Life is made immeasurably richer by the sounds of the world around us, whether it be music, friendly conversation, or waves at the beach. These pleasures, however, may be denied to someone suffering from noise-induced hearing loss (NIHL). Thirty million U.S. workers are exposed to hazardous noise levels, and another 9 million are exposed to chemicals that may damage hearing. The most common occupational disease in the United States, NIHL is almost entirely preventable.
In 1969 the U.S. Department of Labor promulgated noise exposure regulations for companies with federal contracts. The maximum permissible exposure level allowed is an eight-hour time-weighted average (TWA) of 90 decibels, as measured on the A-scale (dBA), which approximates human hearing sensitivity. In 1970 the U.S. Congress created the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). NIOSH conducts health-hazard research as a basis for advising OSHA in the drafting of regulatory standards. In 1971, OSHA expanded the applicability of the 90-dBA noise standard to the majority of the U.S. workforce, and it is currently enforced as amended in 1983.
Since 1972, NIOSH has recommended lowering the permissible exposure level (PEL), as research has determined that a TWA at or above 85 dBA poses excess risk of developing noise-induced hearing loss. OSHA has, to date, not lowered the PEL, due in part to economic considerations. OSHA also allows a 5-decibel increase in the TWA before reducing the permissible duration of exposure by half (the exchange rate). NIOSH recommends a 3-decibel exchange rate, which is more protective, supported by scientific evidence, and is already used by the U.S. Environmental Protection Agency, the Department of Defense, and many nations worldwide. Thus, simply meeting OSHA requirements may not preserve hearing.
Under current OSHA regulations, employees with a TWA of 85 dBA or above must be enrolled in a hearing conservation program (HCP), which includes a baseline hearing threshold exam (an audiogram) followed by annual reexaminations. In addition, employees with a TWA of 90 dBA or above are required to wear effective hearing protection to reduce their in-ear exposure to below the permissible level. If an annual audiogram reveals that the hearing threshold of an employee has worsened by an average of 10 decibels at 2,000, 3,000, and 4,000 Hz, then OSHA notification and specific corrective measures to prevent further deterioration are required. In most jurisdictions, workers suffering a permanent threshold shift to 25 decibels or worse may seek monetary compensation.
In order to prevent excessive in-ear noise exposures, it is best to reduce noise at the source through engineered solutions. A less preferred alternative is the use of personal hearing-protection devices (HPDs), such as ear plugs and muffs. Effective HPD use requires that employees are motivated, well trained, and issued the appropriate HPD. When choosing an HPD, comfort and convenience should be a concern, as an unworn HPD is obviously ineffective. Workplaces with effective hearing conservation programs enjoy less absenteeism and higher worker productivity than those without such programs. In addition, workplaces without hearing conservation programs risk significant potential liability.
Not all noise-induced hearing loss is occupational. Random audiometric screening of the population is showing worsening thresholds, which may be the result of the use of power tools and personal and vehicular sound systems.
(see also: Environmental Determinants of Health; Hearing Disorders; National Institute of Occupational Safety and Health; Occupational Disease; Occupational Safety and Health; Occupational Safety and Health Administration )
Franks, J. R.; Stephenson, M. R.; and Merry, C. J. (1996). Preventing Occupational Hearing Loss—A Practical Guide. Bethesda, MD: U.S. Department of Health and Human Services.
National Institute for Occupational Health and Safety (1998). Criteria for a Recommended Standard Occupational Noise Exposure. Bethesda, MD: U.S. Department of Health and Human Services.
Royster, J. D., and Royster, L. H. (1990). Hearing Conservation Programs Practical Guidelines for Success. Chelsea, MI: Lewis Publishers.
Suter, A. H. (1993). Hearing Conservation Manual. Milwaukee, WI: Council for Accreditation in Occupational Hearing Conservation.
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