The most prevalent occupational disease in the world is noise induced hearing loss (NIHL). It is estimated that a staggering 1.3 billion people suffer hearing loss due to noise exposure, while occupational noise exposure causes between 7 and 21 per cent of hearing loss among workers. In this article, Professor Chris Barlow, Head of Research and Innovation at KP Acoustics Research Labs, argues that the risks of occupational noise exposure merit greater attention.
Occupational noise induced hearing loss (ONIHL) is not a new problem. Reports from the eighteenth century show that copper miners were observed to be suffering from hearing loss, a consequence of constant exposure to the noise generated from hammering metal. Since then, we have at least come a long way, both in our understanding of the problem and in the legal requirements placed on employers.
In the UK, the Control of Noise at Work Regulations (2005) requires employers to prevent or reduce risks to health and safety arising from exposure to noise in the workplace. The regulations, which fall under the legal remit of the Health and Safety at Work Act (1974), require employers to take specific action when certain values are reached, and determine that specific noise exposure levels must not be exceeded. For example, without hearing protection daily or weekly exposure levels must not surpass 85 decibels (A-weighted) and peak sound pressure levels must not exceed 137 decibels (C-weighted). These levels rise to 87 decibels (A-weighted) for daily or weekly exposure and 140 decibels (C-weighted) for peak exposure when hearing protection is taken into account.
Similar rules and regulations exist in most developed countries. One thing that motivates employers to comply with the regulations is the potential litigation costs. In the US, for example, it is estimated that annual compensation resulting from ONIHL is approximately $242.2 million.
However, the main thing that needs to change to tackle the scale of the problem and the risks it entails is not more regulation and threats of legal action. What needs to happen is a greater awareness of the risks of hearing loss and its full implications, both for the individual and wider society. A scientific consensus about the risks of noise exposure and hearing loss clearly exists, but this has not yet fully translated into greater understanding among employers and employees.
Understanding the risks
There are many occupations where a noisy workplace is a potentially significant health and safety issue. Manufacturing and construction are both industries where occupational noise is an obvious concern, but there are other professions where exposure to noise, albeit infrequent, can have serious consequences if mitigative steps are not taken to reduce the risks. In short, it is important to understand that the problem is not limited to one or two industries, but exists anywhere where there is a noisy workplace, from the music industry to airports.
Exposure to noise does not only lead to direct injury to the auditory system, there are also a range of nonauditory effects. Hearing loss itself contributes to other problems such as increased risk of dementia and cardiovascular disease, poorer mental health and reduced outcomes in areas like social integration and even average earnings. As well as the poor outcomes for the individual, the negative impact on society at the aggregate level should also justify greater effort to tackle the problem.
One particularly noteworthy risk associated with hearing loss is the increased likelihood of developing dementia. Older people with mild hearing loss have a twofold increased risk of dementia, while those with severe hearing loss face a fivefold increase. There is also a well-documented correlation between hearing loss and heart disease. Although this is mostly the result of heart problems causing hearing problems, rather than the other way around, there are also studies demonstrating that increased noise exposure raises the risk of cardiovascular problems via its impact on stress levels.
Other significant risks include increased likelihood of developing depression, resulting from communication problems in interpersonal relationships and feelings of isolation. A growing body of scientific literature attests to the nature of the problem, but unfortunately the stigma attached to hearing loss means victims often go many years without reporting the issue.
There are two different types of noise exposure that need to be considered. One is exposure to loud noise over a period of time. Although we are all different, and some bodies are more resilient than others, the human ear is very delicate. Noise exposure is a dose-based concept so exposure to very high levels of noise for short durations, or lower levels for longer durations can both significantly increase the risk of long-term hearing damage.
For example, in the engine room of a ship, the average sound pressure level can be between 105 and 110 decibels. If someone entered that area to carry out some maintenance checks, even very short-term exposure could be severely damaging. In this scenario, without wearing hearing protection you could exceed your recommended maximum daily dose of noise exposure in a couple of minutes.
In a manufacturing plant where levels might average around 90 decibels it would take an unprotected worker about 2.5 hours to exceed the maximum daily dose. However, in both scenarios if the worker was regularly exposed to more noise beyond that point they are likely to incur hearing damage.
This is more common in industries where workers are continually exposed to occupational noise. It is no surprise that research has confirmed that those employed in construction, manufacturing, mining, agriculture, utility, transportation, the military, and musicians are at higher risk of ONIHL. It is therefore important to understand that even if the overall noise level does not appear to be excessive, continued exposure can bring the average level of noise exposure during an eight-hour working day to a level that is likely to significantly increase the risk.
The second type of noise exposure, in contrast, is short term, impulsive noises of very high level such as gunfire, drop hammers and nailguns. These contribute relatively little to the overall sound energy received, but they carry a disproportionately high risk to the hearing system with risks including instantaneous acoustic trauma as well as damage to the inner ear, and occupations exposed to impulsive noises are at the greatest risk of ONIHL.
Be careful with personal protective equipment
An overreliance on personal protective equipment (PPE) is symptomatic of a lack of appreciation of the risks. Equipment like ear defenders should be understood to be a last resort. Occupational and health and safety professionals use the ‘‘hierarchy of control’’ to determine how to implement feasible and effective controls. This approach groups actions by their likely effectiveness and is visualised as an inverted pyramid, with the most effective methods at the base of the pyramid and the least effective at the inverted tip. You might be surprised to learn that protecting workers with PPE is regarded as the least effective.
One common problem with much PPE is that is does not always do what it says on the tin. At KP Acoustics Research Labs, we have worked with many companies to test out noise control products and make sure they can perform in the way intended. As the lab tests are carried out in a carefully controlled environment, they often give a significantly higher performance than is ever obtained in the real world. Issues such as quality of fit, user error, and degradation of the item all affect real world performance of hearing protection – with user error being by far the biggest contributor to real world performance.
User error is easier to fall into than you might assume. Workers who are regularly in noisy environments might become complacent and desensitised to the risks. For example, a common risk unknowingly taken is temporarily lifting your ear defender to have a conversation in a noisy area, instead of moving to a quieter area. In this scenario, the amount of sound energy in that few moments could be enough to exceed the daily amount of energy that is known to be likely to lead to hearing loss. The ear defenders haven’t done their job. Another key error is incorrect insertion of earplugs by untrained users, which can reduce protection by as much as 20 decibels.
If you want to be part of the change that allows us to tackle the world’s single greatest occupational health disease then educating yourself and your employees is the best place to start. Greater awareness and understanding of the risks can lead to the behavioural and administrative changes necessary to keep us safe at work. At KP Acoustics Research Labs, we have a range of CPD courses and can offer bespoke courses to help managers understand their responsibilities. Many of our courses are accredited by the Institute of Acoustics and you can find out more by visiting kpacoustics.com.
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