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Farmers experience hearing loss earlier and more often than the general public, studies show. And a new University of Iowa study showed that hearing loss places farmers at greater risk of injury in the workplace.

An estimated 75 percent of all farmers suffer from some level of hearing loss, compared with one in ten of the general public, according to the New York Center for Agricultural Medicine and Health.

Iowa State University Extension reports that 70 percent of farmers given a routine hearing test had below normal hearing, with 30 percent warranting a hearing aid. Farmers 50 years and older have greater hearing loss than other people of the same age but in different occupations.

But it’s not just older farmers who lose their hearing. Research by the Universities of Missouri, Wisconsin, Nebraska, and Iowa found that as many as a quarter of farmers have a communication handicap from hearing loss by age 30, and high school and college students from farming communities have less hearing ability than their peers.

Iowa study

In the new hearing loss-workplace injury study, Dr. Nancy Sprince, professor of occupational and environmental health at the University of Iowa, found a correlation between hearing loss in farmers and occupational injury. Farmers who had difficulty hearing normal conversation were 80 percent more likely to suffer an injury related to a fall on the farm. Those wearing hearing aids were more than twice as likely to be injured on the job and four times more likely to suffer a machinery-related injury than a person with normal hearing.

Other risk factors were working 50 hours or more a week on a farm, having large livestock on the farm, and taking medications regularly, Sprince said in a news release.

Study participants were part of the Agricultural Health Study, which includes 30,000 Iowa farmers. For the Iowa study, the case group comprised 431 farmers who had been injured on the job in the past year. The control group, with no injuries, numbered 473.

With tractors and sprayers, all-terrain vehicles, hand-held machines like chain saws, and other tools, farms are noisy environments.

Compounding the problem, Sprince noted, is that hearing protection is not always worn. Hearing aids help restore some of the farmers’ auditory abilities, but the best situation is for them to retain as much natural hearing ability as possible.

"In many cases, it is difficult to engineer out noise on the farm, so farmers have to rely on personal protective equipment," Sprince stated. "And too often, they are unaware of the tasks that require hearing protection."

Exposure

According to Kansas State University Cooperative Extension, doubling the distance between the source of the sound and the listener reduces the sound level to one-fourth of what it was at the listener’s original position.

If you must shout to be heard three feet away, the noise level is high enough to cause damage.

The louder the noise, the shorter the exposure time needed for hearing loss to occur.

Though noise exposure limits are regulated by state or federal agencies, self-employed farmers would be wise to pay attention to noise exposure levels for their own protection, according to Sprince. National Institute of Occupational Safety and Health has identified a safe noise level to be less than 85 decibels on an 8-hour, time-weighted average.

For those driving a tractor with an acoustically-insulated cab and performing typical fieldwork, the noise inside the cab is generally around 85 decibels. But if the cab is removed, tractor noise can be around 100 decibels, and safe exposure times are greatly reduced.

Jill Shelley and Michael Dennis of Kansas State University wrote an article entitled "Protect Your Hearing," which can be found on the National Ag Safety Database Web site. They explain that the ears provide two warning signals that noise is too loud: temporary threshold deafness (temporary deafness) and ringing in the ear, known as tinnitus. The first symptom of a permanent hearing loss is usually the inability to hear high-pitched sounds, some of which are important in understanding speech.

Two types of hearing protection are ear muffs and ear plugs. Muffs are generally more effective, but fitting is more difficult if glasses are worn and some of the plastic pieces next to the head can lose their elasticity from repeated drenching from perspiration. Ear plugs fitted by a physician or trained personnel are more effective. However, temporary or disposable inserts are also effective if care is taken in their fitting. Look for a noise-reduction rating of 25 or greater, which is the number of decibels that the hearing protection device will reduce for the wearer.

By half

Be aware that the manufacturer’s rating is developed under perfect conditions, with the wearer receiving fitting instructions. Under actual workplace conditions, safety specialists suggest that the hearing device will provide about half of the manufacturer’s rating. A device with a noise reduction rating of 30, will reduce the decibel level by about 15, which may be enough to bring tractor noise down to acceptable levels. In some instances, both ear muffs and ear plugs may be used to reduce noise to safe levels.

Those continually exposed to loud noises should have periodic hearing tests. If hearing loss is detected, steps should be taken to reduce exposure.

The National Ag Safety Database is a Web-based repository of health, safety, and injury prevention materials for the agricultural community. For more information about hearing loss and other farm safety topics, visit the Web site www.cdc.gov/nasd.