Preventing Occupational Hearing Loss

So, you’ve got your ear plugs and your noise hazard signs in place, but could there be other things in your workplace affecting your employees’ hearing? (And no, we’re not talking about headphones.)

Chemicals that affect the ears (called ototoxicants) can cause hearing loss regardless of noise exposure, and like noise exposure, it can be permanent.

Effects on Hearing

Noise damages cells in your cochlea – that’s the shell-shaped part of your inner ear – and eventually kills them, making things sound muffled. Ototoxicants can affect nerve cells that transmit sounds from your ears to your brain, making it hard to separate sounds, such as speech from background noise. They can also affect your ability to detect time gaps between sounds or detect where sounds are coming from.

Noise and ototoxicants work synergistically – they can produce more profound hearing loss together than individually. This can happen even with chemical and noise exposures below their respective OSHA Permissible Exposure Limits (PELs).

What are some common ototoxic chemicals?

Always check a chemical’s safety data sheet (SDS) for toxicology information (Section 11). Look for words like “neurotoxin,” “ototoxin” or it may indicate that the nervous system is a target organ for the chemical. If you don’t have an up-to-date (2012 or newer) SDS for your chemicals, contact the manufacturer.

Here are some common ototoxic chemicals, but there are many more out there.

Substance Class Chemicals


  • Antibiotics such as streptomycin, gentamycin, or tetracycline
  • Pain relievers such as salicylate* (e.g., aspirin, Pepto-Bismol)
  • Some chemotherapy drugs
Solvents n-Hexane, Toluene, xylenes, styrene, TCE
Asphyxiants Carbon monoxide, hydrogen cyanide, tobacco smoke
Metals Mercury compounds, organic tin compounds, lead

*At manufacturing levels, which is much higher than therapeutic doses.

It is important to note that many common chemicals are included on the list, so exposure data is important. If employees are exposed to an ototoxicant at or above 50% of its exposure limit, they may be at risk for hearing loss.

Listen Up

Ototoixcants can be found in both construction and manufacturing, including in the following sectors:

  • Metal fabrication
  • Machining
  • Leather and textile manufacturing
  • Paper manufacturing
  • Chemical manufacturing
  • Plastic manufacturing

Firefighters, those who refuel vehicles and aircraft and spray pesticides may also be affected.

How Do We Protect our Employees?

If you identify ototoxic chemicals in your workplace:

  1. Include information about them, and what steps the company takes to protect its employees, in your Hazard Communication program and training.
  2. Consider switching out the ototoxic chemical for another, less toxic chemical, or use engineering controls such as enclosures or ventilation to reduce employee exposures.
  3. Utilize engineering controls to reduce noise exposures as well, and you may want to require hearing protection in more areas.
  4. Track employee exposures! Monitor employees and document their exposures. Audiometric testing, which is required as part of hearing conservation plans, may help detect early signs of hearing loss.
  5. The U.S. Army’s Public Health Command recommends including employees who are exposed to ototoxicants at or above 50% of the OSHA PEL and have noise exposures at or above 80 dBA in a hearing conservation program because they may be at risk for hearing loss.