Hearing Loss in Agricultural Workers
It is somewhat paradoxical that a peaceful rural farm can be the same environment
where periods of highintensity noise may result in hearing loss among agricultural
workers. Our 10year study of farmers shows that many audiologists see workers
who have varying concerns about hearing loss prevention and identification.
After a decade of studying the farming population and analyzing the results of audiometric
and survey data, it is apparent, and not surprising, that noise induced hearing
loss (NIHL) is a very large part of the personal lives of most farmers. Because
of this, we suggest that annual hearing tests should begin in rural farming communities
at the age of 10 and be mandated throughout the person´s life. In addition, hearing
protection must be made available to all those in the farming community, and educational
programs should motivate farmers to wear hearing protective devices (HPDs) during
exposure to all highintensity noises.
More than 5,000 hearing evaluations were conducted over a 10-year period. Of those,
4,170 (2,695 males and 1,475 females) were analyzed and summarized. Farmers came
from 34 states and four foreign countries, with the majority residing in Illinois,
Indiana and Iowa. The data reflect an age range of 7-89, with an average of 54 years.
The increased spread of hearing loss from high frequencies through low frequencies
with age and noise exposure is common for this population. Hearing loss of farmers
is very characteristic of a sensorineural, bilateral sloping configuration resulting
from both noise and aging. When age group data were compared to the 1983 hearing
sensitivity values of the U.S. Occupational Safety and Health Administration (OSHA),
all farmer populations, ages 20-60, showed dramatically more hearing loss than the
comparison group. This also was true when the data were compared to the International
Organization for Standardization (ISO) 1990 data.
Analysis of the audiometric results showed approximately a 3 dB difference between
ears of males, with the right ear better than the left. Although relatively small,
this difference in hearing ability is mentioned consistently in the farming literature.
Most of the explanations for this phenomenon relate to more noise arriving at the
left ear than the right. This may happen on a tractor when the farmer looks back
over his right shoulder or due to the doorway being on the left side of a tractor
or combine with a cab. Some have suggested there may be physiological reasons due
to an ear dominance effect.
The primary vehicle for providing information and services to and gathering data
from the farming community for the purposes of this study was the annual Farm Progress
Show, which rotates among Illinois, Indiana and Iowa. The 3day show in late
September attracts more than 250,000 visitors each year.
Sources of Noise
A summary of answers to the 10 survey questions provided a profile of the average
farmer. It was not surprising that 92% of farmers reported being exposed to very
loud noise while involved in farming activities. When asked to rank the loudest
noise sources on the farm, they listed tractors, grain dryers, combines, chain saws,
grain grinding and animals (see Table 1).
In addition, 58% reported exposure to noise outside the farming environment. Firearm
noise proved to be one of the most common sources that may reduce hearing ability
in farmers, as 84% indicated this type of exposure. It may be another reason for
the differential in hearing ability between ears, with more muzzle blast from a
rifle or shotgun getting to the left ear of a right-handed shooter.
Fortunately, hearing protection usage did increase over the 10 years that the study
was conducted, from 30% to 44%; but many farmers are not using HPDs on a regular
basis.
Seventyeight percent of males believed they had a hearing loss, and 81% partially
attributed the loss to noise on the farm. When asked if they would wear a hearing
aid if they knew they had a significant hearing loss, 91% of farmers affirmed they
would; yet only 4% were wearing hearing aids.
Fortythree percent had never had a hearing test. This becomes a challenge for
the audiologist to determine ways to motivate the farmer to obtain hearing tests
and for those with hearing loss to purchase hearing aids.
Hearing test results across the audiometric frequency range for all male subjects
yielded a consistent pattern for both ears that progressed with age and showed significant
decreases at 3000, 4000, 6000 and 8000 Hz (see Figure 1).
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For the decade group aged 10 to 19 years, a 6000 Hz notch is the first apparent
indication of noise-induced hearing loss. The progression of that notch and inclusion
of frequencies such as 4000, 3000 and 2000 Hz is apparent from ages 1070 and
older.
Presence of Presbycusis
The rapid decrease of hearing sensitivity at 8000 Hz tends to obscure the notch
configuration and probably reflects the presence of presbycusis for that higher
frequency. Hearing loss at 4000 Hz seems to progress rapidly up through age 60.
This is true for 3000 Hz as well. At 2000 Hz the hearing loss begins and progresses
more rapidly from age 40 through 89. For 500 Hz the hearing loss appears to begin
at approximately 60 years and increase through age 89.
Additional research on farmers has contributed to the body of knowledge on this
population. A survey was conducted one year after the first hearing conservation
study, and results of that survey indicated a substantial increase in the use of
HPDs from 37% to 73% among those who had been evaluated and later responded
to the questionnaire.
HPD Use Studied
Another study investigated use of the devices and whether they were reducing the
amount of hearing loss among farmers. Fifty individuals who consistently used HPDs
were paired with a group of non-users, and the results showed that significantly
less hearing loss occurred among farmers who had worn protectors.
One project examined the hearing sensitivity of females in the farming community.
Results indicated that hearing loss due to noise does occur among some women and
may start as early as 10 years of age.
The noise notch at 6000 Hz progressed through age 60, and hearing loss at the higher
frequencies continued, which for some may relate more to aging than to noise exposure.
Seventyfive percent of female respondents indicated they had been exposed to
highintensity noise from farm machinery; and there was a trend noted that the
duration of noise exposure was increasing. This may reflect the increased involvement
of women in noisy, workrelated activities on the farm. However, a fairly good
percentage of women (78%) were using HPDs in noisy environments.
An additional finding regarding women noted that they often influence the acquisition
and utilization of health services for their spouses and children and could encourage
family members to practice various health protective behaviors, such as the use
of hearing protectors.
Agricultural Pilots
One last study relating to the agricultural workers concerned noise levels for crop
dusters, or agricultural aerial spraying service personnel. This investigation tested
the hearing of 12 pilots, six from Illinois and six from Colorado. Results indicated
substantially high levels of noise for this population and greater hearing loss
among the pilots than a non-exposed group. The findings suggest that agri-pilots
should be included in a hearing conservation program that includes annual audiometry
and the utilization of HPDs.
In accordance with current literature, it is recommended that educational programs
for hearing loss prevention start in elementary school and continue through the
12th grade. Hearing tests should be provided by audiologists at farm shows and other
farm events as a way of identifying individuals with potential hearing loss or those
at risk for noiseinduced hearing impairment. In addition, hearing protectors
can decrease the amount of hearing loss due to noise and therefore reduce the amount
of communicative difficulties in the everyday lives of farmers.
Since there is a large percentage of farmers with substantial hearing loss, ways
of motivating farmers to accept their hearing loss and seek rehabilitative help
are needed. Efforts should be made to disseminate information about the prevention,
assessment and rehabilitation of hearing loss to the primary health care manager
of the family.
