NOISE AND HEARING LOSS PREVENTION
Hearing Loss Prevention Programs
Recommendations for effective hearing loss prevention practices and the rationale behind them can be found in two of NIOSH publications, the Criteria For a Recommended Standard: Occupational Noise Exposure, and in the Preventing Occupational Hearing Loss – A Practical Guide.
In 1983, a Hearing Conservation AmendmentExternal was added to the OSHA Occupational Noise Exposure Standard (29 CFR 1910.95) requiring that a hearing conservation program be implemented when employee noise exposures equal or exceed an 8 hour time-weighted average sound level of 85 dBA.
NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure
The NIOSH recommended exposure limit (REL) for occupational noise exposure (85 decibels, A-weighted, as an 8-hour time-weighted average [85 dBA as an 8-hr TWA]) was reevaluated using contemporary risk assessment techniques and incorporating the 4000-hertz (Hz) audiometric frequency in the definition of hearing impairment. The new risk assessment reaffirms support for the 85-dBA REL. With a 40-year lifetime exposure at the 85-dBA REL, the excess risk of developing occupational NIHL is 8%—considerably lower than the 25% excess risk at the 90-dBA permissible exposure limit (PEL) currently enforced by the Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA). NIOSH recommends a 3-dB exchange rate, which is more firmly supported by scientific evidence. The 5-dB exchange rate is still used by OSHA and MSHA, but the 3-dB exchange rate has been increasingly supported by national and international consensus. NIOSH recommends an improved criterion for significant threshold shift: an increase of 15 dB in the hearing threshold level (HTL) at 500, 1000, 2000, 3000, 4000, or 6000 Hz in either ear, as determined by two consecutive audiometric tests. The new criterion has the advantages of a high identification rate and a low false-positive rate. The NIOSH criterion no longer recommends age correction on individual audiograms. OSHA currently allows age correction only as an option. Finally, regarding hearing protection, NIOSH indicated that the noise reduction rating (NRR), a single-number, laboratory-derived rating that the U.S. Environmental Protection Agency (EPA) requires to be shown on the label of each hearing protector sold in the United States is not adequate. In calculating the noise exposure to the wearer of a hearing protector at work, NIOSH recommends derating the NRR by subtracting from the NRR 25%, 50%, and 70% for earmuffs, formable earplugs, and all other earplugs, respectively. Today, the issue of hearing protection attenuation is best addressed by testing the performance of hearing protection objectively. This fit testing technology is a huge advancement in efforts to save workers’ hearing (see NIOSH Science Blog: HPD Well-Fit™: The Future is Fit-Testing). Finally, the NIOSH criteria document provides recommendations for the management of hearing loss prevention programs (HLPPs) for workers whose noise exposures equal or exceed 85 dBA. The recommendations include program evaluation, which was not articulated in the previous 1972 criteria document and is not included in the OSHA and MSHA standards.
Preventing Occupational Hearing Loss – A Practical Guide
In 1996, NIOSH published Preventing Occupational Hearing Loss – A Practical Guide, In this document, NIOSH highlights the hierarchy of controls which can be summarized as: 1) first, prevent or contain the escape of the hazardous workplace agent at its source (engineering control); 2) control exposure by relocating the worker to a safe area (administrative controls); and 3) control the exposure with barriers between the worker and the hazard (personal protective equipment). This hierarchy underscores the principle that the best of all prevention strategies is to have no exposure to agents that can cause or contribute to hearing loss. Corporations that have embarked upon Buy-Quiet programs are moving towards the creation of a workplace where there will be no harmful noise. Many companies are automating equipment or setting up procedures that can be operated by workers from a quiet control room free from harmful noise, chemical agents, and heat. When it is not possible to remove the harmful agent or relocate the worker to a safe area, the worker must be protected. In the arena of hearing loss prevention, protection is a many-faceted process that includes exposure assessment, provision of protective equipment, assessment of hearing with appropriate management and follow-up actions, worker education and training, and continuous evaluation of program effectiveness.
Both the Criteria Document and the Practical Guide present attributes of successful hearing- loss prevention programs. Check them for guidance for each of eight components of such a program, which are:
- Noise exposure monitoring
- Engineering and administrative controls
- Audiometric evaluation
- Hearing protection devices
- Education and motivation
- Record keeping
- Program evaluation
- Program audit
Achieving Results in Hearing Loss Prevention in the Workplace
While many workplaces comply with legal or obligatory requirements and implement recommended interventions, few publications document the effectiveness of these actions. The evaluation of intervention effectiveness contributes to improved worker health and safety. NIOSH used two different approaches to address this issue: the first one was to conduct research, including broad systematic reviews on the effectiveness of interventions to prevent occupational noise-induced hearing loss. For more information, see:
- Heyer N, Morata TC, Pinkerton L, Brueck S, Stanescu D, Prince M, Kim H, Sinclair B, Waters M, Estill C, Franks J. (2011). Use of historical data and a novel metric in the evaluation of the effectiveness of hearing conservation program componentsExternal
- Stephenson-CM; Stephenson-MR.  Hearing loss prevention for carpenters: part 1 – using health communication and health promotion models to develop training that worksExternal
- Stephenson-MR; Shaw-PB; Stephenson-CM; Graydon-PS.  Hearing loss prevention for carpenters: part 2 – demonstration projects using individualized and group trainingExternal
- Verbeek JH, Kateman E, Morata TC, Dreschler WA, Mischke C.  Interventions to prevent occupational noise-induced hearing lossExternal
The second approach NIOSH used to obtain evidence on the effectiveness of hearing loss prevention interventions was to create an award program, the Safe-In-Sound Excellence in Hearing Loss Prevention Award™External, to identify and honor excellent real-world examples of noise control and other hearing loss prevention practices and innovations. The Safe-in-Sound Award™ implements a rigorous systematic applicant review process to capture and evaluate the successes and lessons learned from examples of excellence in hearing loss prevention programs. Since 2009, awards are presented annually at the NHCA annual conference by the NIOSH director or his or her representative. Safe-in-Sound Award™ winnerExternal and the program’s outcomesExternal, including values and characteristics were summarized at:
- Meinke DK, Morata TC.  Awarding and promoting excellence in hearing loss preventionExternal.
- Morata T, Meinke D.  Uncovering effective strategies for hearing loss preventionExternal.
Hearing Loss Prevention Program Checklist
Researchers at the University of Washington, University of Michigan, and Yale University recently completed a NIOSH-funded study to evaluate the effectiveness of individual elements of industrial hearing loss prevention programs. The researchers examined programs at 14 facilities operated by a single US metals manufacturing company. Using the results of this evaluation, the researchers developed a hearing loss prevention program checklistExternal to allow program managers and staff to assess their own programs in two ways. First, they can assess compliance with program requirements from the Occupational Safety and Health Administration. Second, they can assess the extent to which they are employing best practices identified by the researchers, as well as NIOSH and other agencies and organizations. To access the checklist, click hereExternal.