Hearing conservation for farmers: source apportionment of occupational and environmental factors contributing to hearing loss

Preventing Occupational Hearing Loss: 50 Years of Research and Recommendations from the National Institute for Occupational Safety and Health

For more than 50 years, the National Institute for Occupational Safety and Health (NIOSH), part of the United States (U.S.) Centers for Disease Control and Prevention (CDC), has been actively working to reduce the effects of noise and ototoxic chemicals on worker hearing. NIOSH has pioneered basic and applied research on occupational hearing risks and preventive measures. The Institute has issued recommendations and promoted effective interventions through mechanisms ranging from formal criteria documents to blogs and social media. NIOSH has conducted surveillance and published statistics to guide policy and target prevention efforts. Over the past five decades, substantial progress has been made in raising awareness of noise as a hazard, reducing the risk of occupational hearing loss, improving the use of hearing protection, and advancing measurement and control technologies. Nevertheless, noise remains a prevalent workplace hazard and occupational hearing loss is still one of the most common work-related conditions. NIOSH continues to work toward preventing the effects of noise and ototoxicants at work and has many resources to assist audiologists in their hearing loss prevention efforts.

Noise exposure and hearing loss among tractor drivers in India

BACKGROUND

Tractors emit high intensity noise and prolonged exposure to high intensity noise causes hearing loss to the drivers.

OBJECTIVE

The aim of this study was to measure noise intensity at the tractor drivers' ear level and hearing loss among tractor drivers.

METHODS

Noise intensity was measured on 6 models of tractors which were operated with 5 different tillage implements. In order to assess hearing loss, audiometric test was performed at 7 frequencies, i.e. 250, 500, 1000, 2000, 4000, 6000, and 8000 Hz, among 30 tractor drivers and 30 control group subjects. All the selected tractor drivers and control group subjects were also interviewed to obtain personal information and noise exposure details.

RESULTS

The tractor drivers were exposed to noise intensity in the range of 91.7-97.5 dB(A). Audiogram analysis shows that the hearing threshold levels were significantly (p < 0.05) higher among the tractor drivers as compared with the control group subjects. The effect was significantly (p < 0.05) more on the left ear as compared with the right ear among the tractor drivers. Increase in age has significant (p < 0.05) effect on the hearing threshold levels on the left ear. Prevalence of high frequency hearing loss was 50% among tractor drivers as compared with 10% among control group subjects. Hearing loss was significantly (p < 0.05) more in the low frequency as compared with the high frequency among the tractor drivers.

CONCLUSION

Indian tractor operators are exposed to high noise levels which may result in hearing loss. It is recommended that hearing conservation programs should be initiated to prevent noise hazards and hearing loss among the tractor drivers.

Urinary pyrethroid metabolite and hearing threshold shifts of adults in the United States: A cross-sectional study

Hearing loss (HL) is a global health problem with a high prevalence and profound socioeconomic impact. Pyrethroids are one of the most commonly used insecticides. Although previous studies have reported the relationship between pyrethroids and neurotoxicity, little is known about the effect of pyrethroid exposure on the auditory system among the general population. This study is aimed to investigate the association of pyrethroid exposure with hearing threshold shifts of adults in the United States. A total of 726 adults, aged from 20 to 69 years from the 2011-2012 National Health and Nutrition Examination Survey (NHANES) data were included in the study. Urinary 3-phenoxybenzoic acid (3-PBA), a general pyrethroid metabolite, was used as a biomarker for pyrethroid exposure. HL was defined as a pure-tone average (PTA) at 0.5, 1, 2, 4 kHz ≥ 20 dB in the better ear. Analyses by using multivariate linear regressions were conducted to explore the associations of urinary 3-PBA with PTA hearing threshold shifts. There were no statistically significant correlations between Ln-transformed 3-PBA and either low-frequency or high-frequency hearing thresholds after adjusting for age, gender, race/ethnicity, education level, firearm noise exposure, occupational noise exposure, recreational noise exposure, serum cotinine, BMI, hypertension, and diabetes. However, associations of 3-PBA with both low-frequency and high-frequency hearing thresholds depended on age (P interaction < 0.0396 and 0.0017, respectively). Positive associations between Ln-transformed 3-PBA and both low-frequency and high-frequency hearing thresholds were observed in participants aged 20-39 years after adjusting confounders (β = 1.53, 95% CI: 0.04-3.01, and β = 3.14, 95% CI: 0.99-5.29, respectively) with the highest tertile (≥ 0.884 μg/g creatinine) of 3-PBA compared with the lowest tertile (< 0.407 μg/g creatinine). The possibility of interaction between 3-PBA and age on the hearing threshold shifts indicated that pyrethroid insecticides were prone to be more toxic to auditory system in younger adults than in older ones. Further studies will be required to confirm these findings.

The audiogram: Detection of pure-tone stimuli in ototoxicity monitoring and assessments of investigational medicines for the inner ear

Pure-tone thresholds have long served as a gold standard for evaluating hearing sensitivity and documenting hearing changes related to medical treatments, toxic or otherwise hazardous exposures, ear disease, genetic disorders involving the ear, and deficits that develop during aging. Although the use of pure-tone audiometry is basic and standard, interpretation of thresholds obtained at multiple frequencies in both ears over multiple visits can be complex. Significant additional complexity is introduced when audiometric tests are performed within ototoxicity monitoring programs to determine if hearing loss occurs as an adverse reaction to an investigational medication and during the design and conduct of clinical trials for new otoprotective agents for noise and drug-induced hearing loss. Clinical trials using gene therapy or stem cell therapy approaches are emerging as well with audiometric outcome selection further complicated by safety issues associated with biological therapies. This review addresses factors that must be considered, including test-retest variability, significant threshold change definitions, use of ototoxicity grading scales, interpretation of early warning signals, measurement of notching in noise-induced hearing loss, and application of age-based normative data to interpretation of pure-tone thresholds. Specific guidance for clinical trial protocols that will assure rigorous methodological approaches and interpretable audiometric data are provided.

Systematic review of occupational hazards at postharvest grain operations

INTRODUCTION

Agriculture stands out in relation to the high number of occupational incidents and diseases. In this sense, grains postharvest operations, such as receiving, precleaning, drying, storage and shipping the grains, are highlighted in the number of injuries and fatalities.

AIM

To identify and extract qualitative and quantitative data related to the main occupational hazards present in grains postharvest operations at preprocessing and storage facilities.

METHODS

A systematic review was carried out in the databases of Science Direct, Scopus and Web of Science for papers published between 1980 and 2019. The abstract should have described a study related to any occupational hazard (physical, chemical, biological, ergonomic and mechanical) and at least one of the occupational hazards should be related to any postharvest operations.

RESULTS AND DISCUSSIONS

In total, 42% of 38 analysed papers were published between 2015 and 2019. Three journals were responsible for 45% of publications related to occupational hazards present in grains postharvest operations. The most part of analysed publications related to confined spaces, grain entrapment, machine entanglement and falls hazards are related to Purdue University's Agricultural Safety and Health Program which applied research in occupational safety at grains postharvest.

CONCLUSIONS

The creation of standardised internationals can collaborate to reduce occupational risks in grain storage units. It is suggested the development of monitoring technologies to obtain real-time information on noise, dust, gases and heat in postharvest operations and equipment. The use of intelligent algorithms can create prevention mechanisms for possible occupational risks and avoid injuries to employees.

Association between pyrethroid pesticide exposure and hearing loss in adolescents

BACKGROUND

Hearing loss in adolescents is a serious public health problem with a high prevalence. Pyrethroids are one of the most widely applied insecticides that have been linked to neurotoxicity. However, there is no study about the effect of pyrethroid insecticide exposure on the auditory system in the general population.

OBJECTIVE

To investigate the association between pyrethroid pesticide exposure and hearing loss in adolescents in the United States.

METHODS

A total of 720 adolescents aged 12-19 years who participated in the National Health and Nutrition Examination Survey (NHANES, 2007-2010) were considered. 3-phenoxybenzoic acid (3-PBA), a urinary metabolite, was applied as a biomarker to assess pyrethroid exposure. Hearing loss in adolescents was defined as a pure-tone average (PTA) > 15 dB in either ear. Multivariate linear and logistic regression analyses were conducted to examine the associations of urinary 3-PBA with PTA hearing thresholds and risk of hearing loss, respectively.

RESULTS

The weighted geometric mean of 3-PBA levels in urine was 0.32 μg/g creatinine, and 7.62% of adolescents had hearing loss. After adjusting for age, sex, race/ethnicity, BMI, serum cotinine, annual family income and exposure to loud noise/music, linear regression analyses found that Ln-transformed 3-PBA was positively correlated with increase of hearing thresholds in either left (β = 0.61, 95% CI: 0.20-1.01) or right ear (β = 0.52, 95% CI: 0.16-0.89). Logistic regression analyses showed that adjusted odds ratio (OR) for hearing loss in adolescents with the highest tertile (≥0.52 μg/g creatinine) of 3-PBA were 3.12 (95% CI: 1.42-6.83) compared with the lowest tertile (<0.18 μg/g creatinine), with significant linear trends across tertiles.

CONCLUSION

Pyrethroid pesticide exposure was positively associated with hearing loss in U.S. adolescents. This study provides new evidence for the association between pyrethroid exposure and auditory function.

A scoping review to identify strategies that work to prevent four important occupational diseases

BACKGROUND

Despite being largely preventable, many occupational diseases continue to be highly prevalent and extremely costly. Effective strategies are required to reduce their human, economic, and social impacts.

METHODS

To better understand which approaches are most likely to lead to progress in preventing noise-related hearing loss, occupational contact dermatitis, occupational cancers, and occupational asthma, we undertook a scoping review and consulted with a number of key informants.

RESULTS

We examined a total of 404 articles and found that various types of interventions are reported to contribute to occupational disease prevention but each has its limitations and each is often insufficient on its own. Our principal findings included: legislation and regulations can be an effective means of primary prevention, but their impact depends on both the nature of the regulations and the degree of enforcement; measures across the hierarchy of controls can reduce the risk of some of these diseases and reduce exposures; monitoring, surveillance, and screening are effective prevention tools and for evaluating the impact of legislative/policy change; the effect of education and training is context-dependent and influenced by the manner of delivery; and, multifaceted interventions are often more effective than ones consisting of a single activity.

CONCLUSIONS

This scoping review identifies occupational disease prevention strategies worthy of further exploration by decisionmakers and stakeholders and of future systematic evaluation by researchers. It also identified important gaps, including a lack of studies of precarious workers and the need for more studies that rigorously evaluate the effectiveness of interventions.

Hearing Loss in Agricultural Workers Exposed to Pesticides and Noise

Agricultural workers who have concurrent exposure to pesticides and noise are at increased risk of hearing loss. We recruited 163 Thai conventional and 172 organic farmers to answer our questionnaires about personal demographics, agricultural activities, and pesticide and agricultural machinery use. This information was used to calculate the years of conventional (pesticide use) farming and the years of agricultural noise exposure, and to estimate semiquantitative metrics for pesticide exposure (cumulative intensity score-years) and cumulative noise exposure (dB(A)-years) for each conventional farmer. All participants underwent pure tone audiometric testing. The mean hearing threshold in the low-frequency band (0.5-2 kHz) and high-frequency band (3-6 kHz) were used for analysis. Years involved in conventional farming and years using agricultural machinery were associated with an increase in the average hearing threshold for the high-frequency band after controlling for age, ever exposed to industrial noise and cigarette smoking. The highest category of cumulative insecticide exposure (score-years), cumulative organophosphates exposure (score-years) and cumulative noise exposure (dB(A)-years) were also associated with an increased high-frequency band hearing threshold among conventional farmers. Results from the full cohort and the subcohort of conventional farmers support each other and the hypothesis that pesticide and noise have an additive effect on hearing, since no model interactions were significant.

Prevention of Noise-Induced Hearing Loss from Recreational Firearms

In the United States and other parts of the world, recreational firearm shooting is a popular sport that puts the hearing of the shooter at risk. Peak sound pressure levels (SPLs) from firearms range from ∼140 to 175 dB. The majority of recreational firearms (excluding small-caliber 0.17 and 0.22 rifles and air rifles) generate between 150 and 165 dB peak SPLs. High-intensity impulse sounds will permanently damage delicate cochlear structures, and thus individuals who shoot firearms are at a higher risk of bilateral, high-frequency, noise-induced hearing loss (NIHL) than peer groups who do not shoot. In this article, we describe several factors that influence the risk of NIHL including the use of a muzzle brake, the number of shots fired, the distance between shooters, the shooting environment, the choice of ammunition, the use of a suppressor, and hearing protection fit and use. Prevention strategies that address these factors and recommendations for specialized hearing protectors designed for shooting sports are offered. Partnerships are needed between the hearing health community, shooting sport groups, and wildlife conservation organizations to develop and disseminate accurate information and promote organizational resources that support hearing loss prevention efforts.

Adverse effects of pesticides on central auditory functions in tobacco growers

OBJECTIVE

To investigate the effects of exposure to pesticides on the central auditory functions (CAF) of Brazilian tobacco growers.

DESIGN

This was a cross-sectional study carried out between 2010 and 2012. Participants were evaluated with two behavioural procedures to investigate CAF, the random gap detection test (RGDT) and the dichotic digit test in Portuguese (DDT).

STUDY SAMPLE

A total of 22 growers exposed to pesticides (study group) and 21 subjects who were not exposed to pesticides (control group) were selected.

RESULTS

No significant differences between groups were observed for pure-tone thresholds. A significant association between pesticide exposure and the results for RGDT and DDT was found. Significant differences between pesticide-exposed and nonexposed subjects were found for RGDT frequency average and DDT binaural average, when including age and hearing level as covariates. Age was significantly associated with RGDT frequency average, DDT left ear score, DDT binaural average and DDT right ear advantage. Hearing levels were not significantly associated with any of the test scores. The relative risk of failing the DDT and RGDT for the study group was 1.88 (95% CI: 1.10-3.20) and 1.74 (95% CI: 1.06-2.86), respectively, as compared with the control group.

CONCLUSIONS

The results showed that tobacco growers exposed to pesticides exhibited signs of central auditory dysfunction characterised by decrements in temporal processing and binaural integration processes/abilities.

Gender differences in use of hearing protection devices among farm operators

Purpose:

Although farm operators have frequent exposure to hazardous noise and high rates of noise-induced hearing loss, they have low use of hearing protection devices (HPDs). Women represent about one-third of farm operators, and their numbers are climbing. However, among published studies examining use of HPDs in this worker group, none have examined gender-related differences. The purpose of this study was to examine gender-related differences in use of hearing protection and related predictors among farm operators.

Materials and Methods:

Data previously collected at farm shows and by telephone were analyzed using t-tests and generalized linear model with zero inflated negative binomial (ZINB) distribution.

Findings:

The difference in rate of hearing protector use between men and women farm operators was not significant. There was no difference between men and women in most hearing protector-related attitudes and beliefs.

Conclusion:

Although men and women farm operators had similar rates of use of hearing protectors when working in high-noise environments, attitudes about HPD use differed. Specifically, interpersonal role modeling was a predictor of HPD use among women, but not for men. This difference suggests that while farm operators of both genders may benefit from interventions designed to reduce barriers to HPD use (e.g., difficulty communicating with co-workers and hearing warning sounds), farm women have unique needs in relation to cognitive-perceptual factors that predict HPD use. Women farm operators may lack role models for use of HPDs (e.g., in peers and advertising), contributing to their less frequent use of protection.

Prenatal exposure to multiple pesticides is associated with auditory brainstem response at 9months in a cohort study of Chinese infants

BACKGROUND

Pesticides are associated with poorer neurodevelopmental outcomes, but little is known about the effects on sensory functioning.

METHODS

Auditory brainstem response (ABR) and pesticide data were available for 27 healthy, full-term 9-month-old infants participating in a larger study of early iron deficiency and neurodevelopment. Cord blood was analyzed by gas chromatography-mass spectrometry for levels of 20 common pesticides. The ABR forward-masking condition consisted of a click stimulus (masker) delivered via ear canal transducers followed by an identical stimulus delayed by 8, 16, or 64 milliseconds (ms). ABR peak latencies were evaluated as a function of masker-stimulus time interval. Shorter wave latencies reflect faster neural conduction, more mature auditory pathways, and greater degree of myelination. Linear regression models were used to evaluate associations between total number of pesticides detected and ABR outcomes. We considered an additive or synergistic effect of poor iron status by stratifying our analysis by newborn ferritin (based on median split).

RESULTS

Infants in the sample were highly exposed to pesticides; a mean of 4.1 pesticides were detected (range 0-9). ABR Wave V latency and central conduction time (CCT) were associated with the number of pesticides detected in cord blood for the 64ms and non-masker conditions. A similar pattern seen for CCT from the 8ms and 16ms conditions, although statistical significance was not reached. Increased pesticide exposure was associated with longer latency. The relation between number of pesticides detected in cord blood and CCT depended on the infant's cord blood ferritin level. Specifically, the relation was present in the lower cord blood ferritin group but not the higher cord blood ferritin group.

CONCLUSIONS

ABR processing was slower in infants with greater prenatal pesticide exposure, indicating impaired neuromaturation. Infants with lower cord blood ferritin appeared to be more sensitive to the effects of prenatal pesticide exposure on ABR latency delay, suggesting an additive or multiplicative effect.

Effects of interventions on use of hearing protectors among farm operators: A randomized controlled trial

OBJECTIVE

The purpose of this study was to compare the effectiveness of three interventions designed to promote hearing protector device (HPD) use.

DESIGN

Randomized controlled trial.

STUDY SAMPLE

Farm operators (n = 491) were randomly assigned to one of five intervention groups: (1) interactive web-based information with mailed assortment of HPDs; (2) Interactive web-based information only; (3) static web-based information with mailed assortment of HPDs; (4) Static web-based information only; or (5) mailed assortment of HPDs only. Data were analysed using a mixed model approach.

RESULTS

HPD use increased among all participants, and increased more among participants receiving the mailed HPDs (with or without information) compared to participants receiving other interventions. Participants receiving the interactive web-based information had comparable increased use of HPDs to those receiving the static web-based information. Participants receiving the mailed HPDs had more positive situational influences scale scores than other participants. Program satisfaction was highest among mailed and web-based information groups.

CONCLUSIONS

A mailed assortment of hearing protectors was more effective than information. Interactive and static information delivered via web were similarly effective. Programs interested in increasing HPD use among farmers should consider making hearing protectors more available to farmers.

Social Desirability Bias in Self-Reporting of Hearing Protector Use among Farm Operators

OBJECTIVE

The purposes of this study were (i) to examine the relationship between reported hearing protector use and social desirability bias, and (ii) to compare results of the Marlowe-Crowne social desirability instrument when administered using two different methods (i.e. online and by telephone).

METHODS

A shortened version of the Marlowe-Crowne social desirability instrument, as well as a self-administered instrument measuring use of hearing protectors, was administered to 497 participants in a study of hearing protector use. The relationship between hearing protector use and social desirability bias was examined using regression analysis. The results of two methods of administration of the Marlowe-Crowne social desirability instrument were compared using t-tests and regression analysis.

RESULTS

Reliability (using Cronbach's alpha) for the shortened seven-item scale for this sample was 0.58. There was no evidence of a relationship between reported hearing protector use and social desirability reporting bias, as measured by the shortened Marlowe-Crowne. The difference in results by method of administration (i.e. online, telephone) was very small.

CONCLUSIONS

This is the first published study to measure social desirability bias in reporting of hearing protector use among farmers. Findings of this study do not support the presence of social desirability bias in farmers' reporting of hearing protector use, lending support for the validity of self-report in hearing protector use in this population.

Protocol of a randomized controlled trial of hearing protection interventions for farm operators

Background

Hearing loss and tinnitus are prevalent in America, and noise-induced hearing loss is a leading cause of hearing loss. Noise-induced hearing loss has negative impact on quality of life, physical and emotional functioning, social life, and employment. In addition, noise-induced hearing loss results in heavy social and economic burdens on families and communities from all ethnic and socioeconomic groups. Farmers are a group that is particularly high risk for noise-induced hearing loss, and is underserved by programs designed to limit that risk. They are among the most noise-exposed group of workers, and experience the second highest prevalence of noise-induced hearing loss among all occupational categories. In agriculture, 1.5 million workers (43.3%) report exposure to hazardous noise. Although use of hearing protection devices (HPDs) would protect them from noise-induced hearing loss, use among farmers is low.

Methods/Design

The purpose of this project is to compare the effectiveness of several approaches to influencing hearing protector use. Approaches include: a) an interactive, predictors-based intervention delivered via the Internet; b) a static informational web site; and c) a mailed sampler of hearing protectors. The goals are to further develop an intervention to promote farmers’ use of HPDs, and compare the effectiveness of the interventions delivered in various combinations. Participants will include 701 farmers. Sites will be affiliates of a major farmer organization. Data will be collected at baseline, 6, and 12 months. A random intercept mixed model will be used to explore the fixed effects of the three NIHL prevention interventions over time while adjusting for age and gender. This project will involve a partnership between the University of Michigan and a major farmer organization to accomplish project aims.

Discussion

Results of this study will be used to inform future research-to-practice studies to increase hearing protector use. Increased use of hearing protectors is expected to reduce rates of noise-induced hearing loss and other negative effects of high noise exposure, and improve quality of life in this high-risk and underserved group.

Trial registration

Clinicaltrials.gov NCT01454895 Registered 14 October, 2011.

Avaliação do sistema auditivo em agricultores expostos à agrotóxicos

Objetivos avaliar o sistema auditivo periférico, por meio de audiometria tonal, em agricultores residentes em área de intenso uso de agrotóxicos no Estado do Rio de Janeiro. Métodos foram avaliados 70 indivíduos, de ambos os gêneros, moradores de Campos dos Goytacazes, com idade variando entre 25 e 59 anos, sendo 35 agricultores e 35 não agricultores. Todos os indivíduos tiveram sua audição periférica avaliada, por meio de audiometria tonal nas frequências de 250, 500, 1.000, 2.000, 3.000, 4.000, 6.000 e 8.000Hz. Foram excluídos indivíduos com alteração de orelha externa e média e/ou com alguma queixa otológica. Além disso, foi realizada anamnese com questões relacionadas à saúde, situação sócio-econômica, educação e exposição ao agrotóxico. Foi considerada perda auditiva, os limiares maiores ou iguais a 25dB em qualquer das frequências testadas. Resultados o Odds Ratio de perda auditiva foi 3,67 vezes (IC95%: 2,08-6,48) maior entre agricultores (94,3%), quando comparados aos não agricultores (25,7%). Além disso, a maior parte das alterações auditivas foi observada nas frequências mais agudas. Conclusão o presente estudo sugere que a atividade agrícola e possivelmente a exposição a agrotóxicos aumenta o risco de perda auditiva.

Effects of common agricultural tasks on measures of hearing loss

BACKGROUND

Among agricultural populations, hearing loss caused by excessive noise exposure is common. However, examinations of associations between exposure to agricultural tasks and hearing loss are limited.

METHODS

Audiometry and lifetime exposure to 11 agricultural tasks were analyzed among 1,568 participants. Gender stratified multivariable linear regression was used to estimate associations between exposure duration and three hearing loss metrics.

RESULTS

Among men, significant associations were observed between hearing loss and hunting or target shooting, all-terrain vehicle (ATV) or motorcycle riding, chain saw use, electric or pneumatic tool use, living on a farm, and all agricultural tasks combined. When all significant exposure metrics were included in a single model, associations remained for hunting or target shooting, electric or pneumatic tool use and living on a farm. Significant associations were sparse among women, and in all cases paradoxical.

CONCLUSIONS

Despite imprecise estimation of noise exposure, specific agricultural tasks were associated with hearing loss.

Effects of a low intensity intervention to increase hearing protector use among noise-exposed workers

BACKGROUND

Farm operators experience exposure to high noise and high prevalence of noise-induced hearing loss, but use of hearing protection in this worker group is low. The purpose of this study was to test a brief intervention to increase farm operators' use of hearing protection.

METHODS

In this one-group pre- and post-test study, a random sample of 32 members of a farmers' organization was supplied a variety of hearing protectors. Participants received an assortment of hearing protectors by mail with manufacturer's instructions for use.

RESULTS

Mean pre-intervention hearing protector use when in high noise in this group was 23% (SD 29). Of the 32 participants, 27 (84%) were exposed to hazardous noise during the study period. Post-intervention mean use of HPDs was 64%, an increase of 41% (t = 5.26, P < 000).

CONCLUSION

Results of this study suggest that overall, hearing protectors were acceptable to farm operators, and that a brief mailed intervention is feasible.

Hearing problems among a cohort of nationally certified EMS professionals

PURPOSE

The objectives of this study were to estimate the prevalence of hearing problems among a national cohort of emergency medical service (EMS) professionals, determine factors associated with hearing problems, and estimate the percentage of EMS professionals who utilize hearing protection.

METHODS

Utilizing results from a questionnaire, individuals who reported hearing problems were compared to individuals who had not. Multivariable logistic regression was performed to identify variables associated with hearing problems. Finally, items regarding use of hearing protection were assessed to estimate the percentage of usage among EMS professionals.

RESULTS

In total, 1,058 (57%) participants responded to the questionnaire. Of those, 1,024 (97%) who completed the hearing problems question were utilized for analysis. There were 153 (14.9%) cases of self-reported hearing problems. The final logistic regression model included lifetime occupational noise exposure 0.99 (95% CI = 0.9997-1.0002), report of previous back problems (odds ratio (OR) = 2.74, 95% CI = 1.8340-4.1042), large community size (OR = 1.67, 95% CI = 1.1211-2.4843), and minority status (OR = 0.61, 95% CI = 0.3719-0.9867). Finally, 213 (20.8%) individuals reported utilizing some form of hearing protection at their main EMS job.

CONCLUSION

The results from this analysis are the first national estimates of the prevalence of self reported hearing problems among EMS professionals. This study was also the first to estimate the percentage of EMS professionals who self reported the utilization of hearing protection.

Socioeconomic inequalities in hearing loss in a healthy population sample: The HUNT Study

We assessed socioeconomic position and hearing loss in a Norwegian population of 17 593 men and women aged 30-54 years in 1984-1986 who were followed for 11 years. We used analysis of variance, logistic regression, and population-attributable fraction analyses to examine associations. Significant socioeconomic inequalities in hearing loss were found among men. Adjusted odds ratios for hearing loss were approximately 1.3 to 1.9 for semi- and unskilled manual workers compared with participants with high occupational class.

The nicotinic receptor of cochlear hair cells: a possible pharmacotherapeutic target?

Mechanosensory hair cells of the organ of Corti transmit information regarding sound to the central nervous system by way of peripheral afferent neurons. In return, the central nervous system provides feedback and modulates the afferent stream of information through efferent neurons. The medial olivocochlear efferent system makes direct synaptic contacts with outer hair cells and inhibits amplification brought about by the active mechanical process inherent to these cells. This feedback system offers the potential to improve the detection of signals in background noise, to selectively attend to particular signals, and to protect the periphery from damage caused by overly loud sounds. Acetylcholine released at the synapse between efferent terminals and outer hair cells activates a peculiar nicotinic cholinergic receptor subtype, the alpha9alpha10 receptor. At present no pharmacotherapeutic approaches have been designed that target this cholinergic receptor to treat pathologies of the auditory system. The potential use of alpha9alpha10 selective drugs in conditions such as noise-induced hearing loss, tinnitus and auditory processing disorders is discussed.

Exposure to hazardous workplace noise and use of hearing protection devices among US workers--NHANES, 1999-2004

BACKGROUND

To estimate the prevalence of workplace noise exposure and use of hearing protection devices (HPDs) at noisy work, NIOSH analyzed 1999-2004 data from the National Health and Nutrition Examination Survey (NHANES).

METHODS

A total of 9,275 currently employed workers aged > or =16 years were included in the weighted analysis. Hazardous workplace noise exposure was defined as self-reported exposure to noise at their current job that was so loud that the respondent had to speak in a raised voice to be heard. Industry and occupation were determined based on the respondent's current place and type of work.

RESULTS

Twenty-two million US workers (17%) reported exposure to hazardous workplace noise. The weighted prevalence of workplace noise exposure was highest for mining (76%, SE = 7.0) followed by lumber/wood product manufacturing (55%, SE = 2.5). High-risk occupations included repair and maintenance, motor vehicle operators, and construction trades. Overall, 34% of the estimated 22 million US workers reporting hazardous workplace exposure reported non-use of HPDs. The proportion of noise-exposed workers who reported non-use of HPDs was highest for healthcare and social services (73.7%, SE = 8.1), followed by educational services (55.5%).

DISCUSSION

Hearing loss prevention and intervention programs should be targeted at those industries and occupations identified to have a high prevalence of workplace noise exposure and those industries with the highest proportion of noise-exposed workers who reported non-use of HPDs.

Hearing loss among Ohio farm youth: a comparison to a national sample

BACKGROUND

Hearing loss is prevalent among adults in the farming community, with some evidence it begins in childhood. Our objective was to compare hearing thresholds of Ohio farm youth to published data on national norms.

METHODS

Baseline data were collected on youth (n = 212) in 1994-1996 with follow-up (n = 132) in 2003-2004 including pure-tone air conduction thresholds at 0.5, 1, 2, 3, 4, 6, and 8 kHz.

RESULTS

When compared to nationally-representative data, study youth had a higher prevalence of hearing loss. The high-frequency range was most affected, particularly at 6 kHz where nearly 50% of the farm youth exhibited some degree of hearing loss at baseline testing. The prevalence of noise-induced threshold shifts, characterized by an audiometric notch, was nearly twice that of the national sample.

CONCLUSIONS

These data suggest that hearing loss, which is common among adult farmers, may be problematic for farm youth as well.

Too late smart: farmers' adoption of self-protective behaviors in response to exposure to hazardous noise

Farmers are exposed to hazardous noise from equipment and livestock and experience high rates of noise-induced hearing loss (NIHL); however, their use of hearing protection devices (HPDs) is low. The purpose of this study was to describe farmers' personal experiences using HPDs, influencing others' use of HPDs, and overcoming barriers to the use of HPDs. A purposive sample of farmers who reported a high frequency of HPD use was selected for face-to-face interviews. Findings indicated that farmers have frequent exposure to hazardous noise. They described their motivation to adopt protective behaviors to avoid hearing loss, noise annoyance, or tinnitus. Many tried to influence others' use of HPD, particularly family members. These farmers have developed a variety of methods to ensure convenient access to HPDs when needed, and have developed effective techniques for overcoming common barriers to protection. Findings from this study will be used to form the foundation for future studies aimed at developing and testing an intervention to increase HPD use and decrease rates of NIHL among farmers.

Hearing loss among licensed pesticide applicators in the agricultural health study

OBJECTIVE

We evaluated self-reported hearing loss and pesticide exposure in licensed private pesticide applicators enrolled in the Agricultural Health Study in 1993 to 1997 in Iowa and North Carolina.

METHODS

Among 14,229 white male applicators in 1999 to 2003, 4926 reported hearing loss (35%). Logistic regression was performed with adjustment for state, age, and noise, solvents, and metals. We classified pesticides by lifetime days of use.

RESULTS

Compared with no exposure, the odds ratio (95% confidence interval) for the highest quartile of exposure was 1.19 (1.04 to 1.35) for insecticides and 1.17 (1.03 to 1.31) for organophosphate insecticides. Odds of hearing loss were elevated for high pesticide exposure events (1.38, 1.25 to 1.54), pesticide-related doctor visits (1.38, 1.17 to 1.62) or hospitalization (1.81, 1.25 to 2.62), and diagnosed pesticide poisoning (1.75, 1.36 to 2.26).

CONCLUSIONS

Although control for exposure to noise or other neurotoxicants was limited, this study extends previous reports suggesting that organophosphate exposure increases risk of hearing loss.

Ethnic, racial, and gender variations in health among farm operators in the United States

PURPOSE

The purpose of this study was to collect baseline prevalence data on the health problems faced by minority, white, and female farm operators.

METHODS

An occupational health survey of farm operators was conducted by the U.S. Department of Agriculture, National Agricultural Statistics Service between February and August 2000. A stratified random sample of farm operators from 50 U.S. states based on the 1997 Census of Agriculture was selected for telephone interview. Interviews were primarily conducted using a computer assisted telephone instrument system.

RESULTS

Population prevalences were calculated for 7137 farm operators. Prevalences were greatest for musculoskeletal discomfort, followed by respiratory problems, hearing loss, and hypertension. Generally, Latino and Asian American operators had lower prevalences for health problems than white non-Latino and white operators, respectively. African-American operators had greater prevalences for hypertension, and osteoarthritis, but lower prevalences for hearing loss, skin problems, heart problems, and cancer than white operators. American Indian or Alaska Native operators had higher prevalences for musculoskeletal problems, skin problems, and hypertension.

CONCLUSIONS

Prevalences for the different ethnicity and race groups are not the same. Studies that combine racial and ethnic groups, or study only white and non-Latino farm operators may overestimate or underestimate the prevalence of health conditions in the entire farm operator population.

Chemobrain: a translational challenge for neurotoxicology

Neurotoxicity is a frequent accompaniment of cancer chemotherapy, and held by many oncologists to be the major dose-limiting side effect. It appears in many forms, but attracted attention during the past decade primarily because of complaints by patients of impaired cognitive function they have labeled as "chemobrain". Neuropsychological testing confirmed the validity of these complaints and has generated a substantial literature examining different aspects of cognitive impairment in various clinical populations undergoing a variety of treatments. Cognitive impairment is far from the only manifestation of neurotoxicity induced by chemotherapy, however. It alters sensory function and motor function as well. A critical need for patients is a suite of methods that will enable clinicians to trace the onset and progression of neurotoxicity so as to guide and balance decisions about the course of chemotherapy. This commentary describes some of the potential methods and encourages neurotoxicologists to enlist their unique skills in the service of these needs.

Hearing difficulty attributable to employment by industry and occupation: an analysis of the National Health Interview Survey--United States, 1997 to 2003

OBJECTIVE

To estimate the national burden of hearing difficulty among workers in US industries and occupations.

METHODS

Data on 130,102 employed National Health Interview Survey respondents between the ages of 18 to 65 years who were interviewed between 1997 and 2003 were analyzed to estimate the population prevalence, adjusted prevalence ratios, and fractions of hearing difficulty attributable to employment.

RESULTS

The estimated population prevalence of hearing difficulty was 11.4% (24% attributable to employment). The adjusted prevalence ratios of hearing difficulty were highest for railroads, mining, and primary metal manufacturing industry. Occupations with increased risk of hearing difficulty were mechanics/repairers, machine operators, and transportation equipment operators.

CONCLUSIONS

Hearing difficulty was differentially distributed across various industries. In industries with high rates, employers and workers should take preventive action to reduce the risk of occupational hearing loss.

NAC for noise: from the bench top to the clinic

Noise-induced hearing loss (NIHL) is an important etiology of deafness worldwide. Hearing conservation programs are in place and have reduced the prevalence of NIHL, but this disorder is still far too common. Occupational and recreational pursuits expose people to loud noise and ten million persons in the US have some degree of noise-induced hearing impairment. It is estimated that 50 million in the US and 600 million people worldwide are exposed to noise hazards occupationally. Noise deafness is still an important and frequent cause of battlefield injury in the US military. A mainstay of hearing conservation programs is personal mechanical hearing protection devices which are helpful but have inherent limitations. Research has shown that oxidative stress plays an important role in noise-induced cochlear injury resulting in the discovery that a number of antioxidant and cell death inhibiting compounds can ameliorate deafness associated with acoustic trauma. This article reviews one such compound, N-acetylcysteine (NAC), in terms of its efficacy in reducing hearing loss in a variety of animal models of acute acoustic trauma and hypothesizes what its therapeutic mechanisms of action might be based on the known actions of NAC. Early clinical trials with NAC are mentioned.

Hearing loss in migrant agricultural workers

BACKGROUND

Farmers have high rates of hearing loss, yet little is known about the hearing status of migrant agricultural workers. We performed a cross-sectional survey to assess the prevalence and impact of hearing loss in this population.

METHODS

One hundred fifty migrant and seasonal agricultural workers were surveyed at a series of health fairs held at migrant camps. A bilingual questionnaire included items related to hearing loss risk factors and subjective hearing difficulties. Pure tone audiometry and tympanometry were performed in a mobile testing van.

RESULTS

More than half the subjects had some degree of hearing loss at audiometric frequencies between 500 and 6,000 Hz, especially in the higher frequencies. Hispanic males in the sample had significantly greater prevalence of high-frequency hearing loss compared to adults in the national Hispanic Health and Nutrition Examination Survey (HHANES). More than 35% of respondents complained of subjective difficulty hearing or understanding speech, yet no workers reported use of hearing aids. Even after adjusting for measured hearing loss, Hispanic farm workers were more likely than their English- speaking counterparts to complain of difficulty hearing or understanding speech, suggesting that language barriers could worsen the impact of hearing loss. Risk factors for hearing loss included age and abnormal tympanometry. Occupational exposures to noise from tractors and other machinery as well as pesticides were frequently reported, while use of hearing protection was rare.

CONCLUSION

Hearing loss is a significant and under-recognized problem in the migrant worker population. Further preventive and treatment efforts are warranted.

Compounds for the prevention and treatment of noise-induced hearing loss

Noise-induced hearing loss (NIHL) is the leading occupational disease and a major contributor to the development of age-related hearing loss. The pharmacological prevention and treatment of NIHL has been under preclinical investigation for the past 20 years. Promising treatments have now been identified and entered into clinical development. Within the next five years, safe and effective drugs could be approved as the first generation of otoprotectants. This review covers strategies that are under investigation for NIHL. Drugs that effectively prevent and treat NIHL will have a significant impact on medical costs, disability compensation and several issues affecting the quality of life.

Challenges and Strategies Related to Hearing Loss Among Dairy Farmers

CONTEXT

Farming is often imagined to be a serene and idyllic business based on historical images of a man, a horse, and a plow. However, machinery and equipment on farms, such as older tractors, grain dryers, and vacuum pumps, can have noise levels, which may be dangerous to hearing with prolonged, unprotected exposure.

PURPOSE

This qualitative study in Ontario, Canada, explored the challenges and coping strategies experienced by dairy farmers with self-reported hearing loss and communication difficulties. Through in-depth interviews, 13 farmers who experience significant hearing loss were questioned about the challenges they face as a result of hearing loss and the strategies they use to overcome or compensate for problems.

FINDINGS

The 2 major challenges encountered by dairy farmers with a hearing loss were: (1) obtaining information from individuals, within groups, and through electronic media; and (2) working with animals, machinery, and noise. To cope with these challenges, participants used strategies identified as problem and emotion focused.

CONCLUSIONS

Four themes arose from analysis of the challenges encountered and strategies used: 1. Hearing loss is experienced as a "familiar," but "private," problem for dairy farmers. 2. Communication difficulties can negatively affect the quality of relationships on the farm. 3. Safety and risk management are issues when farming with a hearing loss. 4. The management or control of excessive noise is a complex problem, because there are no completely reliable yet practical solutions.

Occupational Noise Exposure Assessment in Intensive Swine Farrowing Systems

The scientific literature is lacking in published agricultural noise assessments for employees of swine confinement facilities that have included dosimeter data, octave band analysis, or specific task exposure assessments. This study reports on the former three types of noise assessments in the farrowing stage of swine. Dosimeter data on workers revealed all assessments to be greater than 90 decibels measured on the A-scale (dBA), which exceeds the 85 dBA National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL). RELs were exceeded for all of the employees monitored in the swine facility, as well as the part-time employees who power-washed the farrowing rooms. The recorded time-weighted values were actually underestimated slightly because the dosimeters were set to record only noise at 85 dBA and higher.

Issues of Agricultural Safety and Health

Agricultural work is the most prevalent type of employment in the world. In the United States only a few are engaged in creating food and fiber for many. Agriculture includes farming, ranching, fishing, and forestry, and together they carry significant risk for the development of injury or illness. There are numerous special-population issues related to agriculture. Farmers are old and growing older, many workers are children, and migrant and seasonal help, often foreign born, make up a large percentage of the workforce. It has been only relatively recently that concerns of agricultural safety and health have become a major research focus in the United States.

Noise Exposure and Hearing Loss in Agriculture: A Survey of Farmers and Farm Workers in the Southland Region of New Zealand

Farmers are known to be exposed to intermittent intense noise from a variety of sources, but long-term exposure and the resulting risk of hearing loss have not been well characterized. We studied a cross-sectional random sample of farms on which agricultural workers completed an audiometric test and questionnaire, and performed noise dosimetry on a subsample. Sixty-five percent of farms and a total of 586 workers participated. Noise on the subsample of 60 farms lay in a range between 84.8 to 86.8 dB(A) and hearing losses were consistent with this level of exposure. Age, driving tractors without cabs, and working with metal were important risk factors. Reported compliance with hearing protection was higher than that actually observed. The majority of farmers have a moderate risk of hearing loss, but a significant minority is at high risk. Elimination and isolation of noise sources are the control methods of choice, and if residual hearing protection is required, compliance must be improved.

[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.

Chronic disease and injury in an agricultural county: The Keokuk County Rural Health Cohort Study

The Keokuk County Rural Health Study (KCRHS) was designed as a 20-year, prospective cohort study focusing on chronic disease and injury in an agricultural southeastern Iowa county. The goals of the KCRHS are to prospectively describe, measure, and analyze prevalent rural and agriculturally related adverse health outcomes and their respective risk factors and to provide the basis for future community-based intervention programs to reduce disease and injury incidence. Methods of data collection included in-person interviews, medical screenings, and environmental assessments of homes and farms. All households studied were rural; comparisons were made among farm, rural nonfarm, and town households, between men and women, and between smokers and nonsmokers. The present paper reports selected adult baseline data from Round 1 of this study. Residents of farm households were somewhat younger and better educated than residents of rural nonfarm and town households; smoked less; were more likely to have ridden an all-terrain vehicle; and were more likely to report firearms in the home. Eighty-nine percent of the men and 66% of the women engaged in farming or did so in the past. Men more often reported hearing loss, were more often overweight and obese, more often reported an injury, less often reported asthma, and less often saw a medical practitioner. Women reported poorer emotional health and higher rates of depression symptoms. The KCRHS has identified several modifiable health outcomes and risk factors as candidates for further analysis and targets for community-based prevention and intervention programs.