Hazardous noise and hearing loss at work: The facts

Exposure to persistent noise can occur at the workplace or out of the workplace.

Long-term exposure to noise can cause a person to experience many physical symptoms – whether the noise is hazardous enough to cause noise induced hearing loss (NIHL) or not. These physical symptoms can include:

• increased blood pressure and heart rate
• nervousness and irritability
• insomnia
• reduced concentration
• hypersensitivity to noise
• changes to hormone and cholesterol levels
• increased stomach acid content

People may also experience psychosocial symptoms, such as isolation, depression, fatigue, etc

In addition to these symptoms, many people also develop and suffer from tinnitus, which is a constant ringing sensation in the ear. As a result, many tinnitus sufferers may experience all of the above physical symptoms on a permanent basis.

The harmful effects of hazardous noise are cumulative, which means the damage causing hearing loss increases over time through a series of repeated exposures.

The first indication that a worker may be exposed to hazardous noise levels is a temporary injury known as Temporary Threshold Shift (TTS).

TTS occurs when a person is exposed to hazardous noise that affects the functioning of the inner ear, which can cause temporary hearing loss. After a period of time away from noise, hearing may be restored.

With each further exposure a person has to hazardous or loud noise, the hair cells (cilia) in the cochlea (inner ear) gradually lose their ability to recover, become non-responsive to sound and will eventually die – causing permanent hearing loss.

The effects of NIHL can take some years to be noticed.

At first, most people aren’t aware of any change in their hearing but, over time, it becomes more noticeable, e.g. a worker may have difficulty hearing what family and co-workers say clearly or hearing sounds that are necessary for working safely, like verbal instructions – even warning signals.

The degree of hearing damage is dependent on:

• the level/s of noise a person is exposed to,
• how often and how long they have been exposed to the noise, e.g. workers who are exposed to hazardous noise on a daily basis at work are at a far greater risk of developing NIHL, and
• their susceptibility to noise

Acoustic trauma is the immediate and permanent hearing loss that can result from exposure to peak noise measured in the dB(C) scale. It is caused by impulse or explosive noises, such as explosive power tools; gun shots and fireworks (at close range).

Acoustic trauma injuries are very often associated with intense pain and in some cases the sound pressure can rupture the eardrum.

Acoustic trauma and Acoustic shock are not the same thing

Acoustic trauma is the immediate and permanent hearing loss that can result from exposure to peak impulse or explosive noise that exceeds the exposure standard for noise, which is140dB(C). It is very often associated with intense pain and, in some cases, the sound pressure can rupture the eardrum.

Acoustic shock incidents are sudden, unexpected loud noises, meaning acoustic shock injuries are not caused by hazardous noise, but by a sudden rise in the noise levels.

Acoustic shock symptoms

The effect on individuals can vary greatly for the same increase in sound level.

Immediate symptoms can include:

• a feeling of fullness in the ear
• burning sensations or sharp pain around or in the ear
• numbness, tingling or soreness down the side of face, neck or shoulder
• nausea or vomiting
• dizziness
• tinnitus and other head noises, such as eardrum fluttering.

Later symptoms can include:

• headaches
• fatigue
• feeling off-balance
• hypersensitivity to noise, i.e. a sensitivity to previously tolerated sounds such as loud voices, television and radio
• anxiety

Eliminating hazards at the design or planning stage of new and/or renovated workplaces is often easier and cheaper to achieve than making changes later when the hazards become real risks in the workplace.

You should consider:

• Buy quiet – look for the quietest plant and machinery for the job – ask the manufacturer/supplier for information about noise levels. this means having a purchasing and risk assessment process that reduces noise levels
• the effect on noise levels of building reverberation, the building layout and location of workstations relative to any plant
• installing automated plant and equipment to mechanically and/or remotely undertake work involving hazardous noise
• the type of plant and equipment to be installed. Consider the type of noise they generate (eg continuous; impact; intermittent; etc) and the noise level. Avoid impact noise as far as is reasonably practicable.

Engineering controls can include:

• installing sound insulation and noise dampening materials around noisy plant and equipment or to walls, ceilings, floors, doors, windows and other plant to reduce noise bouncing off hard surfaces.
• fitting noise suppressors to machines
• using vibration stabilising pads
• installing sound-proof partial enclosures, barriers, shields, noise cancelling curtains or acoustic baffles
• fit silencers to liquid or air noise sources to reduce flow velocity and turbulence
• line steel trestles and benches, product bins and scrap bins with wear-resistant rubber
• provide quiet rooms for rest breaks that are fully enclosed with well-sealed doors and windows to reduce background noise levels as far as possible

Substitution controls can include:

• using bending machines, pressing methods or glue instead of hammers
• lower materials carefully instead of dropping
• use mains powered electrical equipment instead of diesel generators
• use radiation drying instead of flow drying
• use laser cutting in place of sawing, grinding or punching
• use hydraulic breaking or bursting techniques rather than pneumatic impact breaking methods for demolition
• lower impact noise by reducing the driving force
• adapting plant and equipment by extending the guarding and line with acoustic dampening material

Isolation controls can include:

• installing a control room to isolate workers
• installing sound isolation booths
• installing remote controlled equipment
• using enclosed cabins on mobile equipment
• separating quiet and noisy areas. Low noise tasks like office work, packaging, cleaning, maintenance and repair work should be carried out in separate low-noise areas

The least effective controls in the hierarchy are administrative actions and personal protective equipment (PPE) because they

• do not stop hazardous noise at the source or in its pathway like the higher level controls
• rely on worker compliance and behaviour, and
• require supervision to ensure worker compliance

Administrative actions should provide a systematic framework that support the higher level WHS controls used and include:

• Provide quiet lunch and rest areas with low background noise levels where workers can spend their breaks away from noise.
• Safe work procedures that are developed in consultation with workers and enable them to undertake work activities safely, e.g.
  • rotate workers to reduce individual exposure times
  • restrict access to noisy areas
  • proper maintenance program for plant, equipment and tools
  • schedule activities involving hazardous noise to be done outside of normal hours or on shifts with fewer workers present, where possible

Workplace noise assessments to identify hazardous noise sources and recommended controls. SafeWork NSW recommends noise assessments are done in any noisy workplace. They should be carried out whenever there is:

• installation or removal of machinery
• a change in workload or equipment operating conditions that are likely to cause a significant change in noise levels
• a change in building structure that’s likely to affect noise levels
• modification of working arrangements that affect the length of time workers would spend in a noisy work environment

In order to get a true indication of a worker’s exposure to any hazardous noise, PCBU’s should:

• conducting a walk-through assessment of the workplace observing the work
• talk to workers about how work is carried out and ask about any problems they may have
• inspect the plant and equipment used during work activities
• observe plant and equipment when in use
• talk to manufacturers, suppliers, industry associations, health and safety specialists and professionals, and
• review any incident and monitor reports.

Any noise assessments must be done in strict accordance with AS/NZS1269.1:2005. A workplace noise assessment will provide the necessary information for you to:

• identify the workers who may be exposed to hazardous noise
• identify the machines and processes that are generating hazardous noise
• work out which high level controls will be the most effective
• also work out what level of hearing PPE that may be required for any leftover risk

SafeWork NSW recommends that the noise management plan includes a systematic workplace hearing conservation program to protect workers from the risk of hearing loss.

Hearing PPE is the last and the least effective control in the hierarchy and should only be used to manage any risk that is leftover after all higher-level controls have been implemented.

Based on the workplace noise exposure levels and the target in-ear noise exposure level, the workplace assessment will determine what level of hearing protection will correctly reduce (attenuate) the noise intensity received in a worker’s ear to the required 80dB(A) in-ear noise exposure level.

All hearing PPE should be:

• tested and approved in accordance with Australian Standard AS/NZS 1270:2002: Acoustics – Hearing protectors. Test results are found on the packaging of the hearing protector
• selected and maintained in accordance with AS/NZS 1269.3:2005 Occupational noise management – hearing protector program

When selecting personal hearing protection, you should consider:

• the worker
• the level of workplace noise
• the target in-ear noise exposure level
• the degree of attenuation required
• the comfort, weight and clamping force of the hearing PPE
• the suitability of the hearing PPE for both the worker and the environment
• its compatibility with spectacles and other protective equipment used by the worker, like hard hats, respirators and eye protection

Always involve your workers in the selection process and offer a reasonable choice from a range of types. Where necessary, obtain professional advice when selecting.

Other considerations for hearing protection are:

• Do not provide hearing PPE that under-protects or over-protects a worker’s hearing
• Workers must always wear hearing PPE whenever they are exposed to hazardous noise
• Never use audio headphones as a substitute for hearing PPE
• Hearing PPE must be regularly inspected and maintained
• Workers must be trained in the proper use, fit, care and maintenance of personal hearing protectors

Read hearing personal protective equipment for more detailed information when considering the correct level of hearing protection.

Once you have implemented control measures to protect health and safety by managing the risk of noise in your workplace, you must maintain and review them to ensure they remain fit for purpose, suitable for the nature and duration of work and be installed, set up and used correctly and reviewed regularly to make sure they are effective.

Specific moments to conduct a review include when:

• the control measure is no longer effective
• before a change at the workplace is being planned
• a new or relevant hazard or risk is identified
• the results of consultation indicate a review is necessary, or
• a health and safety representative requests a review.

Common review methods include workplace inspection, consultation, testing and analysing records and data. You can use the same methods as in the initial hazard identification step to check control measures. You must also consult your workers and their health and safety representatives.

Ototoxic substances are chemicals that can result in hearing loss.

When absorbed into the bloodstream, ototoxic substances may damage the cochlea (inner ear) and/or the auditory nerve pathways to the brain – which can lead to hearing loss and tinnitus.

Hearing loss is more likely if a worker is exposed to a combination of ototoxic substances, or a combination of the substance and noise.

There are three major classes of ototoxic substances:

1. Solvents e.g. butanol, carbon disulphide, ethanol

2. Heavy metals e.g. arsenic, lead, manganese

3. Asphyxiants e.g. acrylonitrile, carbon monoxide, hydrogen cyanide

The most common routes of entry for these ototoxic substances are via skin absorption, inhalation and, to a lesser extent, ingestion (mainly due to poor personal hygiene practices at work).

Work activities that commonly combine noise and ototoxic substances include:

• painting
• printing
• boat building
• construction
• furniture making
• fuelling vehicles and aircraft
• manufacturing, particularly of metal, leather and petroleum products
• degreasing
• firefighting
• weapons firing

Some medications have also been identified as ototoxic substances. These include some anti-cancer, anti-inflammatory, anti-thrombotic, anti-malarial, anti-rheumatic and antibiotic drugs.

Quinine and salicylic acids (such as aspirin) are also considered to be ototoxic substances.

Some ototoxins can be absorbed through the skin and are considered particularly hazardous. Exposure standards for chemicals and noise do not take account of the increased risk to hearing caused by ototoxic substances.

It is recommended that the noise exposure of workers (based on a daily shift) exposed to any ototoxic substances, be reduced to 80 dB(A) or below. They should also undergo audiometric testing and be given information on ototoxic substances.

Control measures such as substitution, isolation and local ventilation should be implemented to eliminate or reduce chemical exposures. Personal protective equipment should be used to prevent skin and respiratory absorption when other controls are insufficient.