Exposure to certain chemicals with or without concomitant noise exposure may also contribute to occupational hearing loss. Hearing loss may impede communication in the workplace and contribute to safety hazards. Occupationally acquired hearing loss may also have an adverse effect on workers’ lives beyond the workplace. No medical means are currently available to prevent or reverse it, although hearing aids are widely used and research on other treatments is ongoing.

Occupational hearing loss is a serious concern, although the number of workers affected is uncertain. Determining the magnitude of the problem has been a persistent challenge because of the lack of national surveillance systems or more narrowly focused longitudinal studies to track workplace exposures to noise or ototoxic chemicals and the incidence or severity of hearing loss among workers. Under new OSHA requirements, implemented in 2004, employers are expected for the first time to record qualifying cases of occupational hearing loss separately from any other illness or injury. This reporting change will help generate welcome data on occupational hearing loss, but those data still have important limitations (see Chapter 2).

Using data from the 1980s and early 1990s, NIOSH estimated that at least 4 million workers in the United States were exposed to workplace noise levels that put them at risk of hearing loss (NIOSH, 1998). Other unpublished analyses suggested that the number may have been as high as 30 million in the early 1990s (NIOSH, 1996). Some workers may also be at risk due to exposure to ototoxic chemicals (NIOSH, 1996, 2005a). In addition, workers may be exposed to hearing hazards through noisy recreational activities (e.g., hunting, woodworking) and may develop hearing loss due to injury, illness, and aging.

A variety of disciplines or areas of expertise are involved in the prevention of occupational hearing loss. Practitioners in industrial hygiene, audiology (specifically occupational audiology), occupational medicine and nursing, noise control engineering, and safety engineering all play roles, as do epidemiologists and basic science researchers studying noise exposure and hearing loss. In addition, certain businesses share an interest in developing technologies for hearing loss prevention. Throughout this report, these groups are described as the communities responsible for occupational hearing loss prevention.


In September 2004, NIOSH requested that the National Academies conduct reviews of as many as 15 NIOSH programs with respect to the impact and relevance of their work in reducing workplace injury and illness and to identify future directions that their work might take. The Hearing Loss Research Program was selected by NIOSH as one of the first two programs to be reviewed.

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