Chemically induced hearing loss: have you assessed the risks?

More than 450 million people worldwide experience hearing loss with inner ear or auditory nerve (sensorineural) hearing loss being the most common type. Exposure to ototoxic (toxic to the ear) pharmaceuticals and chemicals can induce sensorineural hearing loss and exacerbate the risk of noise-induced hearing loss. In fact, the combination of ototoxic drug/chemical exposure plus noise exposure may synergistically increase the risk of industrial hearing loss and other forms of hearing system damage. This is particularly concerning in industrial settings where workers may be exposed to both high noise levels and harmful chemicals.

The facts and impacts

Occupational hearing loss is indeed a significant issue in Australia. According to a study[1], approximately one hundred thousand workers are expected to develop preventable hearing loss over a decade due to current noise exposure levels, which would result in a significant well-being and productivity loss. The impact of such hearing loss extends beyond individual health, affecting overall productivity and economic well-being. Efforts to mitigate these risks through better workplace practices and protective measures are crucial.

Recent findings in Australia and the USA[2][3] have indeed highlighted that occupational exposure to high levels of noise plus ototoxic chemicals is potentially common in the workplace. According to this research, nearly 20% of workers in Australia are exposed to excessive noise and amongst these workers, 80% are also exposed to at least one ototoxic chemical during their workday. This combination can have a synergistic effect, increasing the risk of occupational-associated hearing loss.

Research[4] also shows that common workplace chemicals have been known to cause vestibular damage. Vestibular toxicity will adversely affect balance, walking and the ability to co-ordinate head and eye movements. These effects increase the risks associated with operating machinery and driving. Common industrial chemicals are also capable of irreversibly destroying vestibular function.

The challenges with assessment and prevention

Adding to the challenge of preventing chemically and drug-induced ototoxicity is that these effects are not normally assessed in depth in typical animal-based toxicology testing programs. Simple screening methods such as clinical observations and functional observational battery assessment may not be sufficient to assess the hazard and risk of ototoxicity and vestibular toxicity. Specialised animal models[5][6] are often required to fully assess the hazard and risk. This will often include specialised animal study methods such as cochlear microphonics, summating potential, auditory brainstem response, distortion product otoacoustic emissions, compound action potentials in addition to specialised histopathology.

How SLR can help?

SLR has a multi-disciplinary team of toxicologists, human health risk assessors, acoustics assessors and industrial hygienists who can fully inform you on your workplace hazards and risks regarding occupational hearing loss and vestibular toxicity as well as recommend appropriate risk mitigation. Our toxicology and risk assessment experts can also advise on the hazards and risks of your new chemical or pharmaceutical as well as design, implement, monitor and interpret appropriate testing studies. SLR can also support regulatory submission in relations to ototoxicity and vestibular toxicity testing.

Please contact our experts to discuss.

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References

[1] Productivity Burden of Occupational Noise-Induced Hearing Loss in Australia: A Life Table Modelling Study

[2] Exposure to noise and ototoxic chemicals in the Australian workforce

[3] Evaluating the potential impact of ototoxicant exposure on worker health

[4] Vestibular Toxicity: Causes, Evaluation Protocols, Intervention, and Management

[5] Rodent models in sensorineural hearing loss research: A comprehensive review

[6] Experimental animal models of drug-induced sensorineural hearing loss: a narrative review