Occupational Airways

Volume 6, Issue 2 August 2000 This Issue: On a different note…

· -Induced In this issue we are diverging from our usual focus on occupational Loss respiratory disease to discuss another important occupational health issue, noise-induced · Report Available: (NIHL). NIHL is preventable with consistent and Occupational proper usage of hearing protection. Workers tend not Disease in CT: to seek medical treatment until permanent damage Data for Action has already occurred, and occupational hearing · Summary Table of disorders are rarely reported by physicians and other Number of Reported health care providers. Health care providers can play Cases of Selected an important role in increasing patient awareness of Respiratory Diseases NIHL. Also, physician reporting of occupational hear- in CT ing disorders could lead to prevention activities in the workplace. We hope you find the following article both useful and interesting.

Noise-Induced Hearing Loss

By Peter Rabinowitz, MD, MPH and Judy Sparer, CIH Occupational Airways is Yale Occupational and Environmental Medicine Program, Yale University, School of Medicine produced by the Occupational Health & Case History radio up on his way home after Special Projects Program, work and the next morning he Division of Environmental Epidemiology & A forty-five year old longshore- would find that it was much too Occupational Health, man came to Yale for loud. Now, he reports constant Connecticut Department of with a complaint of tinnitus. He ringing in his . He has , 860/509-7744. has a 20 year work history of difficulty understanding conversa- loading and unloading ships, tions in crowded rooms and has Editor/Coordinator: being around loud engines, trucks been arguing with his wife about Juanita Estrada, Epidemiologist and forklifts, 'impulse' noise from turning up the volume of the TV. the clanking of steel loads against His (Figure 1) reveals Occupational Health Staff: the steel holds, and loud fans in a “notch” of decreased hearing in Carolyn Jean Webb, Director the refrigerated warehouses. He the higher frequencies. Milinda Daye, Epidemiologist Marian Heyman, admits to wearing hearing Epidemiologist/Industrial protection very intermittently. This case is typical for noise- Hygienist induced hearing loss with a

Contributors to His problems began with history of chronic exposure to this edition: sensations of ringing in his ears loud noise, initial temporary Peter Rabinowitz, MD, MPH and decreased hearing at the end losses of hearing acuity Judy Sparer, CIH of a workshift. He would turn the (Continued on page 2) PAGE 2 OCCUPATIONAL AIRWAYS VOLUME 6, ISSUE 2

Figure 1: Audiogram of Patient with Noise-Induced Hearing Loss

Frequency (Hz) 500 1000 2000 3000 4000 6000 8000 0

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50 Hearing Threshold (dB)

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(Continued from page 1) How is Noise measured? (“temporary threshold shifts (TTS)”), and more gradual onset of permanent loss. The hearing Sound is described in terms of intensity deficit typically begins with a “notch” around (perceived as loudness), and frequency 4000 Hz, and with time increases to involve (perceived as pitch). Sound intensity is other frequencies. measured on a logarithmic scale using the unit of decibels (dB). An adjustment to that scale What is noise-induced hearing loss? known as “A-weighting”, or “dBA” emphasizes

sounds at higher frequencies where the is Noise-induced hearing loss (NIHL) is a sen- more sensitive. An increase of 3 decibels in sorineural hearing loss, usually bilateral, with sound level represents a doubling of sound gradual onset, beginning at high frequencies, intensity. Table 1 lists and compares the caused by chronic exposure to excessive sound intensities of some common sounds. levels which damage the hair cells of the .1 It is estimated that 10 million Americans suffer from hearing loss due to occupational Table 1: Intensity of some common sounds noise, making it the second most common type of acquired hearing loss, second only to age- Sound Intensity (decibels) related loss (). Firearms 140-170 dB We hear sound waves because the bones of Pneumatic rock drill 130 dB the conduct the waves to the fluid- filled inner ear. There the hair cells lining the Rock concert 110 dB inside of the are stimulated and transfer Personal stereos 100 dB sound energy to nerve impulses interpreted by the brain as sound. If sound pressures are Many factories 80-99 dB excessive, the hair cells are damaged. While Required of OSHA 85 dBA 8 hour they are able to recover from minor damage, Hearing Conservation average repeated injury leads to cell death. Once lost, Program hair cells do not regenerate. Some ototoxic medications such as aminoglycosides, and Loud restaurant 80 dB some chemical exposures such as solvents and Ordinary conversation 60 dB heavy metals can also damage hair cells, thus increasing risk to workers. Average office 50 dB VOLUME 6, ISSUE 2 OCCUPATIONAL AIRWAYS PAGE 3

How is NIHL evaluated? hearing acuity, sleep, and concentration. Social isolation and depression have been associated The evaluation of a worker with suspected with noise-induced hearing deficits, as have noise-induced hearing loss involves: increased risk of accidents and injury.

· Taking a history of noise exposures, both Treatment occupational and non-occupational · Taking a medical history to exclude medical If the loss is sufficiently severe, hearing aids may improve hearing. Hearing aids are not able · Performing an otoscopic examination to to correct hearing the way glasses can evaluate the outer and middle ear correct vision. They can amplify sounds but not · Conducting Rinne and Weber tests as well fully correct the distortion and background noise. as (if available) to detect problems Noise-induced hearing loss is preventable! · Performing Reducing sources of noise exposure at work If the audiometry suggests significant hearing and at home is the best way to prevent NIHL. If loss, patients should be referred to an the noise level can not be reduced, hearing audiologist for a full hearing evaluation. Since protection can help. A wide variety of hearing noise-induced hearing loss is typically symmetric protectors is available and should be used at (with the exception of single ear exposure as work and at home for noisy . Evidence is growing that proper can increase use of may occur in hunting or the military), patients 3 with asymmetric sensorineural hearing deficits hearing protectors. should be referred to an oto-laryngologist to exclude retrocochlear pathology such as an OSHA and Hearing Conservation acoustic neuroma. OSHA requires that noise levels in the work- If occupational noise or chemical exposure is place, averaging more than 90 dBA over an 8 suspected as the cause of hearing loss, the hour period, be reduced. Employees exposed to physician is required to report the case to the CT noise levels averaging more than 85 dBA must Departments of Labor and Public Health. In be enrolled in a Hearing Conservation Michigan, where there is a special emphasis on Program. Despite such programs, noise- NIHL, more than 1300 cases were reported over induced hearing loss continues to be one of the an 8 year period.2 In Connecticut, however, most common occupational disorders. only 69 cases were reported over a similar period. A Hearing Conservation Program requires engineering and to Why is NIHL Important? reduce noise exposures, training of employees in the use of hearing protection, and annual As hearing loss increases, a person audiometry for noise-exposed workers. The experiences difficulty with speech discrimination, annual audiogram is compared to baseline for especially in background noise. High detection of “standard threshold shifts”, defined frequency hearing is important for distinguishing as a change for the worse of 10 dB average at consonant sounds such as “t”, “p”, or “s”. People the frequencies of 2000, 3000, and 4000 Hz. report that “I can hear you, I just can’t under- Workers who have a 10 dB shift must be stand you”. High pitched sounds like a tele- counseled and rechecked. OSHA allows “age phone ring, and high-pitched voices such as a correction” of the audiogram using a standard child’s are lost; music loses its richness, sounds table. of birds and rain disappear. Tinnitus, another common symptom, further interferes with (Continued on page 4) Division of Environmental Epidemiology & Occupational Health 410 Capitol Avenue, MS# 11OSP P.O. Box 340308 Hartford, CT 06134-0308

Joxel J. Garcia, MD, MBA, Commissioner John G. Rowland, Governor

TO:

(Continued from page 3) in While OSHA refers to a “10 dB shift”, other more sensitive ways of measuring shifts have Connecticut: Data for Action been proposed. NIOSH recommends using a This past June, the Connecticut Department 15 dB change from baseline in any frequency 4 of Public Health released a comprehensive on two successive . NIOSH also recommends against age correction of an report entitled Occupational Disease in individual’s audiogram, on the basis that it is Connecticut: Data for Action. The report provides a history of occupational disease in unreasonable to apply population averages for CT, an overview of national initiatives, presents age effects to an individual. CT occupational disease data compiled from

physician reports of occupational disease, For questions regarding noise-induced describes social and economic impacts of hearing loss, contact: occupational disease, describes the uses of oc- · OSHA (www.OSHA.gov) cupational disease data, and discusses · NIOSH ( http://www.cdc.gov/niosh) recommendations for future directions. · The National Hearing Conservation To receive a copy of this report, please call Association (http://www.hearingconservation.org) the Occupational Health Program at · Peter Rabinowitz MD, MPH at Yale, 860/509-7744. 203/785-4197.

REFERENCES Summary of Number of Reported Cases of Selected Respiratory Diseases in CT* 1. ACOM Noise and Hearing Conservation Committee. CT DPH Occupational Disease Surveillance Data 1989. Occupational noise-induced hearing loss. J Occup Med 31:996. 1997 1998 1999 2000 ODSS Total** 2. Reilly MJ, Rosenman KD, Kalinowski DJ. 1998. Occupational noise-induced hearing loss surveillance in Asthma 27 19 24 5 201 Michigan. J Occ Env Med 40:667-74. RADS*** 4 7 5 2 34 3. Lusk S, Hong OS, Ronis DL, Eakein BL, Kerr MJ. 1999. Early MR: Effectiveness of an intervention to 1 3 1 0 13 increase workers’ use of hearing protection. 3 7 6 0 110 Human Factors 14:487-94. -related 2 10 9 0 118 4. National Institute of Occupational Safety & Health pleural diseases (NIOSH). 1998. Occupational noise exposure: Criteria for a recommended standard, publication no. 98-126. TOTAL 37 46 45 7 476 * As of June 5, 2000. Data subject to change. ** Occupational Disease Surveillance System (ODSS) total since 1/1990 *** Reactive Airways Dysfunction Syndrome

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