Hearing protection field attenuation estimation systems and associated training for reducing workers' exposure to noise.

BACKGROUND: Global Burden of Disease studies identify hearing loss as the third leading cause of years lived with a disability. Their estimates point to large societal and individual costs from unaddressed hearing difficulties. Workplace noise is an important modifiable risk factor; if addressed, it could significantly reduce the global burden of disease. In practice, providing hearing protection devices (HPDs) is the most common intervention to reduce noise exposure at work. However, lack of fit of HPDs, especially earplugs, can greatly limit their effectiveness. This may be the case for 40% of users. Testing the fit and providing instructions to improve noise attenuation might be effective. In the past two decades, hearing protection fit-test systems have been developed and evaluated in the field. They are called field attenuation estimation systems. They measure the noise attenuation obtained by individual workers using HPDs. If there is a lack of fit, instruction for better fit is provided, and may lead to better noise attenuation obtained by HPDs. OBJECTIVES: To assess: (1) the effects of field attenuation estimation systems and associated training on the noise attenuation obtained by HPDs compared to no instruction or to less instruction in workers exposed to noise; and (2) whether these interventions promote adherence to HPD use. SEARCH METHODS: We used CENTRAL, MEDLINE, five other databases, and two trial registers, together with reference checking, citation searching, and contact with study authors to identify studies. We imposed no language or date restrictions. The latest search date was February 2024. SELECTION CRITERIA: We included randomised controlled trials (RCTs), cluster-RCTs, controlled before-after studies (CBAs), and interrupted time-series studies (ITSs) exploring HPD fit testing in workers exposed to noise levels of more than 80 A-weighted decibels (or dBA) who use hearing protection devices. The unit 'dBA' reports on the use of a frequency-weighting filter to adjust sound measurement results to better reflect how human ears process sound. The outcome noise attenuation had to be measured either as a personal attenuation rating (PAR), PAR pass rate, or both. PAR pass rate is the percentage of workers who passed a pre-established level of sufficient attenuation from their HPDs, identified on the basis of their individual noise exposure. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed study eligibility, risk of bias, and extracted data. We categorised interventions as fit testing of HPDs with instructions at different levels (no instructions, simple instructions, and extensive instructions). MAIN RESULTS: We included three RCTs (756 participants). We did not find any studies that examined whether fit testing and training contributed to hearing protector use, nor any studies that examined whether age, gender, or HPD experience influenced attenuation. We would have included any adverse effects if mentioned by the trial authors, but none reported them. None of the included studies blinded participants; two studies blinded those who delivered the intervention. Effects of fit testing of HPDs with instructions (simple or extensive) versus fit testing of HPDs without instructions Testing the fit of foam and premoulded earplugs accompanied by simple instructions probably does not improve their noise attenuation in the short term after the test (1-month follow-up: mean difference (MD) 1.62 decibels (dB), 95% confidence interval (CI) -0.93 to 4.17; 1 study, 209 participants; 4-month follow-up: MD 0.40 dB, 95% CI -2.28 to 3.08; 1 study, 197 participants; both moderate-certainty evidence). The intervention probably does not improve noise attenuation in the long term (MD 0.15 dB, 95% CI -3.44 to 3.74; 1 study, 103 participants; moderate-certainty evidence). Fit testing of premoulded earplugs with extensive instructions on the fit of the earplugs may improve their noise attenuation at the immediate retest when compared to fit testing without instructions (MD 8.34 dB, 95% CI 7.32 to 9.36; 1 study, 100 participants; low-certainty evidence). Effects of fit testing of HPDs with extensive instructions versus fit testing of HPDs with simple instructions Fit testing of foam earplugs with extensive instructions probably improves their attenuation (MD 8.62 dB, 95% CI 6.31 to 10.93; 1 study, 321 participants; moderate-certainty evidence) and also the pass rate of sufficient attenuation (risk ratio (RR) 1.75, 95% CI 1.44 to 2.11; 1 study, 321 participants; moderate-certainty evidence) when compared to fit testing with simple instructions immediately after the test. This is significant because every 3 dB decrease in noise exposure level halves the sound energy entering the ear. No RCTs reported on the long-term effectiveness of the HPD fit testing with extensive instructions. AUTHORS' CONCLUSIONS: HPD fit testing accompanied by simple instructions probably does not improve noise attenuation from foam and premoulded earplugs. Testing the fit of foam and premoulded earplugs with extensive instructions probably improves attenuation and PAR pass rate immediately after the test. The effects of fit testing associated with training to improve attenuation may vary with types of HPDs and training methods. Better-designed trials with larger sample sizes are required to increase the certainty of the evidence.

New Metrics Needed in the Evaluation of Hearing Hazard Associated With Industrial Noise Exposure.

OBJECTIVES: To evaluate (1) the accuracy of the International Organization for Standardization (ISO) standard ISO 1999 [(2013), International Organization for Standardization, Geneva, Switzerland] predictions of noise-induced permanent threshold shift (NIPTS) in workers exposed to various types of high-intensity noise levels, and (2) the role of the kurtosis metric in assessing noise-induced hearing loss (NIHL). DESIGN: Audiometric and shift-long noise exposure data were acquired from a population (N = 2,333) of screened workers from 34 industries in China. The entire cohort was exclusively divided into subgroups based on four noise exposure levels (85 ≤ LAeq.8h < 88, 88 ≤ LAeq.8h < 91, 91 ≤ LAeq.8h < 94, and 94 ≤ LAeq.8h ≤ 100 dBA), two exposure durations (D ≤ 10 years and D > 10 years), and four kurtosis categories (Gaussian, low-, medium-, and high-kurtosis). Predicted NIPTS was calculated using the ISO 1999 model for each participant and the actual measured NIPTS was corrected for age and sex also using ISO 1999. The prediction accuracy of the ISO 1999 model was evaluated by comparing the NIPTS predicted by ISO 1999 with the actual NIPTS. The relation between kurtosis and NIPTS was also investigated. RESULTS: Overall, using the average NIPTS value across the four audiometric test frequencies (2, 3, 4, and 6 kHz), the ISO 1999 predictions significantly (p < 0.001) underestimated the NIPTS by 7.5 dB on average in participants exposed to Gaussian noise and by 13.6 dB on average in participants exposed to non-Gaussian noise with high kurtosis. The extent of the underestimation of NIPTS by ISO 1999 increased with an increase in noise kurtosis value. For a fixed range of noise exposure level and duration, the actual measured NIPTS increased as the kurtosis of the noise increased. The noise with kurtosis greater than 75 produced the highest NIPTS. CONCLUSIONS: The applicability of the ISO 1999 prediction model to different types of noise exposures needs to be carefully reexamined. A better understanding of the role of the kurtosis metric in NIHL may lead to its incorporation into a new and more accurate model of hearing loss due to noise exposure.

Cochrane corner: interventions to prevent hearing loss caused by noise at work.

This Cochrane Corner features "Interventions to prevent hearing loss caused by noise at work", published in 2017. The aim of this Cochrane Review was to find out if hearing loss caused by noise at work is being prevented by current interventions. Tikka et al. identified 29 studies that studied the effect of preventive measures. One study evaluated legislation to reduce noise exposure, eleven studies evaluated effects of personal hearing protection devices and 17 studies evaluated effects of hearing loss prevention programmes (HLPPs). There was some very low-quality evidence that implementation of stricter legislation can reduce noise levels in workplaces and moderate-quality evidence that training of proper insertion of earplugs significantly reduces noise exposure at short-term follow-up. This Cochrane review has identified specific strategies that have shown effectiveness in reducing workplace noise, such as the implementation of stricter legislation and the need for training in the proper use of earplugs and earmuffs to reduce noise exposure to safe levels. The overall quality of evidence for the effectiveness of HLPPs in preventing hearing loss was very low, there was limited follow-up of participants receiving training for insertion of earplugs and no controlled studies examining engineering controls to reduce workplace noise.

Jet fuel exposure and auditory outcomes in Australian air force personnel.

BACKGROUND: Animal data suggest that jet fuels such as JP-8 are associated with hearing deficits when combined with noise and that the effect is more pronounced than with noise exposure alone. Some studies suggest peripheral dysfunction while others suggest central auditory dysfunction. Human data are limited in this regard. The aim of this study was to investigate the possible chronic adverse effects of JP-8 combined with noise exposure on the peripheral and central auditory systems in humans. METHODS: Fifty-seven participants who were current personnel from the Royal Australian Air Force were selected. Based on their levels of exposure to jet fuels, participants were divided into three exposure groups (low, moderate, high). Groups were also categorised based on their noise exposure levels (low, moderate, high). All participants were evaluated by tympanometry, pure-tone audiometry (1-12 kHz), distortion product otoacoustic emissions (DPOAEs), auditory brainstem response (ABR), words-in-noise, compressed speech, dichotic digit test, pitch pattern sequence test, duration pattern sequence test and adaptive test of temporal resolution. All auditory tests were carried out after the participants were away from the Air Force base for a minimum of two weeks, thus two weeks without jet fuel and noise exposure. RESULTS: Jet fuel exposure was significantly associated with hearing thresholds at 4 and 8 kHz; average hearing thresholds across frequencies in the better ear; DPOAEs at 2.8, 4 and 6 kHz; ABR wave V latency in the right ear; compressed speech and words-in-noise. Further analyses revealed that participants with low exposure level to jet fuels showed significantly better results for the aforementioned procedures than participants with moderate and high exposure levels. All results were controlled for the covariates of age and noise exposure levels. CONCLUSIONS: The results suggest that jet fuel exposure, when combined with noise exposure, has an adverse effect on audibility in humans. Taking all the test results into consideration, jet fuel exposure combined with noise exposure specifically seems to affect the peripheral hearing system in humans.

Auditory system dysfunction in Brazilian gasoline station workers.

Objective: To examine the auditory system of Brazilian gasoline station workers using an extensive audiological test battery. Design: This was a cross-sectional study. The audiological evaluation included a questionnaire, pure-tone audiometry, acoustic immittance tests, transient-evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), auditory brainstem response (ABR) and P300 auditory-evoked potentials. Study sample: A total of 77 Brazilian gasoline station workers were evaluated, and their results were compared with those of 36 participants who were not exposed to chemicals or noise at work. The gasoline station employees worked in 18 different gas stations, and the noise area measurements from all gas stations revealed time-weighted averages below 85 dBA. Results: Of the 77 gasoline station workers evaluated, 67.5% had audiometric results within the normal range, but 59.7% reported difficulties in communication in noisy places. Gasoline station workers showed significantly poorer results than non-exposed control participants in one or more conditions of each of the audiological tests used, except P300. Conclusions: The results suggest that the gasoline station workers have both peripheral and central auditory dysfunctions that could be partly explained by their exposure to gasoline.

Use of the kurtosis statistic in an evaluation of the effects of noise and solvent exposures on the hearing thresholds of workers: An exploratory study.

The aim of this exploratory study was to examine whether the kurtosis metric can contribute to investigations of the effects of combined exposure to noise and solvents on human hearing thresholds. Twenty factory workers exposed to noise and solvents along with 20 workers of similar age exposed only to noise in eastern China were investigated using pure-tone audiometry (1000-8000 Hz). Exposure histories and shift-long noise recording files were obtained for each participant. The data were used in the calculation of the cumulative noise exposure (CNE) and CNE adjusted by the kurtosis metric for each participant. Passive samplers were used to measure solvent concentrations for each worker exposed to solvents over the full work shift. Results showed an interaction between noise exposure and solvents for the hearing threshold at 6000 Hz. This effect was observed only when the CNE level was adjusted by the kurtosis metric.

Interventions to prevent occupational noise-induced hearing loss.

BACKGROUND: This is the second update of a Cochrane Review originally published in 2009. Millions of workers worldwide are exposed to noise levels that increase their risk of hearing disorders. There is uncertainty about the effectiveness of hearing loss prevention interventions. OBJECTIVES: To assess the effectiveness of non-pharmaceutical interventions for preventing occupational noise exposure or occupational hearing loss compared to no intervention or alternative interventions. SEARCH METHODS: We searched the CENTRAL; PubMed; Embase; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; and OSH UPDATE to 3 October 2016. SELECTION CRITERIA: We included randomised controlled trials (RCT), controlled before-after studies (CBA) and interrupted time-series (ITS) of non-clinical interventions under field conditions among workers to prevent or reduce noise exposure and hearing loss. We also collected uncontrolled case studies of engineering controls about the effect on noise exposure. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study eligibility and risk of bias and extracted data. We categorised interventions as engineering controls, administrative controls, personal hearing protection devices, and hearing surveillance. MAIN RESULTS: We included 29 studies. One study evaluated legislation to reduce noise exposure in a 12-year time-series analysis but there were no controlled studies on engineering controls for noise exposure. Eleven studies with 3725 participants evaluated effects of personal hearing protection devices and 17 studies with 84,028 participants evaluated effects of hearing loss prevention programmes (HLPPs). Effects on noise exposure Engineering interventions following legislationOne ITS study found that new legislation in the mining industry reduced the median personal noise exposure dose in underground coal mining by 27.7 percentage points (95% confidence interval (CI) -36.1 to -19.3 percentage points) immediately after the implementation of stricter legislation. This roughly translates to a 4.5 dB(A) decrease in noise level. The intervention was associated with a favourable but statistically non-significant downward trend in time of the noise dose of -2.1 percentage points per year (95% CI -4.9 to 0.7, 4 year follow-up, very low-quality evidence). Engineering intervention case studiesWe found 12 studies that described 107 uncontrolled case studies of immediate reductions in noise levels of machinery ranging from 11.1 to 19.7 dB(A) as a result of purchasing new equipment, segregating noise sources or installing panels or curtains around sources. However, the studies lacked long-term follow-up and dose measurements of workers, and we did not use these studies for our conclusions. Hearing protection devicesIn general hearing protection devices reduced noise exposure on average by about 20 dB(A) in one RCT and three CBAs (57 participants, low-quality evidence). Two RCTs showed that, with instructions for insertion, the attenuation of noise by earplugs was 8.59 dB better (95% CI 6.92 dB to 10.25 dB) compared to no instruction (2 RCTs, 140 participants, moderate-quality evidence). Administrative controls: information and noise exposure feedbackOn-site training sessions did not have an effect on personal noise-exposure levels compared to information only in one cluster-RCT after four months' follow-up (mean difference (MD) 0.14 dB; 95% CI -2.66 to 2.38). Another arm of the same study found that personal noise exposure information had no effect on noise levels (MD 0.30 dB(A), 95% CI -2.31 to 2.91) compared to no such information (176 participants, low-quality evidence). Effects on hearing loss Hearing protection devicesIn two studies the authors compared the effect of different devices on temporary threshold shifts at short-term follow-up but reported insufficient data for analysis. In two CBA studies the authors found no difference in hearing loss from noise exposure above 89 dB(A) between muffs and earplugs at long-term follow-up (OR 0.8, 95% CI 0.63 to 1.03 ), very low-quality evidence). Authors of another CBA study found that wearing hearing protection more often resulted in less hearing loss at very long-term follow-up (very low-quality evidence). Combination of interventions: hearing loss prevention programmesOne cluster-RCT found no difference in hearing loss at three- or 16-year follow-up between an intensive HLPP for agricultural students and audiometry only. One CBA study found no reduction of the rate of hearing loss (MD -0.82 dB per year (95% CI -1.86 to 0.22) for a HLPP that provided regular personal noise exposure information compared to a programme without this information.There was very-low-quality evidence in four very long-term studies, that better use of hearing protection devices as part of a HLPP decreased the risk of hearing loss compared to less well used hearing protection in HLPPs (OR 0.40, 95% CI 0.23 to 0.69). Other aspects of the HLPP such as training and education of workers or engineering controls did not show a similar effect.In three long-term CBA studies, workers in a HLPP had a statistically non-significant 1.8 dB (95% CI -0.6 to 4.2) greater hearing loss at 4 kHz than non-exposed workers and the confidence interval includes the 4.2 dB which is the level of hearing loss resulting from 5 years of exposure to 85 dB(A). In addition, of three other CBA studies that could not be included in the meta-analysis, two showed an increased risk of hearing loss in spite of the protection of a HLPP compared to non-exposed workers and one CBA did not. AUTHORS' CONCLUSIONS: There is very low-quality evidence that implementation of stricter legislation can reduce noise levels in workplaces. Controlled studies of other engineering control interventions in the field have not been conducted. There is moderate-quality evidence that training of proper insertion of earplugs significantly reduces noise exposure at short-term follow-up but long-term follow-up is still needed.There is very low-quality evidence that the better use of hearing protection devices as part of HLPPs reduces the risk of hearing loss, whereas for other programme components of HLPPs we did not find such an effect. The absence of conclusive evidence should not be interpreted as evidence of lack of effectiveness. Rather, it means that further research is very likely to have an important impact.

Hearing Impairment Among Noise-Exposed Workers - United States, 2003-2012.

Hearing loss is the third most common chronic physical condition in the United States, and is more prevalent than diabetes or cancer (1). Occupational hearing loss, primarily caused by high noise exposure, is the most common U.S. work-related illness (2). Approximately 22 million U.S. workers are exposed to hazardous occupational noise (3). CDC compared the prevalence of hearing impairment within nine U.S. industry sectors using 1,413,789 noise-exposed worker audiograms from CDC's National Institute for Occupational Safety and Health (NIOSH) Occupational Hearing Loss Surveillance Project (4). CDC estimated the prevalence at six hearing impairment levels, measured in the better ear, and the impact on quality of life expressed as annual disability-adjusted life years (DALYs), as defined by the 2013 Global Burden of Disease (GBD) Study (5). The mining sector had the highest prevalence of workers with any hearing impairment, and with moderate or worse impairment, followed by the construction and manufacturing sectors. Hearing loss prevention, and early detection and intervention to avoid additional hearing loss, are critical to preserve worker quality of life.

Uncovering effective strategies for hearing loss prevention.

Occupational health agencies, researchers and policy makers have recognized the need for evidence on the effectiveness of interventions designed to reduce or prevent workplace injuries and illnesses. While many workplaces comply with legal or obligatory requirements and implement recommended interventions, few publications exist documenting the effectiveness of these actions. Additionally, some workplaces have discovered through their own processes, novel ways to reduce the risk of injury. Peer-reviewed information on the effectiveness of the many strategies and approaches currently in use could help correct weaknesses, or further encourage their adoption and expansion. The evaluation of intervention effectiveness would certainly contribute to improved worker health and safety. This need is particularly relevant regarding noise exposure in the workplace and hearing loss prevention interventions. In a 2006 review of the U.S. National Institute for Occupational Safety and Health (NIOSH) Hearing Loss Research Program, the independent National Academies of Sciences recommended that NIOSH place greater emphasis on identifying the effectiveness of hearing loss prevention measures on the basis of outcomes that are as closely related as possible to reducing noise exposure and work related hearing loss (http://www.nap.edu/openbook.php?record_id=11721). NIOSH used two different approaches to address that recommendation: the first one was to conduct research, including broad systematic reviews on the effectiveness of interventions to prevent occupational noise-induced hearing loss. The second was to create an award program, the Safe-In-Sound Excellence in Hearing Loss Prevention Award™, to identify and honor excellent real-world examples of noise control and other hearing loss prevention practices and innovations.

Interventions to prevent occupational noise-induced hearing loss: a Cochrane systematic review.

OBJECTIVE: To assess the effectiveness of interventions for preventing occupational noise exposure or hearing loss compared to no intervention or alternative interventions. DESIGN: We searched biomedical databases up to 25 January 2012 for randomized controlled trials (RCT), controlled before-after studies and interrupted time-series of hearing loss prevention among workers exposed to noise. STUDY SAMPLE: We included 19 studies with 82 794 participants evaluating effects of hearing loss prevention programs (HLPP). The overall quality of studies was low to very low, as rated using the GRADE approach. RESULTS: One study of stricter legislation showed a favorable effect on noise levels. Three studies, of which two RCTs, did not find an effect of a HLPP. Four studies showed that better use of hearing protection devices in HLPPs decreased the risk of hearing loss. In four other studies, workers in a HLPP still had a 0.5 dB greater hearing loss at 4 kHz (95% CI - 0.5 to 1.7) than non-exposed workers. In two similar studies there was a substantial risk of hearing loss in spite of a HLPP. CONCLUSIONS: Stricter enforcement of legislation and better implementation of HLPPs can reduce noise levels in workplaces. Better evaluations of technical interventions and long-term effects are needed.

Occupational safety and health enforcement tools for preventing occupational diseases and injuries.

BACKGROUND: There is uncertainty as to whether and what extent occupational safety and health regulation and legislation enforcement activities, such as inspections, are effective and efficient to improve workers' health and safety. We use the term regulation to refer both to regulation and legislation. OBJECTIVES: To assess the effects of occupational safety and health regulation enforcement tools for preventing occupational diseases and injuries. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (PubMed), EMBASE (embase.com), CINAHL (EBSCO), PsycINFO (Ovid), OSH update, HeinOnline, Westlaw International, EconLit and Scopus from the inception of each database until January 2013. We also checked reference lists of included articles and contacted study authors to identify additional published, unpublished and ongoing studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs), controlled before-after studies (CBAs), interrupted time series (ITS) and econometric panel studies of firms or workplaces evaluating inspections, warnings or orders, citations or fines, prosecution or firm closure by governmental representatives and if the outcomes were injuries, diseases or exposures.In addition, we included qualitative studies of workers' or employers' attitudes or beliefs towards enforcement tools. DATA COLLECTION AND ANALYSIS: Pairs of authors independently extracted data on the main characteristics, the risk of bias and the effects of the interventions. We expressed intervention effects as risk ratios (RR) or mean differences (MD). We recalculated other effect measures into RRs or MDs. We combined the results of similar studies in a meta-analysis. MAIN RESULTS: We located 23 studies: two RCTs with 1414 workplaces, two CBAs with 9903 workplaces, one ITS with six outcome measurements, 12 panel studies and six qualitative studies with 310 participants. Studies evaluated the effects of inspections in general and the effects of their consequences, such as penalties. Studies on the effects of prosecution, warnings or closure were not available or were of such quality that we could not include their results. The effect was measured on injury rates, on exposure to physical workload and on compliance with regulation, with a follow-up varying from one to four years. All studies had serious limitations and therefore the quality of the evidence was low to very low. The injury rates in the control groups varied across studies from 1 to 23 injuries per 100 person-years and compliance rates varied from 40% to 75% being compliant.The effects of inspections were inconsistent in seven studies: injury rates decreased or stayed at a similar level compared to no intervention at short and medium-term follow-up. In studies that found a decrease the effect was small with a 10% decrease of the injury rate. At long-term follow-up, in one study there was a significant decrease of 23% (95% confidence interval 8% to 23%) in injury rates and in another study a substantial decrease in accident rates, both compared to no intervention.First inspections, follow-up inspections, complaint and accident inspections resulted in higher compliance rates compared to the average effect of any other type of inspections.In small firms, inspections with citations or with more penalties could result in fewer injuries or more compliance in the short term but not in the medium term.Longer inspections and more frequent inspections probably do not result in more compliance.In two studies, there was no adverse effect of inspections on firm survival, employment or sales.Qualitative studies show that there is support for enforcement among workers. However, workers doubt if the inspections are effective because inspections are rare and violations can be temporarily fixed to mislead inspectors. AUTHORS' CONCLUSIONS: There is evidence that inspections decrease injuries in the long term but not in the short term. The magnitude of the effect is uncertain. There are no studies that used chemical or physical exposures as outcome. Specific, focused inspections could have larger effects than inspections in general. The effect of fines and penalties is uncertain. The quality of the evidence is low to very low and therefore these conclusions are tentative and can be easily changed by better future studies. There is an urgent need for better designed evaluations, such as pragmatic randomised trials, to establish the effects of existing and novel enforcement methods, especially on exposure and disorders.

Noise Exposure and Hearing Loss among Workers at a Hammer Forge Company.

The National Institute for Occupational Safety and Health (NIOSH) evaluated continuous and impact noise exposures and hearing loss among workers at a hammer forge company. Full-shift personal noise exposure measurements were collected on forge workers across 15 different job titles; impact noise characteristics and one-third octave band noise levels were assessed at the forge hammers; and 4,750 historic audiometric test records for 483 workers were evaluated for hearing loss trends. Nearly all workers' noise exposures exceeded regulatory and/or recommended exposure limits. Workers working in jobs at or near the hammers had full-shift time-weighted average noise exposures above 100 decibels, A-weighted. Impact noise at the hammers reached up to 148 decibels. Analysis of audiometric test records showed that 82% of workers had experienced a significant threshold shift, as defined by NIOSH, and 63% had experienced a standard threshold shift, as defined by the Occupational Safety and Health Administration (OSHA). All workers with an OSHA standard threshold shift had a preceding NIOSH significant threshold shift which occurred, on average, about 7 years prior. This evaluation highlights forge workers' exposures to high levels of noise, including impact noise, and how their hearing worsened with age and length of employment.

Audiological Tests Used in the Evaluation of the Effects of Solvents on the Human Auditory System: A Mixed Methods Review.

This study aimed to scope the literature, identify knowledge gaps, appraise results, and synthesize the evidence on the audiological evaluation of workers exposed to solvents. We searched Medline, PubMed, Embase, CINAHL, and NIOSHTIC-2 up to March 22, 2021. Using Covidence, two authors independently assessed study eligibility, risk of bias, and extracted data. National Institute of Health Quality Assessment Tools was used in the quality evaluation of included studies; the Downs and Black checklist was used to assess the risk of bias. Of 454 located references, 37 were included. Twenty-five tests were studied: two tests to measure hearing thresholds, one test to measure word recognition in quiet, six electroacoustic procedures, four electrophysiological tests, and twelve behavioral tests to assess auditory processing skills. Two studies used the Amsterdam Inventory for Auditory Disability and Handicap. The quality of individual studies was mostly considered moderate, but the overall quality of evidence was considered low. The discrepancies between studies and differences in the methodologies/outcomes prevent recommending a specific test battery to assess the auditory effects of occupational solvents. Decisions on audiological tests for patients with a history of solvent exposures require the integration of the most current research evidence with clinical expertise and stakeholder perspectives.

Interventions to prevent occupational noise-induced hearing loss.

BACKGROUND: Millions of workers worldwide are exposed to noise levels that increase their risk of hearing impairment. Little is known about the effectiveness of hearing loss prevention interventions. OBJECTIVES: To assess the effectiveness of non-pharmaceutical interventions for preventing occupational noise exposure or occupational hearing loss compared to no intervention or alternative interventions. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; and OSH update to 25 January 2012. SELECTION CRITERIA: We included randomised controlled trials (RCT), controlled before-after studies (CBA) and interrupted time-series (ITS) of non-clinical hearing loss prevention interventions under field conditions among workers exposed to noise. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study eligibility and risk of bias and extracted data. MAIN RESULTS: We included 25 studies. We found no controlled studies on engineering controls for noise exposure but one study evaluated legislation to reduce noise exposure in a 12-year time-series analysis. Eight studies with 3,430 participants evaluated immediate and long-term effects of personal hearing protection devices (HPDs) and sixteen studies with 82,794 participants evaluated short and long-term effects of hearing loss prevention programmes (HLPPs). The overall quality of studies was low to very low.The one ITS study that evaluated the effect of new legislation in reducing noise exposure found that the median noise level decreased by 27.7 dB(A) (95% confidence interval (CI) -36.1 to -19.3 dB) immediately after the implementation of stricter legislation and that this was associated with a favourable downward trend in time of -2.1 dB per year (95% CI -4.9 to 0.7).Hearing protection devices attenuated noise with about 20 dB(A) with variation among brands and types but for ear plugs these findings depended almost completely on proper instruction of insertion. Noise attenuation ratings of hearing protection under field conditions were consistently lower than the ratings provided by the manufacturers.One cluster-RCT compared a three-year information campaign as part of a hearing loss prevention programme for agricultural students to audiometry only with three and 16-year follow-up but there were no significant differences in hearing loss. Another study compared a HLPP, which provided regular personal noise exposure information, to a programme without this information in a CBA design. Exposure information was associated with a favourable but non-significant reduction of the rate of hearing loss of -0.82 dB per year (95% CI -1.86 to 0.22). Another cluster-RCT evaluated the effect of extensive on-site training sessions and the use of personal noise-level indicators versus information only on noise levels but did not find a significant difference after four months follow-up (Mean Difference (MD) -0.30 dB(A) (95%CI -3.95 to 3.35).There was very low quality evidence in four very long-term studies, that better use of HPDs as part of a HLPP decreased the risk of hearing loss compared to less well used hearing protection in HLPPs. Other aspects of the HLPP such as training and education of workers or engineering controls did not show a similar effect.In four long-term studies, workers in a HLPP still had a 0.5 dB greater hearing loss at 4 kHz than workers that were not exposed to noise (95% CI -0.5 to 1.7) which is about the level of hearing loss caused by exposure to 85 dB(A). In addition, two other studies showed substantial risk of hearing loss in spite of the protection of a HLPP compared to non-exposed workers. AUTHORS' CONCLUSIONS: There is low quality evidence that implementation of stricter legislation can reduce noise levels in workplaces. Even though case studies show that substantial reductions in noise levels in the workplace can be achieved, there are no controlled studies of the effectiveness of such measures. The effectiveness of hearing protection devices depends on training and their proper use. There is very low quality evidence that the better use of hearing protection devices as part of HLPPs reduces the risk of hearing loss, whereas for other programme components of HLPPs we did not find such an effect. Better implementation and reinforcement of HLPPs is needed. Better evaluations of technical interventions and long-term effects are needed.

Awarding and promoting excellence in hearing loss prevention.

OBJECTIVE: To describe the rationale and creation of a national award to recognize and promote hearing loss prevention. DESIGN: In 2007, the National Institute for Occupational Safety and Health partnered with the National Hearing Conservation Association to create the Safe-in-Sound Excellence in Hearing Loss Prevention Award™ ( www.safeinsound.us ). The objectives of this initiative were to recognize organizations that document measurable achievements and to share leading edge information to a broader community. RESULTS: An expert committee developed specific and explicit award evaluation criteria of excellence in hearing loss prevention for organizations in different industrial sectors. The general approach toward award criteria was to incorporate current 'best practices' and familiar benchmarks of hearing loss prevention programs. This approach was reviewed publicly. In addition, mechanisms were identified to measure the impact of the award itself. Interest in the award was recorded through the monitoring of the visitor traffic registered by the award web site and is increasing yearly. Specific values and strategies common across award winners are presented. CONCLUSION: The Safe-in-Sound Award™ has obtained high quality field data; identified practical solutions, disseminated successful strategies to minimize the risk of hearing loss, generated new partnerships, and shared practical solutions with others in the field.

Temporary and Permanent Auditory Effects Associated with Occupational Coexposure to Low Levels of Noise and Solvents.

This study aimed to assess temporary and permanent auditory effects associated with occupational coexposure to low levels of noise and solvents. Cross-sectional study with 25 printing industry workers simultaneously exposed to low noise (<80 dBA TWA) and low levels of solvents. The control group consisted of 29 industry workers without the selected exposures. Participants answered a questionnaire and underwent auditory tests. Auditory fatigue was measured by comparing the acoustic reflex threshold before and after the workday. Workers coexposed to solvents and noise showed significantly worse results in auditory tests in comparison with the participants in the control group. Auditory brainstem response results showed differences in III−V interpeak intervals (p = 0.046 in right ear; p = 0.039 in left ear). Mean dichotic digits scores (exposed = 89.5 ± 13.33; controls = 96.40 ± 4.46) were only different in the left ear (p = 0.054). The comparison of pre and postacoustic reflex testing indicated mean differences (p = 0.032) between the exposed (4.58 ± 6.8) and controls (0 ± 4.62) groups. This study provides evidence of a possible temporary effect (hearing fatigue) at the level of the acoustic reflex of the stapedius muscle. The permanent effects were identified mainly at the level of the high brainstem and in the auditory ability of binaural integration.

Use of historical data and a novel metric in the evaluation of the effectiveness of hearing conservation program components.

OBJECTIVES: To evaluate the effectiveness of hearing conservation programs (HCP) and their specific components in reducing noise-induced hearing loss (NIHL). METHODS: This retrospective cohort study was conducted at one food-processing plant and two automotive plants. Audiometric and work-history databases were combined with historical noise monitoring data to develop a time-dependent exposure matrix for each plant. Historical changes in production and HCP implementation were collected from company records, employee interviews and focus groups. These data were used to develop time-dependent quality assessments for various HCP components. 5478 male (30,427 observations) and 1005 female (5816 observations) subjects were included in the analysis. RESULTS: Analyses were conducted separately for males and females. Females tended to have less NIHL at given exposure levels than males. Duration of noise exposure stratified by intensity (dBA) was a better predictor of NIHL than the standard equivalent continuous noise level (L(eq)) based upon a 3-dBA exchange. Within this cohort, efficient dBA strata for males were <95 versus ≥ 95, and for females <90 versus ≥ 90. The reported enforced use of hearing protection devices (HPDs) significantly reduced NIHL. The data did not have sufficient within-plant variation to determine the effectiveness of noise monitoring or worker training. An association between increased audiometric testing and NIHL was believed to be an artifact of increased participation in screening. CONCLUSIONS: Historical audiometric data combined with noise monitoring data can be used to better understand the effectiveness of HCPs. Regular collection and maintenance of quality data should be encouraged and used to monitor the effectiveness of these interventions.

A multicenter study on the audiometric findings of styrene-exposed workers.

OBJECTIVE: The objective of this study was to evaluate hearing loss among workers exposed to styrene, alone or with noise. DESIGN: This cross-sectional study was conducted as part of NoiseChem, a European Commission 5th Framework Programme research project, by occupational health institutes in Finland, Sweden, and Poland. STUDY SAMPLE: Participants' ages ranged from 18-72 years (n = 1620 workers). Participants exposed to styrene, alone or with noise, were from reinforced fiberglass products manufacturing plants (n = 862). Comparison groups were comprised of workers noise-exposed (n = 400) or controls (n = 358). Current styrene exposures ranged from 0 to 309 mg/m(3), while mean current noise levels ranged from 70-84 dB(A). Hearing thresholds of styrene-exposed participants were compared with Annexes A and B from ANSI S3.44, 1996. RESULTS: The audiometric thresholds of styrene exposed workers were significantly poorer than those in published standards. Age, gender, and styrene exposure met the significance level criterion in the multiple logistic regression for the binary outcome 'hearing loss' (P = 0.0000). Exposure to noise (<85 dBA p = 0.0001; ≥85 dB(A) p = 0.0192) interacted significantly with styrene exposure. CONCLUSIONS: Occupational exposure to styrene is a risk factor for hearing loss, and styrene-exposed workers should be included in hearing loss prevention programs.