About Occupatinal Hearing Loss

Occupational Hearing Loss


Occupational hearing loss is one of the most common occupational illnesses in the United States. It is the second most self- reported occupational illness. According to the National Institute of Occupational Safety and Health, more than 30 million US workers are exposed to hazardous noise levels, resulting in noise- induced occupational hearing loss. Many of today's industries produce noise levels of sufficient intensity to permanently damage employees' hearing. The National Institute for Occupational Safety and Heath (NIOSH) recommends that the exposure limit for occupational noise exposure is 85 decibels, A- weighted, as an 8 hour time- weighted average. Exposure at or above this level is considered hazardous. Occupational hearing loss is 100 percent preventable, but once acquired it is permanent and irreversible.

Occupational hearing loss is characterized by a gradual worsening of high frequency hearing thresholds over time. This is caused by chronic and sometimes acute exposure to excessive noise levels. In later stages, hearing loss may spread to middle or low frequencies. The disease is bilateral. In most cases tinnitus is also present. The hearing loss may be temporary at first, but can become permanent overtime. During early stages of hearing loss, sufferers have reported needing to turn up the volume on the television, and having difficulty understanding speech in groups and background noise. As hearing worsens it becomes difficult to hear normal conversations. If a worker has been exposed to noise at 85 dBA for at least ten years, they will develop a hearing impairment by age 65. According to the NIA, one third of hearing loss is due to noise exposure.

The noise thermometer shows activities that are above the recommended 85 dBA.

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Occasionally, a single traumatic exposure to noise in excess of 130- 140 dB sounds pressure level can result in hearing loss. Most often, hearing loss is caused by repeated exposure to noise above 85dBA over long periods. The risk depends on both duration and intensity. Exposure to continuous, varying, intermittent, or impulsive noise shall not exceed 140 dBA. As intensity increases, the amount of time the exposure is "safe" decreases. Statistical calculations help determine safe exposure.

OSHA limits to loud noise exposure for "loud jobs"

90 dB - 8 hrs.
95 dB - 4 hrs.
100 dB - 2 hrs.
105 dB - 1 hr

Jobs that cause Occupational Hearing Loss

50% of manufacturing and utility workers will suffer from occupational hearing loss.

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20% of transportation workers will develop a hearing loss

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44% of carpenters and 48% of plumbers have reported a perceived hearing loss

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90% of coal miners will have a hearing impairment by age 52.

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Occasionally a single traumatic exposure to noise in excess of 130-140 dB sound pressure level can result in hearing loss. Most often, hearing loss is caused by repeated exposure to noise above 85dBA over long periods. The risk depends on both duration and intensity. Exposure to continuous, varying, intermittent, or impulsive noise shall not exceed 140 dBA. As intensity increases, the amount of time the exposure is "safe" decreases. Statistical calculations help determine safe exposure.

-In the U.S., national job exposure if regulated by law

-Both the length of exposure and decibel level are considered

-If the sound is at or greater than the maximum levels recommended, protective measures are taken

-Both the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have initiated efforts to better understand and to limit the occurrence of OHL.

-To ensure that adequate hearing protection is provided by both the employer and by the employees, audiologists who work in the industry, design hearing- conservation programs. The programs help to identify and measure excessive noise areas, consult in the reduction of noise levels, monitor employee hearing, and educate employees.

Other common jobs that cause OHL are farming, jobs involving loud music or machinery, construction workers, and the military.

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Comparisons between sounds at work and the recommended exposure level of 85dB.

-85- 90 is the sound of a motorcycle, snowmobile, and other similar engines

-90 dB is about the loudness of a large truck about 5 yards away

-100 dB is reached by some rock concerts

-120 dB is a jackhammer from 3 feet away

-130 dB is jet engine from 100 feet away

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Prevention
*Prevention measures must be taken by the employer to ensure the protection of the workers hearing.

Noise Exposure Assessment:

*Should meet the American National Standard Measurement of Occupational Noise Exposure

*Initial monitoring of work site to determine noise exposure levels

*Sound level meter or dosimeter may be used

*Monitoring is repeated every two years

*Monitorings are repeated within three months if there is a change of equipment, production process, or maintenance routines.

Instruments:

*Calibrated to ensure measurement accuracy

*Conform to the American National Standard Specification for Sound Level Meters

Hearing Protectors:

*Workers are required to wear hearing protectors
when engaged in work that exposes them to noise that equals or exceeds 85 dBA as an 8 hour TWA

*Workers who exceed 100 dBA should wear double hearing protection

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Reduced Noise:

•Earmuffs subtract 25% of noise

•Slow- recovery formable earplugs subtract 50% of noise

•All other earplugs subtract 75%

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Hearing Protectors:

•Employers train employees at least once a year to select, fit and use a variety of hearing protectors

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Removing Noise:


•There are other methods of removing noise from the workplace other than earplugs. They include:
–Installing a muffler
–Building an acoustic barrier

References:

ADAM, Inc. "Occupational Hearing Loss." Medline Plus. 5 Nov. 2007. URAC. 30 Nov. 2007 http://www.nlm.nih.gov/medlineplus/ency/article/001048.htm>

Kimball, Chad T., ed. Workplace Heath and Safety Sourcebook. US: Omnigraphics, Inc., 2000.

Levy, Wagner, Rest, and James L. Weeks, eds. Preventing Occupational Disease and Injury. Washington, D.C.: American Public Health Association, 2005.

Martin, Fredrick N., and John Greer Clark. Introduction to Audiology. 9th ed. Boston: Pearson, 2006.

May, J.J. "Occupational Hearing Loss." American Journal of Industrial Medicine, vol. 37, 112-120. Jan 2000. http://libproxy.uncg.edu:2158/journal/34471/home