Interventions to prevent occupational noise-induced hearing loss

Advancing noise management in aviation: Strategic approaches for preventing noise-induced hearing loss

As urbanization and population growth escalate, the challenge of noise pollution intensifies, particularly within the aviation industry. This review examines current insights into noise-induced hearing loss (NIHL) in aviation, highlighting the risks to pilots, cabin crew, aircraft maintenance engineers, and ground staff from continuous exposure to high-level noise. It evaluates existing noise management and hearing conservation strategies, identifying key obstacles and exploring new technological solutions. While progress in developing protective devices and noise control technologies is evident, gaps in their widespread implementation persist. The study underscores the need for an integrated strategy combining regulatory compliance, technological advances, and targeted educational efforts. It advocates for global collaboration and policy development to safeguard the auditory health of aviation workers and proposes a strategic framework to enhance hearing conservation practices within the unique challenges of the aviation sector.

Utilizing Artificial Neural Networks for Establishing Hearing-Loss Predicting Models Based on a Longitudinal Dataset and Their Implications for Managing the Hearing Conservation Program

Background

Though the artificial neural network (ANN) technique has been used to predict noise-induced hearing loss (NIHL), the established prediction models have primarily relied on cross-sectional datasets, and hence, they may not comprehensively capture the chronic nature of NIHL as a disease linked to long-term noise exposure among workers.

Methods

A comprehensive dataset was utilized, encompassing eight-year longitudinal personal hearing threshold levels (HTLs) as well as information on seven personal variables and two environmental variables to establish NIHL predicting models through the ANN technique. Three subdatasets were extracted from the afirementioned comprehensive dataset to assess the advantages of the present study in NIHL predictions.

Results

The dataset was gathered from 170 workers employed in a steel-making industry, with a median cumulative noise exposure and HTL of 88.40 dBA-year and 19.58 dB, respectively. Utilizing the longitudinal dataset demonstrated superior prediction capabilities compared to cross-sectional datasets. Incorporating the more comprehensive dataset led to improved NIHL predictions, particularly when considering variables such as noise pattern and use of personal protective equipment. Despite fluctuations observed in the measured HTLs, the ANN predicting models consistently revealed a discernible trend.

Conclusions

A consistent correlation was observed between the measured HTLs and the results obtained from the predicting models. However, it is essential to exercise caution when utilizing the model-predicted NIHLs for individual workers due to inherent personal fluctuations in HTLs. Nonetheless, these ANN models can serve as a valuable reference for the industry in effectively managing its hearing conservation program.

Risk factors associated with occupational noise-induced hearing loss in the Hispanic community health study/study of Latinos: A cross-sectional epidemiologic investigation

The purpose of this study was to estimate the prevalence of occupational noise exposure and risk factors of occupational noise-induced hearing loss (NIHL) in Hispanic/Latino adults included in the baseline wave of the Hispanic Community Health Study/Study of Latinos collected from 2008 to 2011. Sequential multiple linear regression modeled the relationship between occupational NIHL (defined as a 3-, 4-, 6-kHz pure-tone average [PTA]) and occupation type, self-reported noise exposure, cardiovascular disease (CVD) risk score, and hearing protective device (HPD) use. The final model controlled for sex, age, and recreational noise exposure. Among 12,851 included participants, approximately 40% (n = 5036) reported occupational noise exposure "Sometimes" (up to 50% of the time) or "Frequently" (75-100% of the time). In the final fitted model, longest-held occupation and CVD risk were associated with poorer hearing. Specifically, those in non-skilled, service, skilled, and military/police/other job categories had between 2.07- and 3.29-dB worse PTA than professional/office workers. Additionally, a shift in the CVD risk score category from low to medium was associated with a 2.25- and 8.20-dB worse PTA for medium and high CVD risk, respectively. Age and sex were also significantly associated with poorer hearing, such that men presented with 6.08 dB worse PTA than women, and for every one-year increase in age, PTA increased by 0.62 dB (ps < .001). No interactions were seen between noise*sometimes or frequent exposure to other ototoxic agents and PTA (ps = .33 & .92, respectively). The prevalence of occupational noise exposure was high in this cross-sectional investigation of adults from Hispanic/Latino backgrounds. Findings contribute to the extant literature by demonstrating that risk factors for occupational NIHL in adults from varying Hispanic/Latino backgrounds are consistent with those of other previously studied groups.

Road tunnel noise: monitoring, prediction and evaluation of noise-induced hearing loss

Incessant increases in vehicles and massive road networks lead to traffic-related problems and noise pollution. Road tunnels are considered a more feasible and effective solution for solving traffic problems. Compared to other traffic noise abatement strategies, road tunnels also offer enormous benefits to urban mass transit systems. However, the road tunnels that are non-complying with the design and safety standards negatively impact commuters' health of being exposed to the high noise level inside the tunnel, particularly for road tunnels above 500 m in length. The study aims to evaluate the applicability of the ASJ RTN-Model 2013 by validating predicted data with the measurement data at the tunnel portal. The study also investigates the acoustic characteristics of noise inside the tunnel by analysing octave frequencies to inspect the correlation of noise spectrum for noise-induced hearing loss (NIHL) and discussed the possible health effect on the pedestrian and vehicle riders passing through the tunnel. The result shows that people are exposed to a high noise level inside the tunnel. The equivalent sound pressure levels at different locations inside the tunnel along the length observed between 78.9 to 86.5 dB(A), which exceeded the CPCB, recommended permissible limits for road traffic noise. The locations L1, L5, L6 and L7 found higher sound pressure levels at 4 kHz and relates to NIHL. The observed average difference between the measurement and predicted LAeq value at the tunnel portal was 2.8 dB(A) which is highly acceptable and confirms the ASJ RTN-2013 prediction model applicability for predicting tunnel portal noise in the Indian road conditions. The study recommends complete restriction of honking inside the tunnel. Considering the commuter's safety perspective, the road tunnels above 500 m must have separate walk sides for pedestrians with a barrier.

Association of polymorphisms in the catalase gene with the susceptibility to noise-induced hearing loss: A meta-analysis

OBJECTIVES

The association between single nucleotide polymorphisms (SNPs) of the Catalase (CAT) gene and noise-induced hearing loss (NIHL) has been reported in several case-control studies. However, their conclusions are conflicting. This study aimed to determine the association between CAT genetic variants and NIHL susceptibility.

METHODS

We searched PubMed, Embase, CNKI, Wanfang, and Web of Science for eligible English and Chinese studies published up to September 26, 2021. Studies reporting primary data that assessed the association between CAT SNPs and NIHL susceptibility were included. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). The odds ratio (OR), 95 % confidence interval (CI), and P value were calculated to assess the strength of the association. Publication bias was explored using funnel plots and Egger's test.

RESULTS

Our meta-analysis included six articles involving 1428 patients and 2162 healthy controls. For rs208679, a significant association was detected in the allele model (A vs. G: OR = 0.81 [95 % CI, 0.67-0.97], P = 0.02) and the dominant model (AA vs. GG + AG: OR = 0.78 [95 % CI, 0.62-0.98], P = 0.03), but not in the heterozygote model, homozygote model, or the recessive model. For rs769217, rs7943316, and rs769214, no significant association was found in any genetic model. No significant publication bias was observed.

CONCLUSIONS

The rs208679 may be used in the Chinese population as a risk predictor for NIHL. While the rs769217, rs7943316, and rs769214 polymorphisms were not found to be associated with susceptibility to NIHL. Further studies with a larger population and higher quality are required to update the results.

Hearing threshold levels of Australian coal mine workers: a retrospective cross-sectional study of 64196 audiograms

OBJECTIVE

This study examined the hearing threshold levels (HTL) of workers commencing employment in Australian coal mines in the State of New South Wales (NSW). The aim was to establish if some degree of hearing loss was identifiable in the mandatory pre-employment audiograms of workers.

DESIGN

This was an observational, retrospective, repeated cross-sectional study.

STUDY SAMPLE

De-identified audiometric records of 64196 employees entering NSW coal mining in three representative five-year periods between 1991-2015 were utilised.

RESULTS

Although HTLs were lower (better) in more recent years, the results showed clinically significant hearing loss (≥25dBHL) for older workers, 45-60 years. Pure tone average (PTA) hearing losses were greater at the higher frequencies associated with excessive noise exposure (3-6 kHz), than at the speech frequencies (0.5-4 kHz). Hearing loss in the left ears were higher compared to the right ears, with higher prevalence of audiometric notches in males.

CONCLUSION

Almost a fifth (14.8-20.1%) of male workers commencing work in NSW coal mines presented with an audiometric notch at 4 kHz. Further research is required to determine if these notches represent true NIHL, and how the residual hearing of workers may be conserved.

Socio-economic disparity in the global burden of occupational noise-induced hearing loss: an analysis for 2017 and the trend since 1990

OBJECTIVES

To evaluate socio-economic disparity in the global burden of occupational noise-induced hearing loss (ONIHL) using disability-adjusted life-years (DALYs).

METHODS

The numbers of DALYs due to ONIHL, age-standardised DALY rates and national human development index (HDI) data from 1990 to 2017 were collected. The relationship between the age-standardised DALY rates and the 2017 HDI was analysed. A concentration index (CI) and a relative index of inequality (RII) were calculated to evaluate the trend in socio-economic disparity in the burden of ONIHL for the period 1990-2017.

RESULTS

From 1990 to 2017, the global DALYs due to ONIHL increased from 3.3 to 6.0 million, with the highest growth occurring in low-income countries (110.7%). Age-standardised DALY rates due to ONIHL were negatively associated with the HDI (β = -0.733, p<0.001), and these rates were significantly higher in countries with a lower HDI. From 1990 to 2017, the trend in between-country inequality was flat with little fluctuation, the CIs stayed near -0.17, and the RIIs remained near 0.35.

CONCLUSIONS

Over the past few decades, low-income countries have experienced the most rapid growth in DALYs worldwide. A widening socio-economic disparity has persisted in the global burden of ONIHL, with a higher burden in lower socio-economic countries. These data suggest that more prevention programmes and healthcare services should be provided for developing countries.

Does noise exposure during pregnancy affect neonatal hearing screening results?

Objective

The aim is to investigate whether noise is effective on hearing screening tests of neonates born to mothers exposed to noise during pregnancy.

Material and Method

Screening results of 2653 infants from the period of January 2013-May 2017 were evaluated. Transient Evoked Otoacoustic Emissions (TEOAE) and Auditory Brainstem Response (ABR) were used. Infants of 65 mothers exposed to noise (L_Aeq 80-85 dBA/8 hours/day) during pregnancy (Week ± SD; 32.58 ± 2.71) comprised the study group while the control group consisted of infants of 2588 mothers without noise exposure.

Results

Among the 65 infants, 23 (35.4%) passed screening at the first emission test (OAE1); 34 (52.3%) at the second emission test (OAE2); 7 (10.8%) at the ABR stage, 1 (1.5%) infant was referred to a tertiary center. In the control group, 458 (17.7%) infants passed at OAE1; 1822 (70.4%) at OAE2; 289 (11.2%) at ABR stages, 19 (0.7%) infants were referred to a tertiary center. The rate of infants that passed screening at OAE1 in the study group was high (P = 0.00001). Sixty-four (98.46%) infants in the study group and 2569 (99.26%) infants in the control group passed the tests. The difference between the two groups was not significant, indicating that exposure to noise during pregnancy had no unfavorable effects on auditory functions (P = 0.392).

Conclusion

Unfavorable effect of noise exposure during pregnancy was not observed on auditory functions of the infants. The higher rate of infants that passed the screening test at OAE1 stage in the study group raised the question, "Does the exposure of the noise at exposure action levels (80-85 dB A) during pregnancy contribute to auditory maturation of fetus?"

Metrics to assess injury prevention programs for young workers in high-risk occupations: a scoping review of the literature

INTRODUCTION

Despite legal protections for young workers in Canada, youth aged 15-24 are at high risk of traumatic occupational injury. While many injury prevention initiatives targeting young workers exist, the challenge faced by youth advocates and employers is deciding what aspect(s) of prevention will be the most effective focus for their efforts. A review of the academic and grey literatures was undertaken to compile the metrics-both the indicators being evaluated and the methods of measurement-commonly used to assess injury prevention programs for young workers. Metrics are standards of measurement through which efficiency, performance, progress, or quality of a plan, process, or product can be assessed.

METHODS

A PICO framework was used to develop search terms. Medline, PubMed, OVID, EMBASE, CCOHS, PsychINFO, CINAHL, NIOSHTIC, Google Scholar and the grey literature were searched for articles in English, published between 1975-2015. Two independent reviewers screened the resulting list and categorized the metrics in three domains of injury prevention: Education, Environment and Enforcement.

RESULTS

Of 174 acquired articles meeting the inclusion criteria, 21 both described and assessed an intervention. Half were educational in nature (N=11). Commonly assessed metrics included: knowledge, perceptions, self-reported behaviours or intentions, hazardous exposures, injury claims, and injury counts. One study outlined a method for developing metrics to predict injury rates.

CONCLUSION

Metrics specific to the evaluation of young worker injury prevention programs are needed, as current metrics are insufficient to predict reduced injuries following program implementation. One study, which the review brought to light, could be an appropriate model for future research to develop valid leading metrics specific to young workers, and then apply these metrics to injury prevention programs for youth.

A hypothesis study on bionic active noise reduction of auditory organs

BACKGROUND

Noise exposure can lead to hearing loss and multiple system dysfunctions. As various forms of noise exist in our living environments, and our auditory organs are very sensitive to acoustic stimuli, it is a challenge to protect our hearing system in certain noisy environments.

PRESENTATION OF THE HYPOTHESIS

Herein, we propose that our hearing organ could serve as a noise eliminator for high intensity noise and enhance acoustic signal processing abilities by increasing the signal-noise ratio. For suprathreshold signals, the hearing system is capable of regulating the middle ear muscles and other structures to actively suppress the sound level to a safe range.

TESTING THE HYPOTHESIS

To test our hypothesis, both mathematic model analyses and animal model studies are needed. Based on a digital 3D reconstructed model, every structure in the auditory system can be analyzed and tested for its contribution to the process of noise reduction. Products manufactured by this bionic method could be used and verified in animal models and volunteers.

IMPLICATIONS

By mimicking the noise-reduction effect of the sophisticated structures in the hearing system, we may be able to provide a model that establishes a new active-sound-suppression mode. This innovative method may overcome the limited capabilities of current noise protection options and become a promising possibility for noise prevention.

Work-Related Noise Exposure in a Cohort of Patients with Chronic Tinnitus: Analysis of Demographic and Audiological Characteristics

Work-related noise exposure is one of the major factors contributing to the development of adult-onset hearing loss and tinnitus. The aim of this study was to analyze, in patients with chronic tinnitus and long-term occupational noise exposure, (A) characteristics of hearing loss, tinnitus, comorbidities, demographic characteristics and a history of work-related noise exposure and (B) differences among individuals employed in occupations with high and low risk of developing work-related noise-induced hearing loss (NIHL). One hundred thirty six patients with chronic tinnitus and at least a 10 year-long working history were divided into two groups based on the risk of their profession to induce NIHL. Individuals employed in jobs at high risk for NIHL were mostly males and exhibited a poorer hearing threshold, more evident in the left ear. Tinnitus was mostly bilateral; the next largest presentation was left-sided; patients described their tinnitus as buzzing or high-pitched. Correlation between age, length of tinnitus and worse hearing was found. Patients with a higher degree of hearing impairment were mostly males and were more likely to have a family history of hearing loss and at least one cardiovascular comorbidity. Our study shows some differences in individuals with tinnitus and a history of a profession associated with increased exposure to NIHL compared to those without such a history.

Acute acoustic trauma in the French armed forces during 2007-2014

CONTEXT

Despite existing preventive measures, the number of acute acoustic trauma (AAT) cases reported to the French Military Epidemiological Surveillance System (MESS) remains high.

AIMS

The objective of this study was to describe AAT and the preventive measures already implemented.

SUBJECTS AND METHODS

We conducted a descriptive cross-sectional analysis of AAT using data from the MESS for the period 2007-2014. In addition, we reviewed the current prevention measures that exist in the French armed forces.

STATISTICAL ANALYSIS USED

Comparisons between different incidence rates were made by Poisson and quasi-Poisson regression.

RESULTS

Between 2007 and 2014, 10,487 AAT cases were reported to the MESS, with a significant decrease in 2013 (P < 0.001). AAT incidence rates were the highest among those aged <25 years - 14.3 per 1000 person-years (PYs) (P < 0.001), and those in the army; with 8.1 per 1000 PYs (P < 0.001), and men had almost twice the risk of women (P < 0.001). AAT mainly occurred in training schools or at camps during exercises. The main prevention actions identified were the following: official regulations, education, making hearing protection devices (HPDs) available for all service members, and regular hearing monitoring. A working group has been set up and has proposed an informative chapter in the weapon handling instruction book, an AAT simulator, and a new HPD, the 3M® earplug, with an information brochure.

CONCLUSIONS

AAT rates decreased from 2007 to 2014 in the French armed forces. Further analysis is needed to identify the underlying factors involved to improve the prevention actions proposed. The MESS and targeted surveys will assess the impact of the different prevention measures implemented.

Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

BACKGROUND

Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss, is a major health problem, is largely preventable and is probably more widespread than revealed by conventional pure tone threshold testing. Noise-induced damage to the cochlea is traditionally considered to be associated with symmetrical mild to moderate hearing loss with associated tinnitus; however, there is a significant number of patients with asymmetrical thresholds and, depending on the exposure, severe to profound hearing loss as well.

MAIN BODY

Recent epidemiology and animal studies have provided further insight into the pathophysiology, clinical findings, social and economic impacts of noise-induced hearing loss. Furthermore, it is recently shown that acoustic trauma is associated with vestibular dysfunction, with associated dizziness that is not always measurable with current techniques. Deliberation of the prevalence, treatment and prevention of noise-induced hearing loss is important and timely. Currently, prevention and protection are the first lines of defence, although promising protective effects are emerging from multiple different pharmaceutical agents, such as steroids, antioxidants and neurotrophins.

CONCLUSION

This review provides a comprehensive update on the pathophysiology, investigations, prevalence of asymmetry, associated symptoms, and current strategies on the prevention and treatment of noise-induced hearing loss.

Interventions for prevention of bullying in the workplace

BACKGROUND

Bullying has been identified as one of the leading workplace stressors, with adverse consequences for the individual employee, groups of employees, and whole organisations. Employees who have been bullied have lower levels of job satisfaction, higher levels of anxiety and depression, and are more likely to leave their place of work. Organisations face increased risk of skill depletion and absenteeism, leading to loss of profit, potential legal fees, and tribunal cases. It is unclear to what extent these risks can be addressed through interventions to prevent bullying.

OBJECTIVES

To explore the effectiveness of workplace interventions to prevent bullying in the workplace.

SEARCH METHODS

We searched: the Cochrane Work Group Trials Register (August 2014); Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library 2016, issue 1); PUBMED (1946 to January 2016); EMBASE (1980 to January 2016); PsycINFO (1967 to January 2016); Cumulative Index to Nursing and Allied Health Literature (CINAHL Plus; 1937 to January 2016); International Bibliography of the Social Sciences (IBSS; 1951 to January 2016); Applied Social Sciences Index and Abstracts (ASSIA; 1987 to January 2016); ABI Global (earliest record to January 2016); Business Source Premier (BSP; earliest record to January 2016); OpenGrey (previously known as OpenSIGLE-System for Information on Grey Literature in Europe; 1980 to December 2014); and reference lists of articles.

SELECTION CRITERIA

Randomised and cluster-randomised controlled trials of employee-directed interventions, controlled before and after studies, and interrupted time-series studies of interventions of any type, aimed at preventing bullying in the workplace, targeted at an individual employee, a group of employees, or an organisation.

DATA COLLECTION AND ANALYSIS

Three authors independently screened and selected studies. We extracted data from included studies on victimisation, perpetration, and absenteeism associated with workplace bullying. We contacted study authors to gather additional data. We used the internal validity items from the Downs and Black quality assessment tool to evaluate included studies' risk of bias.

MAIN RESULTS

Five studies met the inclusion criteria. They had altogether 4116 participants. They were underpinned by theory and measured behaviour change in relation to bullying and related absenteeism. The included studies measured the effectiveness of interventions on the number of cases of self-reported bullying either as perpetrator or victim or both. Some studies referred to bullying using common synonyms such as mobbing and incivility and antonyms such as civility. Organisational/employer level interventionsTwo studies with 2969 participants found that the Civility, Respect, and Engagement in the Workforce (CREW) intervention produced a small increase in civility that translates to a 5% increase from baseline to follow-up, measured at 6 to 12 months (mean difference (MD) 0.17; 95% CI 0.07 to 0.28).One of the two studies reported that the CREW intervention produced a small decrease in supervisor incivility victimisation (MD -0.17; 95% CI -0.33 to -0.01) but not in co-worker incivility victimisation (MD -0.08; 95% CI -0.22 to 0.08) or in self-reported incivility perpetration (MD -0.05 95% CI -0.15 to 0.05). The study did find a decrease in the number of days absent during the previous month (MD -0.63; 95% CI -0.92 to -0.34) at 6-month follow-up. Individual/job interface level interventionsOne controlled before-after study with 49 participants compared expressive writing with a control writing exercise at two weeks follow-up. Participants in the intervention arm scored significantly lower on bullying measured as incivility perpetration (MD -3.52; 95% CI -6.24 to -0.80). There was no difference in bullying measured as incivility victimisation (MD -3.30 95% CI -6.89 to 0.29).One controlled before-after study with 60 employees who had learning disabilities compared a cognitive-behavioural intervention with no intervention. There was no significant difference in bullying victimisation after the intervention (risk ratio (RR) 0.55; 95% CI 0.24 to 1.25), or at the three-month follow-up (RR 0.49; 95% CI 0.21 to 1.15), nor was there a significant difference in bullying perpetration following the intervention (RR 0.64; 95% CI 0.27 to 1.54), or at the three-month follow-up (RR 0.69; 95% CI 0.26 to 1.81). Multilevel InterventionsA five-site cluster-RCT with 1041 participants compared the effectiveness of combinations of policy communication, stress management training, and negative behaviours awareness training. The authors reported that bullying victimisation did not change (13.6% before intervention and 14.3% following intervention). The authors reported insufficient data for us to conduct our own analysis.Due to high risk of bias and imprecision, we graded the evidence for all outcomes as very low quality.

AUTHORS' CONCLUSIONS

There is very low quality evidence that organisational and individual interventions may prevent bullying behaviours in the workplace. We need large well-designed controlled trials of bullying prevention interventions operating on the levels of society/policy, organisation/employer, job/task and individual/job interface. Future studies should employ validated and reliable outcome measures of bullying and a minimum of 6 months follow-up.

Prevalence of Hazardous Occupational Noise Exposure, Hearing Loss, and Hearing Protection Usage Among a Representative Sample of Working Canadians

OBJECTIVE

The aim of this study was to estimate the prevalence of hearing loss (HL), self-reported occupational noise exposure, and hearing protection usage among Canadians.

METHODS

In-person household interviews were conducted with 3666 participants, aged 16 to 79 years (1811 males) with 94% completing audiometry and distortion-product otoacoustic emission (DPOAE) evaluations. Occupational noise exposure was defined as hazardous when communicating with coworkers at an arm's length distance required speaking in a raised voice.

RESULTS

An estimated 42% of respondents reported hazardous occupational noise exposure; 10 years or more was associated with HL regardless of age, sex or education. Absent DPOAEs, tinnitus, and the Wilson audiometric notch were significantly more prevalent in hazardous workplace noise-exposed workers than in nonexposed. When mandatory, 80% reported wearing hearing protection.

CONCLUSIONS

These findings are consistent with other industrialized countries, underscoring the need for ongoing awareness of noise-induced occupational HL.

The Effects of Acoustic White Noise on the Rat Central Auditory System During the Fetal and Critical Neonatal Periods: A Stereological Study

AIM

To evaluate the effects of long-term, moderate level noise exposure during crucial periods of rat infants on stereological parameters of medial geniculate body (MGB) and auditory cortex.

MATERIALS AND METHODS

Twenty-four male offspring of 12 pregnant rats were divided into four groups: fetal-to-critical period group, which were exposed to noise from the last 10 days of fetal life till postnatal day (PND) 29; fetal period group that exposed to noise during the last 10 days of fetal life; critical period group, exposed to noise from PND 15 till PND 29, and control group. White noise at 90 dB for 2 h per day was used.

STATISTICAL ANALYSIS USED

Variance for variables was performed using Proc GLM followed by mean comparison by Duncan's multiple range test.

RESULTS

Numerical density of neurons in MGB of fetal-to-critical period group was lower than control group. Similar results were seen in numerical density of neurons in layers IV and VI of auditory cortex. Furthermore, no significant difference was observed in the volume of auditory cortex among groups, and only MGB volume in fetal-to-critical period group was higher than other groups. Estimated total number of neurons in MGB was not significantly different among groups.

CONCLUSION

It seems necessary to prevent long-term moderate level noise exposure during fetal-to-critical neonatal period.

Occupational noise-induced hearing loss in auto part factory workers in welding units in Thailand

Objectives:

Most workers in auto part factories in Thailand are usually exposed to excessive noise in their workplace. This study aimed to assess the level of occupational noise-induced hearing loss and investigate risk factors causing hearing loss in auto part factory workers in the welding units in Thailand.

Methods:

This was a cross-sectional study. One hundred eighty subjects were recruited from 356 workers in the welding unit of three factories. Sixty eligible subjects in each factory were selected by systemic random sampling. The subjects were interviewed using a face-to-face questionnaire. Noise exposure levels and audiograms were measured by a noise dosimeter and an audiometer, respectively.

Results:

The findings confirmed that noise exposure levels of 86-90 dB (A) and exceeding 90 dB (A) significantly increased the risk of hearing loss in either ear. A noise exposure level exceeding 90 dB (A) significantly increased the prevalence of hearing loss in both ears. Regarding, a 10-pack-year smoking history increased the prevalence of hearing loss in either ear or both ears. In addition, subjects with employment duration exceeding 10 years significantly developed hearing loss in either ear.

Conclusions:

The engineering control or personal control by wearing hearing protection device should be used to decrease noise exposure levels lower than 85 dB (A) for 8 h. Moreover, if the exposure level reaches 85 dB (A) for 8 h, the employer needs to implement a hearing conservation program in the workplace.

Soft tissue conduction as a possible contributor to the limited attenuation provided by hearing protection devices

CONTEXT

Damage to the auditory system by loud sounds can be avoided by hearing protection devices (HPDs) such as earmuffs, earplugs, or both for maximum attenuation. However, the attenuation can be limited by air conduction (AC) leakage around the earplugs and earmuffs by the occlusion effect (OE) and by skull vibrations initiating bone conduction (BC).

AIMS

To assess maximum attenuation by HPDs and possible flanking pathways to the inner ear.

SUBJECTS AND METHODS

AC attenuation and resulting thresholds were assessed using the real ear attenuation at threshold (REAT) procedure on 15 normal-hearing participants in four free-field conditions: (a) unprotected ears, (b) ears covered with earmuffs, (c) ears blocked with deeply inserted customized earplugs, and (d) ears blocked with both earplugs and earmuffs. BC thresholds were assessed with and without earplugs to assess the OE.

RESULTS

Addition of earmuffs to earplugs did not cause significantly greater attenuation than earplugs alone, confirming minimal AC leakage through the external meatus and the absence of the OE. Maximum REATs ranged between 40 and 46 dB, leading to thresholds of 46-54 dB HL. Furthermore, calculation of the acoustic impedance mismatch between air and bone predicted at least 60 dB attenuation of BC.

CONCLUSION

Results do not support the notion that skull vibrations (BC) contributed to the limited attenuation provided by traditional HPDs. An alternative explanation, supported by experimental evidence, suggests transmission of sound to inner ear via non-osseous pathways such as skin, soft tissues, and fluid. Because the acoustic impedance mismatch between air and soft tissues is smaller than that between air and bone, air-borne sounds would be transmitted to soft tissues more effectively than to bone, and therefore less attenuation is expected through soft tissue sound conduction. This can contribute to the limited attenuation provided by traditional HPDs. The present study has practical implications for hearing conservation protocols.

A Scan of CDC-Authored Articles on Legal Epidemiology, 2011-2015

OBJECTIVE

The Centers for Disease Control and Prevention (CDC) conducts research on legal epidemiology, the scientific study of law as a factor in the cause, distribution, and prevention of disease. This study describes a scan of articles written by CDC staff members to characterize the frequency and key features of legal epidemiology articles and their distribution across CDC departments and divisions.

METHODS

CDC librarians searched an internal repository for journal articles by CDC staff published from January 1, 2011, to May 31, 2015. Researchers reviewed and coded the abstracts to produce data on key features of the articles.

RESULTS

Researchers identified 158 CDC-authored legal epidemiology articles published in 83 journals, most frequently in Preventing Chronic Disease (14 publications), Journal of Public Health Management Practice (10 publications), and Morbidity and Mortality Weekly Report (9 publications). Most articles concerned the use and impact of law as a deliberate tool of intervention. Thirteen articles addressed the legal infrastructure of public health, and 3 assessed the incidental or unintended effects of nonhealth laws. CDC-authored articles encompassed policy making, implementation, and impact. Literature reviews and studies mapping laws across multiple jurisdictions constituted one-quarter of all publications. Studies addressed laws at the international, national, state, local, and organizational levels.

CONCLUSION

Results of the scan can be used to identify opportunities for the agency to better support research, professional development, networking, publication, and tracking of publication in this emerging field.

Maternal Occupational Exposure to Noise during Pregnancy and Hearing Dysfunction in Children: A Nationwide Prospective Cohort Study in Sweden

BACKGROUND

Many women of childbearing age are occupationally active, which leads to a large number of pregnancies potentially exposed to occupational exposures. Occupational noise has been identified as a risk factor for hearing impairment in adults. However, very few studies have assessed the effect of occupational noise on the fetus.

OBJECTIVES

The aim of this study was to investigate whether occupational exposure to noise during pregnancy is associated with hearing dysfunction in children.

METHODS

This population based cohort study included 1,422,333 single births in Sweden 1986-2008. Data on mothers' occupation, smoking habits, age, ethnicity, body mass index, leave of absence, and socioeconomic factors were obtained from interviews performed by prenatal care unit staff at approximately 10 weeks of gestation and from national registers. Occupational noise exposure was classified by a job-exposure-matrix as < 75, 75-84, or ≥ 85 dBLAeq,8h. Diagnosed cases of hearing dysfunction (ICD-10 codes H90.3-7, 91.0, 91.2-3, 91.8, 93.1-2) were identified from a register of specialized medical care. Cox proportional hazards models were used to estimate associations.

RESULTS

In the full sample, containing a mixture of part-time and full-time workers during pregnancy, the adjusted HR for hearing dysfunction associated with maternal occupational noise exposure ≥ 85 vs. < 75 dBLAeq,8h was 1.27 (95% CI: 0.99, 1.64; 60 exposed cases). When restricted to children whose mothers worked full-time and had < 20 days leave of absence during pregnancy, the corresponding HR was 1.82 (95% CI: 1.08, 3.08; 14 exposed cases).

CONCLUSIONS

This study showed an association between occupational noise exposure during pregnancy and hearing dysfunction in children. In view of mechanistic evidence and earlier indicative epidemiological and experimental findings, the results support that pregnant women should not be exposed to high levels of noise at work.

CITATION

Selander J, Albin M, Rosenhall U, Rylander L, Lewné M, Gustavsson P. 2016. Maternal occupational exposure to noise during pregnancy and hearing dysfunction in children: a nationwide prospective cohort study in Sweden. Environ Health Perspect 124:855-860; http://dx.doi.org/10.1289/ehp.1509874.

Occupational noise exposure and hearing: a systematic review

Purpose

To give a systematic review of the development of noise-induced hearing loss (NIHL) in working life.

Methods

A literature search in MEDLINE, Embase, Web of Science, Scopus, and Health and Safety Abstracts, with appropriate keywords on noise in the workplace and health, revealed 22,413 articles which were screened by six researchers. A total of 698 articles were reviewed in full text and scored with a checklist, and 187 articles were found to be relevant and of sufficient quality for further analysis.

Results

Occupational noise exposure causes between 7 and 21 % of the hearing loss among workers, lowest in the industrialized countries, where the incidence is going down, and highest in the developing countries. It is difficult to distinguish between NIHL and age-related hearing loss at an individual level. Most of the hearing loss is age related. Men lose hearing more than women do. Heredity also plays a part. Socioeconomic position, ethnicity and other factors, such as smoking, high blood pressure, diabetes, vibration and chemical substances, may also affect hearing. The use of firearms may be harmful to hearing, whereas most other sources of leisure-time noise seem to be less important. Impulse noise seems to be more deleterious to hearing than continuous noise. Occupational groups at high risk of NIHL are the military, construction workers, agriculture and others with high noise exposure.

Conclusion

The prevalence of NIHL is declining in most industrialized countries, probably due to preventive measures. Hearing loss is mainly related to increasing age.

Electronic supplementary material

The online version of this article (doi:10.1007/s00420-015-1083-5) contains supplementary material, which is available to authorized users.

Immediate and delayed cochlear neuropathy after noise exposure in pubescent mice

Moderate acoustic overexposure in adult rodents is known to cause acute loss of synapses on sensory inner hair cells (IHCs) and delayed degeneration of the auditory nerve, despite the completely reversible temporary threshold shift (TTS) and morphologically intact hair cells. Our objective was to determine whether a cochlear synaptopathy followed by neuropathy occurs after noise exposure in pubescence, and to define neuropathic versus non-neuropathic noise levels for pubescent mice. While exposing 6 week old CBA/CaJ mice to 8-16 kHz bandpass noise for 2 hrs, we defined 97 dB sound pressure level (SPL) as the threshold for this particular type of neuropathic exposure associated with TTS, and 94 dB SPL as the highest non-neuropathic noise level associated with TTS. Exposure to 100 dB SPL caused permanent threshold shift although exposure of 16 week old mice to the same noise is reported to cause only TTS. Amplitude of wave I of the auditory brainstem response, which reflects the summed activity of the cochlear nerve, was complemented by synaptic ribbon counts in IHCs using confocal microscopy, and by stereological counts of peripheral axons and cell bodies of the cochlear nerve from 24 hours to 16 months post exposure. Mice exposed to neuropathic noise demonstrated immediate cochlear synaptopathy by 24 hours post exposure, and delayed neurodegeneration characterized by axonal retraction at 8 months, and spiral ganglion cell loss at 8-16 months post exposure. Although the damage was initially limited to the cochlear base, it progressed to also involve the cochlear apex by 8 months post exposure. Our data demonstrate a fine line between neuropathic and non-neuropathic noise levels associated with TTS in the pubescent cochlea.

Adenosine amine congener as a cochlear rescue agent

We have previously shown that adenosine amine congener (ADAC), a selective A₁ adenosine receptor agonist, can ameliorate noise- and cisplatin-induced cochlear injury. Here we demonstrate the dose-dependent rescue effects of ADAC on noise-induced cochlear injury in a rat model and establish the time window for treatment. Methods. ADAC (25–300 μg/kg) was administered intraperitoneally to Wistar rats (8–10 weeks old) at intervals (6–72 hours) after exposure to traumatic noise (8–16 kHz, 110 dB sound pressure level, 2 hours). Hearing sensitivity was assessed using auditory brainstem responses (ABR) before and 12 days after noise exposure. Pharmacokinetic studies investigated ADAC concentrations in plasma after systemic (intravenous) administration. Results. ADAC was most effective in the first 24 hours after noise exposure at doses >50 μg/kg, providing up to 21 dB protection (averaged across 8–28 kHz). Pharmacokinetic studies demonstrated a short (5 min) half-life of ADAC in plasma after intravenous administration without detection of degradation products. Conclusion. Our data show that ADAC mitigates noise-induced hearing loss in a dose- and time-dependent manner, but further studies are required to establish its translation as a clinical otological treatment.

Preventive occupational health interventions in the meat processing industry in upper-middle and high-income countries: a systematic review on their effectiveness

OBJECTIVE

To investigate the effectiveness of occupational health interventions in the meat processing industry on work and health-related outcomes.

METHODS

A systematic literature review was performed. PubMed, Embase, and The Cochrane Library were searched. Studies were included when they reported on an intervention among employees in the meat processing industry and with outcomes related to work or health. Studies were assessed on risk of bias, and data were synthesized by type of intervention.

RESULTS

A total of 13 articles reporting on two randomized controlled trials and nine non-randomized intervention studies were retrieved. Studies were categorized into three topics: ergonomics programs, skin protection, and Q fever vaccination. All studies had high risk of bias. Based on four studies, there was limited evidence for workplace health and safety programs showing reductions in musculoskeletal injury severity, reduction of lost work days, and reduction of costs and claims for several musculoskeletal disorders. There was limited evidence for added rest breaks resulting in improved productivity at the end of a workday and in reductions of perceived discomfort in various body regions at the end of the workday. One study on skin protection showed reductions of eczema prevalence, although evidence was moderate. Based on four studies, there was high-quality evidence for strong effectiveness of Q fever vaccination.

CONCLUSION

This review presents evidence for the effectiveness of a variety of workplace interventions. There was limited evidence for effectiveness of ergonomic interventions, moderate evidence of a skin protection intervention, and strong evidence for Q fever vaccination.

Auditory and non-auditory effects of noise on health

Noise is pervasive in everyday life and can cause both auditory and non-auditory health effects. Noise-induced hearing loss remains highly prevalent in occupational settings, and is increasingly caused by social noise exposure (eg, through personal music players). Our understanding of molecular mechanisms involved in noise-induced hair-cell and nerve damage has substantially increased, and preventive and therapeutic drugs will probably become available within 10 years. Evidence of the non-auditory effects of environmental noise exposure on public health is growing. Observational and experimental studies have shown that noise exposure leads to annoyance, disturbs sleep and causes daytime sleepiness, affects patient outcomes and staff performance in hospitals, increases the occurrence of hypertension and cardiovascular disease, and impairs cognitive performance in schoolchildren. In this Review, we stress the importance of adequate noise prevention and mitigation strategies for public health.

Google Scholar as replacement for systematic literature searches: good relative recall and precision are not enough

BACKGROUND

Recent research indicates a high recall in Google Scholar searches for systematic reviews. These reports raised high expectations of Google Scholar as a unified and easy to use search interface. However, studies on the coverage of Google Scholar rarely used the search interface in a realistic approach but instead merely checked for the existence of gold standard references. In addition, the severe limitations of the Google Search interface must be taken into consideration when comparing with professional literature retrieval tools.The objectives of this work are to measure the relative recall and precision of searches with Google Scholar under conditions which are derived from structured search procedures conventional in scientific literature retrieval; and to provide an overview of current advantages and disadvantages of the Google Scholar search interface in scientific literature retrieval.

METHODS

General and MEDLINE-specific search strategies were retrieved from 14 Cochrane systematic reviews. Cochrane systematic review search strategies were translated to Google Scholar search expression as good as possible under consideration of the original search semantics. The references of the included studies from the Cochrane reviews were checked for their inclusion in the result sets of the Google Scholar searches. Relative recall and precision were calculated.

RESULTS

We investigated Cochrane reviews with a number of included references between 11 and 70 with a total of 396 references. The Google Scholar searches resulted in sets between 4,320 and 67,800 and a total of 291,190 hits. The relative recall of the Google Scholar searches had a minimum of 76.2% and a maximum of 100% (7 searches). The precision of the Google Scholar searches had a minimum of 0.05% and a maximum of 0.92%. The overall relative recall for all searches was 92.9%, the overall precision was 0.13%.

CONCLUSION

The reported relative recall must be interpreted with care. It is a quality indicator of Google Scholar confined to an experimental setting which is unavailable in systematic retrieval due to the severe limitations of the Google Scholar search interface. Currently, Google Scholar does not provide necessary elements for systematic scientific literature retrieval such as tools for incremental query optimization, export of a large number of references, a visual search builder or a history function. Google Scholar is not ready as a professional searching tool for tasks where structured retrieval methodology is necessary.