Non-acoustic environmental factor influences on occupational hearing impairment: a preliminary discussion paper

Recently, several review papers have been published on environmental factors affecting hearing. But no mention was made of the ototoxic substances or agents to which industrial workers may be exposed apart from noise. This paper is a preliminary discussion of data on the numerous agents which ototoxicity is suspected or demonstrated on animals and on humans and on their probable site of disorder. These include carbon monoxide, heavy metals such as lead, arsenic and mercury, organic solvents such as toluene, xylene and styrene. Allergenic chemicals and climatic conditions are also considered as being possibly associated with occupational middle ear dysfunction. Effects of vibration on hearing and synergistic interactions between noise and vibration are also examined. Research priorities are discussed in terms of the likelyhood of exposure and suspected toxicity. Based on known mechanisms of ototoxicity, is is suggested that potent nephrotoxic substances are also strong toxic agents to the inner ear. The risk of damage to the ear of the foetus from noise exposure of the pregnant woman is also considered. It is concluded that systematic investigation of potential ototoxic chemicals from the workplace should be conducted as it was done for drugs for which case studies showed damage to hearing