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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health 1 Introduction The National Institute for Occupational Safety and Health (NIOSH) was established by the Occupational Safety and Health Act of 1970 (U.S. Congress, 1970). Today the agency is part of the Centers for Disease Control and Prevention of the U.S. Department of Health and Human Services. NIOSH is charged with the responsibility to “conduct … research, experiments, and demonstrations relating to occupational safety and health” and to develop “innovative methods, techniques, and approaches for dealing with [those] problems” (U.S. Congress, 1970). Its research targets include identifying criteria for use in setting worker exposure standards and exploring new problems that may arise in the workplace. NIOSH does not have the authority to establish or enforce regulations on workplace safety and health. Regulatory and enforcement authority rests with such agencies as the Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA). Prevention of occupational hearing loss has been part of the NIOSH research portfolio from the time the agency was established. A principal cause of occupational hearing loss is the cumulative effect of years of exposure to hazardous noise.1 1 NIOSH considers workplace exposure to 8-hour time-weighted average noise levels of 85 dBA or higher or any exposure to levels of 140 dB SPL (sound pressure level) or higher to be hazardous to hearing (NIOSH, 1998).
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health 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. STUDY CHARGE AND EVALUATION COMMITTEE 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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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health The Committee to Review the NIOSH Hearing Loss Research Program was convened by the Institute of Medicine (IOM) in late 2005. The Statement of Task for the committee is as follows: The National Institute for Occupational Safety and Health (NIOSH) has requested that the National Research Council (NRC) and the Institute of Medicine review as many as 15 of its programs with respect to their impact, relevance, and future directions. Each program review will be conducted by a separate committee. The IOM will convene the Committee to Review the NIOSH Hearing Loss Research Program. The committee will examine the following issues for the Hearing Loss Research Program: Progress in reducing workplace illness and injuries through occupational safety and health research, assessed on the basis of an analysis of relevant data about workplace illnesses and injuries and an evaluation of the effect that NIOSH research has had in reducing illness and injuries. Progress in targeting new research to the areas of occupational safety and health most relevant to future improvements in workplace protection. Significant emerging research areas that appear especially important in terms of their relevance to the mission of NIOSH. The committee will evaluate the Hearing Loss Research Program using an assessment framework developed by the NRC/IOM Committee to Review the NIOSH Research Programs. The evaluation will consider what the NIOSH program is producing as well as whether the program can reasonably be credited with changes in workplace practices, or whether such changes are the result of other factors unrelated to NIOSH. For cases where impact is difficult to measure directly, the committee reviewing the Hearing Loss Research Program may use information on intermediate outcomes to evaluate performance. The study committee was selected to include members with expertise in audiology, biological mechanisms of noise-induced hearing loss and ototoxicity, noise control engineering, occupational health and safety, hearing conservation programs, epidemiology, and program evaluation. Committee members have varied experience in settings such as academia, industry, labor unions, and federal and state agencies charged with monitoring and regulating worker health and safety. As specified in the Statement of Task, the committee performed its review
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health using evaluation guidance, referred to as the Framework Document, which was developed by the National Academies’ Committee for Review of NIOSH Research Programs. (The Framework Document is included as Appendix A of this report.) The study committee was given the discretion to determine the period to be covered by the review and chose to focus on the period since 1996 because it coincided with important organizational changes in the Hearing Loss Research Program and the introduction of the National Occupational Research Agenda (NORA). In relation to noise hazards, the review task was interpreted as applying only to hearing loss because of the name and mission of the program under review. Consideration of possible nonauditory health effects of noise exposure was excluded. The committee met three times from January 2006 through March 2006 and conducted additional deliberations through four conference calls and e-mail. In addition, a subset of the committee visited facilities used by the NIOSH Hearing Loss Research Program staff at the Pittsburgh Research Laboratory and the Robert A. Taft Laboratory in Cincinnati, Ohio. Committee members also visited facilities at the University of Cincinnati, where testing of powered hand tool noise emissions is being done under contract to NIOSH. The committee’s review of the NIOSH Hearing Loss Research Program was based in large part on written materials provided by NIOSH (see Appendix C).2 Information gathering included presentations made by NIOSH staff and other invited guests in open sessions of committee meetings in January and February (see Appendix B). The committee also invited comments from stakeholders, that is, organizations and individuals with a potential interest in the NIOSH Hearing Loss Research Program. The population of potential stakeholders is diverse and not easily defined. As a result, the committee made an effort to reach a varied national and international audience in federal and state agencies, industry, labor, and academia, but could not attempt to make this information-gathering effort a comprehensive or systematic survey of the program’s stakeholders because of the short time frame for its work. (Additional detail on committee methods and a list of stakeholders who provided information to the committee are available in Appendix B.) THE NIOSH HEARING LOSS RESEARCH PROGRAM The NIOSH Hearing Loss Research Program describes its mission as “to provide national and world leadership to reduce the prevalence of occupational hear- 2 Some of the materials provided to the committee are available online at the NIOSH website http://www.cdc.gov/niosh/nas/hlr/.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health ing loss through a focused program of research and prevention” (NIOSH, 2005a). The following overview of the program is based on information provided to the committee by NIOSH. History of the NIOSH Hearing Loss Research Program One of the earliest products of the Hearing Loss Research Program was the publication in 1972 of Criteria for a Recommended Standard: Occupational Exposure to Noise (NIOSH, 1972), which provided the basis for a recommended standard to reduce the risk of developing permanent hearing loss as a result of occupational noise exposure. This work made an important contribution to the noise exposure standard for general industry promulgated by OSHA in the early 1980s. NIOSH published its first compendium of hearing protection devices in 1976, and in 1990 first published Preventing Occupational Hearing Loss: A Practical Guide. The Hearing Loss Research Program was originally based in Cincinnati, Ohio. The program staff was part of the Physical Agents Effects Branch in the Division of Biomedical and Behavioral Sciences (DBBS). In 2000, DBBS and the Division of Physical Sciences and Engineering (DPSE) were merged to form the Division of Applied Research and Technology (DART). After the merger, most of the Cincinnati-based intramural activities were conducted by personnel in the Engineering and Physical Hazards Branch of DART. The Engineering and Physical Hazards Branch resulted from the merger of what had been the DBBS Physical Agents Effects Branch and the DPSE Engineering Control Technology Branch. The researchers and laboratories did not change location (NIOSH, 2006c). In 1996, personnel and facilities, including research laboratories in Pittsburgh and Spokane, were transferred to NIOSH from the disestablished U.S. Bureau of Mines (NIOSH, 2005a). At the time, the Bureau of Mines had a small research effort on hearing loss prevention in the mining sector. The NIOSH Hearing Loss Research Program expanded to include activities based at the Pittsburgh Research Laboratory (PRL) and to a limited extent at the Spokane Research Laboratory (SRL). Initially, only about three researchers were involved in hearing loss research at PRL (Lotz, 2006a; NIOSH, 2006d). With growth of the research team in Pittsburgh, a Hearing Loss Prevention Branch was established at PRL in 2003. Hearing Loss Research Program Structure As of 2006, four NIOSH divisions and three NIOSH offices are involved in the Hearing Loss Research Program (NIOSH, 2005a):
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health Division of Applied Research and Technology (DART) Pittsburgh Research Laboratory (PRL) Division of Surveillance, Hazard Evaluations, and Field Studies (DSHEFS) Education and Information Division (EID) Office of Extramural Programs (OEP) Office of Health Communications (OHC) Office of Research and Technology Transfer (ORTT) The current organizational configuration of NIOSH is shown in Figure 1-1, and units specifically engaged in activities that are part of the Hearing Loss Research Program are highlighted in Figure 1-2. This distribution of activities across organizational units means that the program functions as a matrix organization, in which the people who carry out the work of the program are assigned to divisions and laboratories throughout the organization, rather than operating as an administrative entity within NIOSH. Goals, Objectives, and Future Plans as Presented by NIOSH As noted above, the mission of the Hearing Loss Research Program is to provide national and world leadership to reduce the prevalence of occupational hearing loss through a focused program of research and prevention (NIOSH, 2005a). A revised noise criteria document prepared by the program and published in 1998 (NIOSH, 1998) identified the following research needs in occupational hearing loss: Noise Control Impulsive Noise Nonauditory Effects of Noise Auditory Effects of Ototoxic Chemical Exposures Exposure Monitoring Hearing Protectors Training and Motivation Program Evaluation Rehabilitation Between 1998, when these goals were articulated, and 2005, the Hearing Loss Research Program sought to advance research in each area except the nonauditory effects of noise. Program staff reported to the committee that this area was not addressed because of the conflicting data in the published literature and the staff’s
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health FIGURE 1-1 NIOSH organization chart, as of December 2005. SOURCE: NIOSH, 2005b. need to prioritize the allocation of limited resources. NIOSH also considered that research activities directed at reducing noise exposure and its auditory effects would help prevent any nonauditory effects of exposure. During this period, the Hearing Loss Research Program was also influenced by the broader NIOSH agenda. In 1996, using input received from the occupational health and safety community at large, NIOSH developed NORA. Under NORA, 21
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health FIGURE 1-2 Location of Hearing Loss Research Program activities in NIOSH. The Hearing Loss Research Program operates as a matrix organization, with its activities conducted in several NIOSH units. Units involved in carrying out activities of the Hearing Loss Research Program are shaded. The units conducting or providing funding for program activities are shown with solid borders. Units supporting program activities other than research are indicated by dashed borders. The program is overseen by a manager and coordinator who are based within administrative units, as indicated in the figure. Other units are shown to indicate the administrative relationship between the units involved in the Hearing Loss Research Program and the NIOSH organizational structure. NORA is not an administrative unit as such, but it is a program that is a potential source of funding and priorities for the Hearing Loss Research Program. Solid lines connect units with formal administrative relationships, and dotted lines represent advisory or consultative relationships. The Hearing Loss Research Program leadership is designated by and responsible to the NIOSH director, and it acts through advisory and consultative relationships with various NIOSH units. NOTE: NORA, National Occupational Research Agenda. SOURCE: NIOSH, 2005a; Lotz, 2006b,c.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health topics were identified as priority areas, with “hearing loss” and “mixed exposures” being the two areas in which the Hearing Loss Research Program was primarily involved. The program has also done work related to the NORA priority topics “control technology and personal protective equipment,” “exposure assessment methods,” and “intervention effectiveness research” (NIOSH, 2005a). In 2000, the Hearing Loss Research Program, informed by input from NORA participants, successfully developed a proposal for NORA funding for a coordinated set of projects for fiscal years (FY) 2001–2005. The proposal was designed to address gaps in the overall research program and emphasized the mining and construction sectors (NIOSH, 2005a). The work on hearing loss prevention done at PRL also falls under the purview of the NIOSH Mining Safety and Health Research Program. In the past few years, this program developed a strategic plan—the Mining Research Plan—that includes the following as one of its goals: “Reduce noise-induced hearing loss (NIHL) in the mining industry.” Intermediate goals and corresponding performance measures were defined for this and other strategic goals in the plan (see Chapter 3) (NIOSH, 2005a). In 2004, the Hearing Loss Research Program began its own strategic planning effort to coincide with the end of its 5-year NORA activities and the announcement of a new alignment of NIOSH research programs. A Futures Workshop was held in April 2005 “to bring stakeholders and internal and external researchers
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health together to discuss emerging topics and priorities” (NIOSH, 2005a). The program’s strategic planning effort has been deferred until the conclusion of this IOM evaluation. The Futures Workshop and identification of emerging research needs are discussed further in Chapter 3. One outgrowth of the Futures Workshop, however, was the adoption in 2005 of four new research goals to describe the current scope of the Hearing Loss Research Program’s activities: Contribute to the Development, Implementation, and Evaluation of Effective Hearing Loss Prevention Programs Reduce Hearing Loss Through Interventions Targeting Personal Protective Equipment Develop Engineering Controls to Reduce Noise Exposures Contribute to Reductions in Hearing Loss Through the Understanding of Causative Mechanisms The research topics that the program had pursued since 1998 are encompassed under these new goals. NIOSH used the four goals to organize the material provided to the committee, and the committee in turn used them to conduct its review (see Chapter 2). In early 2006, the Hearing Loss Research Program changed Goal 4 to “Improve Understanding of Occupational Hearing Loss Through Surveillance and Investigation of Risk Factors.” In 2006, NIOSH launched the second decade of NORA, replacing the 21 priority research areas established in 1996 with a sector-based approach to its research portfolio and to developing partnerships and obtaining input from stakeholders. NIOSH and its partners will form Research Councils for eight industry sectors: agriculture, forestry, and fishing; mining; construction; manufacturing; wholesale and retail trade; transportation, warehousing, and utilities; services; and health care and social assistance. “Hearing loss prevention” is one of 15 cross-sector programs under the new organization. Program Resources Staffing Approximately 40 full-time equivalent positions, including contributions from 30 professional staff members, are currently involved in the intramural hearing loss research effort. This team includes 14 engineers, 5 audiologists, 4 psychologists, and single representatives of other professional disciplines, including physics, industrial hygiene, geology, nursing, sociology, computer science, and scien-
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health tific communication. The staff is distributed among research teams in Cincinnati and Pittsburgh, with roughly half of the research staff and the program manager located in Pittsburgh. Funding Displayed in Table 1-1 is annual funding for intramural and extramural activities under the Hearing Loss Research Program for the period 1997–2005. Intramural funding supports staff salaries and benefits, as well as contracts for goods and services related to staff research activities. The Hearing Loss Research Program also receives support for intramural work through interagency collaborations and participates in cooperative research and development agreements (CRADAs) with private companies to work cooperatively in technology development efforts. As a result of the matrix nature of the Hearing Loss Research Program, the program’s intramural funding level is the sum of the financial resources that the individual NIOSH organizational units decide to apply to work on hearing loss prevention or noise control activities. During the period covered by this review, the largest portion of the program’s intramural funding—69 percent in FY 2005—has come from the Mining Safety and Health Research Program at PRL. To respond to congressional guidance, NIOSH applies PRL funds only to mining safety and health issues. Extramural activities have accounted for more than 30 percent of the Hearing Loss Research Program’s overall funding since 1997. The extramural program is administered and funded through the NIOSH Office of Extramural Programs in Atlanta. TABLE 1-1 NIOSH Hearing Loss Research Program Funding by Fiscal Year, 1997–2005 Year Intramural Extramural Total 1997 $1,860,060 $ 632,405 $2,492,465 1998 $1,903,709 $ 908,010 $2,811,719 1999 $1,941,845 $1,555,768 $3,497,613 2000 $2,396,139 $1,312,928 $3,709,067 2001 $3,661,900 $1,791,830 $5,453,730 2002 $4,176,396 $2,304,960 $6,481,356 2003 $4,311,735 $1,526,709 $5,838,444 2004 $5,253,587 $1,698,416 $6,952,003 2005 $5,164,358 $2,327,408 $7,491,766 SOURCE: NIOSH, 2006a.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health Facilities Research facilities for the Hearing Loss Research Program include specialized laboratories, a mobile audiometric research facility, and instrumentation and equipment to provide comprehensive field study capabilities. The laboratories include the following facilities (NIOSH, 2005a): An acoustic test chamber (in Pittsburgh) is used for precision measurement of total sound emissions from large equipment. This reverberation chamber was accredited in 2005 by the National Voluntary Laboratory Accreditation Program (NVLAP) for sound power measurements in accordance with International Organization for Standardization (ISO) 3741 (ISO, 1999) and American National Standards Institute (ANSI) S12.51 (ANSI, 2002). Two hearing protector laboratories (one in Cincinnati and one in Pittsburgh), which were fully remodeled in 2003, include a reverberation room and computers and software to run standard hearing protector testing protocols. The laboratory in Pittsburgh is accredited by NVLAP for the measurement of real-ear attenuation of hearing protection devices in accordance with test standard ANSI 12.6-1997 R2002 (ANSI, 1997). Two clinical audiometric suites (one in Cincinnati and one in Pittsburgh) contain clinical audiometers (which include extended high-frequency test capability), tympanometers, otoacoustic emission measurement systems, and a hearing aid analyzer. The Cincinnati facility also includes a small audiometric test room similar to those commonly found in occupational settings. A small-animal noise exposure and test facility has been installed at the University of Cincinnati Biological Sciences Department with NIOSH funding. The university facility is equipped to test auditory evoked potentials and otoacoustic emissions in laboratory animals. Two anechoic chambers (a large chamber in Pittsburgh and a smaller one in Cincinnati) are used for evaluations with acoustic test fixtures. A hemi-anechoic room in Pittsburgh, which will accommodate construction equipment, was nearly complete in early 2006. An education and training laboratory in Cincinnati can be used to conduct studies with groups of participants examining training issues and evaluating materials, including electronic and web-based training. A 172 m3 anechoic chamber at the University of Cincinnati is equipped with a 24-channel computerized data acquisition system. This chamber is used by the Hearing Loss Research Program on a collaborative basis.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health Laboratory facilities also include metal-working and carpentry shops with suitable equipment and hand tools. Expert technician support is also available for these shops. Research Administration Intramural research projects carried out by the Hearing Loss Research Program are selected from investigator-initiated proposals. Since 2002, leadership within each NIOSH division or laboratory with activities in the program has been responsible for obtaining external peer review of proposals for assessment of their scientific quality. Selection of proposals for funding is based on considerations of scientific quality and on management review for relevance and potential for transfer to the workplace. Annual reviews for each project are carried out by the respective divisions or laboratories (NIOSH, 2005a, 2006b). Extramural research supported by NIOSH is also investigator-initiated. Grant applications in response to Program Announcements or Requests for Applications are submitted to the Center for Scientific Review of the National Institutes of Health. This center manages the independent review of grant applications for scientific merit. Subsequent reviews for programmatic relevance are conducted by senior NIOSH scientists. The Hearing Loss Research Program reported that it has been guided in its selection of major emphases for research by the goals described earlier in this chapter. In the past, the program’s focus had largely been on developing new knowledge and increasing capacity. In the last few years and with the establishment of the NIOSH r2p (“Research to Practice”) program, the focus has shifted toward consideration of the impact of the research program in the workplace (NIOSH, 2005a). EVALUATION APPROACH The committee was charged with reviewing the Hearing Loss Research Program to evaluate the relevance of its work to improvements in occupational safety and health and the impact that NIOSH research has had in reducing workplace illnesses and injuries. The Framework Document directs that relevance be evaluated in terms of the degree of research priority and connection to improvements in workplace protection. It identifies factors to take into account, including the frequency and severity of health outcomes and the number of people at risk, the structure of the program, and the degree of consideration of stakeholder input (see
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health Appendix A). The impact of the program’s research is to be evaluated in terms of its contributions to worker health and safety. The evaluation is to take the form of qualitative assessments as well as the assignment of scores between 1 and 5 for the relevance and impact of the Hearing Loss Research Program’s research and other activities. The guidance in the Framework Document reflects the terminology and organization of a logic model adopted by NIOSH to characterize the steps in its work. The logic model used by the Hearing Loss Research Program appears as Figure 1-3. An examination of goals, inputs, activities, and outputs was used to assess the relevance of the program’s research. End outcomes and intermediate outcomes were the principal focus for the evaluation of the impact of the program’s research. External factors were taken into consideration in the evaluation. The terms used and the details of the committee’s evaluation are presented in Chapter 2. The study charge also directs the committee to review the progress that the Hearing Loss Research Program has made in identifying new research and provides the committee the opportunity to identify emerging research areas relevant to the program’s mission. According to the Framework Document, the committee’s identification of emerging research areas is to be done using members’ expert judgment rather than a formal research needs identification effort. THE COMMITTEE’S REPORT The remainder of the report presents the findings from the committee’s evaluation. Chapter 2 presents the committee’s review of the NIOSH Hearing Loss Research Program and the ratings for the program’s relevance and impact in reducing workplace injury and illness. In Chapter 3, the committee reviews the Hearing Loss Research Program’s mechanisms for identifying emerging issues in occupational hearing loss and noise control and identifies issues that may warrant future attention. In Chapter 4, the committee identifies opportunities to strengthen the NIOSH Hearing Loss Research Program and increase the relevance and impact of the program’s efforts.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health FIGURE 1-3 Logic model for the Hearing Loss Research Program. SOURCE: NIOSH, 2005a.
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Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health REFERENCES ANSI (American National Standards Institute). 1997. ANSI S12.6. American National Standard Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. New York: Acoustical Society of America. American National Standards Institute. 2002. ANSI S12.51/ ISO 3741:1999. Acoustics—Determination of Sound Power Levels of Noise Sources Using Sound Pressure—Precision Methods for Reverberation Rooms. ANSI S12.51. New York: Acoustical Society of America. ISO (International Organization for Standardization). 1999. ISO 3741: 1999. Acoustics—Determination of Sound Power Levels of Noise Sources Using Sound Pressure—Precision Methods for Reverberation Rooms. Geneva, Switzerland: ISO. Lotz WG (NIOSH). 2006a. RE: info request. E-mail to L Joellenbeck, Institute of Medicine. May 26. Lotz WG (NIOSH). 2006b. RE: seek technical review of figure and caption. E-mail to L Joellenbeck, Institute of Medicine. July 21. Lotz WG (NIOSH). 2006c. RE: seek technical review of figure and caption. E-mail to L Joellenbeck, Institute of Medicine. August 1. NIOSH (National Institute for Occupational Safety and Health). 1972. NIOSH Criteria for a Recommended Standard: Occupational Exposure to Noise. Pub. No. HSM 73-11001. Cincinnati, OH: NIOSH. NIOSH. 1996. Draft Document—Criteria for a Recommended Standard Occupational Noise Exposure: Revised Criteria 1996. Noise Pollution Clearinghouse (NPC) Online Library. [Online]. Available: http://www.nonoise.org/library/niosh/criteria.htm [accessed June 14, 2006]. NIOSH. 1998. Criteria for a Recommended Standard. Occupational Noise Exposure: Revised Criteria 1998. DHHS (NIOSH) Pub. No. 98-126. Cincinnati, OH: NIOSH. NIOSH. 2005a. NIOSH Hearing Loss Research Program: Overview. In: NIOSH Hearing Loss Research Program: Evidence for the National Academies’ Committee to Review the NIOSH Hearing Loss Research Program. Cincinnati, OH: NIOSH. Pp. 19–40. NIOSH. 2005b. NIOSH Overview. In: NIOSH Hearing Loss Research Program: Evidence for the National Academies’ Committee to Review the NIOSH Hearing Loss Research Program. Cincinnati, OH: NIOSH. Pp. 7–17. NIOSH. 2006a. NIOSH Hearing Loss Research Program: Intramural Projects and Budget Distribution, 1997–2005. Unpublished document provided to the Committee to Review the NIOSH Hearing Loss Research Program. Cincinnati, OH: NIOSH. NIOSH. 2006b. NIOSH Hearing Loss Research Program: Peer Review Process for Intramural Research. Unpublished document provided to the Committee to Review the NIOSH Hearing Loss Research Program. Cincinnati, OH: NIOSH. NIOSH. 2006c. NIOSH Hearing Loss Research Program: Research Staff Distribution by Organizational Unit. Unpublished document provided to the Committee to Review the NIOSH Hearing Loss Research Program (January 23). Cincinnati, OH: NIOSH. NIOSH. 2006d. NIOSH Hearing Loss Research Program: Research Staff Distribution by Organizational Unit. Unpublished document provided to the Committee to Review the NIOSH Hearing Loss Research Program (January 30). Cincinnati, OH: NIOSH. U.S. Congress. 1970. The Occupational Safety and Health Act of 1970. Public Law 91-596. Washington, DC: U.S. Congress.
Representative terms from entire chapter: