Ototoxins in the Workplace

A new informational bulletin developed by OSHA and NIOSH raises awareness of ototoxin exposure in the workplace, provides examples of ototoxic chemicals, lists the industries and occupations at risk, and provides prevention information.

The hearing loss caused by chemicals can be very similar to a hearing loss caused by excessive noise. The fact that noise exposure is so common in modern societies might explain the delay in recognizing the risk to hearing that these chemicals can pose. Pure tone audiometry is a basic clinical test used to determine a person’s hearing sensitivity at specific frequencies, i.e., the softest sound that can be perceived in a quiet environment. It clearly identifies various hearing loss characteristics, but not its cause. Other hearing tests such as word recognition or otoacoustic emission tests examine other auditory functions.

In some cases, these tests can help differentiate the effects of chemicals from the effects of noise, since chemicals might affect the more central portions of the auditory system (nerves or nuclei of the central nervous system, the pathways to the brain or in the brain itself). These hearing deficits may have a more pronounced impact on the worker’s life because not only are sounds be perceived as less loud, but also as distorted. Word recognition may be compromised, particularly in background noise, making it difficult, for instance, to hold a conversation in a busy restaurant or at a party.

According to the CDC, this hearing impairment affects many occupations and industries, from machinists to firefighters.

The first step in preventing exposure to ototoxins to know if they are in the workplace. The publications cited in the bulletin identify known ototoxins. Toluene, styrene, carbon monoxide, acrylonitrile, and lead. When there is no information on a certain chemical’s ototoxicity, information on the chemical’s general toxicity, nephrotoxicity, and neurotoxicity may provide clues about the potential ototoxicity.