Noise-induced Hearing Loss In Workers Research Articles

A risk model for occupational noise-induced hearing loss in workers.

Occupational hearing loss is one of the most common work-related diseases with various risk factors and considerable negative impacts on both physical and mental well-being of affected workers. Occupational noise-induced hearing loss (ONIHL) has a complex interaction with personal, environmental and occupational factors. This study aimed to develop a risk model for ONIHL in workers by identifying risk factors and their interactions. The subjects were 605 males in an industrial factory in Arak, Iran. The study took place between 2022 and 2023. The sociodemographic and occupational characteristics were collected by a health technician using questionnaires and medical records. Hearing status was assessed using audiometry by a qualified audiologist. Hearing loss was analyzed by univariate logistic analysis including age, smoking, medical history, type of occupation, and some workplace hazards. The risk model was generated by logistic regression. Hearing loss in the participants was 44.13% (n = 267). In univariate logistic analysis, age (OR: 2.93,95% CI: 1.848-4.656), smoking (OR: 1.80, 95% CI: 1.224-2.655), work experience (OR: 1.06, 95% CI: 1.016-1.107), previous exposure to noise (OR: 1.60, 95% CI: 1.112-2.312) or vibration (OR: 1.68, 95% CI: 1.150-2.475) and type of occupation (OR: 2.126, 95% CI: 1.055-4.285) were associated with an increased risk of ONIHL (P < 0.05). It was found that vibration exposure, work experience, previous noise exposure, type of occupation as well as age and smoking significantly affected the likelihood of developing ONIHL. This risk model could help management to prevent ONIHL and enhance application-oriented research on the condition.

Risk assessment on noise-induced hearing loss of 488 workers in a petrochemical plant

Objective: To assess the risk of noise-induced hearing loss in workers from a petrochemical plant. Methods: In October 2020, 488 male workers exposed to noise in a petrochemical plant in Guangdong Province were selected by cluster sampling. Acoustics-Estimation of Noise-Induced Hearing Loss (ISO 1999: 2013) was used to assess the risk of noise-induced hearing loss of workers, and individual fit testing was used to evaluate the sound attenuation obtained by the workers. The risk assessment results and fitness test results of workers with different hearing levels were compared. Results: The average noise exposure equivalent sound level of the workers in the petrochemical plant was 86.7 dB (A) . The median of PARs (personal attenuation ratings) was 16 (4, 23) dB. There were statistically significant differences in age and service years among workers with different hearing results (P<0.05) , but no statistically significant differences in noise intensity and PARs (P>0.05) . According to risk assessment results of ISO 1999: 2013, the current risk of high-frequency hearing loss in 488 workers were negligible risk and acceptable risk. The risk of noise-induced deafness weredivided into three levels: negligible risk in 452 workers (92.7%) , medium risk in 27 workers (5.5%) and high risk in 9 workers (1.8%) . The risk of high-frequency hearing loss in next 5 to 15 years for workers with noise exposure level of >94 to 97 dB and >97 dB or above would be medium risk or above. The risk of noise-induced deafness in next 5 to 15 years for workers exposed to noise withlevel of 91 to 94 dB would be medium risk or above. Conclusion: The risk of noise-induced hearing loss in workers from the petrochemical plant is high in next 5 to 15 years, and noise prevention and control measures need to be strengthened. ISO1999: 2013 assessment method may underestimate the risk of hearing loss among workers.

Risk assessment of noise-induced hearing loss among workers in railway transportation equipment manufacturing enterprises

To analyze the noise exposure and hearing loss of workers in railway transportation equipment manufacturing enterprises, and to assess the risk of hearing loss caused by noise. From 2018 to 2020, an investigation was carried out on 3 railway transportation equipment manufacturing enterprises in Hubei Province and Hunan Province. A total of 840 noise-exposed workers were selected, the individual noise exposure level(L_(Aeq·8 h)) and hearing loss level were measured, the cumulative noise exposure(CNE) was calculated, and the relationship between hearing loss and technological process, working time and CNE were analyzed. ISO1999:2013 was used to calculate the change of hearing threshold and the risk of noise-induced hearing loss after 40 years old. The median age of workers was 32 years old, and the median working age for noise exposure was 10 years. The distribution of positions is mainly welding, machining, assembly and painting.79.5%(120/151) of the individual noise exposure doses exceeded 85 dB(A), and the average L_(Aeq.8 h) was 89.9(A). There were significant differences in the proportion of hearing loss among workers in different process units(χ~2= 29.597, P&lt;0.001), and the proportion of hearing loss in the preparation and steel structure units was higher. The proportion of hearing loss showed an upward trend with the increase of working years(χ~2=164.462, P&lt;0.001), and the high-frequency combined speech-frequency hearing loss(26.7%) increased significantly after working for more than 20 years. With the increase of CNE, the proportion of high-frequency hearing loss and the proportion of high-frequency combined speech-frequency hearing loss increased accordingly(χ~2=192.544, P&lt;0.001). The proportion of high frequency combined speech frequency hearing loss increased significantly in the group with CNE greater than 105 dB(A)·years. It is predicted that the risk of hearing loss caused by noise in assemblers appears earliest and the risk is the greatest. The risk of high noise-induced frequency hearing loss of assemblers was 3.6%-8.6% at the age of 40, 20.2% at the age of 50, 22.0% at the age of 60. The risk of high-frequency combined speech-frequency hearing loss of assemblers was 1.2%-6.2% at the age of 50 and 8.6% at the age of 60. The noise hazard is serious and widely distributed in railway transportation equipment manufacturing enterprises, and the proportion of hearing loss increases with the increase of working time and CNE. Although ISO1999:2013 predicts that there may be an underestimation of noise-induced hearing loss in workers, it can be used as an early warning of hearing loss to identify the potential risk of hearing loss in the population.

Application of ISO 1999:2013 (E) model in risk assessment of hearing loss caused by industrial noise

To assess the risk of hearing loss caused by industrial noise exposure of welders and assemblers in a mechanical equipment manufacturing enterprise, and to explore the practical application and possible underestimation of ISO 1999∶2013(E) model. A total of 829 noise-exposed male workers from a mechanical equipment manufacturing enterprise were selected as study subjects. The questionnaire survey was administered, and individual noise exposure level(L_(Aeq.8 h)) and hearing loss level were measured. The risk assessment method of ISO 1999∶2013(E) was used to calculate the change of hearing threshold level and the risk of noise-induced hearing loss. By comparing the median of permanent hearing threshold shift caused by actual noise with the median of ISO1999 predicted value, the reason of the difference between the predicted value of ISO 1999∶2013(E) model and the actual value was analyzed. The L_(Aeq.8 h )was 89.5 dB(A), 77.4%(n=62)of the individual noise exposure levels exceeded 85 dB(A), and 24.6% of the participants(n=829) had different degrees of hearing loss. There was significant difference in hearing loss rate between welding and assembly positions(χ~2=10.07, P&lt;0.01). The risk of noise-induced high-frequency hearing loss of 90% welders was 11.2% at the age of 50, and 14.0% at the age of 60. The risk of noise-induced deafness of 90% welders was 4.3% at the age of 60. The risk of high noise-induced frequency hearing loss of 90% assemblers was at the range of 4.0%-9.0% at the age of 40, 20.8% at the age of 50, and 22.5% at the age of 60. The risk of noise-induced deafness of 90% assemblers was at the range of 1.4%-6.4% at the age of 50, and 9.0% at the age of 60. Compared with actual median of permanent hearing threshold shift, ISO1999∶2013(E) predictions underestimated the median of permanent hearing threshold shift at 10.7 dB. The noise hazards of welding and assembly positions in mechanical equipment manufacturing enterprises are high relatively. ISO1999∶2013(E) can be used to predict the risk of noise-induced hearing loss in workers, but attention should be paid to the risk underestimation of this model.

The effects of dyslipidemia on noise-induced hearing loss in petrochemical workers in the Southwest of Iran.

Research has shown that the decrease in the inner diameter of vessels caused by hyperlipidemia lowers the capacity for blood oxygen delivery to the cochlea. This leads to impaired cochlear metabolism and causes hearing problems. The effects of dyslipidemia on noise-induced hearing loss in workers were examined. This descriptive cross-sectional study was performed on 692 male employees in a petrochemical industry in the southwest of Iran exposed to 85 dB noise. Clinical audiometry and blood sample tests were used to evaluate the hearing and prevalence indices of dyslipidemia (cholesterol, triglyceride, HDL and LDL). The data were analyzed using SPSS software version 25 (p = 0.05). The results showed that the prevalence of dyslipidemia was 24.5% with abnormal relative triglyceride frequency of 49.5%, HDL of 28%, LDL of 33%, and total blood cholesterol level of 37.8%. There was no significant relationship between NIHL and dyslipidemia (p > 0.09). However, the major NIHL drops at different frequencies were in the individuals with dyslipidemia. The parameters age and dyslipidemia increased NIHL odds ratio (95% C.I.) by 1.130 (1.160-1.100) and 1.618 (2.418-1.082) respectively. The rate of hearing loss in individuals with dyslipidemia increases at different frequencies and it leads to an increase of the OR of NIHL in individuals with dyslipidemia. We can control dyslipidemia and its effective factors. The NIHL is more common in people exposed to noise.

Comparative analysis of the potential and actual risk of noise-induced hearing loss in employees of “noise” industries

Introduction. The high incidence of noise-induced hearing loss (NIHL) makes it possible to attribute the problem of prevention and prediction of the risk of NIHL to the number of socially significant ones. The aim of the study is to conduct a comparative assessment of the potential risk of hearing loss caused by noise according to GOST R ISO 1999-2017, and the actual risk of NIHL in workers of “noise” industries according to epidemiological research. Materials and methods. The calculation of the potential risk of hearing loss according to GOST R ISO 1999-2017 included assessing age, noise and total hearing loss at noise exposure with 85, 90, 95 and 100 dBA. The actual risk of NIHL was evaluated on survey data of 600 miners and 600 workers of processing plants. Results. The calculation of the probable risk according to GOST R ISO 1999-2017 and the assessment of the actual risk according to epidemiological studies showed that the risk of NIHL depends on both noise exposure and age. As the levels of noise affecting an employee increase, the risk of an NIHL becomes more determined by the effect of noise. At noise levels 85, 90 and 95 dBA, the probable risk calculated under GOST R ISO 1999-2017 coincides with the actual risk established according to epidemiological studies. At the same time, for miners exposed to high-intensity noise 100 dBА, the real risk was not as high as could be assumed from the calculated data. Conclusion. The results obtained allow stating that the GOST ISO 1999-2017 standard with a high degree of potential risk allows predicting the group risk of hearing loss due to noise exposure, to quantify the degree of risk and can be used for the formation of risk groups for NIHL and the development of programs for the preservation of hearing.

Factores asociados a hipoacusia inducida por ruido en trabajadores de una empresa metalmecánica de Talara, Piura periodo 2015 – 2018

Introducción: La hipoacusia es una enfermedad ocupacional frecuente y ocasiona deterioro en la calidad de vida de los trabajadores. Objetivo: Identificar la prevalencia y los factores asociados a hipoacusia inducida por ruido en trabajadores de una empresa metalmecánica. Material y Métodos: Estudio transversal analítico. Se utilizaron datos de historias clínicas ocupacionales para determinar la frecuencia de hipoacusia debido a ruido y sus potenciales factores asociados (edad, sexo, antecedentes personales). Se construyeron modelos de regresión simple y múltiple, estimando razones de prevalencia (RP) utilizando modelos lineales generalizados, familia Poisson y función de enlace log. Resultados: De 1543 trabajadores, la media de edad fue 36.7 años y la mayoría era hombre (93,6%). Solo el 8,2% reportó enfermedad y/o accidente laboral previo a la evaluación ocupacional. El 10,7% presentó hipoacusia debido al ruido. La frecuencia de presentar hipoacusia incrementaba 10% por cada año adicional de edad (RP=1.10, IC95%: 1,09-1,12, p&lt;0,001) y tener el antecedente de enfermedad/accidente laboral incrementaba 75% la frecuencia de presentar hipoacusia (RP=1,75, IC95%: 1,28-2,40, p&lt;0,001). Conclusión: La prevalencia de hipoacusia debido a ruido fue baja, La edad en años y el antecedente de enfermedad/accidente laboral se asociaron de forma positiva a presentar hipoacusia. Se sugiere realizar un seguimiento anual de audiometrías, con especial énfasis en los antecedentes ocupacionales asociados a hipoacusia debido al ruido.

Analysis of Polymorphisms Associated with Base Excision Repair in Patients Susceptible and Resistant to Noise-Induced Hearing Loss.

Objective Noise-induced hearing loss (NIHL) is one of the most common occupational health risks in both developed and industrialized countries. It occurs as a result of interactions between genetic and environmental factors. Nevertheless, inherited genetic factors contributing to NIHL are not well understood. Therefore, we aim to investigate whether genetic mutations in three important base excision repair genes (OGG1, APEX1, and XRCC1) may influence susceptibility to NIHL. Methods Three SNPs in OGG1, APEX1, and XRCC1 were genotyped from 1170 noise-exposed workers and were classified into 117 most susceptible and 117 most resistant individuals. Results Results showed that the rs1799782 TT genotype located in the XRCC1 coding region and rs1130409 GG/GT in the APEX1 coding region were associated with increased risk for NIHL in a Chinese population. Compared to the rs1799782 C allele frequency, the T allele frequency was increased in the sensitive group (adjusted OR = 1.51, 95%CI = 1.01 to 2.26, P = 0.043). The rs1130409 G allele frequency was also increased in the sensitive group compared to the resistant group (adjusted OR = 1.59, 95%CI = 1.10 to 2.31, P = 0.015). Moreover, rs1130409 and drinking had a statistically significant interaction (P = 0.0002), while rs1799782, rs1130409, and smoking also had a statistically significant interaction (P < 0.0001). Conclusions XRCC1 rs1799782 and APEX1 rs1130409 may have potential as biomarkers for the screening of susceptibility to NIHL in workers exposed severe noise.

Prevalence of Noise-Induced Hearing Loss in Workers with Noise Exposure in Panyananthaphikkhu Chonprathan Medical Center, Srinakharinwirot University

Objective: To determine the prevalence of noise-induced hearing loss (NIHL) in workers in Panyananthaphikkhu Chonprathan Medical Center, Srinakharinwirot University (PCMC). The risk factors associated with noise-induced hearing loss were evaluated.Material and Methods: A cross-sectional study was conducted to analyze the data of 82 patients (43 males and 39 females) between June 2018 and July 2018. Subjects were between 20 and 59 years of age. All of them worked in loud environments in PCMC, using extended high-frequency audiometry (EHFA). The results of hearing loss in thegroup of EHFA and conventional audiometry were compared using the chi-squared test, McNemar’s chi-squared test and Fisher’s exact test. Multivariate logistic regression analysis was used for evaluating the risk factors.Results: The prevalence of NIHL was 41.5%. The risk factors associated with NIHL were smoking [odds ratio (OR)=5.6, p-value=0.002 (95% confidence interval (CI)=1.66-18.86)] and age over 40 years [OR=10.38, p-value&lt;0.001 (95% CI=2.82-38.24)].Conclusion: Epidemic NIHL continues to increase in the workplace, particularly in individuals with an age of over 40 years who smoke. Early detection of this irreversible disorder of the inner ear should be attempted.

Investigation into the relationship between mitochondrial 12 S rRNA gene, tRNA gene and cytochrome oxidase Ⅱ gene variations and the risk of noise-induced hearing loss

Objective: To explore the relationship between mitochondrial 12 S rRNA gene variation, tRNA gene variation and cytochrome oxidase Ⅱ gene point mutations and the risk of noise-induced hearing loss (NIHL). Methods: A nested case-control study was performed that followed a cohort of 7 445 noise-exposed workers in a steel factory in Henan province, China, from January 1, 2006 to December 31, 2015. Subjects whose average hearing threshold was more than 40 dB(A) in high frequency were defined as the case group, and subjects whose average hearing threshold was less than 35 dB(A) in high frequency and less than 25 dB (A) in speech frequency were defined as the control group. Subjects was recruited into the case group (n=286) and the control group (n=286) according to gender, age, job category and time of exposure to noise, and a 1∶1 case-control study was carried out. We genotyped eight single nucleotide polymorphisms in the mitochondrial 12 S rRNA gene, the mitochondrial tRNA gene and the mitochondrial cytochrome oxidase Ⅱ gene using SNPscan high-throughput genotyping technology from the recruited subjects. The relationship between polymorphic sites and NIHL, adjusted for covariates, was analyzed using conditional logistic regression analysis, as were the subgroup data. Results: The average age of the recruited subjects was (40.3±8.1) years and the length of service exposure to noise was (18.6±8.9) years. The range of noise exposed levels and cumulative noise exposure (CNE) was 80.1- 93.4 dB (A) and 86.8- 107.9 dB (A) · year, respectively. For workers exposed to noise at a CNE level<98 dB (A) · year, smokers showed an increased risk of NIHL of 1.88 (1.16-3.05) compared with non-smokers; for workers exposed to noise at a CNE level ≥98 dB(A) · year, smokers showed an increased risk of NIHL of 2.53 (1.49- 4.30) compared with non-smokers. For workers exposed to noise at a CNE level<98 dB (A) · year, the results of univariate analysis and multifactor analysis, adjusted by smoking and CNE, suggested that the risk of NIHL in workers exposed to noise carrying the GG genotype (G827A) was lower than that of NIHL workers exposed to noise carrying the AA genotype (G827A) [OR (95% CI) were 0.18 (0.04- 0.82) and 0.19 (0.04- 0.88), respectively]. Conclusion: Smoking increased the risk of NIHL in the present study. For workers subjected to a CNE<98 dB(A)·year, the mitochondrial genetic variant G827A was found to be significantly associated with the risk of NIHL.

Noise-induced hearing loss and combined noise and vibration exposure.

While there is a wide body of literature addressing noise-induced hearing loss (NIHL) and hand-arm vibration syndrome (HAVS) independently, relatively few studies have considered the combined effects of noise and vibration. These studies have suggested an increased risk of NIHL in workers with vibration white finger (VWF), though the relationship remains poorly understood. To determine whether hearing impairment is worse in noise-exposed workers with VWF than in workers with similar noise exposures but without VWF. The Quebec National Institute of Public Health audiometric database was used in conjunction with work-related accident and occupational diseases data from the Quebec workers' compensation board to analyse differences in audiometry results between vibration-exposed workers in the mining and forestry industries and the overall source population, and between mining and forestry workers with documented VWF and those without VWF. The International Organization for Standardization (ISO) 7029 standards were used to calculate hearing loss not attributable to age. 15751 vibration-exposed workers were identified in an overall source population of 59339. Workers with VWF (n = 96) had significantly worse hearing at every frequency studied (500, 1000, 2000 4000 Hz) compared with other mining and forestry workers without VWF. This study confirms previous findings of greater hearing loss at higher frequencies in workers with VWF, but also found a significant difference in hearing loss at low frequencies. It therefore supports the association between combined noise and hand-arm vibration (HAV) exposure and NIHL.

Noise-induced hearing loss in workers exposed to urban stressors

The technological and industrial progress together with the intensification of vehicular traffic and the adoption of new social habits are the cause of an increasing noise pollution with possible negative effects on the auditory system. This study aims to assess the noise exposure levels and the effects on the hearing threshold in outdoor and indoor male workers of a big Italian city. The study was carried out on 357 outdoor male workers, exposed to urban noise and on a control group of 357 unexposed indoor workers. Noise levels were measured in 30 outdoor and indoor areas. The subjects underwent tonal liminal audiometry in order to determine the value of their hearing threshold. During their working activity, outdoor and indoor workers are exposed to different noise levels LEX<80dB(A). At mid–low frequencies (250–2000Hz), the results show significant differences in the average values of hearing threshold between the two groups in both ears and for all age classes; there are no significant differences between the two groups at higher frequencies. The outdoor noise levels measured are not usually ototoxic and the hearing loss at mid–low frequencies is not characteristic of the exposure to industrial noise. For these reasons the Authors hypothesize that the results may be due to the combined effect of the exposure to noise and to ototoxic air pollutants. The impairment of speech frequencies is disabling and involves the risk of missed forensic recognition.

Effect of cigarette smoking on noise-induced hearing loss in workers exposed to occupational noise in China

Excessive exposure to high noise level environments has the potential to cause noise-induced hearing loss (NIHL), and cigarette smoking has also been shown to have a potential adverse effect on hearing. The aim of this study was to determine whether smoking interacts with noise in the development of hearing loss, and if so, the extent of the contribution from smoking on NIHL. A cross-sectional study was designed to assess the effect of smoking on NIHL in 517 male workers (non-smokers: N = 199; smokers: N = 318) exposed to a high-level industrial noise environment in China. Shift-long temporal waveforms of the noise that workers were exposed to for evaluation of noise exposures, and audiometric threshold measures were obtained on all selected subjects. The subjects used hearing protection devices only within the last 1-2 years. The results suggest that smoking has an adverse effect on NIHL in workers exposed to high level industrial noise, i.e., the median high frequency hearing thresholds were significantly greater in smokers than non-smokers exposed to noise for more than 10 years. This effect was observed at 4.0 and 6.0 kHz. Smoking did not have an adverse effect on NIHL in workers exposed to noise less than 10 years. Multivariate regression analysis revealed that the odds ratio (OR) for high frequency hearing loss (i.e., hearing threshold greater than 40 dB at 4.0 kHz) were 1.94 for smokers in comparison to non-smokers. The results suggest that: (1) smokers have a higher risk of developing high frequency hearing loss than non-smokers with a similar occupational noise exposure, and (2) the interaction between cigarette smoking and high-level noise exposure may be additive. There is a need to develop and analyze a larger database of workers with well-documented exposures and smoking histories for better understanding of the effect of smoking on NIHL incurred from high-level industrial noise exposures. A better understanding of the role of smoking may lead to its incorporation into hearing risk assessment for noise exposure.

Hearing Conservation Program: A Review of Best Practices for the United States Air Force

In this article, authors review the recent literature in hearing conservation best practices to contribute to the Air Force Hearing Conservation Program (HCP) quality improvement measures. The cited research addresses HCP successes and deficits, revealing a need for increased health behavior theory-based training for workers, improved hearing protection device (HPD) usage, and more documentation of program evaluation. Worker training, based on health behavior theory, has the potential to increase HPD use, a critical component in HCP. HPDs should be fit-tested, monitored, and adjusted to meet workers' needs and should allow for communication without overprotection. Evaluation and consistent record-keeping of the HCP and audiological measures are critical to provide feedback for managers to make adjustments as necessary. In the military environment, it is pertinent to evaluate the program using the Department of Defense’s Defense Occupational Environmental Health Readiness System, Hearing Conservation and Data Repository (DOEHRS-HC/DR) and adapt the HPD inventory to the unique needs of military personnel. Though best practice guidelines for program management have not been proven, the research continues to evolve; only long-term studies will determine the true effectiveness of preventing noise-induced hearing loss in workers.

Self-Assessment of Hearing Status and Risk of Noise-Induced Hearing Loss in Workers in a Rolling Stock Plant

Noise measurements and questionnaire inquiries were carried out for 124 workers of a rolling stock plant to develop a hearing conservation program. On the basis of that data, the risk of noise-induced hearing loss (NIHL) was evaluated. Additionally, the workers’ hearing ability was assessed with the (modified) Amsterdam inventory for auditory disability and handicap, (m)AIADH. The workers had been exposed to noise at A-weighted daily noise exposure levels of 74-110 dB for 1-40 years. Almost one third of the workers complained of hearing impairment and the (m)AIADH results showed some hearing difficulties in over half of them. The estimated risk of hearing loss over 25 dB in the frequency range of 3–6 kHz was 41–50% when the standard method of predicting NIHL specified in Standard No. ISO 1999:1990 was used. This risk increased to 50–67% when noise impulsiveness, coexposure to organic solvents, elevated blood pressure and smoking were included in calculations.

Occupational Hearing Loss in Korea

In this article, current status of noise exposure in workplaces, trend of workers with noise-induced hearing loss (NIHL), and prevalence of NIHL in workers by industry and job category in Korea were reviewed. In addition, trends of research on the audiological effects such as hearing loss from noise and occupational hearing loss from non-noise in Korea were addressed through reports in industrial audiology. Though noise exposure level has improved, noise still shows the highest rate of cases exceeding exposure limit among workplace hazards. NIHL is the most common occupational disease except work-related disease such as musculoskeletal disorders and cerebrovascular diseases, and NIHL prevalence is thought to be much higher than reported in official publications. Noise affecting hearing comes from various sources such as workplaces, military settings, areas with exposure to high noise, and specific noise sources. There is also occupational hearing loss by non-noise including chemicals such as organic solvents and heavy metals, barotrauma, and trauma due to welding spark. Noise affects daily life through audiological effects such as hearing loss and tinnitus, non-audiological physical effects (e.g., cardiovascular), and psychosocial and behavioral effects. Development of systematic and comprehensive hearing conservation programs for lowering the noise level in workplaces and preventing the NIHL, and preparation of technological, administrative system for its settlement at workplace are urgently needed.

Reliability and validity of industrial audiometry: implications for hearing conservation program design.

Hearing conservation in industry relies heavily on monitoring audiometry to detect early noise-induced hearing loss in workers who are exposed to potentially damaging noise, with or without hearing protectors. The "real-world" reliability and validity of these measurements, as well as otoscopic observations in industry, have not been extensively investigated. In addition, there is considerable controversy over the selection of a definition of "significant threshold shift" in industrial audiometry. These and related issues were considered in a series of three studies utilizing data from an active hearing conservation program. Test-retest variability in industry is much higher than has been reported for clinical settings; this variability is reduced by pure-tone averaging. Workers referred for otologic evaluation were found to have hearing levels which were, on the average, about 5 dB better than indicated by plant audiometry, even without excluding 4% of referred workers who had unilateral deafness and showed "shadow curves" on the plant audiograms. Otoscopic data obtained by the plant audiometrists were uncorrelated with the results of otoscopy by consultant otologists. Techniques borrowed from decision theory and signal detection theory were used to evaluate possible criteria for significant threshold shift. Criteria based on pure-tone averaging were superior to those based on a certain amount of threshold shift for any frequency tested. It is proposed that a significant threshold shift be defined as a 10 dB or greater change for the worse for either the 0.5, 1, 2 kHz pure-tone average or the 3, 4, 6 kHz pure-tone average, in either ear, and that such shifts be validated by prompt retesting. Even with this criterion, a substantial number of shifts (most shifts, in some situations) will be either spurious or attributable to disorders other than noise-induced hearing loss, such as presbycusis. Otologic referral in cases of large or repeated shifts may prevent unjustified administrative actions, to the advantage of both workers and management. A practical consequence of the use of monitoring audiometry may be a de facto lowering of the permissible exposure level to 85 dBA TWA.