Prevalence of permanent hearing threshold shift among workers of Indian iron and steel small and medium enterprises: a study

Occupational noise exposure and noise-induced hearing loss (NIHL) have been recognized as a problem among workers in Indian industries. The major industries in India are based on manufacturing. There are appreciable numbers of casting and forging units spread across the country. The objective of this study is to determine the prevalence of permanent hearing threshold shift among the workers engaged in Indian iron and steel small and medium enterprises (SMEs) and compared with control group subjects. As a part of hearing protection intervention, audiometric tests were conducted at low (250-1000 Hz), medium (1500-3000 Hz), and high (4000-8000 Hz) frequencies. The occurrence of hearing loss was determined based on hearing threshold levels with a low fence of 25 dB. Comparisons were made for hearing threshold at different frequencies between the exposed and control groups using Student's t test. ANOVA was used for the comparison of hearing threshold dB at different frequencies among occupation and year of experience. A P value <0.05 was considered as statistically significant. All data were presented as mean value (SD). Over 90% of workers engaged in various processes of casting and forging industry showed hearing loss in the noise-sensitive medium and higher frequencies. Occupation was significantly associated with NIHL, and hearing loss was particularly high among the workers of forging section. The analyses revealed a higher prevalence of significant hearing loss among the forging workers compared to the workers associated with other activities. The study shows alarming signals of NIHL, especially in forging workers. The occupational exposure to noise could be minimized by efficient control measures through engineering controls, administrative controls, and the use of personal protective devices. Applications of engineering and/or administrative controls are frequently not feasible in the developing countries for technical and financial reasons. A complete hearing conservation programme, including training, audiometry, job rotation, and the use of hearing protection devices, is the most feasible method for the protection of industrial workers from prevailing noise in workplace environments in the developing countries.     

Noise exposure and hearing loss among sand and gravel miners

The objectives of this study were to describe workplace noise exposures, risk factors for hearing loss, and hearing levels among sand and gravel miners, and to determine whether full shift noise exposures resulted in changes in hearing thresholds from baseline values. Sand and gravel miners (n = 317) were interviewed regarding medical history, leisure-time and occupational noise exposure, other occupational exposures, and use of hearing protection. Audiometric tests were performed both before the work shift (following a 12-hour noise-free interval) and immediately following the work shift. Full shift noise dosimetry was conducted. Miners' noise exposures exceeded the Recommended Exposure Limit (REL) of the National Institute for Occupational Safety and Health (NIOSH) for 69% of workers, and exceeded the Mine Safety and Health Administration's action level for enrollment in a hearing conservation program for 41% of workers. Significantly higher noise exposures occurred among employees of small companies, among workers with a job classification of truck driver, among males, and among black workers. Hearing protection usage was low, with 48% of subjects reporting that they never used hearing protection. Hearing impairment, as defined by NIOSH, was present among 37% of 275 subjects with valid audiograms. Black male workers and white male workers had higher hearing thresholds than males from a comparison North Carolina population unexposed to industrial noise. Small but statistically significant changes in hearing thresholds occurred following full shift noise exposure among subjects who had good hearing sensitivity at baseline. In a logistic regression model, age and history of a past noisy job were significant predictors of hearing impairment. Overall, sand and gravel workers have excessive noise exposures and significant hearing loss, and demonstrate inadequate use of hearing protection. Well-designed hearing conservation programs, with reduction of noise exposure, are clearly needed.     

听力保护计划在金属制品行业的实施和效果评估

目的 评估听力保护计划在金属制品行业的实施效果。
方法 选取28家金属制品企业推行听力保护计划, 内容包括噪声监测、听力测试、噪声控制、护听器使用和职工培训等五方面。
结果 听力保护计划实施2年后, 企业在噪声工程防护、工人护听器使用和工人培训教育方面均较计划实施前有改善, 作业场所噪声监测合格率有逐年上升趋势(P < 0.05)。实施听力保护计划2年后, 新上岗工人暂未出现高频标准听阈位移(HSTS), 已在岗接噪作业工人发生HSTS的共有6人, 占在岗工人总数2.27%。
结论 听力保护计划是一项综合的噪声防治策略, 能有效地防止职业性噪声聋的发生, 而管理者的重视和措施的落实是计划有效实施的保证。
     

Hearing impairment among workers exposed to excessive levels of noise in ginning industries

Cotton ginning workers have a risk of hearing loss due to excessive noise levels at the workplace environment. In this study, estimates of typical sound levels prevailing at the workplace environment and its effects on hearing ability of the exposed workers were made among cotton ginning workers. Data on self-reported health status was collected by a questionnaire survey at 10 cotton ginning industries located at Jalgaon district of Maharashtra state, India. The cotton ginning workers were exposed to continuous noise levels between 89 and 106 dBA. The hearing ability of the subjects was accessed by pure tone audiometry. The results of audiometry show mild, moderate and moderately severe degree of hearing impairment among the cotton ginning workers. The data generated during the study show that hearing loss was significantly associated with period of exposure to the workplace noise (P <0.0001). The prevalence of audiometric hearing impairment defined as a threshold average greater than 25 dB hearing level was 96% for binaural low-frequency average, 97% for binaural mid frequency average and 94% for binaural high-frequency average in the cotton ginning workers. We recommend the compulsory use of personal protective equipment like ear plug by the cotton ginning workers at the workplace environment. A regular maintenance of ginning and pressing machineries will avoid the emission of excessive noise at the workplace environment of cotton gins. A regular periodic medical examination is necessary to measure the impact of workplace noise on the health of cotton ginning workers.     

听力损伤的累积噪声暴露阈值研究

目的根据不同累积噪声暴露量与工人语频听力损伤发生率间的关系,探讨和评价引起职业性听力损失的临界累积噪声暴露阈值.方法应用Logistic回归模型分析1 435名不同累积噪声暴露强度的听阈数据.结果语频损伤和高频损失发生率随暴露水平而增高;累积噪声暴露量与语频损伤发生率的Logistic回归分析显示,听阈水平随累积噪声暴露量增高而上升并有明显相关性;预测模型显示语频损伤的临界累积噪声暴露阈值为100dB(A).结论听力损伤的临界累积噪声暴露阈值100dB(A)与我国现执行的噪声卫生标准具有一致性,可探讨作为对个体职业噪声暴露危害程度警告的阈值指标.     

The accuracy of self-reported high noise exposure level and hearing loss in a working population in Eastern Saudi Arabia

Objective: To determine the accuracy of questions in identifying subjects occupationally exposed to high noise level and those with hearing loss using noise dosimeter and pure-tone air conduction audiometry as the gold standards.Design: A cross-sectional study involving 259 noise-exposed workers selected randomly from two factories in Eastern Saudi Arabia. Personal noise exposure was determined using a noise dosimeter. The hearing impairment for each subject was assessed using otoscopic examination and audiometry. Each subject completed a comprehensive questionnaire including questions about noise exposure and hearing loss.Results: Eighty five percent of the total workers reported exposure to high noise level, compared to 76% found to be exposed to a high noise level defined as more than 85dB (A) as determined by noise dosimeter. The prevalence of audiometric hearing loss (threshold average of 25dB HL or more in any ear) was 32.4% for the low frequency average (0.5, 1 and 2kHz), 47.9% for the all frequency average (0.5, 1, 2. 4 and 8kHz) and 65.6% for the high frequency average (4 and 8kHz). However, the percentage of the subjects who reported hearing loss ranged between 3.9% and 85.3% depending on the question used as indicator of hearing loss.The question “Do you consider the noise level where you are working now high?” was the most sensitive in correctly identifying subjects exposed to a noise level of more than 85dB (A) (sensitivity=93.4%) and subjects with hearing loss (sensitivity>86%) compared with other questions evaluated. However, it overestimated the prevalence rate determined by audiometryConclusion: We conclude that in industries where facilities for an objective assessment of noise exposure and hearing loss are not available, questions addressing noise exposure and hearing loss might be a useful alternative means for screening subjects exposed to high noise level and those with hearing loss for the purpose of designing and implementing hearing conservation program.     

Audiometric findings in petrochemical workers exposed to noise and chemical agents

This study investigated the occurrence of hearing loss among workers of a petrochemical industry during a period of five years. The records of environmental noise and solvents measurements and the results of annual audiometry performed by the company were examined. The audiometric results of workers from olefin operational areas 1 and 2 and aromatic plant areas exposed to solvents and noise and utility area workers exposed only to noise were analyzed for the standard threshold shift (STS). Despite the low exposures to solvents and a moderate exposure to noise, 45.3% of workers had hearing losses and 29.6% had STS.     

Hearing loss in workers exposed to toluene and noise

In this study we investigated the risk of hearing loss among workers exposed to both toluene and noise. We recruited 58 workers at an adhesive materials manufacturing plant who were exposured to both toluene and noise [78.6-87.1 A-weighted decibels; dB(A)], 58 workers exposed to noise only [83.5-90.1 dB(A)], and 58 administrative clerks [67.9-72.6 dB(A)] at the same company. We interviewed participants to obtain sociodemographic and employment information and performed physical examinations, including pure-tone audiometry tests between 0.5 and 6 kHz. A contracted laboratory certified by the Council of Labor in Taiwan conducted on-site toluene and noise exposure measurements. The prevalence of hearing loss of >or=25 dB in the toluene plus noise group (86.2%) was much greater than that in the noise-only group (44.8%) and the administrative clerks (5.0%) (p<0.001). The prevalence rates were 67.2, 32.8, and 8.3% (p<0.001), respectively, when 0.5 kHz was excluded from the estimation. Multivariate logistic regression analysis showed that the toluene plus noise group had an estimated risk for hearing loss>or=25 dB, 10.9 times higher than that of the noise-only group. The risk ratio dropped to 5.8 when 0.5 kHz was excluded from the risk estimation. Hearing impairment was greater for the pure-tone frequency of 1 kHz than for that of 2 kHz. However, the mean hearing threshold was the poorest for 6 kHz, and the least effect was observed for 2 kHz. Our results suggest that toluene exacerbates hearing loss in a noisy environment, with the main impact on the lower frequencies.     

杭州某电器厂工人职业性听力损害调查研究及相关因素分析

目的调查研究噪声对杭州地区某电器厂工人听力的影响,并探讨其影响因素。方法采用精密脉冲声级计测定电器厂噪声作业环境的噪声强度,采用听力计检测噪声作业工人的听力状况,测定听力损害罹患率,将听力损害与接噪工龄、工种、性别、年龄进行统计学分析。结果该电器厂噪声性质为中高频连续稳态噪声,平均噪声强度92.34±8.62 dB（A）,工人职业性听力损害的罹患率为19.97%,听力损害随接噪工龄增加而升高,各工龄组间比较差异有显著性（P〈0.05）;不同工种听力损害的检出率由高到低依次为磨工、铆工、冲压、折弯工、总装、剪板、焊接。结论生产性噪声对作业工人的听力损害有显著影响。     

2020年中国工业企业接触噪声劳动者听力损失流行病学特征分析

目的 了解中国工业企业接触噪声劳动者听力损失的流行病学特征,为制定预防控制策略提供科学依据。方法 从“职业病与健康危害因素监测”信息系统中提取2020年采矿业、制造业和电力、热力、燃气及水生产和供应业三大门类行业噪声作业劳动者的职业健康档案,从行业、地区、性别、年龄、工龄和企业规模等维度对听力障碍和双耳高频平均听阈损失两个听力损失指标进行分析。结果 本研究共收集噪声作业劳动者职业健康检查个案303.45万人,听力障碍检出人数为81.57万人,检出率为26.88%,高频听力损失检出人数为26.55万人,检出率为8.75%。采矿业企业中劳动者的听力障碍和高频听损检出率分别为29.96%和10.11%,均高于其他行业工业企业。听力障碍检出率较高地区为西南、中南和华东地区,分别为30.21%、29.99%和29.90%;高频听损检出率较高地区为中南和西南地区,分别为11.12%和9.78%。男性听力障碍和高频听损检出率均高于女性,分别为28.60%和9.98%,且听力障碍和高频听损检出率均呈现随年龄和工龄增长而递增的趋势。小微型企业听力障碍和高频听损检出率分别为37.56%和12.36%,均高...     

Hearing loss among workers at an oil refinery in Taiwan

In this study, the authors determined the characteristics of noise-induced hearing loss (NIHL) and its association with hearing-loss-related symptoms (HLRSs) among workers at an oil refinery in Taiwan. Workers from the refinery (N = 384) who had chronic noise exposure (range = 73 to 89 dBa; mean = 81.2, standard deviation = 5.4 dBa) were enrolled in the study. Workers chronically exposed to noise levels that were less than 85 dBa experienced slight hearing loss at high frequencies [(3k + 4k + 6k)/3]. Workers with > or = 1 HLRSs had increased hearing loss at low frequencies [(0.5k + 1k + 2k)/3] and high frequencies (odds ratios = 7.2 and 3.7, respectively). An increased hearing threshold shift for high frequencies (3k, 4k, and 6k Hz) was found in workers who had chronic noise exposure for more than 15 yr. These findings indicate that self-reported HLRSs provide valuable early warning signs of NIHL.     

Hearing status among aircraft maintenance personnel in a commercial airline company

The aim was to study subjective and objective hearing loss in a population of aircraft maintenance workers and identify predictors. A total of 327 aircraft maintenance personnel answered a self-administered work environment questionnaire (response rate 76%) and underwent audiometric test. The mean values for the hearing threshold at 3, 4, and 6 kHz for the ear with the most hearing loss were compared with a Swedish population database of persons not occupationally exposed to noise. Equivalent noise exposure during a working day was measured. Relationships between subjective and objective hearing loss and possible predictors (age, years of employment, self-reported exposure to solvents, blood pressure, and psycho-social factors) were analyzed by multiple logistic regression. At younger ages (<40 years), aircraft maintenance workers had higher hearing thresholds (1-3 dB) compared to the reference group, but such a difference was not found in older employees. Relationships were found between age and objective hearing loss, and between exposure to solvents and reported subjective hearing loss. Equivalent noise exposure during working days were 70-91 dB(A) with a maximal noise level of 119 dB(A). Aircraft maintenance workers are exposed to equivalent noise levels above the Swedish occupational standard, including some very high peak exposures. Younger employees have a higher age-matched hearing threshold level compared with a reference group. Thus, there is a need for further preventive measures.     

Hearing impairment among mill workers in small scale enterprises in southwest Nigeria

This cross-sectional study was conducted among mill workers in a large market in Ibadan, southwest Nigeria. These workers are engaged in small scale businesses with little or no regulation of work exposures. Questionnaires administered to mill workers sought information on personal characteristics, length of time engaged in the job, type of milling done and symptoms of hearing impairment. Noise exposure and hearing impairment were assessed among 85 mill workers. Audiometry was done on mill workers and 45 controls with no known exposure to noise and no history of aural disease. Noise levels at work stations ranged from 88-90dB for small mills and 101-105 for larger mills. None of the workers used hearing protection. Analysis based on total number of ears showed that 56% of the workers had hearing impairment ranging from mild (49%) moderate (6.4%) to severe (0.6%) whilst 33% of the controls had hearing impairment which was mild (26%), moderate (7%) and no severe losses, P = 0.001. There was no association between age and hearing impairment but prevalence of hearing impairment was highest among those who had been engaged in the trade for more than 20 years. There is a need for regulation of small scale enterprises to protect the health of workers. Health education and provision of low cost ear plugs will reduce the occurrence and severity of hearing impairment among these low income workers.     

High-level handwashing compliance in a community teaching hospital: a challenge that can be met!

Handwashing is the most important and least expensive measure for preventing the transmission of hospital-acquired infection. Compliance, however, rarely exceeds 40%, even in intensive care units. The present study evaluated the effectiveness of the authors' infection control programme in relation to handwashing compliance of healthcare workers. Ten nursing students observed 300 uninformed staff members and recorded their handwashing practices throughout the working day. The observations were categorized by profession, gender, age, hospital unit and type of delivered care. In 1035 opportunities that required handwashing, the overall compliance was 76%. Healthcare workers washed hands before (68%) and after patient care (80%). Females complied more than males (69 vs. 80%, P<0.0001) and nurses more than physicians (81 vs. 69%, P<0.001). In intensive care units, overall compliance exceeded 97%, while in other wards and in the emergency departments, it approximated 61%. More handwashing was observed during the evening shift compared with the morning shift (P=0.02). Despite the high compliance, only 30% washed their hands for the required 10-20s. In conclusion, compliance with handwashing in the authors' institution is the highest reported to date, and reflects the intensive and incessant educational infection control programme.     

Prevalence of permanent threshold shifts in the United States Air Force hearing conservation program by career field, 2005–2011

The purpose of this study was to describe changes in hearing, using the permanent threshold shift metric, among United States Air Force servicemembers, including active duty, Reserve and Air National Guard components, for demographics, job categories, and career fields. In the United States Air Force, only servicemembers who are occupationally exposed routinely to hazardous noise are monitored. Audiogram records and demographic variables were analyzed for servicemembers from 2005–2011 using data from the Department of Defense system that captures occupational hearing tests worldwide. Results suggest that occupational hearing loss was larger in males than females, in officers than enlisted populations, and in Reserve and Air National Guard than in active duty. Compared to similar civilian career fields, active duty has lower prevalence rates for occupational hearing loss overall, although Reserve and Air National Guard prevalence rates were more similar to the civilian reported rates. The proportion of personnel with permanent threshold shifts varied between 4.6–16.7% within active duty career fields, which includes 76% of the population for study timeframe. Permanent threshold shift was larger in small job categories, and in jobs that are not considered exposed to hazardous noise routinely which is comparative with results from civilian data analysis of occupational hearing loss. Further investigation into testing practices for Air Force specific groups, use of the system for nonoccupational hearing testing, and challenges to follow-up compliance is warranted. Increased surveillance procedures for occupational hearing loss are needed to address concerns on the prevalence of servicemember hearing loss, the role of recreational and lifestyle factors to contribute the high reported hearing loss prevalence of veterans compared to nonveterans.     

The Nord-Trøndelag Norway Audiometric Survey 1996-98: unscreened thresholds and prevalence of hearing impairment for adults > 20 years

As supplement to a general health screening examination (HUNT-II), we conducted a puretone audiometry study in 1996-98 on adults (>20 years) in 17 of 23 municipalities in Nord-Tr?ndelag, Norway, including questionnaires on occupational and leisure noise exposure, medical history, and symptoms of hearing impairment. The study aims to contribute to updated normative hearing thresholds for age and gender, while evaluating the effects of noise exposure, medical history, and familial or genetic influences on hearing. This paper presents the unscreened hearing threshold data and prevalence of hearing impairment for different age groups and by gender. Valid audiometric data were collected from 62% (n=50,723) of 82,141 unscreened invited subjects (age-range 20-101 years, mean=50.2 years, SD=17.0 years). Two ambulant audiometric teams each conducted 5 parallel self-administered, pure-tone hearing threshold examinations with the standard test frequencies 0.25-0.5-1-2-3-4-6-8 kHz (manual procedure when needed). Tracking audiometers were used in dismountable booths with in-booth noise levels well within ISO criteria, except being at the criterion around 200 Hz. The data were electronically transferred to a personal computer. Test-retest correlations for 99 randomly drawn subjects examined twice were high. The mean thresholds recorded were some dB elevated from "audiometric zero" even for age group 20-24 years. As also found in other studies, this might indicate too restrictive audiometric reference thresholds. Males had slightly better hearing < or =0.5 kHz for all age groups. Mean thresholds were poorer in males > or = 30 years from > or =2 kHz, with maximal gender differences of approximately 20 dB at 3-4 kHz for subjects aged 55-74 years. Weighted prevalence data averaged over 0.5-1-2-4 kHz showed hearing impairment >25 dB hearing threshold level of 18.8% (better ear) and 27.2% (worse ear) for the total population--for males 22.2% and 32.0%, for females 15.9% and 23.0%, respectively. Mean hearing loss > or =10 dB at 6 kHz registered for both genders even in age groups 20-24 years may be partly due to calibration artefacts, but might possibly also reflect noise-related socio-acusis.     

职业性噪声对暴露人群健康效应初步分析

目的分析工业作业场所职业性噪声对暴露人群的健康效应。方法于2005年随机抽取南方某市部分噪声暴露工厂,按《作业场所噪声测量规范》(WS/T69-1996)进行测点选择和测量噪声强度[dB(A)],按照《职业健康监护管理办法》对其职业性噪声暴露人群进行健康检查,并对4家产生稳态噪声、4家产生脉冲噪声的工厂的暴露人群的健康效应进行比较分析。结果共对84家工厂的1374个噪声作业点进行噪声强度测定,噪声平均强度83.40[dB(A)],作业点噪声强度90[dB(A)]以上占23.22%(319/1374),85~89[dB(A)]占25.47%(350/1374),85[dB(A)]以下占51.31%(705/1374),超标率为48.69%(699/1374);7464例噪声暴露工人的健康检查结果显示,听力损伤检出率为20.47%(1528/7464),心电图异常检出率7.32%(546/7464),心率异常检出率为3.93%(293/7464),血压偏高检出率为3.71%(277/7464);稳态噪声和脉冲噪声的平均强度分别为84.96、88.49[dB(A)],两者的等效噪音强度差异无统计学意义(P>0.05);脉冲噪声暴露人群的听力损伤、血压偏高检出率均高于稳态噪声的(P>0.01)。暴露人群的听力损伤检出率与暴露水平存在正相关关系(rs=0.952 4,P<0.01)。结论职业性噪声暴露对人群健康效应的影响表现为脉冲噪声对噪声暴露者的危害比稳态噪声大;噪声强度和噪声暴露者的听力损伤检出率存在剂量反应关系。     

Hearing conservation programs (HCPs): the effectiveness of one company's HCP in a 12-hr work shift environment

An existing hearing conservation program (HCP), originally designed when an 8-hr work shift schedule was in effect, was evaluated at a plant site where a 12-hr work shift schedule is now utilized. The study included the following phases: a noise analysis of the work environment, HCP evaluation through the use of audiometric data base analysis (ADBA), applying ADBA procedures and a comparison of the shift in hearing threshold levels (HTLs) for the 8-hr and 12-hr work shifts, and an evaluation of the hearing protection devices (HPDs) being used at the facility over the 12-hr work shift by measuring temporary threshold shift (TTS). The mean measured employee time-weighted average (TWA) in the process area where the TTS study was conducted was 92 dBA. It was found that the existing HCP is at best marginal. The most likely causes of this less-than-desirable rating are inadequate audiometric testing procedures and inadequate HPD utilization. Furthermore, it was concluded that, at this time, the introduction of the 12-hr work shift has had no impact on the level of effectiveness of the HCP. In evaluating the three HPDs in use at the facility (3-M foam earplug, E-A-R foam earplug, and Bilsom Soft earplug), it was found that they all offered effective protection from noise at all audiometric test frequencies (0.5 to 6 kHz) except 0.5 kHz. All three HPDs exhibited TTS at 0.5 kHz with the TTS measured significant at the p less than 0.05 level for the E-A-R and 3-M wearer groups.     

噪声性听力损失易感性与SOD1单倍型的关联研究

目的探讨噪声性听力损失(noise-induced hearing loss,NIHL)易感性与中国汉族人群铜锌超氧化物歧化酶(SOD1)基因存在的单倍型之间的关联。方法利用病例对照研究,通过比较在同一噪声暴露强度下噪声作业人员的左耳3 000 Hz频段听阈位移情况,筛选出听阈位移最大的10%个体作为易感人群组,共201例;听阈位移最小的10%个体作为耐受人群组,共202例。并进行相关的职业卫生调查和问卷调查。抽取易感人群和耐受人群空腹外周静脉血5 ml用于Qiagcn试剂盒方法抽提基因组DNA,TaqMan探针法化学荧光等位基因鉴别试验检测单核苷酸多态性(SNP),用Haploview软件进行单倍型的计算和2组比较。结果 NIHL易感人群噪声暴露强度中位数和上下四分位数间距为86.90(83.05,92.90),耐受人群噪声暴露强度中位数和上下四分位数间距为86.90(83.73,92.70),2组比较,差异无统计学意义,P>0.05。易感人群3 000 Hz左耳平均听阈位移水平为(40.23±9.53)dB,显著高于耐受人群的听阈位移水平(16.15±2.58)dB,P<0.01;所有SNPs位点基因型频率在2组人群中分布均符合遗传学Hardy-Weinberg平衡,与分布频率最高的单倍型CGGA相比,单倍型TATG是NIHL的保护因素,OR值和95%CI分别为0.56(0.38,0.82);单倍型CATG是NIHL的危险因素,OR值和95%CI为1.58(1.08,2.31)。结论在中国汉族人群中,NIHL易感性与SOD1单倍型有关。     

Hearing loss in workers exposed to carbon disulfide and noise

Simultaneous exposure to carbon disulfide and noise may have a combined effect on hearing impairment. In this study we investigated hearing loss in 131 men with exposure to noise [80-91 A-weighted decibels; dB(A)] and CS(2) (1.6-20.1 ppm) in a viscose rayon plant. These men were compared with 105 men in the adhesive tape and electronic industries who were exposed to noise only and with 110 men employed in the administrative office of the rayon plant who were exposed to low noise and no CS(2). We conducted interviews to obtain sociodemographic information and exposure assessments, and we performed physical examinations, including hearing tests. Results showed that the prevalence of hearing loss of > 25 dB hearing loss (dBHL) in rayon workers (67.9%) was much higher than that in administrative workers (23.6%) and in the adhesive tape and electronic industrial workers (32.4%). Hearing loss occurred mainly for speech frequencies of 0.5, 1, and 2 kHz. When the CS(2) exposure was measured by the product of CS(2 )exposure level and employment years, the adjusted odds ratios of hearing loss of > 25 dBHL in rayon workers, compared with administrative workers, were 3.8 [95% confidence interval (CI), 1.5-9.4] for those with the exposure of 37-214 year-ppm, 14.2 (95% CI, 4.4-45.9) with 215-453 year-ppm exposure, and 70.3 (95% CI, 8.7-569.7) with exposure of > 453 year-ppm. The study suggests that CS(2) exposure enhances human hearing loss in a noisy environment and mainly affects hearing in lower frequencies.