Thais C. Morata

Audiometric findings in workers exposed to low levels of styrene and noise

Learning ObjectivesExplain whether and how exposure of workers to styrene in the course of making fiberglass products, and to high noise levels, interact to produce bilateral high-frequency hearing loss.Recall the personal and environmental factors that were significantly associated with hearing loss in this study.Discuss how these findings relate to past studies in animals and styrene-exposed workers, and take note of relevant public health considerations.Audiometry and exposure measurements were conducted on workers from fiberglass and metal products manufacturing plants and a mail distribution terminal (N = 313). Workers exposed to noise and styrene had significantly worse pure-tone thresholds at 2, 3, 4, and 6 kHz when compared with noise-exposed or nonexposed workers. Age, noise exposure, and urinary mandelic acid (a biologic marker for styrene) were the variables that met the significance level criterion in the multiple logistic regression. The odds ratios for hearing loss were 1.19 for each increment of 1 year of age (95% confidence interval [CI], 1.11–1.28), 1.18 for every decibel >85 dB(A) of noise exposure (95% CI, 1.01–1.34), and 2.44 for each millimole of mandelic acid per gram of creatinine in urine (95% CI, 1.01–5.89). Our findings suggest that exposure to styrene even below recommended values had a toxic effect on the auditory system.

Chemical exposure as a risk factor for hearing loss

Learning ObjectivesDiscuss the interaction of noise and exposure to industrial chemicals in compromising auditory function.Present what is known about possible mechanisms of noise- and chemical-induced ototoxicity.Compare the merits of various test procedures that might help in assessing chemical-induced hearing loss. In 2002, the National Institute for Occupational Safety and Health and the National Hearing Conservation Association cosponsored the “Best Practices Workshop: Combined Effects of Chemicals and Noise on Hearing.” This article summarizes the main results of the Workshop. Its goals were to review the knowledge of chemical ototoxicity and to stimulate participant discussion on how to address this risk. Speakers provided an overview of the effects of chemicals on the auditory system (http://www.cdc.gov/niosh/noise/noiseandchem/noiseandchem.html). Research priorities were discussed in concurrent working group sessions. The Workshop concluded with a panel of the groups’ facilitators reporting on these sessions. The following key issues were identified: rationale and proposal of a list of priority chemicals; valid procedures for exposure (animal studies), exposure assessment, and audiological testing; need for mechanistic research and a Response Level; recommendations for preventive actions; and information dissemination.

Young people: Their noise and music exposures and the risk of hearing loss

In the past two decades, the number of publications on the risk of acquired hearing loss among children and young adults has increased substantially. The introduction of MP3 players and a lawsuit that followed, which alleges that such devices pose a risk to the user’s hearing, caught the general public’s attention through news media coverage. While a decision in the case remains pending, this issue has brought widespread scrutiny to the question of potential risks to young people’s hearing but relates to only one of many ways in which youths may be exposed to loud noise. Sources of excessive sound exposure in children and youths are many, from toys, arcade games, music, and work. Data from Sweden found the presence of the audiometric high frequency notch in groups as young as ten years old (Axelsson et al, 1981; Costa et al, 1998). Sound pressure levels of toys have also been documented, and several countries have adopted sound level labels, to alert consumers of the risk. The global process of urbanization has reduced the number of children working on farms worldwide. However, young people continue to be employed in that industry, as well as in other industries. The proportion of children working, as well as their work conditions and legal protections, varies from country to country. But social and economic changes, the new personal music devices, and the perception of ever increasing intensity levels during concerts and at nightclubs has made music exposure the most studied source of excessive sound exposure to children and youths in several countries. New products and organizations have been created with the goal of reducing hearing risks (hearing loss and tinnitus) due to music exposure. The term music-induced hearing loss is now used for a condition akin to noise-induced hearing loss. Both noiseand music-induced hearing loss are characterized by a notch in the 4000 to 6000 Hz region of the audiogram, are linked to a chronic, extended exposure, and progress at a rate proportionate to exposure conditions. But noise is defined as an unwanted sound, whereas music is often quite the opposite. Numerous publications have reported an elevated prevalence of musicinduced hearing disorders, primarily among musicians. Other studies have examined other professionals exposed to music, attendees of discos or concerts, and users of personal listening devices. Still, not all evidence available confirms increased risk with increasing exposures, and the possibility of a toughening protective effect of such exposures has even been suggested (Fleisher and Muller, 2005). A study of ten thousand people conducted in Germany reported that orchestra musicians, despite their exposure, had the best hearing thresholds among several occupations and non-exposed groups (Fleisher and Muller, 2005). Moreover, in the 18-to-25-year-old group unexposed to occupational noise only a minimal difference (not statistically significant) was seen between people who regularly go to discotheques and those who have never been there. Similar findings were reported for Walkman users (Mostafapour et al, 1998). Rabinowitz et al (2006) examined whether the hearing status of young US adults has worsened over the past 20 years by comparing yearly prevalence of hearing loss in the baseline audiograms of 2526 individuals ages 17 to 25, beginning employment between 1985 and 2004. The prevalence of high frequency hearing loss decreased over the twenty-year period, while the prevalence of audiometric ‘notches’ remained constant. Their results suggest that despite concern about widespread recreational noise exposures, the prevalence of hearing loss among a group of young US adults has not significantly increased over the past two decades. Is it too soon to detect the effects of more recent technology? Possibly yes, since the findings from the study do not demonstrate any systematic, measurable effect on entrance audiograms. On October 19 and 20, 2006 the first ever conference on ‘Noise-Induced Hearing Loss in Children at Work and Play’ took place in Covington, Kentucky, USA. It was partially funded by a grant from the National Institute for Occupational Safety and Health (NIOSH) and jointly sponsored by NIOSH, the National Institute on Deafness and other Communication Disorders, the National Hearing Conservation Association, the Marion Downs Hearing Center, the Oregon Health and Science University, and the University of Northern Colorado. (http:// www.hearingconservation.org/conf_childrenconf.html). The sub-themes of the conference reflected the work being done internationally. They included:

Estudo dos efeitos auditivos e extra-auditivos da exposição ocupacional a ruído e vibração

Aim: The present study aimed to investigate the health complaints and the audiological findings of 2 groups of workers. Study design: Clinical prospective randomized. Material and method: Group 1 was exposed to high sound pressure levels and vibration transmitted by hands and arms through the use of power brush cutter/string trimmers. Group 2 was exposed to high sound pressure levels and whole-body vibration transmitted by heavy machinery such as vibrating compactor rollers, skid-steer loaders, backhoes and compact hydraulic excavators. The 73 participants underwent an interview, otoscopy, and pure-tone audiometry. Regarding general health, group 2 workers, exposed to whole-body vibration presented the highest number of complaints. Results: All the participants from group 1 use hearing protectors and 11% of them complained about tinnitus. Not all workers from group 2 use hearing protectors and 17% of them 2 reported tinnitus. However, group 1 workers, exposed to hand-arm vibration was the group with the highest percentage of abnormal audiograms. Conclusion: This study revealed a series of weaknesses in the health surveillance of these populations and indicated the need for the implementation of preventive programs focusing on their exposures to noise and vibration.

Working in Noise with a Hearing Loss: Perceptions from Workers, Supervisors, and Hearing Conservation Program Managers

Objective: Workers with hearing loss face special problems, especially when working in noise. However, conventional hearing conservation practices do not distinguish between workers with normal hearing versus impaired hearing. This study collected information from workers with self-reported noise exposure and hearing loss, supervisors of such workers, and hearing conservation program managers through focus groups and in-depth interviews to evaluate their perspectives on the impact of hearing loss on safety and job performance, the use of hearing protection, and information needed to appropriately manage hearing-impaired workers who work in noisy environments. Results: Concerns about working in noise with a hearing loss could be grouped into the following 10 categories: impact on job performance, impact on job safety, impaired ability to hear warning signals, impaired ability to monitor equipment, interference with communication, stress and/or fatigue, impaired communication caused by hearing protector use, reduced ability to monitor the environment as the result of hearing protector use, concerns about future quality of life, and concerns about future employability. Mostly, there was an agreement between the perceptions of workers, supervisors, and hearing conservation program managers regarding difficulties associated with hearing loss and consequent needs. These findings suggest that noise-exposed workers with hearing loss face many of the same problems reported in the literature by noise-exposed workers with normal hearing, with additional concerns primarily about job safety as the result of a reduced ability to hear environmental sounds, warning signals, and so forth. Conclusions: The study outlines potential challenges regarding job safety and hearing conservation practices for noise-exposed, hearing-impaired workers. Awareness of these issues is a necessary first step toward providing appropriate protective measures for noise-exposed, hearing-impaired workers.

Hearing Loss from Combined Exposures among Petroleum Refinery Workers

Workers from a refinery (n = 438) were interviewed, had their hearing tested and had their exposures to noise and solvents assessed. Measurements suggested that most exposures to noise and solvents were within exposure limits recommended by international agencies; however, the prevalence for hearing loss within the exposed groups ranged from 42 to 50%, significantly exceeding the 15-30% prevalence observed for unexposed groups. The adjusted odds ratio estimates for hearing loss were 2.4 times greater for groups from aromatics and paraffins (95% CI 1.0-5.7), 3 times greater for the maintenance group (95% CI 1.3-6.9) and 1.8 times greater for the group from shipping (95% CI 0.6-4.9), when compared to unexposed workers from the warehouse and health clinic. The results of acoustic reflex decay tests suggest a retrocochlear or central auditory pathway involvement in the losses observed in certain job categories. These findings indicate that factors in addition to noise ought to be considered when investigating and preventing occupational hearing loss.

Peripheral and central auditory dysfunction induced by occupational exposure to organic solvents

Objective: To examine the effects of solvent exposure on hearing function, through an audiological test battery, in a population not occupationally exposed to high levels of noise. Methods: One hundred ten workers from a coating factory were studied. Jobs at the factory were divided into three different levels of solvent exposure. Hearing status was assessed with a test battery including pure-tone hearing thresholds (0.5–8 kHz), high-frequency hearing thresholds (12 and 16 kHz), and dichotic listening measured through dichotic digits test. Multiple linear regression models were created to explore possible association between solvent exposure and each of the hearing outcomes. Results: Significant associations between solvent exposure and the three hearing outcomes were found. Covariates such as age, gender, race, and ethnicity were also significantly associated with the studied hearing outcomes. Conclusions: Occupational exposure to solvents may induce both peripheral and central auditory dysfunction. The dichotic digits test seems as a sensible tool to detect central auditory dysfunction associated with solvent exposure. Hearing loss prevention programs may use this tool to monitor hearing in solvent-exposed workers.

Audiological findings in workers exposed to styrene alone or in concert with noise.

Audiological testing, interviews and exposure measurements were used to collect data on the health effects of styrene exposures in 313 workers from fiberglass and metal-product manufacturing plants and a mail terminal. The audiological test battery included pure-tone audiometry, distortion product otoacoustic emissions (DPOAE), psychoacoustic modulation transfer function, interrupted speech, speech recognition in noise and cortical response audiometry (CRA). Workers exposed to noise and styrene had significantly poorer pure-tone thresholds in the high-frequency range (3 to 8 kHz) than the controls, noise-exposed workers and those listed in a Swedish age-specific database. Even though abnormalities were noted on DPOAE and CRA testing, the interrupted speech and speech recognition in noise tests were the more sensitive tests for styrene effects. Further research is needed on the underlying mechanisms to understand the effects of styrene and on audiological test batteries to detect changes in populations exposed to solvents.

Aceitação de protetores auditivos pelos componentes de banda instrumental e vocal

There are barriers to effective hearing protection among musicians. AIM: To investigate the acceptance of hearing protection aids in members of an instrumental and voice music band. MATERIAL AND METHOD: A prospective study of 34 members of the Municipal Indaial Band. Sound pressure levels were measured during a rehearsal, indicating mean levels ranging from 96.4 dB(A) to 106.9 dB(A). Subjects answered questionnaires and underwent audiometry. They attended a lecture in which folders and hearing protection aids were provided; subjects were asked to try using the protectors for 3 months. RESULTS: At the end of the study period, 56.2% reported not liking hearing protection, while 43.7 % accepted such protection. The most common complaints were discomfort with sounds (58.8 %) and tinnitus (47%). 77.1% said that music might cause hearing impairment. A statistically significant difference was observed in the right ear at 4 and 6 kHz and at the left ear in 3, 4 and 6 kHz when median thresholds were compared with those from unexposed controls. CONCLUSION: Although most subjects seemed aware of the risk, few took preventive measures against hearing loss. This suggests the need for periodic educational campaigns and specific legislation tailored to music professionals.

Saúde auditiva de trabalhadores expostos a ruído e inseticidas

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.