Effects of coexposure to noise and mixture of organic solvents on hearing in dockyard workers

Questionnaire and audiometric data of 701 dockyard workers (517 noise and organic solvent mixture-exposed and 184 noise-only-exposed) were referred to 205 control subjects not exposed to either noise or solvents. The odds ratio (OR) of hearing loss was significantly increased by approximately 3 times in the noise-only group and by almost 5 times in the noise and solvent group. A moderate effect of solvent ototoxicity, in addition to noise, was observed on hearing threshold at a frequency 8 kHz. ORs for hearing loss were 1.12 for each increment of 1 year of age, 1.07 for every decibel of lifetime noise exposure (dB-A), and 1.004 for each increment of the index of lifetime exposure to solvents. The results suggest an additive damaging effect of coexposure to noise and organic solvents to the auditory organ.     

Ototoxic effects of occupational exposure to styrene and co-exposure to styrene and noise

Ototoxicity of styrene and the synergistic action of styrene and noise have been shown in rats. The respective data in humans are scarce and equivocal. This study evaluated the effects of occupational exposure to styrene and combined exposures to styrene and noise on hearing. The study group, comprised of 290-yacht yard and plastic factory workers, was exposed to a mixture of organic solvents, having styrene as its main compound. The reference group, totaling 223 subjects, included (1) white-collar workers, exposed neither to solvents nor noise and (2) metal factory workers, exposed exclusively to noise. All subjects were assessed by means of a detailed questionnaire and underwent otorhinolaryngological and audiometric examinations. Multiple logistic regression analysis revealed almost a 4-fold (or 3.9; 95% CI = 2.4-6.2) increase in the odds of developing hearing loss related to styrene exposure. The factors adjusted for were: age, gender, current occupational exposure to noise, and exposure to noise in the past. In cases of the combined exposures to styrene and noise, the odds ratios were two to three times higher than the respective values for styrene-only and noise-only exposed subjects. The mean hearing thresholds--adjusted for age, gender, and exposure to noise--were significantly higher in the solvent-exposed group than in the unexposed reference group at all frequencies tested. A positive linear relationship existed between an averaged working life exposure to styrene concentration and a hearing threshold at the frequencies of 6 and 8 kHz. This study provides the epidemiological evidence that occupational exposure to styrene is related to an increased risk of hearing loss. Combined exposures to noise and styrene seem to be more ototoxic than exposure to noise alone.     

Effect of combined occupational exposure to noise and organic solvents on hearing

Noise exposure has been commonly regarded as the main hazard of occupational hearing loss. Recent studies indicate that several chemicals, including organic solvents have ototoxic effects. This study aimed at evaluating the hearing of workers exposed to both noise and a mixture of organic solvents at concentrations anticipated as safe. The study comprised three groups. The first one included 70 workers exposed to noise only, the second group consisted of 93 workers exposed to organic solvents and noise, and the control group included 59 individuals exposed to neither noise nor organic solvents. The three groups were matched for age, socioeconomic status, and smoking habit. The results of this study revealed that there was no statistically significant difference between the two exposed groups as regards the duration of exposure. There was a highly statistically significant difference between the two exposed groups as regards the different types of hearing loss (conductive deafness, sensory neural hearing loss, and mixed type) compared with the control one. Our study reported that sensory neural hearing loss occurred earlier in subjects with combined exposure to noise and solvents at a mean duration of exposure (16.38?±?9.44 years) compared to (24.53?±?9.59 years) the subjects with sole exposure to noise. The difference between the two groups was statistically significant regarding this type of hearing impairment (p < 0.05). There was a positive significant correlation between hearing impairment and duration of exposure in the two exposed groups. As regards the results of the environmental monitoring, both noise exposure levels (dB) and levels of different organic solvents measured (mg/m(3)) in different work departments were less than the levels recommended by Egyptian Environmental Law No. 4 for 1994. It is recommended that in the case of combined exposure, noise and solvent levels should be lowered than the permissible limits recommended for either alone.     

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.     

Evaluation of combined effect of organic solvents and noise by the upper limit of hearing

To clarify the combined effects of organic solvents and noise on hearing, the upper limit of hearing was measured in 48 male workers exposed to organic solvents and/or noise in a factory producing plastic buttons. Measuring the organic solvent concentrations in working environments and breathing zone air, and the noise level in workplaces were also done. The readings suggested that most exposures to organic solvents and/or noise were within the occupational exposure limits. The prevalence rate of the upper limit of hearing below 75th percentile curve was higher in workers exposed to organic solvents and noise than expected (25 percent) and the other groups, whereas it was about 25 percent in the noise and control groups. The results suggest that the probable combined effects of organic solvents and noise on hearing should be considered even when the exposures are within the occupational exposure limits.     

Occupational noise exposure and hearing loss of workers in two plants in eastern Saudi Arabia.

OBJECTIVE: To determine the prevalence of hearing loss associated with occupational noise exposure and other risk factors. DESIGN: A cross-sectional study involving 269 exposed and 99 non-exposed subjects (non-industrial noise exposed subjects) randomly selected. Current noise exposure was estimated using both sound level meter and noise-dosimeter. Past noise exposure was estimated by interview questionnaire. Otoscopic examination and conventional frequency (0.25-8 kHz) audiometry were used to assess the hearing loss in each subject. RESULTS: 75% (202 subjects) from the exposed group were exposed to a daily Leq above the permissible level of 85 dB(A) and most (61%) of these did not and had never used any form of hearing protection. Hearing loss was found to be bilateral and symmetrical in both groups. Bivariate analysis showed a significant hearing loss in the exposed vs non-exposed subjects with a characteristic dip at 4 kHz. Thirty eight percent of exposed subjects had hearing impairment, which was an 8-fold higher rate than that found for non-exposed subjects. Multivariate analysis indicated exposure to noise was the primary, and age the secondary predictor of hearing loss. Odds of hearing impairment were lower for a small sub-group of exposed workers using hearing protection (N=19) in which logistic regression analysis showed the probability of workers adopting hearing protective devices increased with noise exposure, education, and awareness of noise control. Hearing loss was also greater amongst those who used headphones to listen to recorded cassettes. CONCLUSION: Gross occupational exposure to noise has been demonstrated to cause hearing loss and the authors believe that occupational hearing loss in Saudi Arabia is a widespread problem. Strategies of noise assessment and control are introduced which may help improve the work environment.     

甲苯与职业性噪声接触对听力损失的联合作用

目的 探讨甲苯与噪声联合接触对听力损失的影响。 方法 选择珠海市两家企业中同时接触甲苯和噪声人员78例为混合接触组,单纯接触噪声人员75例为噪声接触组,不接触职业病危害因素的办公室和后勤人员90例为对照组,进行现场甲苯浓度和噪声强度检测,对三组研究对象进行纯音测听检查,并对结果进行统计学分析。 结果 接触组各作业点甲苯浓度、噪声强度均超过国家职业接触限值。混合接触组与噪声接触组在高频段(3.0 kHz、4.0 kHz、6.0 kHz)听阈值差异有统计学意义(P均<0.05)。混合接触组与对照组比较,各频段听力差异均有统计学意义(P均<0.05)。混合接触组、噪声接触组的语频听力异常检出率(25.6%、22.7%)均高于对照组(2.2%),差异均有统计学意义(P<0.05/3);混合接触组的高频听力异常检出率(51.3%)均大于噪声组(24.0%)和对照组(7.8%),差异有统计学意义(P<0.05/3)。工龄≥ 5年者,混合接触组与噪声接触组听力损害发生率差异有统计学意义(P<0.05)。 结论 甲苯与噪声联合接触对听力损害有协同作用,应充分考虑联合接触因素的职业安全防护。     

噪声作业工人的畸变产物耳声发射观察

目的观察畸变产物耳声发射（DPOAE）在早期发现噪声性听力损失方面的应用价值。方法对54例非噪声作业工人（对照组）和96例纯音听阈正常的噪声作业工人（噪声组）进行纯音测听和DPOAE测试，比较两组的纯音听阈、DPOAE幅值和引出率。结果①噪声组和对照组各频率纯音听闻比较，差异无显著性（P〉0．05）；②噪声组的DPOAE幅值在3kHz、4kHz、6kHz处明显下降，与对照组比较有统计学意义（P〈0．01）；③噪声组在3kHz、4kHz和6kHz三个频率处的DPOAE引出率明显降低，与对照组比较，差异有显著性（P〈0．05，P〈0．01）：结论DPOAE能早期发现噪声性听力损失。     

Combined effects of noise and mixed solvents exposure on the hearing function among workers in the aviation industry

This study aims to evaluate the effect of occupational exposure to noise and organic solvents on hearing loss in the aviation industry. The study population comprised 542 male workers, who worked in avionics jobs in Kimhae, Korea, who kept records of work environment evaluations and medical examinations. The Cumulative Exposure Index (CEI) was constructed to assess the lifetime cumulative exposure of the workers, and pure tone audiometry (PTA) data of the workers from their biannual medical surveillance was used to assess hearing loss. The prevalence of hearing loss found in the group exposed to noise and mixed solvents simultaneously (54.9%) was higher than those in the other groups (6.0% in the unexposed, 17.1% in the noise-only, and 27.8 % in the exposed to only a solvents mixture). The relative risks, adjusted for age, were estimated to be 4.3 (95 % CI 1.7-10.8) for the noise-only group, 8.1 (95% CI 2.0-32.5) for the noise and solvents group, and 2.6 (95 % CI 0.6-10.3) for the solvents-mixture group. These suggest that chronic exposure to mixed solvents had a toxic effect on the auditory system. This raises the issue of whether hearing conservation regulations should be applied to all workers exposed to solvents.     

南京市噪声作业人员听力损失情况及其影响因素分析

目的 分析南京市噪声岗位作业人员职业健康体检的纯音听力测试(pure tone audiometry,PTA)结果,以期对职业性噪声聋的防治提供科学依据。方法 以2020年1月1日至10月31日在南京市职业病防治院进行职业健康体检并进行PTA的6 614名噪声作业人员为研究对象,询问一般情况、职业史和病史,进行体格检查、PTA、实验室检查等。双耳各频阈值比较采用t检验,双耳各频异常检出率比较采用χ²检验,采用二元Logistic回归分析噪声性听力损失(noise-induced hearing loss,NIHL)的危险因素。结果 6 614名噪声作业人员中,听阈测试异常1 779例,占26.90%。NIHL有678例,占10.25%。不同性别、合并有害因素、吸烟、饮酒的噪声作业人员NIHL检出率差异均有统计学意义(均P<0.01),NIHL检出率随着年龄、接噪工龄增加而增加(均P<0.01),而血压正常组和血压异常组检出率差异无统计学意义(P>0.05)。二元Logistic回归分析结果显示,男性(OR=2.305)、年龄≥31岁(OR=2.1...     

Mixed solvent exposure and hearing impairment: an epidemiological study of 3284 men. The Copenhagen male study

Animal experiments and human studies have indicated an effecton auditory functions from exposure to organic solvents. Inthis study the relationship between self-assessed hearing problemsand occupational exposure to solvents was investigated in across-sectional design with 3284 participating men aged 53–74years. Exposure to solvents for five years or more resultedin an adjusted relative risk (RR) for hearing impairment of1.4 (95 per cent Cl: 1.1–1.9) in men without occupationalexposure to noise. Factors adjusted for were age, noise traumas,chronic middle ear infection and family history of hearing impairment.The prevalence of hearing impairment in men not exposed to organicsolvents was 24 per cent and the attributable risk from solventexposure was 9.6 per cent. Exposure for less than five yearshad no effect on hearing capacity. Occupational exposure tonoise for five years or more had an effect twice that of solvents,RR: 1.9 (95 per cent Cl: 1.7–2.1). In men exposed to bothsolvents and noise the effect of the latter dominated and noadditional effect from solvents was found. A subsample of 51men was examined with pure tone audiometry and 20 of 21 menwho reported abnormal hearing also fulfilled an audiometriccriterion for hearing impairment. In conclusion a damaging effecton hearing ability from long-term solvent exposure was foundin the present study. The relative effect was moderate but witha high background frequency of hearing problems in the unexposedsample the absolute effect, ie attributable risk, was considerableand of both clinical and preventive importance.     

Occupational exposure to insecticides and their effects on the auditory system

The objective of this investigation was to study the effects of occupational exposure to organophosphates and pyrethroid insecticides on the central auditory system. The study group consisted of 98 workers exposed to insecticides and 54 non-exposed workers. Data on work history, medical history, present diseases, occupational and non-occupational exposure to noise or chemicals and lifestyle factors were obtained through an interview. Central auditory system functions were assessed through frequency patterns and duration patterns testing. Fifty-six percent of the exposed workers had hearing dysfunction at the central level and its relative risk was 7.58 for the group with exposure to insecticides (95% CI 2.9- 19.8) when compared to the non-exposed group. The group exposed to insecticides and noise had a relative risk for central disorders of 6.5 (95% CI 2.2-20.0) when compared to the non-exposed group and 9.8 (95% CI 1.4-64.5) when compared to the group exposed only to noise. The finding suggests that exposure to organophosphates and pyrethroid products can induce damage to central auditory system. Further research is needed on the ototoxic mechanisms of these chemicals, and on hearing loss prevention measurements that are applicable and adequate to such risks and populations.     

Hearing health of workers exposed to noise and insecticides

OBJECTIVE: To examine the peripheral auditory disorders in a group of workers exposed to organophosphate and pyrethroid insecticides, used in vector control campaigns. METHODS: The prevalence study examined a population of 98 individuals who sprayed insecticides in campaigns for the prevention of Dengue, Chagas disease and Yellow fever. The sampling approach was finalistic, and included the workers in a health district of Pernambuco, during the year 2000. A questionnaire was used to collect data on occupational and non-occupational risks, safety measures utilized, family history of auditory problems and health symptoms. Previous noise exposure history was also investigated, since noise can be a confounding factor for hearing loss. Hearing sensitivity and middle ear function were assessed by pure tone audiometry. RESULTS: Among those exposed to insecticides, 63.8% demonstrated a hearing loss. For the group of workers exposed to both noise and insecticides, hearing loss was observed in 66.7% of the cases. The median exposure time necessary to detect high-frequency losses was 3.4 years for workers exposed to both agents and 7.3 years for workers exposed to insecticides only. Hearing thresholds were poorest among workers exposed to both agents. Auditory damage for those with combined exposures to the two factors was more severe than the hearing losses observed among those exposed only to insecticides. CONCLUSIONS: There is evidence that exposure to insecticides was associated with peripheral sensorioneural hearing loss and that noise exposure can potentiate the ototoxic effects of insecticides. It is necessary to evaluate this possible association through epidemiological studies.     

A weight of evidence approach for the assessment of the ototoxic potential of industrial chemicals

There is accumulating epidemiological evidence that exposure to some solvents, metals, asphyxiants and other substances in humans is associated with an increased risk of acquiring hearing loss. Furthermore, simultaneous and successive exposure to certain chemicals along with noise can increase the susceptibility to noise-induced hearing loss. There are no regulations that require hearing monitoring of workers who are employed at locations in which occupational exposure to potentially ototoxic chemicals occurs in the absence of noise exposure. This project was undertaken to develop a toxicological database allowing the identification of possible ototoxic substances present in the work environment alone or in combination with noise exposure. Critical toxicological data were compiled for chemical substances included in the Quebec occupational health regulation. The data were evaluated only for noise exposure levels that can be encountered in the workplace and for realistic exposure concentrations up to the short-term exposure limit or ceiling value (CV) or 5 times the 8-h time-weighted average occupational exposure limit (TWA OEL) for human data and up to 100 times the 8-h TWA OEL or CV for animal studies. In total, 224 studies (in 150 articles of which 44 evaluated the combined exposure to noise and a chemical) covering 29 substances were evaluated using a weight of evidence approach. For the majority of cases where potential ototoxicity was previously proposed, there is a paucity of toxicological data in the primary literature. Human and animal studies indicate that lead, styrene, toluene and trichloroethylene are ototoxic and ethyl benzene, n-hexane and p-xylene are possibly ototoxic at concentrations that are relevant to the occupational setting. Carbon monoxide appears to exacerbate noise-induced hearing dysfunction. Toluene interacts with noise to induce more severe hearing losses than the noise alone.     

噪声作业场所环境危险因素对噪声性听力损失的影响

目的 探讨噪声作业场所除噪声外其他环境危险因素对个体听力损失的影响,从环境因素出发寻找噪声性听力损失(NIHL)的高危易感人群.方法 采用病例对照研究方法,选择南方某市某大型空调生产企业连续性噪声暴露强度在75～120 dB范围内2400名作业工人为研究对象,比较同一噪声暴露组内噪声作业人员的左耳3000 Hz频段听阈位移情况,筛选出听阈位移最大的10%个体作为本研究的易感人群组,共202例;听阈位移最小的10%个体作为耐受人群组,共204例.并对两组人群进行作业场所职业卫生调查和问卷调查,通过单因素和多因素分析环境因素对噪声性听力损失的影响.结果 单因素logistic回归分析发现,噪声作业人员中吸烟、饮酒、工作接触有机溶剂、接触重金属、接触高温、接触粉尘人群是NIHL的高危易感人群.进一步的多因素分析发现,仅工作过程中接触高温是NIHL的高危因素,噪声暴露中同时接触高温的NIHL危险度是单纯噪声暴露的1.804倍(95%CI:1.101～2.958).结论 噪声作业同时有高温暴露的人群是NIHL的高危易感人群.     

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.     

Noise and solvent,alcohol and solvent: two dangerous interactions on auditory function

While noise exposure is the most significant contributor to occupational hearing loss, recent evidence points to solvents and their interactions as additional contributors to occupational deafness. Furthermore, due to the metabolic competitive inhibition between aromatic solvents and ethanol, the solvent toxicity can be even enhanced in certain circumstances. So, two dangerous interactions: noise and solvents, solvents and ethanol deserve to be taken into consideration in an exhaustive preventive policy. Based on the investigations reviewed in the present study, it appears that the combined effects of an exposure to noise and solvent exceed the summation of the damage produced by each agent alone. Such a statement can be also made for a combined exposure to solvent and ethanol. It is therefore important to bear in mind that noise effects can be exacerbated by non-acoustic agents. Thus, if our noise regulations have to be more effective, it is necessary to take into consideration the ototoxic effects of noise in a multifactorial environment.     

Shooting, sensorineural hearing loss, and workers' compensation

Pure-tone audiograms of 29,953 workers with histories of shooting and occupational noise exposure were analyzed. The analysis was based on the asymmetry of hearing loss. Results of this study show that shooting is related to asymmetrical hearing loss, suggesting that shooting may cause an additional amount of hearing loss other than that due to occupational noise exposure. Asymmetry was found to increase as the length of shooting history increased and was significant only at 2 kHz and above and most prominent at 4 kHz. Results also indicated that as long as compensable frequencies remain below 3 kHz the shooting effect is not likely to influence compensation for workers with histories of less than ten years of shooting.     

低浓度铬接触与噪声共同作用对听力影响

目的 探讨低浓度铬及其无机化合物与噪声共同作用对听力损失的影响。 方法 以某汽车制造企业中同时接触低浓度铬与噪声的419名男性员工为接触组,以接触噪声但不接触铬的766名男性员工为对照组,检测工作场所职业病危害因素,结合职业健康检查结果进行分析。 结果 接触组高频听力损失的检出率为10.73%,对照组为4.31%,两组比较,差异有统计学意义(χ2=18.221,P<0.05),接触组听力损失发生的相对危险度是对照组2.49倍。 结论 同时接触低浓度铬和噪声可使听力损失发生的风险增高。