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Hearing Loss in Migrant AgriculturalWorkersPeter M. Rabinowitz MD, MPH a , Kanta D. Sircar MPH a , SanelaTarabar MD, MPH a , Deron Galusha MS a & Martin D. Slade MPH aa Yale University School of Medicine, Occupational andEnvironmental Medicine Program , New Haven, CT, USAPublished online: 11 Oct 2008.
To cite this article: Peter M. Rabinowitz MD, MPH , Kanta D. Sircar MPH , Sanela Tarabar MD, MPH ,Deron Galusha MS & Martin D. Slade MPH (2005) Hearing Loss in Migrant Agricultural Workers, Journalof Agromedicine, 10:4, 9-17, DOI: 10.1300/J096v10n04_04
To link to this article: http://dx.doi.org/10.1300/J096v10n04_04
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ORIGINAL RESEARCH
Hearing Loss in Migrant Agricultural WorkersPeter M. Rabinowitz, MD, MPH
Kanta D. Sircar, MPHSanela Tarabar, MD, MPH
Deron Galusha, MSMartin D. Slade, MPH
ABSTRACT. Background: Farmers have high rates of hearing loss, yet little is known about thehearing status of migrant agricultural workers. We performed a cross-sectional survey to assess theprevalence and impact of hearing loss in this population.
Methods: One hundred fifty migrant and seasonal agricultural workers were surveyed at a seriesof health fairs held at migrant camps. A bilingual questionnaire included items related to hearingloss risk factors and subjective hearing difficulties. Pure tone audiometry and tympanometry wereperformed in a mobile testing van.
Results: More than half the subjects had some degree of hearing loss at audiometric frequencies be-tween 500 and 6000 Hz, especially in the higher frequencies. Hispanic males in the sample had signifi-cantly greater prevalence of high-frequency hearing loss compared to adults in the national HispanicHealth and Nutrition Examination Survey (HHANES). More than 35% of respondents complained ofsubjective difficulty hearing or understanding speech, yet no workers reported use of hearing aids. Evenafter adjusting for measured hearing loss, Hispanic farm workers were more likely than their Eng-lish-speaking counterparts to complain of difficulty hearing or understanding speech, suggesting that lan-guage barriers could worsen the impact of hearing loss. Risk factors for hearing loss included age andabnormal tympanometry. Occupational exposures to noise from tractors and other machinery as well aspesticides were frequently reported, while use of hearing protection was rare.
Conclusion: Hearing loss is a significant and under-recognized problem in the migrant worker popula-tion. Further preventive and treatment efforts are warranted. [Article copies available for a fee from TheHaworth Document Delivery Service: 1-800-HAWORTH. E-mail address: <[email protected]>Website: <http://www.HaworthPress.com> © 2005 by The Haworth Press, Inc. All rights reserved.]
Peter M. Rabinowitz, Kanta D. Sircar, Sanela Tarabar, Deron Galusha and Martin D. Slade are affiliated with theYale University School of Medicine, Occupational and Environmental Medicine Program, New Haven, CT.
Address correspondence to: Peter M. Rabinowitz, MD, MPH, Yale Occupational and Environmental MedicineProgram, Yale University School of Medicine, 135 College Street, New Haven, CT 06510 (E-mail: [email protected]).
The authors thank Jacqueline Solimini for assistance with the survey administration and data entry, EdwardSapian and ConnectiCOSH for their organization of the health fairs, as well as Bruce Gould, MD, and VictoriaBarreras, MPH, for coordination of clinical activities.
This project was made possible by support from the Northeast Center for Agricultural and Occupational Health,Grant # U01/CCU208030. The Hearing Center, Ansonia, CT, assisted with the audiometric screening.
Journal of Agromedicine, Vol. 10(4) 2005Available online at http://www.haworthpress.com/web/JA
© 2005 by The Haworth Press, Inc. All rights reserved.doi:10.1300/J096v10n04_04 9
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KEYWORDS. Hearing loss, noise occupational, agricultural workers’ diseases, migrant agricul-tural workers, Hispanics
BACKGROUND
Hearing loss is one of the most common sen-sory deficits. The prevalence increases withage, and the primary causes of acquired hearingloss are excessive noise exposure (noise-in-duced hearing loss, or NIHL) and age-relatedhearing loss (presbycusis).
Occupational noise exposure has been rec-ognized as a risk factor for hearing loss sinceancient times. More recently, farmers havebeenfound tohavean increasedriskofhigh fre-quency, sensorineural hearing loss, presum-ably due to noise and possibly pesticide expo-sures.1,2 Sources of noise exposure in agriculturalsettings include tractors3,4 and other noisy farmmachinery.5 Since some pesticides have neuro-toxic properties, their role in hearing loss hasbeen investigated. A history of crop spraying inthe previous year has been associated with in-creased risk of hearing loss.1
While the majority of studies of hearing lossin agriculture have focused on self-employedfarmers, little or nothing is known about thehearing status of the approximately 2.5 millionmigrant agricultural workers in the UnitedStates. Migrant workers have disproportionaterates of a number of other health conditions re-lated both to occupational exposures andsocioeconomic factors. These include musculo-skeletal disorders, pesticide-related conditions,traumatic injuries, respiratory conditions, der-matitis, infectious diseases, cancer, eye condi-tions, and mental illness.6 Migrant workers areexposed to noise sources from tractors andother machinery, and are also at risk for pesti-cide exposures. Whether such exposures arecausing elevated rates of hearing loss in mi-grantworkers is currentlyunknown,however.
Hispanics, who make up a majority of themigrant farm worker population, have signifi-cant rates of hearing loss.7 The reasons for highratesof hearing loss maybe related to socioeco-nomic factors,8 but it may also be related to oc-cupational or non-occupational noise expo-sure. There is evidence that hearing loss mayhave a disproportionate impact in Hispanicpopulations, perhaps related to the difficulty of
having both hearing impairment and limitedEnglish skills.9 In a study of noise-exposedworkers who were predominantly Hispanic,lower acculturation scores were associatedwith lesseffectiveuseofhearingprotection.10
We therefore conducted a cross-sectionalsurvey of a largely Hispanic population of mi-grant agricultural workers. The aims of the sur-vey were to determine whether rates of hearingloss appeared to be increased compared tocomparison populations, whether measuredhearing loss was associated with reported hear-ing difficulties, and whether significant associ-ations could be found between hearing loss andoccupationalexposures tonoiseandpesticides.
METHODS
The study protocol and questionnaire werereviewed and approved by the Human Investi-gation Committee for the Yale School of Medi-cine. During the agricultural season of 2001and 2002, volunteers were recruited fromhealth fairs held at different migrant camps andfarms in the Connecticut River valley. Aftergiving informed verbal consent, volunteerscompleted a short questionnaire regardingnoise exposures, medical risk factors for hear-ing loss, and hearing loss symptoms. They sub-sequently had tympanometry using a GrasonStadler tympanometer, and then entered a mo-bile van audiometric booth for pure toneaudiometry performed by certified audiometrictechnicians and a supervising audiologist. Thesound levels in the testing booth were in com-pliance with OSHA standards. Due to equip-ment failures, tympanometry could not becompleted on all subjects.
Study personnel administered the question-naire, with bilingual personnel administeringthe instrument in Spanish to those volunteerswho only spoke Spanish. Subjects received acopy of their hearing results and those with ab-normal results were referred for medical fol-low-up. All participants received instruction inthe use of hearing protectors, and were givensamples of earplugs.
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Altogether, 150 individuals completed thesurvey. Questionnaire responses were enteredinto a Microsoft Access database, and the datawere exported into SAS 8.02 for analysis. Sim-ple univariate and frequency analyses wereperformed on demographic variables.
Individuals were considered to have hearingloss if the hearing threshold (in either ear) atany frequency between 500 and 6000 Hz ex-ceeded 25 dB.11 For each individual, we deter-mined whether such loss occurred either in thelower frequencies of 500, 1000, and 2000 or thehigher frequenciesof 3,000, 4000, and 6000 Hz(where noise-induced hearing loss typically isfirst detected12). We determined the presenceof hearing impairment according to AmericanMedical Association (AMA) and AmericanAcademy of Otolaryngology Head and NeckSurgery (AAOHNS) criteria13,14 as a lossgreater than 25 dB for the average hearingthreshold level at the frequencies of 500, 1000,2000, and 3000 Hz in either ear. For tympano-metry, a pressure range of �100 to 100 DaPaand peak pressure of 0.3-1.9 cm3 were consid-ered normal.15
To determine correlates of subjective diffi-culty hearing and/or understanding speech, weperformed simple and multiple logistic regres-sions between this self-reported condition andage, gender, and ethnicity as well as thepresence of hearing loss.
In order to compare hearing loss among sur-vey participants to a reference population, weused data from the 1982-84 Hispanic Healthand Nutrition Examination Survey (HHANES).16
HHANES was a large systematic sample ofU.S. individuals of primarily Mexican, PuertoRican, and Cubandescent.17 TheNationalCen-ter for Health Statistics has recommended thatin analyses of HHANES data, these groupsshould not be lumped into one “Hispanic” cate-gory.18 For the purposes of the comparison toHHANES, six farm workers from CentralAmerica in the farm worker sample weregrouped with those of Mexican origin, whileone Hispanic male from Jamaica was analyzedtogether with the Puerto Ricans in the sample.The audiometric testing component of HHANESwas limited to the frequencies of 500, 1000,2000, and 4000 Hz. In order to focus on highfrequency hearing loss possibly related to oc-cupation, we compared the prevalence of hear-
ing loss at the noise-sensitive frequency of4000 Hz between male Hispanic farm workersin the survey and males in the HHANES sam-ple. We confirmed that hearing loss at 4000 Hzin the farm worker survey was well-correlatedwith loss at 3000, 4000, and 6000 Hz: of the 78individuals with loss at either 3000, 4000, or6000 Hz, 50 (64%) had loss at 4000 Hz.
A logistic regression model was used to cal-culate bivariate and adjusted odds ratios for as-sociations between demographic and occupa-tional factors and hearing loss. In all themultivariate analyses, a backward eliminationmethod was used, with a selection criterion of p =0.05 in order to select the variables remainingin the final model.
RESULTS
Demographics
As Table 1 shows, the study population waspredominantly male. There was a wide agerange,although themedianagewas less than35years. Most of the workers were from Spanish-speaking countries and territories, especiallyPuerto Rico and Mexico. The African Ameri-cans in the sample were all from Jamaica. Thepredominant crop currently worked was tobacco,although some participants worked other crops,including a commercial nursery and an appleorchard. The respondents reported a median of4 years working in agriculture. During the restof the year, participants reported a variety ofother occupations, most commonly farm workin other parts of the United States or in theirhome countries, but also construction and ser-vice industry jobs.
Hearing Status
Table 2 shows the prevalence of measuredand reported hearing loss for study subjects,grouped according to tympanometry testingstatus. Overall, 12% of individuals had hearingimpairment by AMA/AAOHNS criteria, andmore than 35% of respondents complained ofsubjective difficulty hearing or understandingspeech due to hearing problems. Despite this,no respondents reported use of hearing aids
Original Research 11
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(data not shown). Hearing loss was more com-mon in the higher frequencies of 3000, 4000,and 6000 Hz compared to the lower frequen-cies of 500, 1000, and 2000 Hz (52% vs. 16%,respectively). The 23 individuals with abnor-mal tympanometry (indicating middle ear dys-function) were more likely to have hearingimpairmentas well as hearing loss athigher fre-quencies. Subjectivecomplaintsof hearing dif-ficulty, however, did not differ significantly bytympanometry status.
Factors Associated with Hearing Difficulty
Table 3a shows the bivariate and adjustedassociations between reported difficulty hearing
orunderstandingspeechandbothdemographicfactors and measured low and high frequencyhearing loss. In this table, hearing loss is de-fined as a categorical variable (hearing thresh-old level in at least one frequency greater than25 dB). In both the bivariate and multivariatelogistic regression models, hearing loss at thehigher frequencies of 3000, 4000, and 6000 Hzwas significantly associated with difficultyhearing or understanding speech (OR = 2.30, p= 0.02). Hispanic ethnicity also showed astrong association with reported hearing diffi-culty, even after adjusting for age, gender,tympanometry status and measured hearingloss (OR = 4.43, p < 0.01).
Table 3b shows the same bivariate andmultivariate analysis of perceived hearing dif-ficulty, using low and high frequency hearingthreshold averages in the worse ear to definehearing status as a possible contributing vari-able. In this analysis, Hispanic ethnicityremained an important explanatory variable(OR = 3.56, p = 0.02). Measured hearing status,as determined by high frequency hearingthreshold average, was also significantly asso-ciated with reported hearing difficulty (OR =1.04 per 1 dB increment in threshold average, p <0.01).
Prevalence of Risk Factors for Hearing Loss
Table 4 shows the prevalence of reportedrisk factors for hearing loss in the study pop-ulation, including occupational and recre-ational noise exposures, self-reported pesti-cide exposures, and medical conditions.Although exposures to noise sources werecommonly reported, only 14% of subjectsresponded “yes” to the question “do you usehearing protection?” The reported use ofhearing protection varied by type of agricul-ture, with 36% of commercial nursery work-ers versus 10% of apple workers and 7% oftobacco workers reporting use of hearingprotection in the past (p < 0.001).
For the 99 study subjects with normaltympanometry (see Table 2), these risk factorswere tested for possible association with high-frequency hearing loss. In a multivariate lo-gistic regression model that also included ageand ethnicity, only age (OR = 1.06, p < 0.01)
12 JOURNAL OF AGROMEDICINE
TABLE 1. Demographics of Study Population (N =150)
Age (median, range) 34 (18-75)
Male–No. (%) 140 (93.3)
Race/Ethnicity–No. (%)
Hispanic 112 (74.7)
African American 31 (20.7)
White, non Hispanic 2 (1.3)
Unknown 5 (3.3)
Country of Origin (%)
Mexico 61 (40.7)
Jamaica 32 (21.3)
Puerto Rico 26 (17.3)
Guatemala 17 (11.3)
U.S.A. 7 (4.7)
Dominican Republic 3 (2.0)
Honduras 2 (1.3)
Unknown 2 (1.3)
Type of Agriculture (%)
Tobacco 97 (64.7)
Commercial nursery 33 (22.0)
Apple orchard 20 (13.3)
Years in agriculture(median, range)
4.0 (0-35)
Other Jobs During Year (%)
Construction/Manufacturing 31 (20.7)
Agriculture 66 (44.0)
Services/Other 13 (8.7)
None or unknown 40 (26.7)
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and ear infections (OR = 3.76, p = 0.03) show-ed a significant association with hearing lossat the noise-sensitive frequencies of 3000,4000, and 6000 Hz. In particular, no signifi-cant associations were found for reportedexposure to tractor or machinery noise, guns,loud music, or a noisy job during the rest of theyear.
Comparison with the Hispanic HANESPopulation
Figure 1 shows, by age category, the preva-lenceof hearing loss at 4000 Hz in MexicanandPuerto Rican male agricultural workers com-pared to that of Mexican and Puerto Ricanmales in the HHANES survey. In all age
Original Research 13
TABLE 2. Hearing Problems and Tympanometry Results (N = 150)
Outcome Tympanometry Status p *
Total(N = 150)
Normal(N = 99)
Abnormal(N = 23)
Notperformed(N = 28)
Hearing Loss–No. (%)
Low frequency † 24 (16.0) 13 (13.1) 7 (30.4) 4 (14.3) 0.12
High frequency ‡ 78 (52.0) 51 (51.5) 17 (73.9) 10 (35.7) 0.02
Hearing Impairment ††–No. (%) 18 (12.0) 7 (7.1) 6 (26.1) 5 (17.9) 0.02
Difficulty hearing or understandingspeech–No. (%)
53 (35.3) 37 (37.4) 9 (39.1) 7 (25.0) 0.44
† loss greater than 25 dB in any of the frequencies 500, 1 K, or 2 KHz in either ear‡ loss greater than 25 dB in any of the frequencies 3 K, 4 K, or 6 KHz in either ear†† loss greater than 25 dB in the average of frequencies 500, 1 K, 2 K, and 3 KHz in either ear* Differences between the 3 groups evaluated using chi-square test
TABLE 3a. Factors Associated with Difficulty Hearing or Understanding Speech: Hearing Loss as a Cat-egorical Variable (N = 150)
Bivariate Model Multivariate Model*
OR (95% CI) p OR (95% CI) p
Demographic Factors
Age 0.99 (0.97,1.02) 0.67 – –
Male 1.30 (0.32,5.24) 0.72 – –
Hispanic ethnicity 3.70 (1.33,10.29) 0.01 4.43 (1.55,12.64) < 0.01
Tympanometry
Normal (reference) 1.00 – – –
Abnormal 1.08 (0.43,2.73) 0.88 – –
Unknown 0.56 (0.22,1.44) 0.23 – –
Hearing Loss
Low frequency † 1.69 (0.70,4.10) 0.24 – –
High frequency ‡ 1.91 (0.96,3.78) 0.06 2.30 (1.12,4.69) 0.02
† loss greater than 25 dB in any of the frequencies 500, 1 K, or 2 KHz in either ear‡ loss greater than 25 dB in any of the frequencies 3 K, 4 K, or 6 KHz in either ear* – variables removed from the model after backward selection procedure
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groups, the farm workers had substantiallyhigher rates of high-frequency hearing lossthan the comparison HHANES population.
DISCUSSION
The findings of this study indicate that mi-grantagriculturalworkers mayhavedispropor-
tionately high rates of hearing loss. Hearingloss was present even in workers in the youngerage categories, while overall, 12% of the sub-jects had hearing loss that met AMA criteria forhearing impairment, and more than 50% of theindividuals in the sample had hearing loss � 25dB at one or more audiometric frequencies.Testing for middle ear dysfunction was abnor-mal in 19% of those tested, and this dysfunctionwas associated with greater risk of hearing lossand subjective hearing difficulty. Overall,more than 35% of the farm workers reportedsubjective difficulty with hearing or under-standing speech. These complaints were in-creased among Hispanics, even after adjustingforageandpresenceofhearing loss, suggestingan effect of language barriers on the impact ofhearing loss. Mexican and Puerto Rican malefarm workers had greater hearing loss at thenoise sensitive frequency of 4000 Hz com-pared to the HHANES comparison population.While reported exposures to noise and pesti-cides were common, use of hearing protectionwas rare. These findings have relevance for cli-nicians providing medical care for migrantworker populations, as well as occupationalhealth professionals interested in reducinghealth risks for agricultural workers.
14 JOURNAL OF AGROMEDICINE
TABLE 3b. Factors Associated with Difficulty Hearing or Understanding Speech: Hearing ThresholdAverages as Continuous Variables (N = 150)
Bivariate Model Multivariate Model*
OR (95% CI) p OR (95% CI) p
Demographic Factors
Age 0.99 (0.97,1.02) 0.67 – –
Male 1.30 (0.32,5.24) 0.72 – –
Hispanic ethnicity 3.70 (1.33,10.29) 0.01 3.56 (1.26,10.03) 0.02
Tympanometry
Normal (reference) 1.00 – – –
Abnormal 1.08 (0.43,2.73) 0.88 – –
Unknown 0.56 (0.22,1.44) 0.23 – –
Hearing Threshold Average
Low frequency † 1.03 (0.99,1.07) 0.12 – –
High frequency ‡ 1.91 (1.02,1.08) 0.003 1.04 (1.01,1.08) <0.01
† Average hearing threshold at 0.5,1, and 2 KHz (worse ear)‡ Average hearing threshold at 3, 4, and 6 KHz (worse ear)* – variables removed from the model after performing a backward selection procedure
TABLE 4. Prevalence of Risk Factors for HearingLoss (N = 150)
Reported Exposures–No. (%)Machinery 53 (35.3)Tractors 54 (36.0)Pesticides 78 (52.0)Use of hearing protection 21 (14.0)Fired a rifle or pistol 32 (21.3)Noisy job rest of the year 53 (35.3)Loud music 87 (58.0)
Medical Risk Factors–No. (%)Allergy 28 (18.7)Head Injury 29 (19.3)Ear Infection 27 (18.0)Family history 19 (12.7)
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The study design was limited by the conve-nience nature of the sample. Screenings tookplace at migrant health fairs where other activi-ties were also taking place over a period of sev-eral hours, and the screening effort was limitedby time and space constraints. While we do nothave definite figures about the total number ofpersons who attended the fairs, an estimate that10-20% of attendees received hearing screen-ing appears reasonable. Since we were not ableto test the entire population at the fair, muchless all workers, it is possible that some degreeof selection bias occurred, and that the resultsof the survey are not representative of all mi-grant workers as a group. For example, individ-uals with existing hearing loss or perceivedhearing difficulties may have been more moti-vated to participate in the study, leading to anoverestimate of hearing loss in the population.On the other hand, it is possible that individualswith significant hearing problems would havedeclined to participate in the survey out ofreluctance to be identified, despite theanonymous survey design. Such a phenomenonwould lead to an underestimate of hearing lossprevalence in the population.
The prevalent finding of hearing loss was of-ten accompanied by subjective difficulty withhearingand understandingspeech. This associ-ation was confirmed in a multivariate modelthat adjusted for age, gender, ethnicity, andtympanometry status. At the same time, while12% of the sample had hearing loss that met cri-teria for “hearing impairment,”noneof thesub-jects reported current use of hearing aids. Astudy of Hispanic adults in the HHANES sam-ple found hearing aid usage rates between 2 and12% among hearing impaired individuals.8That this is a lower rate than the 14-55% hear-ing aid usage prevalence reported for a largelyCaucasian population may reflect access tocare difficulties as well as cultural perceptionsabout the treatment of hearing loss, although inthe general U.S. population, rates may be al-mostas low.19 Similarly, thehigh rateofmiddleear dysfunction in this sample of adults may bea reflection of dietary factors, allergy, orinfection related to socioeconomic status.
The association between Hispanic ethnicityand speech perception difficulties, even adjust-ing for actual hearing loss or measured hearingthreshold averages, suggests an effect of lan-
Original Research 15
HHANESCT FarmWorkers
Perc
ent o
f sub
ject
s w
ith >
25
dB h
earin
g lo
ss a
t 4K
Hz85
80
75
70
65
60
55
50
45
40
35
30
2520
15
10
5
0Puerto Rican Puerto Rican Puerto RicanMexican Mexican Mexican
< = 25 yrs 26-40 yrs > 40 yrs
FIGURE 1. Prevalence of hearing loss at 4000 Hz by age catagory: Male Hispanic farm workers vs.males in the HHANES survey.
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guage barriers on perception of hearing diffi-culty. In human speech, consonant sounds arehigher frequency than vowels, and individualswith high-frequency hearing loss consequentlymay experience difficulties with speech dis-crimination, especially in situations of back-ground noise. This problem may be exacer-bated when one is trying to understand a secondlanguage. Virtually all of the Hispanics werefrom Spanish-speaking countries or territorieswhere Spanish would be the first language spo-ken in the home. It is possible that these work-ers, living in a country where they encounteredEnglish as a second language, would be moreaware of hearing difficulties for a given degreeof actual hearing loss than their English-speak-ing counterparts. Such difficulty could inter-fere with their acculturation into U.S. society.An alternative explanation would be that theHispanics in the sample were less reluctant toadmit hearing difficulty than the non-Hispanicworkers.
While the rate of high-frequency hearingloss was greater in the Hispanic male migrantagricultural workers compared to a referencepopulation (HHANES), we were not able toidentify occupational sources of noise or pesti-cides that correlated well with measured hear-ing loss. One possible explanation was that thebrevity of the questionnaire that was designedto rapidly screen participants for significantfactors related to hearing loss could have led toexposure misclassification. One importantlimitation of our exposure assessment was thelack of information regarding dose and fre-quency of exposure. Another possibility for thelack of correlation is that noise exposures inother jobs couldbe playinga greater role. Manyof the farm workers reported spending time inconstruction and other activities during the restof the year. Age was significantly associatedwith hearing loss, while this could representpurely the effect of presbycusis, it is also possi-ble that the association reflected in part the cu-mulative impact of noise and chemical expo-sures, which are also associated with age.Future studies of hearing loss in migrantworkers should explore such exposure issues ingreater detail.
Despite a high prevalence of reported expo-sures to noise sources, only 14% of the subjectsreported using hearing protection. Other stud-
ies of Hispanic workers have shown thatperceived self-efficacy and barriers to hearingprotection use are important predictors of ac-tual use.20 It was encouraging that workers inthe commercial nursery, with higher preva-lence of reported noise exposures, were morelikely to wear hearing protection. There ap-pears, however, to be room for further im-provements in training and enforcement ofhearing protector use in migrant agriculturalworker populations.
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RECEIVED: 10/11/2004REVISED: 03/08/2005
ACCEPTED: 06/21/2005
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