REGULAR AND prolonged occupational exposure of the hands to high levels of vibration can cause the distressing and disabling condition known as handarm vibration syndrome (HAVS).
The symptoms can include numbness and tingling in the fingers, with loss of dexterity, painful attacks of vibration white finger (loss of finger blood supply), joint pain, stiffness and reduced grip strength.
Vibration exposure is also thought to increase the risk of carpal tunnel syndrome (CTS). The Health and Safety Executive (HSE) says that around 2 million people working in Great Britain are at risk.
There are many sources of vibration exposure at work. The most obvious are hand-held power tools such as road breakers, hammer drills, grinders and chainsaws. Other sources include handguided machines (eg mowers, rollers, plate compactors) and handfed machines such as pedestal grinders.
Employers have a common law duty of care – and a statutory duty – to protect their employees from health risks at work. Regulations dealing specifically with risks from vibration first came into force in 2005, but information and guidance has been available to employers for many years. The courts have decided various dates of knowledge for defendants, depending on the industry sector and the circumstances of the case, ranging from 1975 up to 1994.
In a successful claim for damages arising from vibration-related ill health, it is necessary to demonstrate causation and prove liability. Medical evidence deals with causation and is required to exclude any likely causes of a claimant’s symptoms other than vibration exposure, and to provide a diagnosis of HAVS (perhaps subject to confirmation of the alleged exposure) and an opinion on the severity of the condition.
The role of the engineering expert witness is to assist the court in determining liability. That usually includes an assessment of the level of the claimant's daily exposure to vibration – the ‘A(8)’ value – which depends on both the magnitude (level) of the vibration and the daily duration of the claimant’s exposure to it.
The assessment generally involves interpretation of witness and/or documentary evidence relating to the claimant's use of the work equipment; a site inspection can be useful in that respect.
The engineer may wish to measure the vibration magnitudes, but that is not always possible, particularly if the workplace or the tools no longer exist, and it may be necessary to rely on measurements made elsewhere. The likely A(8) is then compared with British Standard guidance on the likelihood of finger blanching in an exposed population, to help the court decide the foreseeability of risk and the likelihood of disease.
The exposure level is also compared (depending on the dates of the alleged exposure) with an ‘action level’ recommended by the HSE in 1994.
Where foreseeable risk has been established the engineering expert witness is likely also to be asked to comment on what actions if any could and/or should have been taken by the defendant to control the risk to the claimant. That may include investigation of the working method – could the job have been done differently to eliminate or minimise the need to use vibrating tools or equipment? – and whether the defendant provided and maintained tools and equipment that were suitable for the task. Also, was the claimant given appropriate information, instruction and training on the correct use of vibrating tools and equipment, the nature of vibration risks and how to control them?
It should be understood that it may not be possible for an employer to eliminate vibration exposures or reduce them to a completely ‘safe’ level. A possible defence of a claim would be that the defendant recognised the risk to the claimant’s health and took all reasonably practicable measures to minimise the exposure and the risk. It may be necessary to demonstrate that an appropriate health surveillance system was in place to deal with the residual risk, so that early symptoms of vibrationrelated ill health could be detected in individual employees and steps taken to prevent the development of the condition to a disabling degree.