Research with carpenters probes misconceptions about the nature of hearing disorders, reasons for non-compliance with hearing protection and recommendations.
Researchers have uncovered several misconceptions about hearing loss in a study of carpenters, Carol Merry Stephenson, a researcher with the National Institute for Occupational Safety and Health, said April 3.
Although there is an acknowledgment that working on a noisy construction site will result in some work-related hearing loss, workers believe that using hearing aids will restore hearing in the same way that glasses can restore vision, Stephenson said.
That is wrong, she said.
Even the best and most expensive digital hearing aids cannot restore hearing lost in the higher decibel ranges, which is the level that is damaged first by exposure to loud noise.
A hearing aid "only makes the fuzzy sounds louder," she said.
In several years of interviews and training sessions with carpenters, Stephenson also discovered that many had more fear of tinnitus--a persistent ringing in the ears--than of mild hearing loss.
This fear of tinnitus "was absolutely a big surprise. We weren't even looking for it," she said.
Stephenson found that using the testimony of a fellow worker who has tinnitus was effective in impressing on workers the need to use hearing protection on the job, she said.
Although tinnitus has other causes, including the use of certain medications, ear or sinus infections, and head and neck trauma, up to 90 percent of all tinnitus patients have some level of noise-induced hearing loss, according to the American Tinnitus Association.
Hearing loss is the second most reported occupational illness for American workers after musculoskeletal disorders. Approximately 30 million workers are exposed to hazardous noise on the job and an additional nine million are at risk for hearing loss from other agents such as solvents and metals, according to NIOSH.
But while hard hats and safety glasses have become accepted protections used by construction workers, the same is not true for ear plugs or other hearing protectors.
"It's so rare to go on a construction site where people are actually wearing hearing protection," she said. When they do find a worker using hearing protection it is often because the individual is concerned about being able to participate in an outside activity such as working as a musician, she said.
The Occupational Safety and Health Administration requires hearing conservation programs and engineering controls when workplace exposures exceed certain levels, but research shows that few companies make comprehensive efforts in this area.
Surveys have found that construction workers do know their hearing is at risk.
However, many workers believed that because hearing loss occurs slowly they wouldn't notice it until they were ready to retire. Workers also told Stephenson that they are more concerned about the more immediate and apparent hazards of working on a construction site than about losing their hearing someday.
One way to demonstrate to workers that hearing loss is not a problem that they can wait to worry about in 20 years, Stephenson asks them to monitor their own hearing by using a simple test. She tells them to set the volume on the radio in the morning on the way to the job site and notice what happens after a day of work.
"If you find yourself turning it up on the way home, you've probably suffered some hearing loss, even if only the temporary kind," she said.
Also, many believe that hearing protection is cumbersome or even dangerous, if it blocks the sounds of voices or of back-up alarms on construction equipment.
Complexities of Choosing Protection
There is some validity to that concern since choosing the right hearing protection is complex, Stephenson said.
"If you have normal hearing, hearing protectors will block out miscellaneous noise and you'll hear voices and back-up," she said.
But workers who already have some hearing loss can have trouble understanding speech and hearing back-up beeps if they are wearing hearing protection. In this case, the solution may be to use a less-strong protection device.
"Now their ears are still protected and they're not at risk," she said.
Another misconception that crops up among the employers who are concerned about hearing loss is that bigger is better. They purchase the strongest hearing protection and mandate its use, even if that may not be the right answer for all workers.
"What we're trying to teach people, is look at the task you're going to do."
Stephenson's work began in 1993 when NIOSH was called out to conduct a health hazard evaluation with carpenters, Stephenson said.
"We found this rampant hearing loss," she said.
Their studies found that 25 year-old carpenters frequently have the hearing of a non-noise exposed worker at age 50.
What was surprising about that was that when the amount of noise to which the carpenters were exposed was measured with dosimeters, it did not equate with the type of damage being measured. The damage reflected exposure to higher noise levels, so they are postulating that perhaps the impulsive type noise to which carpenters are exposed may somehow be more damaging than previously suspected.
After the health hazard evaluation, NIOSH worked with the United Brotherhood of Carpenters to develop a research plan and educational materials, she said.
Over the next several years, NIOSH researchers will follow 300 apprentice carpenters with audiograms to monitor the status of their hearing. The carpenters will also be participating in different types of training to determine which type of training is most effective, she said.
"We're trying to focus more attention on the engineering controls side of the house," she said.
This is needed because studies find that even safety professionals don't wear their hearing protection as much as they should when in a noisy situation. This is another reason that efforts must be directed towards engineering out some of the noise, whether that is through designing quieter tools or blocking sounds with simple tools such as putting a wooden sound barrier around a noisy piece of equipment like a gasoline-powered generator.
Engineer It Out
Stephenson presented some of the research to a recent meeting of the Advisory Committee on Construction Safety and Health, which advises the Occupational Safety and Health Administration. Several members stressed the need for NIOSH to focus on ways to engineer out the noise rather than rely too heavily on workers using hearing protection.
Stephenson said the researchers follow the NIOSH hierarchy of controls for any workplace hazard which calls for first attempting to remove the hazard or removing the worker before relying on worker protections.
"I really do look at hearing protection as a stopgap measure until we engineer out the noise," she said.
New NIOSH Projects
NIOSH is beginning five new projects this year intended to fill research gaps about noise-induced hearing loss, Stephenson said. These projects, involving the NIOSH laboratories in Cincinnati, Pittsburgh and Spokane, include:
- an investigation of databases that are available related to hearing loss;
- definition and assessment of engineering noise controls;
- outreach effort to small construction companies and mining operations via the World Wide Web;
- accommodation of noise-exposed, hearing impaired workers; and
- noise-sampling strategies and exposure response models.