We’ve all been there: you’re the second arriving engine to a room and contents fire. The first due engine made a great push and knocked down the fire as you were arriving. Command has tasked you to go to the second-floor bedroom where the fire occurred to conduct overhaul. As you ascend the stairs, you determine the environment appears good enough to enter without donning supplied air, as you will just be conducting some quick overhaul and the window already self-vented during the fire. An officer arrives and requests you put on your SCBA mask while overhaul is conducted. What you don’t realize is the officer isn’t just looking out for your respiratory health, but also protecting your hearing, because of ototoxic chemicals.
What is an Ototoxic Chemical?
If you asked firefighters what the number one hazard that can cause hearing loss in the fire service is, I would bet my house that the majority would say running power equipment or sirens. Most firefighters are completely unaware that certain chemicals, known as ototoxic chemicals, can also cause significant hearing loss. There are over 100 substances that have been identified as being ototoxic to varying degrees. Common ototoxic substances include arsenic, benzene, carbon disulfide, carbon monoxide, styrene, trichloroethylene, toluene, xylene, aspirin, and ibuprofen.
Ototoxic chemical exposure occurs through various means including skin absorption, inhalation, or ingestion. Once the exposure occurs, the chemical makes its way into the bloodstream where it then targets the hair cells of the auditory nerve, cochlea, and other parts of the auditory system. Exposures to ototoxic chemicals can be acute or chronic, and hearing loss may be sudden or gradual over time. Additionally, hearing loss can be bilateral or unilateral with no specific reasoning.
How Ototoxic Chemicals Impact Hearing
Once the exposure occurs, hearing loss normally occurs in a manner consistent with tinnitus, where a ringing in the ears obstructs or reduces hearing ability. Tinnitus can also lead to chronic dizziness and loss of balance, which can cause numerous other issues. Studies conducted to analyze hearing loss in large groups of randomly sampled firefighters typically yield results showing between 30% to 40% of the sampled firefighters suffering from mild to severe hearing loss. Hearing loss from ototoxic chemicals can also cause difficulty with speech differentiation, specifically with words that sound similar. You may also experience a feeling of fullness in your ears. Difficulty hearing with background noise is another common issue for victims of ototoxic chemical-induced hearing loss.
Hazardous Noise
Exposure to ototoxic chemicals in combination with exposure to hazardous levels of noise will exacerbate hearing loss. Being exposed to noise over 85 dB regularly is enough to cause hearing damage if no hearing protection is utilized. Combine this with an ototoxic substance working away at your auditory system, and you have a fast track to significant permanent hearing loss. A chainsaw, commonly used by firefighters, puts out around 109 dB and can cause hearing loss after just two minutes of run time. A mechanical siren on fire apparatus can put out around 123 dB. Being exposed to both of these items regularly without proper protection must be considered.
Where Are Ototoxic Chemicals Found?
The most common manner in which firefighters come in contact with ototoxic chemicals is through exposure to smoke. Modern-day homes and furnishings contain a variety of plastics, coatings, and materials that, when they burn, release a vast array of hazardous substances that firefighters can inhale. These substances include carbon monoxide, hydrogen cyanide, benzene, styrene, and many others. A simple solution is proper use of personal protective equipment.
Respiratory protection, in the form of a supplied air respirator such as an SCBA, will prevent the inhalation of ototoxic chemicals during fire suppression and overhaul operations. With inhalation being a primary route of entry for ototoxic vapors, this is an easy step to eliminate the possibility of exposure.
Skin Protection
Skin protection, in the form of structural firefighting clothing, will provide resistance to skin absorption of ototoxic chemicals. Of course, fire departments must properly wash and maintain structural turnout gear at various intervals depending on the level of use. Without proper cleaning, the ototoxic chemicals would saturate the clothing and absorb through the user’s skin over time.
Air monitoring for ototoxic chemicals is not an option for many fire departments. Almost all gas meters on fire apparatus measure substances such as carbon monoxide, but the other substances discussed require specialty monitoring equipment not carried by most fire departments. A single gas monitor for hydrogen cyanide is a great investment for use during overhaul operations. Based on the difficulty in monitoring for the substances, it is best to assume the atmosphere is hazardous during overhaul and utilize proper PPE regardless.
Occupational Safety and Health
The Occupational Safety and Health Administration (OSHA) outlines the permissible exposure limits to these substances under 29 CFR 1910 Subpart Z titled “Toxic and Hazardous Substances”. Within this section 1910.1000 Table Z-1 lists the exact numbers at which employees must use personal protective equipment. Carbon monoxide, depending on the length of exposure, is usually limited to between 25 ppm-35 ppm. Most gas meters will alarm for evacuation at 35 ppm. While not deadly at that level, any amount of carbon monoxide can contribute to hearing loss over time. Substances such as hydrogen cyanide have even lower limits at 4.7 ppm as supported by NIOSH studies.
Many employers in general industry that have employees exposed to hazardous levels of noise above the OSHA permissible exposure limits must enroll employees in a hearing conservation program as outlined in 29 CFR 1910.95. An effective hearing conservation program involves a baseline audiogram to establish current hearing levels. Subsequent annual audiograms then look for a standard threshold shift (loss of hearing) greater than that of normal aging.
Loss of hearing is a recordable event on the company OSHA 300 log. While the standard does not require a hearing conservation program for exposure to ototoxic chemicals, the program would be effective to monitor for this hazard just as it is for hazardous noise. While optional, it would be beneficial for the health and safety of firefighters for every department to implement this program. A well-managed hearing conservation program would identify hearing loss early. Then firefighters can employ controls to prevent further damage. This could involve changes to procedures within the department, additional training, or even point to improper fit of respiratory protection facepieces allowing smoke and ototoxins to leak into the user.
Conclusion
It is critical that we teach our firefighters about the hidden dangers of ototoxic chemicals and hearing loss as a whole. A loss of hearing in the fire service can become a career-ending situation. We inherently need to hear to take direction, communicate with command, be alert for changing conditions or hazards, and work cooperatively with our fellow first responders. On the other side, who wants to go through the remainder of their life not being able to listen to their favorite music, having to watch television with subtitles, limited interaction with family, children, or friends? We sign up for this job to help people, not to harm ourselves intentionally. The next time you’re exposed to smoke, wear your respiratory protection. It’s not just saving you from cancer, but also from the loss of your hearing and your future quality of life!
Author Bio
Brian Daboul is a 14-year veteran of the Mine Hill Fire Department in New Jersey where he served as chief from 2018-2021. He also handles all of the department’s occupational safety and training. Brian is a certified safety manager through the National Association of Safety Professionals and has 13 years of experience with safety strategy and program development in general industry at a senior management level. He is also the founder and principal consultant for BGD Safety and Compliance LLC serving general industry and fire departments.
—
References
Occupational Safety and Health Administration ECFR – Section 29CFR 1910.95 “Occupational Noise Exposure”. Osha.gov/laws-regs/regulations/standardnumber/1910/1910.95
Occupational Safety and Health Administration ECFR – Section 29CFR 1910.1000 “Air Contaminants”. Osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000
Lexie Hearing – “Chemicals That Can Cause Hearing Loss” Published 10-27-2021. Updated 03-23-2023. https://lexiehearing.com/us/library/chemicals-that-can-cause-hearing-loss
Hain, Timothy C. MD – “Carbon Monoxide Inducing Hearing Loss”. Published 03-05-2021. http://dizziness-and-balance.com/disorders/hearing/carbon_monoxide.html
Millet, Barbara; Rajguru, Suhrud M; Schaefer Solle, Natasha; Snapp, Hillary A; – “Prevalence of Hearing Loss and Perceptions of Hearing Health and Protection among Florida Firefighters”. Published 03-05-2023. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10001319/
