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How NIOSH has contributed to the Health of Workers

The NIOSH HLR program has been working for more than three decades to prevent occupationally-induced hearing loss by pursuing a diversified portfolio of research issues. NIOSH is the primary federal agency doing research on occupational hearing loss, the factors which cause it, and methods of preventing it. The HLR program has been a leader in research results, policy recommendations, training occupational health professionals in hearing loss, and dissemination of practical information to the public.

The HLR program is a modest-sized program that serves a large worker population at risk of occupational hearing loss spread across nearly every sector of the economy. In spite of this daunting combination of factors, we are proud to claim that the HLR program has made contributions to the health of workers. Documentation of those contributions makes up the bulk of this report. The purpose of this summary is to highlight our contributions to help guide EC members through a thorough evaluation of the program.

For a number of reasons, it is difficult to concisely summarize the contributions of any diversified research program. Different types of research take different amounts of time to produce outputs. They experience levels of support and staffing that may not be commensurate with their relative costs. External factors may shift in valence and intensity at critical points and in different directions for each research path. Research outputs may have great potential for health protection but little utility in rapidly changing workplaces. It is difficult to judge the contributions of different kinds of research outputs to health outcomes because the paths of new knowledge through a society are so difficult to map.

With those caveats, we think that the following seven accomplishments represent the most important contributions of the HLR program to the hearing health of workers.

Two Criteria Documents
(see Research Goal 1.1)
These two documents contributed to setting policies, regulations and research directions for the nation and the world. The first one, released in 1973, contained recommendations which formed the basis of the Occupational Safety and Health Administration (OSHA) Hearing Conservation Amendment, 29 CFR 1910.95. The second, released in 1998, though not yet resulting in any changes in OSHA regulation, has been influential in the policies of many organizations. It established the basis for preferring research-based best practices in hearing loss prevention programs over minimal compliance with existing regulations.  Recommendations such as the 3 dB exchange rate[1] have impacted best practices and policies across the U.S., e.g., the Department of Defense (DOD), National Aeronautics and Space Administration (NASA), the American Academy of Audiology (AAA), and the Department of Transportation (DOT). Both Criteria Documents have been cited by a number of organizations.

Development of Occupational Hearing Loss Epidemiology
(see Research Goals 4.1, 4.2) Epidemiologic data related to occupationally-induced hearing loss has been almost non-existent. HLR program efforts have taken two tracks – surveillance of noise-induced hearing threshold shifts and development of reference population databases. Until 2004, there was no national system to determine how many workers had developed occupationally-induced hearing loss. There was also no reliable system for tracking the results of hearing loss prevention programs. Based on HLR program recommendations and technical support, OSHA implemented a method to record incidences of occupational hearing loss on the OSHA Log 300 (29 CFR, 1904.10). Beginning in January, 2004, it is now possible to track occupational hearing loss, including the ability to categorize the incidence of such hearing loss as a function of a number of important variables (e.g., work sector). Based on the availability of these data, the research community will be able to develop new research efforts focused on specific problem areas.

Population-based reference data on hearing levels in U.S. adults were obtained in the 1960’s and early 1970’s, but had not been updated since. The HLR program initiated a collaborative effort with the National Institute on Deafness and other Communication Disorders (NIDCD), and the National Center for Health Statistics (NCHS) to design and field a surveillance effort capable of answering basic questions about hearing in the population. Beginning in 1997, we have successfully fielded this effort. It has defined the hearing acuity of U.S. adults, aged 20-69, as a function of age, gender, ethnicity, and history of occupational and non-occupational noise exposure. We now have the first valid reference hearing levels that can be used to determine whether or not hearing is stable, getting better or getting worse at the population level. These baseline data are also critical in evaluating excess risk of hearing loss in various occupational sub-populations.

Training and Education Programs
(See the HLR Program Overview for more information about programs to educate OSH professionals and Research Goals 1.6, 1.8, and 1.9 regarding employee and youth training programs)
Through the education of OSH professionals by academic institutions selected regionally throughout the U.S., NIOSH Education and Research Centers (ERCs) have provided a steady supply of expertise in hearing loss research and prevention to private, government, labor, and non-profit organizations. In the last 10 years, NIOSH has supported hundreds of graduate-level courses that were either entirely about hearing loss or had substantial parts of the course in that area. A study by the Inspector General of the Department of Health and Human Services (DHHS) in 1996 revealed that more than 80% of NIOSH-supported students went on to careers in occupational safety and health.

Education and training programs to prevent occupational hearing loss among employees (including young workers) have traditionally focused on merely transferring content information on hearing loss from an instructor or training medium to the worker. HLR program research has shown that merely providing information is insufficient to produce behavior change. By applying current models of health communication, we have demonstrated a positive influence on workers’ attitudes, beliefs, and behaviors, particularly with regard to the use of hearing protection. This research is being employed in studies now under way in the U.S. Navy and in carpenter apprentice training centers. Results of these efforts are expected to establish a template for best practices regarding how hearing loss prevention training should be conducted in noise-exposed sectors throughout the U.S.

Testing Standard and Rating System for Hearing Protection Devices
(see Research Goal 2.1)
The HLR program developed a testing standard and rating system that reflects the real-world use of hearing protection devices (HPDs). This research provided the scientific basis for the revision of the American National Standards Institute (ANSI) consensus standard on the measurement of the attenuation provided by hearing protection devices. The new procedures provided occupational safety and health professionals with an improved ability to predict protected exposure. Further developments are expected to lead to selection guidelines for hearing protection appropriate for hearing-impaired workers that will maximize audibility and minimize their risk of additional hearing loss due to noise exposure. The testing standard and rating system hold promise for protection of workers, but they are not required by regulations, and employers have not yet embraced this technology in hearing conservation programs.

Engineering Noise Controls in Mining and Construction
(see Research Goal 3.1) The HLR program’s success with the development of a coated flight bar for continuous mining machines is a good example of engineering noise control research and development. We developed coated flight bars for the continuous mining machine conveying system that resulted in a reduction of approximately 7 dB(A) of operator exposure.  Similar HLR program success with wet drilling technologies for mine roof bolting and quieter construction hand tools have the potential to provide the industry and regulatory agencies with new and effective engineering controls.

Historically, most industries have relied heavily on the use of personal protection or on administrative controls to reduce worker exposure because there was a lack of available engineering controls. This research has opened the door for regulatory agencies to emphasize the primacy of engineering controls in reducing noise exposures.

Ototoxic Chemical Effects
(see Research Goal 4.6)
Some chemicals commonly found in industry, construction, and agriculture are hazardous to hearing, and thus, are referred to as ototoxic. When combined with noise, some of them may exacerbate the effects on hearing. Through a number of domestic and international partnerships, the HLR program has worked to identify hazardous chemicals. It has worked to bring this issue to the attention of employers, public health professionals and policy makers. A number of standards and guidelines have been impacted by this stream of research, particularly abroad. The program has produced dozens of articles and given many presentations about this research.

Support for the Research Process
(see Research Goals 4.3, 4.5, and 4.6, and the descriptions of Workshops and Conferences)
The HLR program has exhibited a leadership role in a number of research communities. That leadership has been intellectual, organizational, and financial. We have conducted a number of conferences, workshops, and meetings to advance science and contribute to workplace outcomes. Examples include our series of National Occupational Research Agenda (NORA) sponsored “Best Practices” workshops in partnership with the National Hearing Conservation Association (NHCA), our consensus meeting which led to the first Practical Guide, and the national and international standards committees on which HLR staff serve.

A recent example is “The Mouse as an Instrument in Hearing Research 2” held in October, 2005 in Bar Harbor, Maine. The meeting brought together molecular biologists and hearing researchers to talk about technology which could be transferred from one discipline to another. Another example is the “Futures Meeting” we held in April, 2005. It provided a venue to discuss research directions with hearing loss experts from academia and industry.


[1] US Congress [1970]. Occupational Safety And Health Act of 1970, Public Law 91-596, 29 USC 651, Sec. 2-b.


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