is an important early indicator of permanent hearing loss.”
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Individuals with noise-induced hearing loss may experience significant morbidity due to hearing loss, concomitant tinnitus, and impaired speech discrimination. On the job, such hearing loss can impact worker communication and safety. Other conditions associated with hearing loss may be depression, social isolation,12 and increased risk of accidents.13
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The organization that represents occupational physicians recently issued a position statement on noise induced hearing loss. This statement was developed by the ACOEM Noise and Hearing Conservation Committee and peer-reviewed by ACOEM.

Most of the statement is reprinted here. The full statement is available at their web-site:
http://www.acoem.org/guidelines/article.asp?ID=53

Definition
Occupational noise-induced hearing loss, as opposed to occupational acoustic trauma, is hearing loss that develops slowly over a long period of time (several years) as the result of exposure to continuous or
intermittent loud noise. Occupational acoustic trauma is a sudden change in hearing as a result of a single exposure to a sudden burst of sound, such as an explosive blast.
The diagnosis of noise-induced hearing loss is made clinically by a medical professional and should include a study of the noise exposure history.

Characteristics
The principal characteristics of occupational noise-induced hearing loss are as follows:
• It is always sensorineural, affecting hair cells in the inner ear.
• Since most noise exposures are symmetric, the hearing loss is typically bilateral.
• Typically, the first sign of hearing loss due to noise exposure is a “notching” of the audiogram at 3000, 4000, or 6000 Hz, with recovery at 8000 Hertz (Hz).2 The exact location of the notch depends on multiple factors including the frequency of the damaging noise and the length of the ear canal.
Therefore, in early noise-induced hearing loss, the average hearing thresholds at 500, 1000, and 2000 Hz are better than the average at 3000, 4000, and 6000, and the hearing level at 8000 Hz is usually better than the deepest part of the “notch.” This “notching” is in contrast to age-related
hearing loss, which also produces high frequency hearing loss, but in a down-sloping pattern without recovery at 8000 Hz.3
• Noise exposure alone usually does not produce a loss greater than 75 decibels (dB) in high frequencies, and 40 dB in lower frequencies. However, individuals with superimposed age-related losses may have hearing threshold levels in excess of these values.
The rate of hearing loss due to chronic noise exposure is greatest during the first 10-15 years of exposure, and decreases as the hearing threshold increases. This is in contrast to age-related loss, which accelerates over time.
• Most scientific evidence indicates that previously noise-exposed ears are not more sensitive to future noise exposure and that hearing loss due to noise does not progress (in excess of what would be expected from the addition of age-related threshold shifts) once the exposure to noise is
discontinued.4

Volume 5, No. 4 Winter 2002-2003
Position Statement of the American College of Position Statement of the American College of Position Statement of the American College of
Occupational and Environmental Medicine (ACOEM) on Noise Noise Noise-Induced Hearing Loss Induced Hearing Loss

Induced Hearing Loss
• In obtaining a history of noise exposure, the clinician should keep in mind that the risk of noise induced hearing loss is considered to increase significantly with chronic exposures above 85 dBA for an 8-hour time-weighted average (TWA). In general, continuous noise exposure over the years is more damaging than interrupted exposure to noise which permits the ear to have a rest period.
However, short exposures to very high levels of noise in occupations such as construction or firefighting may produce significant loss,5,6 and measures to estimate the health effects of such intermittent noise are lacking. When the noise exposure history indicates the use of hearing
protective devices, the clinician should also keep in mind that the real world attenuation provided by hearing protectors may vary widely between individuals.7

Additional Considerations in the Evaluation of the Worker with Suspected Noise-induced Hearing Loss

Clinicians evaluating cases of possible noise-induced hearing loss should keep in mind the following clinical concerns:
• While noise-induced hearing loss is typically bilateral, asymmetric sources of noise such as sirens or gunshots can produce asymmetric loss. When evaluating cases of asymmetric loss, referral to rule out a retro-cochlear lesion is first warranted before attributing the loss to noise.
Co-exposure to ototoxic agents such as solvents, heavy metals, and tobacco smoke may act in synergy with noise to cause hearing loss.9 However, the role of such cofactors – as well as the role of cardiovascular disease, diabetes, and neurodegenerative diseases – remains poorly understood.
Individual susceptibility to the auditory effects of noise varies widely, but the biological basis for this also remains unclear.10
• Over a period of years of prolonged noise exposure, hearing loss due to noise expands to involve additional frequencies. This, together with the effects of aging, may reduce the prominence of the “notch.” Therefore, in older individuals, the effects of noise may be difficult to distinguish from presbycusis without access to previous audiograms.11
Individuals with noise-induced hearing loss may experience significant morbidity due to hearing loss, concomitant tinnitus, and impaired speech discrimination. On the job, such hearing loss can impact worker communication and safety. Other conditions associated with hearing loss may be depression, social isolation,12 and increased risk of accidents.13 Workers with evidence of hearing loss require an individualized approach that takes into account the need to communicate safely and effectively, and the need for protection from additional damage due to noise.
• Since the loss of hearing due to noise is not reversible, early detection and intervention is critical to improving prevention of this condition. A 10 dB confirmed threshold shift from baseline in pure tone average at 2000, 3000, and 4000 Hz (OSHA standard threshold shift), while not necessarily resulting in significant impairment, is an important early indicator of permanent hearing loss.
Therefore, individuals in hearing conservation programs who exhibit such 10 dB threshold shifts on serial audiometric testing should be carefully evaluated and counseled regarding avoidance of noise and correct use of personal hearing protection.
• Age correction of audiograms is a method of age standardization allowing comparisons of hearing loss rates between populations. Applying age correction to the surveillance audiograms of a noise exposed population results in fewer confirmed 10 dB shifts being reported. Therefore, when applying age correction to the audiometric results of an individual who has experienced a threshold shift, the clinician should consider whether in that individual a preventable noise component of hearing loss is playing a role.

Research Priorities
In an effort to shed light on some of the gaps in the current knowledge, ACOEM proposes the establishment of a research agenda for noise-induced hearing loss, and recommends research be conducted in the following areas:
• the relationship between specific noise exposures and risk of hearing loss, including impact noise, fluctuating noise, and noise at different frequencies, in order to improve protective exposure
– 2 –
guidelines for noise exposure;
• early indicators of hearing loss, including the use of emerging audiologic technology such as otoacoustic emissions;
• the role of cofactors in hearing loss, including solvents, metals, vibration, heat, and carbon monoxide;
• the biology of noise-induced hearing loss, including the role of antioxidant compounds in prevention and recovery and whether noise damage continues to progress after noise exposure stops;
• individual susceptibility to noise-induced hearing loss, including the molecular basis for such susceptibility;
• the relationship of noise-induced hearing loss to other medical conditions, including cardiovascular disease, diabetes, and neurodegenerative diseases including age-related hearing loss;
• the impact of noise-induced hearing loss on individuals and their families and the development of rehabilitation strategies to maximize function and minimize disability;
• the behavioral aspects of noise avoidance and protection, including the effectiveness of training programs for hearing loss prevention.
Evaluation of the Effectiveness of a Hearing Conservation Program
To date, there is no universally accepted method of evaluating the effectiveness of a hearing conservation program. Hearing conservation programs include aspects of administrative controls, engineering controls,
audiometric surveillance, and training. Occupational physicians can actively participate with employers in improving all these aspects of hearing conservation programs through ongoing evaluation of program
outcomes and processes.

References
1ACOM Noise and Hearing Conservation Committee. Occupational noise-induced hearing loss. JOM. 1989;31(12):996.
2McBride DI, Williams S. Audiometric notch as a sign of noise induced hearing loss. Occup Environ Med. 2001;58(1):46-51.
3
Coles RR, Lutman ME, Buffin JT. Guidelines on the diagnosis of noise-induced hearing loss for medicolegal purposes. Clini
Otolaryngology Allied Sci. 2000;25(4):264-73.
4
Rosenhall U, Pedersen K, Svanborg A. Presbycusis and noise-induced hearing loss. Ear & Hearing. 1990;11(4):257-63.
5
Lusk SL, Kerr MJ, Kauffman SA. Use of hearing protection and perceptions of noise exposure and hearing loss among
construction workers. Amer Indust Hygiene Asso J. 1998;59(7):466-70.
6Tubbs RL. Noise and hearing loss in firefighting. Occup Med. 1995;10(4):843-56.
7
Berger EH, et al. Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection
devices. Part III. The validity of using subject-fit data. J Acoustical Soc Amer. 1998;103(2):665-72.
8
OSHA. 1910.95 CFR Occupational Noise Exposure: Hearing Conservation Amendment (Final Rule). Fed Reg. 1983;48:9738-
9785.
9
Morata TC. Assessing occupational hearing loss: beyond noise exposures. Scand Audiology. Supplementum. 1998;48:111-6.
10Ward WD. Endogenous factors related to susceptibility to damage from noise. Occup Med. 1995;10(3):561-75.
11Consensus conference. Noise and hearing loss. JAMA. 1990;263(23):3185-90.
12Hetu R, Getty L, Quoc HT. Impact of occupational hearing loss on the lives of workers. Occup Med. 1995;10(3):495-512.
13Zwerling C, et al., Occupational injuries among older workers with visual, auditory, and other impairments. A validation study.
JOEM. 1998;40(8):720-3.
– 3 –
Advisory Board
Phyllis Berryman, RN
Michigan Occupational
Nurses’ Association
Patricia Brogan, Ph.D.
Wayne State University
Wayne Holland, Ph.D.
Michigan Speech-Language-
Hearing Association
Jerry Punch, Ph.D.
Michigan State University
Constance Spak, M.A., CCC-A
University of Michigan
Michael Stewart, Ph.D.
Better Hearing
Central Michigan University
Jeffrey Weingarten, M.D.
Michigan Otolaryngology Society
Project SENSOR Staff
At the Michigan Department
of Consumer and Industry Services
Douglas J. Kalinowski, C.I.H., M.S.,
Deputy Director
Bureau of Safety and Regulations
Project SENSOR, Co-Director
John Peck, C.I.H., M.S., Chief
Occupational Health Division
Bill Deliefde, M.P.H.
Regional Supervisor
Project SENSOR-MDCIS Liaison
Debbie Wood
Division Chief Secretary
At Michigan State University—
College of Human Medicine
Kenneth D. Rosenman, M.D.
Professor of Medicine
Project SENSOR, Co-Director
Mary Jo Reilly, M.S.
Project SENSOR Coordinator
Amy Sims, B.S.
Project SENSOR NIHL Coordinator
Now Hear This…, Editor
Project SENSOR Office Staff:
Tracy Carey
Ruth VanderWaals
Patient Interviewers:
Danielle Arnold Amy Krizek
Jaime Hope Diana Okuniewski
Now Hear This is published quarterly by Michigan
State University-College of Human Medicine
with funding from the Michigan Department of
Consumer and Industry Services and is available
at no cost. Suggestions and comments are welcome.
(517) 353-1846
MSU-CHM
117 West Fee Hall
East Lansing, MI 48824-1316
Michigan Law Requires the
Reporting of Known or Suspected
Occupational NIHL
Reporting can be done by:
FAX
517-432-3606
Telephone
1-800-446-7805
E-Mail
ODREPORT@ht.msu.edu
Web
http://www.chm.msu.edu/oem
Mail
MDCIS Div. of Occ. Health
P.O. Box 30649
Lansing, MI 48909-8149
Suggested Criteria for Reporting
Occupational NIHL
1. A history of significant exposure to noise
at works; AND
2. A STS of 10 dB or more in either ear at an
average of 2000, 3000 & 4000 Hz. OR
3. A fixed loss.*
*Suggested definitions: a 25 dB or greater loss in
either ear at an average of: 500, 1000 & 2000
Hz; or 1000, 2000 & 3000 Hz; or 3000, 4000 &
6000 Hz; or a 15 dB or greater loss in either ear
at an average of 3000 & 4000 Hz.
Michigan State University
College of Human Medicine
117 West Fee Hall
East Lansing, MI 48824-1316
Phone (517) 353-1955
Address service requested.
In this issue:
The ACOEM position statement on
Noise-Induced Hearing Loss
Printed on recycled paper.
Now Hear This…

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