There is sufficient evidence and research dating back to the 16th century that noise exposure can cause hearing loss. Ramazzini’s published notes on the Diseases of Workers, which identified how Italian coppersmiths suffered noise-induced hearing loss (NIHL) after years of hammering and forge work. However, some OHS professionals may only recently be aware of ototoxicity, also known as ‘poison of the ear’. Exposure to ototoxic chemicals can cause headaches, dizziness, tinnitus (ringing inside the ears) and occupational-induced hearing loss (OIHL), as Gordon Pringle explains.
Pharmaceuticals
Various medication has already been identified as causing ototoxic affects in patients; from simple Ibuprofen, antibiotics like aminoglycosides and even antimalarial drugs (RNID, no date). Often after long-term treatment, patients have reported hearing loss, tinnitus, or problems with their balance as the small fragile hairs of the inner ear are damaged.
Industrial chemicals
More relevant to the occupational environment are the various chemicals which have an ototoxic effect. Recent studies including by the World Health Organization (2021, pp. 21) now cite solvents, heavy metals, asphyxiant gases, nitriles, and some pesticides within the list of ototoxic chemicals. These substances can have a severe effect on the workforce and their hearing and balance once inhaled, absorbed, or ingested in an occupational setting.
Prevention
Within the workplace we are already aware of occupational exposure limits (OEL’s) to limit the effect of chemicals on workers, however limited inclusion of their ototoxic effect is considered within the levels set in the Health and Safety Executive’s EH40.
Identification is important within Control Of Substances Hazardous to Health (COSHH) assessments to know which ototoxic chemicals are in the workplace and how the workforce is exposed. Then the hierarchy of control, starting where possible with the elimination of these chemicals, should be employed.
A good start to identification would include checking the manufacturers’ Safety Data Sheets of any paints, cleaning solvents and even gardening and agricultural supplies. Key constituents with known ototoxic effects include:
However, some ototoxic chemicals may also be a by-product of processes, specifically carbon-monoxide.
Most of these everyday chemicals, like benzene from petrol fumes, are likely to be with us in the workplace for some time so elimination is a limited possibility, as is substitution. Therefore, engineering controls such as segregation, local ventilation, dilution and general ventilation will play a large role in control measures, along with supervisory control to ensure exposure is suitably controlled. Only then should personal protective equipment be considered – although all routes of entry for these chemicals into the body should be reviewed. Absorption, ingestion and inhalation are all possible routes into the bloodstream which can then transport the chemicals into the inner ear, even absorption through the eyes should be considered both for gas absorption and liquid splashes.
Good medical screening should be implemented to ensure any predisposed workers are identified.
This is especially important if hearing loss is already a problem for the individual or if they are already taking a known ototoxic medication.
Where any ototoxic damage is suspected, then a suitable medical professional should be consulted as soon as possible to prevent any worsening of the condition or even to achieve possible reversal if caught early enough.
Care should also be taken when employees are expected to use these chemicals as they can cause dizziness and imbalance, putting them at further risk, e.g. when working at height or operating machinery.
Some ototoxic chemicals are all around us from non-industrial sources such as exhaust fumes from our cars or within cigarette smoke.
Conclusion
Through identification, assessment and control you should ensure your workforce are protected from the debilitating impact of OIHL through ototoxicity. You should:
Controls must be put in place for ototoxic damage from chemicals in the workplace, the effects of which can then be compounded with medication used within the workforce, smoking or chemicals used in the home.
References:
RNID, (no date) Types and causes of hearing loss and deafness.
Available at: https://rnid.org.uk/information-and-support/hearing-loss/types-of-hearing-loss-and-deafness/ototoxic-drugs-and-hearing-loss/ (Accessed: 15 July 2022)
World Health Organization (2021) World Report on Hearing. Available at: https://apps.who.int/iris/bitstream/handle/10665/339913/9789240020481-eng.pdf?sequence=1 (Accessed: 15 July 2022)
Gordon Pringle started his Occupational Safety and Health journey as an Environmental Health Technician in the Royal Army Medical Corps finishing his military career as a member of the Mobile Health Instructional Team. He has a wealth of experience (over 25 years) across various industries including cinema, oil, and gas and more recently Facilities Management. Gordon is a Fellow of the Royal Society for Public Health and a chartered member of IOSH. He now works for Arcus FM as a HSQE Business Partner, and he is also the Chair of the North Cumbria District of IOSH.
