Ototoxicity: A Covert Noise-Safety Issue to Include in Lab-Safety Procedures

The human body is a wonderfully interconnected system. This can be a boon or a bane for researchers seeking to heal the body and for lab safety teams seeking to protect it. As we recently noted, lab-safety issues aren’t always obvious. One postdoctoral fellow almost lost her sight due to the covert impact of UV light. For this reason, we are focusing today on another covert noise-safety concern that has come to our attention.

Introducing Ototoxicants

We usually assume that hearing will be adversely affected by loud noises or perhaps physical damage to the ear drum or to cochlear hair cells, which receive and transmit sound. However, ototoxicants, in the form of chemical compounds, are additional threats to the ear. Exposure can occur through inhalation, skin absorption, or ingestion—none of which have any direct connection with noise or hearing.

Ototoxic chemicals travel through the bloodstream and damage the ear. Two types can impair a person’s ability to hear or hear clearly: Neurotoxicants damage the nerve fibers that support hearing and balance; and cochleotoxicants damage those cochlear hair cells, impairing the ability to hear.

Multiple substance classes contain ototoxic chemicals. These include pharmaceuticals such as furosemide and streptomycin (although toxicity at therapeutic doses is limited, certain labs may routinely handle significantly larger quantities of these substances); solvents such as toluene and ethylbenzene; asphyxiants such as carbon monoxide and hydrogen cyanide; nitriles such as acrylonitrile and cis-crotononitrile; and metals compounds that include germanium dioxide, mercury, tin, and lead.

Why Ototoxicants Are a Noise-Safety Issue

The impact of ototoxicants on the human body is not straightforward. It can act alone or in tandem with loud noise in the lab or workplace. Hearing loss can be amplified if people are exposed to ototoxins concurrently with loud noises. Furthermore, noise and ototoxins have a synergistic effect, exponentially increasing the potential damage. Impulse noise seems to particularly exacerbate the effects of ototoxicants.

No single-exposure threshold exists for ototoxicity. Damage rates vary for each particular chemical based on compound family; chemical properties; exposure route, concentration and duration; noise synergy; and individual body tolerances and risk factors, including age.

Ototoxicant Hearing Effects and Lab Safety

Ototoxicants affect not only the ears but also the central portions of the auditory system, including the brain, which varies the effects of ototoxicants. In addition to the loss of hearing, people affected may lose the ability to hear clearly and distinguish sounds. For example, they may not be able to determine the direction from which a sound is coming. They may lose the ability to sense a time gap between sounds or the ability to differentiate sounds with a similar frequency.

Such speech-discrimination dysfunctions can become a major lab-safety issue. If someone does not correctly sense the direction of a sound, they may run toward a dangerous situation instead of away from it. The inability to hear clearly could result in misunderstood directions. The inability to hear coworkers’ warnings could lead to a lab accident.

What does all this mean for lab-safety protocols? OSHA recommends audiometric tests to determine loss of hearing acuity or comprehension. However, they note that such tests will not determine the cause of any loss in hearing or comprehension.

Labs that handle any ototoxic substances (see the OSHA article for a more complete list) should consider addressing all noise-safety issues, such as enclosing mass spec roughing pumps in dedicated lab furniture, by using our IonBench MS. To learn more about the noise-dampening effects of IonBench dedicated lab furniture, contact Tim Hawkins today at tim.hawkins@farhawk.com or 1-888-669-1233.