In many industries, it’s common knowledge that long-time workers are hard of hearing. Some jobs involve higher exposures to noise and therefore are more damaging to workers’ hearing. Two University of Washington research teams have spent the past five years studying which industries, trades, and tasks are most harmful.

Workers in the metal fabrication industry, such as this machinist monitoring a lathe, face exposure to damaging levels of high frequency noise. Sue Swan

In addition to publishing their findings in academic journals, the researchers have developed booklets that will take their recommendations onto the shop floor or construction site where workers and managers can use them. This is part of the department’s mandate to work with employers and workers in Washington state to prevent industrial and occupational disease.

Earlier studies by Bill Daniell, an associate professor in occupational and environmental medicine, showed a sharp rise in the number of hearing loss claims to the state’s workers’ compen-sation system (see 1997–99 biennial report). Various industries have approached our department for help in reducing these costs and preserving workers’ hearing.

There are several types of occupational hearing loss. Acute traumatic loss comes from a single event such as an explosion, sudden pressure change, or physical trauma. Short-term, or temporary, hearing loss can occur after brief exposures to very high levels of noise (such as a loud concert) and goes away after a recovery period of hours to days. Chronic occupational hearing loss—which is permanent and irreversible—is usually caused by long-term, repeated exposure to loud noise, but has also been linked to chemical exposure. Metals such as lead, organic mercury, and manganese, and organic solvents such as carbon disulfide, trichloroethylene, styrene, and toluene have been implicated.

Many people imagine everything would go quiet if they lost their hearing. Unfortunately, one of the most annoying things about occupational hearing loss is that it is often accompanied by tinnitus, or ringing in the ears. Hearing loss can cause social isolation. Employees with hearing loss are at risk if they can’t hear warning signals. They also may find it hard to communicate with coworkers.

Daniell’s study found that chronic occupational hearing loss costs Washington employers more than $50 million a year through workers’ compensation claims, and the number of claims increased 12-fold between 1984 and 1998.

WASHINGTON INDUSTRY

Daniell first became interested in occupational hearing loss when he noticed the abrupt upturn in workers’ compensation claims. Over the past five years, his team has studied 10 industries, starting with a pilot project conducted in foundries.

The research team (Milton Eng, Robert Leo, Sebrina Somers, Sue Swan, and David Yu) selected eight industries with high rates of hearing loss claims. The team evaluated noise exposures and hearing conservation programs at seven to ten work sites in each industry. Researchers interviewed 76 managers and 1557 employees, measured full-shift noise exposures of 983 employees using personal dosimeters, and observed hearing protector use by 876 workers.

Nearly every workplace was noisy enough to require a hearing conservation program, yet only half of observed employees used hearing protection when they should have. Interviews showed that workers are more aware and more likely to use hearing protection when management is involved in the program.

Researchers reviewed hearing test records and found that in one industry, road construction, nearly 40% of workers had hearing loss that was moderately severe or worse.

CONSTRUCTION WORK

“We have amassed and analyzed a huge database on noise levels in 11 construction trades,” said Noah Seixas, professor of industrial hygiene and safety. “Now we can put those findings to work for the workers.”

Sebrina Somers

His research team, which included Susan Brower, Bryan Goldman, Rick Neitzel, Sebrina Somers, and a number of graduate students, found that all trades and most tasks—even eating lunch or cleaning up—often exposed workers to enough noise to warrant hearing protection. Yet workers reported using hearing protection—earplugs or muffs—less than half of the time they were exposed at levels that could be damaging.

Workers in the noisiest trades were operating engineers and cement masons; in the quietest, sheet metal workers and insulation workers. Operating engineers had the highest use of hearing protection and cement masons the lowest.

WHY THE LOW USE?

Both studies found low usage of hearing protection in some noisy environments. But why?

Previous researchers have found that construction workers’ biggest fear was that they wouldn’t hear warning shouts or signals, such as the back-up beep of a truck. They were more concerned about the imme-diate dangers of construction work than about the long-term threat of hearing loss. They also thought earmuffs or plugs would be uncomfortable to wear all day, and they feared looking foolish to coworkers.

Seixas has become interested in behavioral research to better understand why knowledge doesn’t always translate into safe behavior. By understanding these barriers, he hopes to develop a more effective prevention program for construction workers.

IS IT FROM WORK?

There is no question that construction workers are exposed to harmful levels of noise at work, but what about their off-the-job activities, such as playing loud music or riding motorcycles?

Seixas’ team followed construction workers to measure their off-the-job noise exposures, then compared these levels to their noise exposure at work. The noise levels associated with off-the-job activities were almost always much lower than levels experienced during construction work, meaning that non-work activities present much less risk of hearing damage than work activities for most people.

RECOMMENDATIONS

• Earmuffs or plugs with a noise reduction rating of 14 to 20 decibels often offer enough protection for many workers, yet let warning sounds come through. Unfortunately, employers often provide hearing protectors with the highest protection available (33 decibels), which may prevent workers from being able to communicate and hear important sounds.
• The employer should provide at least two–preferably more—types of hearing protectors free to workers who are exposed to high noise levels.
• Individual fitting and training on hearing protectors should be part of a company’s hearing loss prevention program. It should be done every year or two.
• Employers with a hearing loss prevention program are required to provide annual training, which should be supplemented with training throughout the year.
• Employers should make sure employees can identify areas and tasks where hearing protection is required.
• Supervisors and managers should serve as role models, wearing hearing protectors in noisy areas, even on short visits.
  

Carpenters, operating engineers, and masonry restoration workers have high noise exposures as do all trades in the construction industry. Nicole Irby