Acoustic Injuries in Agriculture 35

35

Acoustic Injuries in Agriculture

J

E. L

D

K. M

Key words: noise hazards, hearing loss, hearing tests, equipment noise

reduction

It is paradoxical that the quiet rural farm is also the same environment where periods of high intensity noise may result in hearing loss among agricultural workers. The U.S. National Institute of Occupational Safety and Health (NIOSH) estimates that noise is a significant occupational health hazard for 84% of the agricultural workforce. Since health and safety professionals may encounter agricultural workers with concerns about hearing loss prevention, hearing loss identification and hearing rehabilitation, this chapter was written to inform the reader about these issues as they relate to farming (1).

Noise Hazards

Typically, sound becomes hazardous to the inner ear when the intensity and duration of the exposure exceed a particular criterion level. In industry, the levels of 85 to 90 dBA are considered hazardous to workers exposed to noise for an 8-hour work. However, high level sounds (>100 dBA) are especially hazardous even for brief periods of time (< 15 minutes). Agricultural work- ers may find themselves at an increased risk for noise-induced hearing loss (NIHL) during the long hours of equipment operation at certain times of the year due to seasonal demands on work schedules (2,3).

Farmers operate a variety of equipment capable of producing hazardous sound levels. Table 35.1 is compiled from research studies and investigations and lists most of the common noise sources and levels (in dBA) reported in the farm environment (4–7). Farmers rank ordered the loudest noise sources on the farm as follows: tractors, grain dryers, combines, chainsaws, grain grinding, and animals. One agricultural noise source rarely catalogued but fre- quently associated with farming is firearm noise. The majority (84% to 90%) of farmers do report having firearm noise exposures. These peak sound pres- sure levels (SPL) can range from 143 dB to 173 dB depending on the gauge or

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caliber fired. These findings indicate that in addition to the typical farm noises, firearm noise is a component of most farmers’ noise exposure profile.

In addition, farmers (58%) commonly reported high levels of noise exposures outside the farm. These additional exposures include noise from non-agricul- tural employment settings as well as hobbies or entertainment (4–9).

Hearing Test Results

Numerous studies documenting NIHL in the farming population have been published. The NIHL is characteristically bilateral, sensory-neural (due to inner ear/cochlear damage) in nature with a greater degree of hearing loss in the higher frequencies than the lower test frequencies. It is common to find a notched audiometric configuration (noise notch) with greater loss at 3000, 4000, or 6000 Hz than at the adjacent frequencies. Figure 35.1 shows the hearing sensitivity of 2,695 males from a large farming community, by age decade, which were obtained in a 10-year cross-sectional study conducted in the Midwestern United States. The majority of the farmers came from Illinois, Iowa, and Indiana, but 34 states and 4 foreign countries were repre- sented. The characteristic notched configuration disappears from the audio- metric profile for most farmers at age 70 years and beyond as the hearing loss at 8000 Hz progresses. This is attributed to the presumed accelerated aging effect (presbycusis) in the later years. Between the ages of 20 to 60 years, farmers show dramatically more high frequency hearing loss than would be expected for their non-noise exposed peers after subtracting an age correction factor for each frequency as identified by OSHA 29CFR 1910.95 or ISO 1990: B.5. Unfortunately, the ability to differentiate the magnitude of NIHL from farm noise versus all other sources of noise exposure is more complex (2,4,9,10–16).

TABLE35.1. Typical noise sources and sound levels in farming.

Noise source Noise levels (dBA)

Tractor 74–112

Grain dryer 81–102

Combine 80–105

Chainsaw 77–120

Grain grinding 93–97

Pig squeals 85–115

One-row beet puller 94

Orchard sprayer 85–106

Pneumatic conveyor 100

Riding mower 79–89

Garden tractor 88–94

Shotguns and rifles 143–173 (Peak)

Crop dusting aircraft 83–116

Sources: Data from Lankford, Zurales et al. (6), Dobie (5), and Lankford et al. (7).

Another intriguing characteristic of the NIHL of farmers is an apparent

difference in the magnitude of the loss at the higher frequencies (2000 to

8000 Hz) between ears. On average, there is about 3 dB more hearing loss

noted for the left ear than for the right ear. Three explanations have been

offered for this observed difference. First, is the left ear position relative to

the noise source. For example, on a tractor without a cab, it is not unusual

for the farmer to position the left ear forward while looking backward to

monitor the pulled implement (plow, disc, rake, hoe, etc.). This places the

left ear in a more direct exposure path to the noise from the engine. In addi-

tion, cab doors (until recently) on tractors and combines have been tradi-

tionally on the left side and provide a potential avenue for sound leakage

from that direction. Several equipment manufacturers are now producing

tractors with doors on both sides of their equipment. Second, the ear dif-

ference may be due to the high incidence (90 % +) of firearm noise exposure

among this population. Because most individuals are right handed and long

guns (rifles and shotguns) place the left ear in a position facing the muzzle

blast, the left ear is at greater risk than the right ear, which may be partially

shielded due to a head-shadow effect from the blast. Lastly, the third reason

might relate to a possible anatomical/physiological difference which may make one ear more sensitive and/or vulnerable to damage than the other (8).

Women and adolescents engaged in farming activities are also at risk for NIHL. In general, the audiometric configuration and progression of the hearing loss is similar to that of males, but the magnitude is significantly reduced. Theiler reported that 75% of females in her study reported high- intensity noise exposure from farm machinery, some beginning as young as 10 years of age. It was also noted that women may be receiving increased exposures due to greater involvement in the noisy work on the modern farm.

Early reports of NIHL among children and adolescents on the farm indicate that noise notches can be seen in this younger population as well. The dis- tinction between home and work noise exposures can be ambiguous for the rural farm family. It is not uncommon for young children to accompany their parents on tractors or for adolescents, especially males, to begin operating large noisy machinery at a young age (17,18).

Equipment Noise Reduction

Noise control or the elimination of hazardous noise from the farm environ- ment is the ideal solution for the prevention of NIHL. To their credit, many equipment manufacturers have incorporated quiet design specifications in recent years, some in response to the need for regulatory compliance with national or international standards such as the European Union Directive 98/37/EC. For example, cabs on farm equipment are both a source of comfort and safety for the farmer. Essentially, all contemporary combines have cabs though many older and smaller tractors do not. An important cab enclosure benefit is the exclusion of hazardous noise. Most comparative sound level assessments demonstrate a 20 dB reduction in noise levels for equipment with original cabs, which are well maintained and kept in good working condition.

However, for older equipment many small farm operations or those in more underdeveloped countries, economics may preclude the upgrade to newer and quieter equipment. Consequently, personal hearing protection (earplugs/ear- muffs) is the realistic alternative for many farmers (19,20).

Personal Hearing Protection

The majority of male farmers do not report using hearing protection on a

regular basis. Initial survey results from 1989 indicate only 30% reported

using hearing protection devices (HPDs). This percentage rose to 44% when

resampled 10 years later. Only 24.6% of high school students reportedly used

hearing protection in an agricultural safety intervention study. However, in

the Theiler study, a fairly high percentage of women (78%) were using HPD’s

in noisy environments. Engstrand, investigated the usage of hearing protec-

tors and whether they were reducing the amount of hearing loss among male farmers. Fifty farmers who consistently used HPD’s were paired with a group of non-users; the results showed that significantly less hearing loss occurred for farmers who had worn protectors. Since firearm noise exposure is quite pervasive in the farming population and the exposure levels are so high, HPDs should be utilized for this activity as well. There are specialized HPDs designed for firearm noise sources that afford protection while maintaining adequate communication during shooting activities. These devices include passive earmuffs, electronic earmuffs, and both passive and electronic custom earplugs. Although the costs for the electronic and custom protectors are rel- atively high, the benefits should be considered priceless (21,22).

For some farmers, the issue may not be whether to wear hearing protection but rather which type of hearing protector to choose. With over 400 varieties of hearing protection databased on the electronic NIOSH Hearing Protector Device Compendium, the need for technical and practical guidance for proper selection is evident. In general, the laboratory-based Noise Reduction Rating (NRR) is a poor guide to real-world protection. Ideally, the best hear- ing protector is the one the individual will wear routinely because it is com- fortable, effective, and compatible with working conditions as well as communication demands (23).

Intervention Strategies

Farmers are often located in rural, isolated environments. Therefore their access to information and services concerning hearing loss prevention is geo- graphically restricted. One approach that has proven successful in reaching farm families is to make information and services available at state and county fairs, regional farm shows, and health screenings sponsored by farm agencies, medical clinics, universities, and hospitals.

One successful U.S. outreach program was held at the Farm Progress Show over a 10-year period. This show attracted over 250,000 annually dur- ing the 3-day event. The primary attraction for farmers included the equip- ment manufacturers, seed companies, chemical producers, university agricultural school displays, and various demonstration plots. However, coordinated efforts by health and safety professionals allowed for respira- tory, blood pressure, cholesterol, vision, skin, and hearing assessments.

Mobile audiometric testing facilities made the hearing assessments per-

sonal, convenient, efficient, and valid. It also afforded the opportunity to

distribute sample hearing protectors, hearing loss prevention literature, and

hearing test results. Farm family members were immediately counseled

regarding their hearing status and advised of any referrals for medical

and/or rehabilitative hearing services. One additional outcome of this par-

ticular intervention program was the enhanced usage of hearing protectors

as documented by Pytko (24). When male participants were surveyed one

year after the farm show intervention program, the utilization of HPDs had increased from 37% to 73% (6,24).

Another intervention approach has been used in Canada. Hearing loss pre- vention literature was mailed to farmers in rural areas in Saskatchewan. For those who inquired, hearing tests were subsequently provided at a local com- munity site. During the hearing test appointments, health professionals were able to provide additional information about noise exposure, hearing loss prevention strategies, and the proper use of hearing protectors (25).

Two other recent approaches designed to disseminate hearing loss preven- tion information include the farm safety camp and the Internet. Farm safety camps are designed to reach farm youth. Hearing safety can be one of the many sessions offered during these interactive camps, and it can be formatted into an entertaining, game activity. Certainly the Internet affords the farming community with new and ever-changing opportunities to access educational materials and health information. As with most internet topics, the reliabil- ity, validity, and continuity of these hearing loss prevention materials are var- ied. The National Hearing Conservation Association (NHCA) website (www.hearingconservation.org) offers professional educational opportunities and a variety of resources for hearing loss prevention efforts (26).

Recommendations

It is apparent and not surprising that NIHL is a very large part of the per- sonal lives of most farmers. Therefore, annual hearing tests should begin in the rural farming communities at 10 years of age. Hearing should be moni- tored on an annual basis throughout a farmworker’s life. It is recommended that educational programs regarding hearing loss prevention should start in elementary school and continue through the 12

grade. It is also suggested that audiologists provide hearing tests at farm shows and other public agri- cultural events as a way of identifying individuals with existing hearing loss or those with a potential risk for NIHL.

Free earplug samples and hearing protection literature should be included in most intervention programs targeting farmers. This introduces the farm family to HPDs and allows them to use a protector the next time they are exposed to high intensity noise. It is important that the farmers be informed of local, regional or mail-order resources for purchasing additional hearing protection once the outreach effort is completed.

A large percentage of farmers have substantial NIHL hearing loss and will

experience the personal and social consequences of the impairment. Conse-

quently, it is important that any outreach effort include strategies to motivate

farmers to accept their hearing loss and seek rehabilitative help, including the

purchase of hearing aids. Local medical and audiological professional

resources should be identified in advance of the intervention effort.

Female members of the farm family appear to have the most influence on the acquisition and utilization of health services for their spouses and children.

Therefore, hearing loss prevention and hearing rehabilitation education should directly involve the woman in the farm family. She may be in the best position to encourage family members to practice better health protective behaviors, such as the regular and proper use of hearing protectors. Encouragement and praise appear to be needed to reinforce healthful behaviors (27).

Ultimately, each of us has a potential role to play in the effort to identify hazardous agricultural sound, decrease individual noise exposures, and min- imize the long-term personal, social, and financial impact of hearing-impair- ment on farm workers. Every farmer, regardless of age, deserves the opportunity to appreciate the rural farm soundscape, filled with early morn- ing bird songs, wheat beards brushing in an afternoon breeze, and cricket chirps signaling the end of a long day in the field.

Acknowledgment. Portions of this chapter were published in Advance for Audiologists 4(5): 34–37 and are reprinted here with permission of Merion

Publications Inc.

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