Noise exposure is one of the most common health risk factors, and workers are exposed to sound pressure levels capable of producing hearing loss. Occupational noise-induced hearing loss (NIHL) is a major compensable industrial disease and entails substantial economic costs.
Exposure to excessive noise also entails largely unrecognised costs to organisations by way of increased employee turnover and absenteeism, lowered performance and possible contribution to accidents. As well as the economic cost for employers, NIHL imposes a severe burden on health and social services, and the economy as a whole. Noise exposure is one of the most common health risk factors.
Millions of labourers worldwide are exposed to sound pressure levels capable of producing hearing loss.
Occupational exposure to loud noise can damage the hair cells of the organ of Corti, akin to the body’s microphone, causing progressive and irreversible hearing loss, a condition known as noise-induced hearing loss (NIHL).
To the individual affected, the social handicaps of NIHL are also severe. NIHL is irreversible and leads to communication difficulties, impairment of interpersonal relationships, social isolation and a very real degradation in the quality of life. The family and others close to the affected person often experience secondary consequences of the condition. While NIHL cannot be fully reversed, the advancement in hearing aid technology can overcome some of the problems. Of those people affected, 20 per cent or more also suffer from tinnitus (ringing in the ears).
Noise in an occupational setting is regarded as unwanted or damaging sound that is experienced in the workplace. The level of noise in a workplace is a problem when it has the potential to damage employees’ hearing. A standard maximum noise exposure level is 85 decibels (A-weighted) averaged over an eight-hour period and a peak level of 140 decibels (C-weighted). This relates to noise measured at the employee’s ear.
Occupational noise-induced hearing loss (ONIHL) is a significant health and economic problem, the burden of which is borne by workers and their families, business owners and managers, and the wider society.
Exposure to excessive occupational noise is associated with many adverse effects besides loss of hearing. It has also been linked to annoyance and fatigue and to serious health conditions such as hypertension. Proper workplace and equipment design and adequate management practices can control occupational noise levels and workers’ exposure, thereby reducing the risk of hearing loss and other adverse outcomes. However, research suggests that several personal and institutional factors affect stakeholders’ willingness, ability or opportunity to implement or use the most effective noise control and hearing loss prevention strategies.
The World Health Organization 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. There are many causes of hearing loss including infections, tumours, structural problems, exposure to certain chemicals and pharmaceuticals (ototoxins), ageing, and exposure to loud noise. Exposure to loud noise from all sources accounts for about 20% of adult-onset hearing loss, although some research suggests that this proportion may be considerably higher. About 75% of moderate or greater hearing loss worldwide is adult-onset.
NIHL is an irreversible condition that can have a terrible impact on a person’s life. If you are exposed to loud noise continually over a period of time, the nerve receptors in your inner ear may eventually die, and once damage occurs it cannot be repaired. Hearing loss can also result from exposure to sudden loud noises, such as explosions, gun shots or heavy hammering. These types of noises are commonly referred to as ‘impact’ noises and, if loud enough, can cause immediate, permanent damage. Permanent hearing loss may also be accompanied by tinnitus or ringing in the ears. Damage to hearing can occur from exposure to very loud noise for a short time or prolonged exposure to moderate noise levels. Some factors, such as ototoxic chemicals, may interact with noise to produce hearing loss that is greater than that associated with the combined effects of the individual causes.
The National Code of Practice for Noise Management and Protection of Hearing at Work provides practical guidance on how the national standard can be achieved. The national code of practice is intended to assist employers, employees, unions, management, health and safety committee representatives, safety officers, occupational health and safety professionals and others requiring guidance on understanding and reducing workplace noise exposure.
The levels specified in the national standard are the maximum acceptable exposure levels for noise in the workplace; however, over long periods repeated noise exposure at between 75 and 85 decibels may be a small risk to some people. With progressively increasing levels, the risk becomes greater. Workplace noise levels lower than 85 decibels are, therefore, desirable if practicable.
In addition to noise being defined as any unwanted or damaging sound, further definitions included in the National Standard for Occupational Noise [NOHSC: 1007(2000)] are as follows.
LAeq,8h is the eight-hour equivalent continuous A-weighted sound pressure level in dB(A) referenced to 20 micropascals. It means that steady noise levels which would, in the course of an eight-hour period, cause the same A-weighted sound energy as that due to the actual noise over a working day.
LC,peak or peak noise level means the C-weighted peak sound pressure level in decibels are measured by a sound level meter with a peak detector-indicator characteristic.
Personal hearing protectors
Personal hearing protectors come in the form of a device or pair of devices worn by a person or inserted in the ears to protect hearing.
The preferred solution to excessive exposure to loud noise is to completely eliminate the source of the noise. When this is not possible or reasonably practicable, the legal requirement is to minimise exposure through a hierarchy of controls. From highest to lowest ranking the hierarchy of controls, in general, includes the following:
• Substitute the noise source with quieter machinery or processes • Isolate the noise source from workers • Apply engineering solutions • Apply administrative solutions • Provide personal hearing protectors
Engineering controls include redesigning or modifying the noise source or workplace, fitting silencers and mufflers, undertaking regular maintenance, and installing noise guards or enclosures. Administrative controls include scheduling noisy work for when fewest workers are present, placing warning signs and providing quiet areas for breaks. Ear muffs and ear plugs are the most common types of personal hearing protectors (PHPs) and should only be relied upon when none of the high-order controls are reasonably practicable.
Within the hierarchy of controls, highest priority is given to the source of the noise followed by the path of transmission and, finally, the point of reception (the exposed worker). The general notion is that preventative action by the worker should be the last resort. A comprehensive noise management programme would include, therefore, strict adherence to the hierarchy of controls as well as noise exposure and hearing assessments; education with respect to risks, solutions and responsibilities; and training on noise control and personal protection. Thorne (2006), however, observed that it is common for one or more components of a comprehensive programme to be missing, with a major reason for this being overreliance on PHPs. With this in mind, the terms noise management programme or noise control programme, rather than hearing conservation programme, are believed to place a greater emphasis on noise elimination or isolation instead of PHPs.
Noise management and hearing conservation
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, 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
• Provide personal hearing protectors, e.g. ear muffs and ear plugs – when none of the above are reasonably practicable
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.
Barriers to effective noise control
The occupational noise literature highlights several personal and institutional factors that reduce the likelihood that effective noise controls will be adopted in the workplace. These so-called barriers to effective noise control and ONIHL prevention include a belief that the term ‘hearing conservation programme’ refers only to personal hearing protection and audiometry. In addition, the gradual, hidden and often uncertain course of hearing loss tends to reduce its priority as a work health and safety issue. Other important barriers identified in the literature include the belief that noise control is difficult, the belief that personal hearing protectors are uncomfortable and interfere with warning signals, the perceived stigma associated with admitting to having hearing loss, and the lack of managerial commitment to work health and safety.
A series of research studies undertaken for the present project investigated these and other potential barriers (as well as potential enablers) in detail. The studies included focus groups with workers, managers and employers; nation-wide surveys of over 1,100 workers and 1,000 managers and employers; and in-depth face-to-face semi-structured interviews with 50 employers, managers, work health and safety representatives and union representatives. While the surveys also included noise-exposed people from other industries, each study focussed on five at-risk industry groups: construction; manufacturing; transport and storage; agriculture, forestry and fishing; and hospitality and entertainment.
Overall, findings from the studies suggest that the strongest barriers include an over-reliance on personal hearing protectors, infrequent and improper use of personal hearing protectors, lack of prominence of noise as a serious work health and safety issue, and lack of consideration of potential benefits of effective noise control.
Other important barriers include:
• Business size – small or medium-sized businesses are less likely than large businesses to have effective noise control
• Insufficient knowledge of the effects of loud noise on hearing and hearing loss on quality of life
• Belief that noise control costs too much
• Fatalism – belief that hearing loss is inevitable
• Optimism – belief that hearing loss ‘will not happen to me’
• Self-efficacy – low confidence about being able to do anything about noise
• High inertia about doing something about noise and hearing loss
• Work cultures that are resistant to change
Enablers and interventions
This research project found that increased awareness, prominence, self-efficacy, economic and regulatory incentives, and managerial commitment are the most promising enablers of the adoption of effective control. Based on these findings, several intervention strategies are proposed for overcoming barriers to effective noise control and ONIHL prevention. The major interventions are:
1. Provide education about the dangers of exposure to loud noise, the risk of hearing loss, the effect of hearing loss on quality of life, and the available noise control and hearing loss prevention options. The findings of the present research suggest that this may be achieved by visits from regulators, the influence of peers and role models, and by other social marketing strategies.
2. Raise awareness of the potential benefits of effective noise control by developing easily accessible and useable noise control cost-benefit models and templates. Business owners and managers could access these templates from government or industry websites. Government and industry education campaigns could be used to make employers and managers aware of the templates’ availability and purpose.
3. Increase the likelihood and visibility of the enforcement of existing noise control regulations. Many participants in the current research project acknowledged a need for greater enforcement of noise control regulations by the work health and safety regulatory authorities. In addition, there was a belief that increasing the legal and economic consequences of non-compliance (i.e. raising the level of the sanctions as well as the likelihood of sanction) may increase the economic relevance of noise control and hearing loss prevention.
Significantly decrease the risk of noise injury in the workplace by following the order of the control measures specified below, using the hierarchy of risk controls. The list is set out with the most effective approaches first. Only use a less effective approach if it is not reasonably practicable to use a more effective one. In many instances, a combination of approaches will result in the best solution.
1. Eliminate the cause of the noise
The most effective measure is to remove the source of the noise, so you should always try to do this first.
Example: Get rid of noisy plant
2. Substitute quieter plant or processes, or implement engineering measures
If the source of the noise can’t be eliminated, consider using quieter equipment, processes, or engineering controls.
Example: Purchase quieter equipment (e.g. quiet compressor) or use a quieter process (e.g. welding instead of riveting in large scale construction).
Introduce engineering controls to:
• Avoid metal-on-metal impacts
• Reduce vibration
• Isolate vibrating machinery
• Silence air exhausts and blowing nozzles
• Erect enclosures around machines to reduce the amount of noise emitted into the workplace or environment
• Use barriers and screens to block the direct path of sound
• Use absorptive materials to minimise noise reflection within the building
3. Use administrative controls
If you can’t change the equipment or processes, try to change the way the work is done.
Example: Position noise sources further away from employees, minimise the number of employees working in noisy areas or do noisy work out of normal working hours. Job rotation can also help to limit employees’ exposure to noise.
4. Provide hearing protectors
If the above measures do not totally solve the problem, and they have been applied as far as practicable, then hearing protectors must be used to ensure that employees’ exposure to noise does not exceed the standard.
Overall, it is important to review the current risk controls regularly to ensure they are implemented correctly and to monitor their effectiveness. It is imperative to review (and, where necessary, revise) your risk controls whenever changes are made to the workplace that could affect noise levels, such as changes to the way work is done or to the equipment used. A review is also necessary if there is a report of hearing loss in the workplace, if you become aware of any new information about any noise levels, or if a health and safety representative requests one. Employees and Health and Safety Representatives must be consulted when reviewing risk controls.
A comprehensible message from the academic and empirical research is that both regulatory enforcement and education are vital for achieving more effective noise control and ONIHL prevention. Employers, managers and workers need to be made aware of the real risks and available solutions – and they need clear, concise, and readily available guidance on how to achieve these solutions.
The necessary action is to eliminate occupational noise at the source through good planning and design techniques. This will become a valuable health contribution for the health and wellbeing of our workers.
It’s in our best interests to listen to the next generation and hear their wise words, but this can only happen by ensuring we design out and eliminate noise exposure from the source.
Published: 11th Aug 2016 in Health and Safety Middle East