Understanding Noise-Induced Hearing Loss

Hearing loss has long been thought to be an unpleasant but inevitable side effect of aging. And aging is indeed the most common cause of hearing loss. But within the past year, two reports from the Centers for Disease Control and Prevention (CDC) have documented the startling degree to which noise—both in the workplace and elsewhere in our daily lives—contributes to hearing damage.

Findings published in the CDC's Feb. 7, 2017 Morbidity and Mortality Weekly Report (MMWR) demonstrated that 23.5 percent of people aged 20-69 who reported having good or excellent hearing had some degree of hearing loss, as measured by the presence of an audiometric notch (either unilateral or bilateral). While people exposed to loud noises at work were twice as likely to have hearing loss—nearly one-third of them had either a bilateral or unilateral notch—19.9 percent of those studied who reported no exposure to loud or very loud noise at work also had some degree of hearing loss.

Daily noise exposure

It's important to note that this report was based on data from the 2011–2012 National Health and Nutrition Examination Survey (NHANES), said Anne Schuchat, MD, the CDC's acting director. “The NHANES survey allows us to not only rely on people's symptoms, or what they're aware of, but on documented testing. It's surprising that a sizeable population of young adults already had noise-induced hearing damage, and that they didn't work in noisy workplaces. Our emphasis in the past has largely been on reducing worker exposure to noise, but community or home noises are probably causing a lot of damage that is not evident.”

Although the new study did not pinpoint where participants were getting their noise exposure, Schuchat cited some examples of common community sources of hearing damage such as:

  • two hours of exposure to a leaf blower at 90 decibels can cause substantial hearing damage with repeated exposures over time;
  • 14 minutes at a sporting event with a noise level of 100 decibels can cause damage with repeated exposure; and
  • two minutes at a rock concert with levels of 110 decibels can cause damage, again with repeated exposure.

The new CDC report comes less than a year after another CDC report, published in MMWR April 22, 2016, which assessed hearing impairment in the workplace. Investigators compared the prevalence of hearing impairment within nine U.S. industry sectors using the audiograms of 1,413,789 noise-exposed workers from CDC's National Institute for Occupational Safety and Health (NIOSH) Occupational Hearing Loss Surveillance Project. They estimated six levels of hearing impairment and calculated the impact that this impairment had on a person's quality of life as measured in annual disability-adjusted life years (DALYs).

Work-related hearing impairment was found in all of the job sectors examined, although some areas were at particularly high risk. The mining sector had the highest prevalence of workers with any impairment (17%) and with moderate or worse impairment (3%), followed by construction (any impairment = 16%, moderate or worse impairment = 3%), and manufacturing (14% and 2%). Public safety, which includes police protection, fire protection, corrections, and ambulance services, had the lowest prevalence of workers with any impairment (7%).

Across all industries, 2.53 healthy years were lost annually for every 1,000 noise-exposed workers—and most of this loss was traceable to mild hearing impairment, which accounted for 52 percent of all healthy years lost, while moderate impairment accounted for 27 percent.

The good news is that noise levels in business sectors like manufacturing do seem to be going down, said exposure scientist Richard Neitzel, PhD, associate chair of environmental health sciences at the University of Michigan School of Public Health. “But newer job sectors present a whole new set of unknowns when it comes to noise exposure. What about the barista who's next to the coffee grinder all day? And musicians and performers are working with stronger and more powerful systems, creating levels of sound that weren't possible 20 years ago. Meanwhile, people are carrying around devices they can listen to music on for 18 hours a day, right in their ears, at very high volume. It's too early to know what the effects on hearing will be, but we need to err on the side of caution with this generation that is experiencing unprecedented exposures to noise.”