Occupational hearing loss continues to be one of the most pervasive problems facing today’s workers. More than 30 million Americans across many fields are regularly exposed to hazardous noise levels (Franks et al., 1996; NIH, 2002). In the mining industry, hearing loss is the second most reported injury, representing 20.9 percent of diseases newly reported to the Mine Safety and Health Administration (MSHA) in 2004 (MSHA, 2006). In addition, 25 percent of the mining population
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health 9 Review of Noise-Induced Hearing Loss Prevention Research Key Findings and Recommendations for Noise-Induced Hearing Loss Prevention Research The moderate reductions in noise exposures resulting from partial cabs on surface drilling rigs, coated flight bars on continuous miners, a new dust collector fan design, a jacketed tail roller, and substituting mist for water in roof bolters are important. The Mining Program should accelerate development of engineering controls for mining activities aimed at meeting the NIOSH Recommended Exposure Limit for noise exposure. The rank-ordering of noise exposures for all mining occupations should be performed based on relative exposure levels and the number of people affected. More research should be conducted on speech intelligibility in the midst of high-noise areas and while wearing hearing protection devices, noise control for metal or nonmetal mining, and noise control in longwall mining. Individuals who have experienced hearing loss (particularly older miners) need to be protected from further hearing loss. Verbal and possibly nonverbal communication should be improved to ensure the safety of hearing impaired individuals is not compromised. New noise partnerships should be pursued with stakeholders in mining segments other than coal mining. Occupational hearing loss continues to be one of the most pervasive problems facing today’s workers. More than 30 million Americans across many fields are regularly exposed to hazardous noise levels (Franks et al., 1996; NIH, 2002). In the mining industry, hearing loss is the second most reported injury, representing 20.9 percent of diseases newly reported to the Mine Safety and Health Administration (MSHA) in 2004 (MSHA, 2006). In addition, 25 percent of the mining population
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health is reported to be exposed to levels exceeding the permissible exposure limit (PEL) of 90 dBA (sound level in dB after applying the A-weighting filter). In response, noise is considered by the National Occupational Research Agenda (NORA; http://www.cdc.gov/niosh/nora) to be a high-priority research area for disease and injury prevention, and it continues to be a top priority in NORA-2 (NIOSH, 2005b). In 1997, MSHA established health standards for occupational noise exposure aimed “to prevent the occurrence and reduce the progression of occupational noise-induced hearing loss among miners” (30 CFR Part 62). The 2001 promulgation of Title 30 in the Code of Federal Regulations (30 CFR Part 62), Occupational Noise Exposure, emphasizes the primacy of engineering and administrative noise controls and fuels increased interest in noise-induced hearing loss prevention research by all stakeholders, including universities, manufacturers, government offices, industry associations, labor, mining companies, professional associations, and foreign entities. STRATEGIC GOALS AND OBJECTIVES Strategic goal 2 of the National Institute for Occupational Safety and Health (NIOSH) Mining Program is to “reduce noise-induced hearing loss (NIHL) in the mining industry,” with the “… ultimate long-term measure of success … the elimination of new cases of NIHL.” While it will take decades to assess whether the Mining Program has achieved this goal, the Mining Program has more immediate and quantifiable goals of reducing noise exposure by 25 percent in 5 years and 50 percent in 10 years. These goals, while noble, are not under the direct purview of NIOSH or its Mining Program and can be achieved only with the cooperation of all stakeholders (manufacturers, other government agencies, management, and labor). For example, hearing loss that results from other sources can be hard to separate from occupational sources and would threaten the success of this goal. More appropriate objectives, such as the four intermediate goals listed in Table 9-1, involve producing the technologies and awareness that have the potential to reduce NIHL. The intermediate goals in Table 9-1 are adequate and address the primary barriers to solving the noise problem. Adequate time lines and performance measures were given for each intermediate goal. Some goals—such as 1 and 2— are quantifiable, based on delivering the outputs of the research program (e.g., measured sound powers produced by a machine), monitoring the MSHA database for reports of hearing loss, and performing follow-on surveillance. Other goals—such as 3 and 4—are more difficult to quantify because they involve attitudinal and subjective data.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health TABLE 9-1 Intermediate Goals and Performance Measures of NIHL Prevention Research and Committee Comments Intermediate Goala Performance Measurea Committee Comments 1. Develop and maintain a noise source-worker exposure database for prioritizing noise control technology This goal will be achieved through development of a database of noise source-exposure relationships and equipment noise for all mining commodities and its use by the mining industry and MSHA by 2008 In its current form, not directly tied to reducing noise exposure (primary goal). There are no quantifiable performance or success measures given. End result is not actionable by NIOSH: it cannot force stakeholders to adopt and use the information 2. Develop engineering noise control technologies applicable to surface and underground mining equipment The goal for existing noise controls will be achieved by disseminating comprehensive procedures for the evaluation and application of suitable noise controls in underground and surface metal, nonmetal, and coal mines within 3, 4, and 5 years, respectively. The goal for noise control development will be achieved if the industry implements effective new noise controls that reduce the noise overexposure of miners by 25% (versus the baseline values) by 2009 Same comments as for goal 1, above; actually reducing noise exposure by 25% is not actionable by NIOSH, but NIOSH can increase awareness of noise control technologies 3. Empower workers to acquire and pursue more effective hearing conservation actions This goal will be achieved through measures of dissemination and use of communication, training, and empowerment tools by 2006. A key measure will be the actual noise dose reduction attained through increased prevention behavior and use of dose monitoring systems Needs quantifiable performance measure 4. Improve the reliability of communication in noisy workplaces This goal will be achieved to the extent that key stakeholders acquire, accept, and implement the guidelines on alleviating communications issues by 2006 Same comments as for goal 1 above aSOURCE: NIOSH, 2005a.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health REVIEW OF INPUTS Planning Inputs MSHA data (MSHA, 2006) support the seriousness of NIHL in the mining industry. Noise exposures and incidence of hearing impairment are higher than average among miners. NIOSH has entered into a Noise Partnership with many stakeholders that include the United Mine Workers of America (UMWA), the Bituminous Coal Operators of America (BCOA), the National Mining Association (NMA), MSHA, and several mining equipment manufacturers and suppliers (NIOSH, 2006d).1 Planning inputs to the Mining Program NIHL research program are considered adequate because NIHL is established as the most prevalent disease among the nation’s workforce. No distinction has been made as to whether certain mining populations are more vulnerable than others, although the entire mining population is exposed and at risk. Production Inputs Resources committed to NIHL research have increased in some cases and decreased in others. Hearing loss prevention saw a substantial increase in full-time equivalents (FTEs) from 9 in 1998 to 25 in 2005 (see Table 2-3). While the total budget for the noise program increased, discretionary spending dropped from 30 percent in 1998 to a low of 12 percent in 2004. Discretionary spending then increased to 22 percent in 2005 due to a substantial budget increase by Congress that year, with the additional funds used to support more staff and to construct new facilities, such as the hemi-anechoic chamber. Since in-house research is supported with discretionary funds, presumably any decrease will negatively impact in-house research efforts. In terms of the overall budget, more than 10.2 percent of the 2005 Mining Program budget was spent on hearing loss prevention (HLP) compared to the 4.7 percent spent for HLP in 1998, reflecting the increased emphasis on this subject. 1 The noise partnership was formed in response to the passage of a new noise rule in 1999 (30 CFR Part 62). The partnership provides opportunities for collaborative research with stakeholders related to the Hearing Loss Prevention Program at NIOSH’s Pittsburgh Research Laboratory. The program goal is to reduce noise exposures of the nation’s miners through research efforts associated with worker noise exposure and related sources, noise control technologies, worker empowerment and education, and improved hearing protection devices.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health REVIEW OF ACTIVITIES Hearing loss prevention activities in the Mining Program relate to the seven projects listed in Table 9-2. Each of the projects relates to a corresponding intermediate goal. These projects provide a good mix of surveillance, study, and evaluation of health hazards; development and evaluation of controls; education; technology transfer; and training. Some of the most important issues identified earlier are being addressed in the engineering NIHL prevention studies (3, 4, and 7) and have the potential to significantly reduce noise exposures in mining. Hearing loss surveys indicate most drill operators over 40 years of age have NIHL (NIOSH, 2005a). One problem addressed by the Mining Program is that as mining productivity increases through the use of larger and faster equipment and process developments, noise levels and exposures increase as well. REVIEW OF RESEARCH OUTPUTS A total of 67 of the 1,428 (4.7 percent) Mining Program outputs are related to hearing loss prevention. While the productivity seems low compared to other areas of the Mining Program, it is not surprising, given that the noise program was recently rekindled—from 3 workers in 1998 to more than 20 in 2001—and that it takes time to perform the surveillance required to identify key problems. Outputs appear to address concerns of populations affected by excessive noise levels. Furthermore, the information outputs and tools (software, videos) can be adopted by small business to include in their training programs. Some cross-agency collaboration (Pittsburgh Research Laboratory; Division of Applied Research and Technology; Division of Surveillance, Hazard Evaluations, and Field Studies; and others) is reported, although cross-agency collaboration could be strengthened. Of the 67 outputs, 13 are linked to intermediate outcomes discussed later. A variety of outputs have been produced and the findings disseminated through a number of venues. Printed media include more than two dozen conference and journal publications, safety bulletins, NIOSH Information Circulars, a book chapter, and a public report. The Mining Program has also produced numerous in-house reports that have been shared with industry partners to help improve their noise management strategies. At least one stakeholder reported posting noise contour maps developed by NIOSH so that employees can see first hand where the high-noise areas are in the processing plants. In addition, NIOSH has produced three promising and feasible control technologies that are included in the MSHA Public Information Bulletin (PIB) 30 CFR Part 62. Equipment manufacturers and mine operators look to such documents to solve their noise problems. Other products include training aids, such as the hearing loss simulator software, various web documents, a training video, and others.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health Nearly 10 workshops have been conducted around the country, including one for the Noise Partnership, one for the National Ground Water Association Expo, and many for state or regional well-water associations. The outputs convey surveillance findings, address educational challenges, and target high-priority NIHL prevention topics through engineering or administrative controls. The wide variety of products ensures that all segments of the population can be reached. Noticeably absent, however, are patents related to noise control research. While cumbersome in many respects (cost, time, licensing agreements, collaborative environment, etc.), they would ensure that NIOSH gets due credit for its research developments. REVIEW OF TRANSFER ACTIVITIES Transfer activities include a mix of conference presentations and publications, collaborations with industry partners, development of databases outlining exposure assessments, development of engineering and administrative controls, and educational products. A coherent plan to transfer activities is being executed. A wide variety of publication types (conference and journal papers, book chapters, information bulletins or circulars, and reports) has been created. This diverse mix of publications reaches all segments of the mining industry, including equipment manufacturers, academics, mine operators, labor, and safety or hygiene officials. The Internet is well used to disseminate publications and training aids, such as software and videos. Some stakeholders testified that the Mining Program is a “technical conduit” for new technology, and there is anecdotal evidence to show that it has been successful at communicating. Stakeholders also emphasized that noise should continue to be a high-focus area for mining research. A few transfer activities merit special attention. The Noise Partnership, between the Mining Program and its stakeholders, conducts semiannual workshops to facilitate two-way information exchange. The Hearing Loss Prevention Unit (mobile audiology van) has visited 42 locations around the country and performed hearing tests on more than 5,400 workers, including more than 1,900 miners. This van serves a dual purpose: in addition to conducting hearing tests, it serves as a research aid using data gathered from the hearing tests. A Hearing Loss Simulator software program allows workers to experience first hand the effects of hearing loss that can be expected for their given exposure levels. Finally, instructing miners in the “roll-pull-hold” method of inserting foam earplugs, while not particularly new, offers a fun and “catchy” method of remembering the correct way of inserting earplugs. The last two activities—the Hearing Loss Simulator and the roll-pull-hold method—are activities aimed directly at miners. In addition, many stakeholders provided anecdotal evidence that these NIOSH activities have made an impact in the workplace.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health TABLE 9-2 Noise-Induced Hearing Loss Prevention Projects and Committee Assessment of Relevance and Impact Project Titlea Intermediate Goal Descriptiona Relevance Impact 1. A Health Hazard Study of Surface Drilling Operations 1 Noise dosimetry and time-at-task measurements to determine the extent of noise exposures from each process in surface drilling. Development of a universal, partial cab for surface drilling rigs Recent data have shown that most well drillers over the age of 40 have NIHL Results have the potential to reduce noise exposures of well drillers through administrative and engineering controls 2. Cross-Sectional Survey: Noise Exposure Patterns and Sources 1 Surveillance establishing noise exposure profiles for various mining occupations, mining equipment noise emission profiles, and exposure-response relationships The magnitude of the problem and critical areas requiring research will be assessed. A baseline to gauge future noise control efforts will be established Survey results will identify and rank-order the most critical noise problems in the industry and provide a baseline to gauge future performance 3. Definition and Assessment of Engineering Noise Controls 2 Evaluate the efficacy of various noise control technologies In situ measurements will offer realistic measures of performance Publication of in situ measurement results could prove helpful to manufacturers of other large equipment outside the mining industry 4. Engineering Noise Controls for Roof Bolting Machines 2 Determine and implement appropriate engineering controls to reduce excessive exposure to noise on the job and prevent additional cases of NIHL related to roof bolting machine operators Roof bolter operators suffer the third-worst overexposure to noise (MSHA, 2006) Controls could reduce exposures to roof-bolter noise and bring them into compliance
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health 5. Health Communication Interventions for Hearing Loss Prevention 3 This effort addresses problematic attitudes and behaviors regarding personal protective equipment and safeguarding hearing through knowledge and skills training These efforts are complemented by two other substantial educational products: hearing loss simulator software and the “roll-and-hold” method of inserting foam hearing protectors An additional 9 dB in the noise reduction rating (NRR) was achieved by the roll-and-hold method in a laboratory setting. Education can empower miners to care for their hearing 6. Hearing Loss Prevention: Hearing Protection and Audibility Considerations 4 Develop recommendations and strategies for mine operators and mine workers that will improve the audibility of spoken communication and hazard or warning signals in the mining environment while preventing additional cases of NIHL More advanced muffs, with active electronics and internal microphones, can provide active cancellation of noise signals as well as noise measurements behind the hearing protection device (HPD). Actual attenuations provided by HPDs tend to be highly variable and much lower than the reported values, owing to imperfect usage (Berger et al., 2000) The project has the potential to improve communication, which is hampered by the use of conventional HPDs 7. Pilot Study on Coal Cutting Noise Related to Continuous Mining Machines 2 Determine the significance of cutting noise relative to the noise exposure of continuous mining machine operators Continuous miners create the greatest number of noise overexposures (MSHA, 2006). While conveyor and dust scrubber noise has been addressed, no attention has been given until now to the noise generated by cutting coal. The contribution of cutting noise will be determined by in situ underground measurements Publication of in situ measurement results could prove helpful to manufacturers of other large equipment outside the mining industry aSOURCE: NIOSH, 2005a.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health REVIEW OF INTERMEDIATE OUTCOMES AND CAUSAL IMPACT Three intermediate outcomes for hearing loss prevention are listed in the Mining Program Briefing Book (NIOSH, 2005a): Motivating prevention behaviors with the NIOSH Hearing Loss Simulator, Noise reduction of roof bolting machines using wet and mist drilling, and Reducing noise on continuous mining machines using coated flight bars. The Hearing Loss Simulator software appears to be a very successful training aid, judging from the number of requests (>300), including organizations such as the National Hearing Conservation Association, Council for Accreditation in Occupational Hearing Conservation, equipment manufacturers, and safety organizations from 11 different countries. It is clear that the software tool has general appeal for educating workers and officials on the perils of hearing loss, while empowering the worker through education. Reports from users of the software tool describe a greatly increased understanding of the effects of NIHL and changed attitudes toward protecting their hearing. The Hearing Loss Simulator software has been far-reaching, having received a lot of interest outside the mining community and around the globe. Reduced exposure to noise will result in reduced NIHL (ISO, 1990; ANSI, 1996). New control technologies (mist drilling,2 and coated flight bars for continuous miners3) have been developed with significant noise reductions. The mist-drilling system provides a more sustainable mining practice by using less water than traditional methods. In addition, the mining environment is made more comfortable and potentially safer, since pooled water on the mine floor is reduced. Engineering measurements show that the sound power levels of roof bolters and continuous mining machines have been reduced, which in turn has resulted in reduced noise levels (and exposures) at the operator position (NIOSH, 2005a). Unlike long-term exposure and audiometric records, laboratory data are objective and directly attributable to NIOSH efforts, since they demonstrate the before and after noise exposures. Significant reductions of 2 to 7 dBA for the roof bolter and 7 dBA for the continuous miner were reported. Laboratory tests also show reductions of 8 to 15 dBA from the partial cab being developed for the drilling rig. Typically, field tests will show less improvement, although these results are encouraging nevertheless. Similarly the “roll-pull-hold” method of inserting foam earplugs is reported to improve the effec- 2 See NIOSH Information Bulletin P04-18, 2005, available at http://www.msha.gov/regs/complian/PIB/2004/pib04-18.pdf [accessed November 10, 2006]. 3 See NIOSH Information Bulletin P04-18, 2005, available at http://www.msha.gov/regs/complian/PIB/2004/pib04-18.pdf.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health tive noise reduction rating (NRR) by 9 dB in a laboratory setting. Note that for each 5 dBA reduction in noise exposure, the corresponding dose would be cut in half (for the 5 dB exchange rate promulgated in 30 CFR Part 62). NIOSH advocates use of a 3 dB exchange rate, which if adopted would result in more significant reductions in dose per given reduction in sound level (NIOSH, 1998), albeit for higher overall doses. The committee would expect a reduction in NIHL with industry acceptance and implementation of NIOSH recommendations. It is not clear to the committee why the Mining Program does not better advocate the use of earmuffs or circumaural hearing protectors, which have been shown to deliver a significantly higher percentage of the laboratory attenuation in the field than earplugs (NIOSH, 1998; Berger et al., 2000). Earmuffs are generally more reliable and less dependent upon user skill, training, and motivation, but admittedly are construed as more uncomfortable by some workers. Perhaps most importantly, the proposed equipment changes for engineering noise-induced hearing loss prevention appear economically and technically feasible. Further, some are designated by MSHA as providing “promise” of reducing noise exposure (MSHA, 2004b). Due to the strong collaborative efforts between labor, industry, manufacturers, and government, equipment changes were adopted quickly. Coated flight bars are manufactured and available through Joy Mining Machinery, which also makes a retrofit mist drilling kit for the J. H. Fletcher & Co. roof bolter. Reportedly, these products are already in use and are being evaluated in situ, but no quantitative data are given. No distinction between gender differences or protecting vulnerable populations has been made. Considerations of particularly vulnerable groups should be built into research designs from the beginning to produce information on any special problems that may cause vulnerability. It should also be noted that reducing noise exposures should theoretically provide benefit to all segments of the mining workforce. REVIEW OF END OUTCOMES The desired end outcome, as expressed by the Mining Program, is to reduce the incidence of NIHL in the mining population. Aside from the limitations to achieving these goals mentioned earlier, it will take decades to assess the impact of the noise program outputs, which are just emerging. It is too early to establish any trends. Field tests to evaluate innovations are ongoing. As for the end outcomes associated with the Hearing Loss Simulator, the best evaluation data were self-reported, based on attitudinal surveys given to workers before and after using the software. More extensive research is planned to better quantify the effects of this and other research.
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health ASSESSMENT OF RELEVANCE AND IMPACT It is difficult to rate the budding noise research group within the Mining Program, but ratings are based on the moderate contribution of intermediate outcomes, as well as the promise that current projects have to continue to deliver innovations for noise control. It will take multiple decades to realize the ultimate end outcome—the reduction or elimination of NIHL. Reductions in noise exposure are generally accepted to translate into a reduction in noise dose, and given the lack of data regarding the actual reduction rates of NIHL, the committee is using exposure reduction as a proxy to measured end outcomes. The moderate reductions in noise exposures to operations from adding a partial cab to surface drilling rigs, coating the flight bars of continuous miners, new dust collector fan design, jacketed tail roller, and substituting mist for water in roof bolters (drills) are significant (9, 7, 5, 3, and 2-7 dBA, respectively). The most popular makes of roof bolter and continuous miner were targeted for modification so that research results have the greatest chance of adoption by the mining industry. The simplified roll-pull-hold method of foam earplug insertion (the most popular type of hearing protection device [HPD]) has resulted in a reported 9 dB increase in NRR under ideal circumstances. The ongoing surveillance program has established the most pressing noise problems in the mining industry as well as baseline measurements to eventually assess the efficacy of control technologies. Aside from refining the goals under the purview of NIOSH, the rank ordering of noise exposures for all mining occupations should be determined based on relative exposure levels and the number of people affected. To date, no investigation of vulnerable populations, gender differences, and so forth, has been conducted, presumably to make most efficient use of the resources available. The Mining Program should continue to ensure that it reaches all segments of the mining community with new information, especially smaller mines and equipment manufacturers. More research should be conducted on speech intelligibility in the midst of high-noise areas and while wearing HPDs. New noise partnerships should be organized with the metal and nonmetal mining sectors and more NIHL research should be conducted for this mining segment. Longwall mining, though affecting relatively few, is a particularly noisy occupation that should ultimately be addressed. PROGRESS IN TARGETING NEW RESEARCH The Mining Program assesses research needs in multiple ways: (1) by studying the MSHA accident and injury database (MSHA, 2006); (2) by conducting noise surveys; and (3) by collecting input from stakeholders. Noise surveys include noise contour mapping, dosimetry, and time-at-task observations (the “gold standard”
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Mining Safety and Health Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health of surveying). Stakeholder interaction is enhanced through the Noise Partnership group, previously mentioned. It appears that the Noise Partnership is heavily focused on coal mining noise. If this is the case, it should be expanded to include metal and nonmetal mining. Signature Accomplishment: Education and Training Through Mobile Audiometric Testing The Hearing Loss Prevention Unit (HLPU), developed by the Mining Program, consists of a sound-insulated 32-foot trailer containing four independent, computer-controlled audiometric testing stations. The HLPU travels around the country to conferences and to remote mine locations educating miners and their families about noise-induced hearing loss and hearing protection. Not only can it conduct hearing evaluations, but it is also used by the Mining Program for training—such as teaching workers the proper way to insert hearing protectors—and for research projects. A counseling area inside the booth contains audiovisual equipment used to present educational materials. The HLPU can be configured to perform a wide range of research tasks, including hearing test feedback as part of training programs, training in proper use of hearing protectors, and supporting more effective hearing loss programs aimed at protecting the hearing of the nation’s miners. The Hearing Loss Prevention Unit developed by the Mining Program.
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