Ototoxic chemicals: Chemicals that can cause hearing loss

Jobs where workers are often exposed to both noise and these chemicals include: 

• painting and printing
• boat building and construction
• furniture making
• making metal, fibreglass, leather and petroleum products
• aircraft maintenance
• assay laboratories
• radiator repair
• fuelling vehicles and aircraft
• firefighting
• spraying pesticides
• weapons firing. 

Researchers are still working out how much exposure to these chemicals – alone or with noise – is needed to cause hearing damage.

Current safety standards for chemicals and noise do not account for the extra risk to hearing. Safety data sheets (SDS) often do not warn about potential hearing loss either.

Until the standards are updated, workers exposed to any of the chemicals in Table 1 should:

• have their noise exposure kept at or below 80 dB(A) over an 8-hour day
• have regular hearing tests
• be told about the risks of ototoxic chemicals.

Yearly hearing tests are strongly recommended for workers whose chemical exposure in the air reaches 50% or more of the Safe Work Australia exposure standard for that chemical – regardless of noise levels. This applies even if the worker wears respiratory protection.

If no air monitoring has been done, a yearly hearing test is recommended for workers with frequent or long-term exposure to an ototoxic chemical where any of the following apply:

• it is not known how well the ventilation works, or there is no ventilation
• workers have reported health problems that may be linked to the chemical  
• it is hard to tell how much exposure workers are getting. Some chemicals can also be absorbed through the skin (see Table 1). If skin contact cannot be controlled and is ongoing, yearly hearing tests are also recommended.

For workers already having hearing tests due to noise exposure, the person reviewing the results should also consider whether the worker is exposed to ototoxic chemicals.  

If a worker reports hearing problems but their hearing test results are normal, refer them for more detailed testing. Standard hearing tests may not pick up damage caused by chemical exposure.  

To reduce exposure to these chemicals:

• replace the chemical with a safer one where possible
• use barriers or local ventilation to limit exposure
• use personal protective equipment (PPE) such as gloves and respirators when other controls are not enough

Table 1. Possible workplace ototoxic chemicals (source: Morata T.C. [2007] Promoting hearing health and the combined risk of noise-induced hearing loss and ototoxicity, Audiological Medicine, Vol.5, Issue 1, pp33-40.)

Some medications can also damage hearing, including certain:

• Anti-cancer drugs
• Anti-inflammatory drugs
• Anti-malarial and anti-rheumatic drugs
• Anti-thrombotic drugs
• Loop diuretics
• Antibiotics. 

Workers should be told about how these medications can affect hearing as part of their workplace training. Encourage workers to talk to their doctor or pharmacist if they have any concerns about their medication.