In light of new research pointing towards a link between incessant noise in the workplace and cardiovascular disease, Simon Bull offers some pointers on hearing conservation methods and practices.
Persistent noise at work could more than double the risk of heart disease, a new study by researchers at the University of British Columbia suggests.1
Of course, it is early days for research in this area and it is, after all, only one study. Nevertheless, with more than 1 million employees in Great Britain exposed to high levels of noise that can put their hearing at risk,2 the research could indicate a significant additional risk of heart disease to many workers.
The study looked at 6307 people in the US, all of whom were employed and all over the age of 20. It then went on to compare those exposed to ‘loud’ noise at work against those who were not – with ‘loud’ defined as loud enough to force workers to shout to be heard. The study found that employees who endure chronic exposure to noise on the job are more than twice as likely to suffer serious heart disease and high-blood pressure than those in quieter occupations.
A further report from the World Health Organisation identified a chronic 50dB night-time level (i.e. a persistent level at 50dB) as being sufficient to cause strain on the cardio-vascular system.3 Translated into the workplace, where levels of 80dB are considered acceptable, current occupational noise levels could be a far bigger problem than previously thought.
It has been known for some time that continual noise exposure causes many more health problems other than hearing damage. A search on Wikipedia lists such conditions as hypertension, bowel movements, sleep disturbance, tinnitus and even premature ejaculation!4 The relative risks of developing these types of conditions are not clear, which is why this latest study could be an important step in our understanding. Consequently, employers may have to rethink how they approach the issue of noise exposure in their workplaces and how to control its effects.
Industry needs to recognise that noise levels cannot be controlled with the use of hearing protection alone, while many employers will also consider further measures to bring down noise exposure to much lower levels as either cost-prohibitive, or technically problematic.
The role of hearing protection
The Control of Noise at Work Regulations 2005 do not consider health conditions other than noise-induced hearing loss.5 What the Regulations and accompanying guidance do say, however, is that noise should always be reduced so far as is reasonably practicable, irrespective of the legal thresholds at which certain action should be taken, or whether or not hearing protection is used.
Logically, if there is a responsibility to reduce the risk caused by noise exposure and it turns out that persistent noise well below the level of 80dB(A) does indeed present a risk of heart disease, then surely there is a direct duty to significantly reduce levels well below current best practice.
An added complication is that, according to the guidance to the Regulations, “protectors that reduce the level at the ear to below 70dB should be avoided”. This may sound contradictory to the requirement to reduce noise to as low a level as practical, but hearing protection that provides too high a protection value can ‘mask’ other sounds, such as warnings and alarms.
However, before even thinking of reducing noise to much lower levels, it is essential that companies begin by implementing a hearing conservation programme, as this will form the foundations of any future noise-reduction efforts. This is a process that involves three main parts, all of which must be effectively implemented for the system to work: health surveillance, risk assessment and noise control.
Health surveillance
It is important to remember that there will only ever be a small number of people in any organisation who are truly at risk of suffering noise-induced hearing loss. Such people may simply be more susceptible to hearing damage. Alternatively, they might not wear hearing protection properly, or they might just be exposed to noise more than anyone realised.
Finding out who among their workforce are at heightened risk will require employers to carry out health surveillance for noise-induced hearing loss, which really amounts to one thing – hearing tests. Questionnaires and interviews will form part of a comprehensive testing programme, together with audiometry. As well as a person who is competent to conduct the audiometry tests, companies will also need a system for dealing with any results that highlight a potential problem.
Noise at work risk assessment
Assessing the risk of injury to an employee from noise means working out how much noise they are being exposed to – it is as simple as that! The Control of Noise at Work Regulations state the levels of exposure that are known to cause problems but, if there are potential health risks at levels below these thresholds, it is even more important to know what levels workers are exposed to in practice, so that any reductions can be quantified in consideration of all the risks posed by the noise. It is also true that employers may struggle to defend a compensation claim for noise-induced hearing loss without actual measurements in the workplace.
The biggest mistakes
There are two main mistakes that are consistently made by people carrying out noise at work assessments.
The first mistake is a really basic one, which is simple to correct and concerns the measurement position. The guidance to the Regulations says the noise should be measured at the position of the operator’s head, preferably without the operator being present! If they do need to be present then the measurement should be made at least 15cm away but near enough to be representative.
Without proper training, there is a strong temptation for employers to produce noise maps as a means of carrying out risk assessment. Noise maps are simply a plan of a workplace with noise levels shown at various points and sometimes with contour lines joining levels of equal loudness together, the idea being to show what noise levels are at any given place in a factory. For risk assessment, measurements should only ever be taken at the operator’s head position at their places of work; noise maps have no place in this process and should only be used if there is a specific need – for example, in noise control when mapping out noise-activated signage.
The second mistake people make is based on the understanding of exposure and what the action values actually mean in practice.
The lower action value in the Noise at Work Regulations is set at 80dB(A), but this value is only relevant if the exposure is for eight hours. If an employee works at a machine where the sound level is a constant 80dB(A), then he will only be at the action level if he stays in that area of noise for a full eight hours. If the process is only worked for four hours, then that employee would only experience half the exposure. To put it another way, if the noise level is well above 80 or 85dB, but the time spent in that area is only short such that the exposure is below 80dB, then the worker will not exceed the legal exposure level.
A further complication is that an employee may work on two or more different processes in one eight-hour period. Thankfully, the HSE website includes a tool that can be used to calculate the daily noise exposure, even if several tasks are involved.6
Noise control
The idea that control is the way to deal with noise in the workplace is implicit in the title of the legislation. This is also backed up by the fact that hearing protection must only be considered as a ‘last resort’ measure. Furthermore, it is now suggested that hearing protection alone cannot protect against certain non hearing-related risks associated with noise at work.
Controlling noise should involve an engineering process but, in this regard, health and safety professionals cannot be expected to design, or implement noise-control measures, as this is a specialist field of work. Having said that, there are some actions that safety practitioners can adopt, which can yield significant results, and others that should be treated with caution.
It’s a circle of life
Hearing conservation should be viewed as a circular process, in which all the parts highlighted above are interdependent. Surprisingly, there are many companies that don’t have a fully functional line of communication between health and safety and occupational health. The results of audiometric testing should trigger specific assessments, which, in turn, should guide the process of control and the use of PPE. Conversely, audiometric testing should also be prompted by risk assessments, highlighting certain people in high-risk jobs. This process should go round until you achieve an air-tight system that truly stops people suffering hearing problems as a result of their work.
References
1 Wen Qi Gan, H W (2010): ‘Exposure to occupational noise and cardiovascular disease in the United States: the National Health and Nutrition Examination Survey 1999–2004’, in Occupational and Environmental Medicine, http://oem.bmj.com/content/early/2010/09/06/oem.2010.055269.abstract?sid=b669c493-0594-4bf4-b8b4-787e36998ba3
2 www.hse.gov.uk/noise/index.htm
3 WHO (2005): Quantifying burden of disease from environmental noise: Second technical meeting report. Bern, Switzerland: World Health Organisation
4 Wikipedia – Health effects from noise (accessed 11 November, 2010) http://en.wikipedia.org/wiki/Health_effects_
from_noise
5 HSE (2005): Controlling noise at work: The Control of Noise at Work Regulations 2005, HSE Books
6 www.hse.gov.uk/noise/calculator.htm
Simon Bull is managing director of Castle Group Ltd.
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