Preventing occupational hearing loss

Occupational noise-induced hearing loss is a common causes of deafness around the world. Prolonged exposure to noise at work can lead to irreversible hearing loss called sensorineural hearing loss. It is due to the damage of the nerve cells of the inner ear. Once destroyed, these nerve cells would not recover. The resulting hearing impairment will be permanent, leading to hearing loss. When a person works in a noisy environment, the damage caused to his hearing will be in direct proportion to the intensity of the noise and the duration of exposure time.

The World Health Organisation defines disabling hearing impairment in adults as permanent hearing threshold level of 41 decibels or greater. At this level of impairment most people can only distinguish words spoken at one metre if they are spoken in a raised voice.

Workers of certain industries and occupations who are at risk of noise-induced hearing loss include:

Factories for garments, machinery and manufacturing items

• Construction
• Jobs involving loud music like musicians and orchestra conductors
• Mining industry
• Jobs involving the personnel to use drilling and other machinery
• Airline ground maintenance
• Truck, bus or train drivers
• Agriculture and farming with machinery
• Military, police and firefighters

Sources of non-occupational noise include high-volume music and church bands and exposure to noise from traffic during travel. Children may be exposed to high levels of noise from some toys that make noise; they may be affected by long term exposure to traffic noises.

The preferred solution to excessive noise exposure is to completely eliminate the source of the loud noise. When this is not possible or practical, the legal requirement is to minimise exposure through a hierarchy of controls such as the following:

• substitute the noise source with quieter machinery or processes
• isolate the noise source from workers
• apply engineering solutions (e.g. fit mufflers, redesign the noise source, and install noise guards or enclosures)
• apply administrative solutions (e.g. schedule noisy work for when fewest workers are present, provide signs and quiet areas for breaks), and when none of the above are reasonably practicable
• provide personal hearing protectors (e.g. ear muffs and plugs).

Within this hierarchy, priority is given to the source of the noise, followed by the path of transmission and, as a last resort, the exposed worker. A comprehensive hearing conservation programme or noise control programme should include strict adherence to the hierarchy of controls as well as assessments of noise exposure and hearing; education with respect to risks, solutions and responsibilities; and training on noise control and personal protection.