Vibration white finger
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Vibration white finger (VWF) is a secondary form of Raynaud's disease, an industrial injury triggered by continuous use of vibrating hand-held machinery. Vibration white finger is the vascular component hand-arm vibration syndrome or HAVS.
Vibration white finger is characterized by episodic blanching of the fingers in response to cold. Other symptoms can include numbness, tingling (parasthesia) and pain in the hands and fingers, but these are now believed to be a separate neurologic component of HAVS. The thumb is not normally affected. Smoking and stress are also thought to be factors. There are various medications that cause Raynaud's Disease, including beta blocker drugs, and various diseases, such as scleroderma, that can have similar symptoms. These other causes must be ruled out before a diagnosis of vibration white finger can be arrived at. In extreme cases, the sufferer may lose fingers. The effect is cumulative. When symptoms first appear, they may disappear after a short time. If exposure to vibration continues over months or years, the symptoms can become worse and become permanently present.
The disease was first linked to power tools by Professor Loriga in Italy in 1911, with the Taylor-Pelmear scale for assessing the condition published in 1975, but it was not listed as a prescribed disease in the United Kingdom until 1985, and the Stockholm scale introduced in 1987. In 1997 the Miners High Court awarded £127,000 in compensation to seven coal miners for vibration white finger. A UK government fund set up to cover subsequent claims by ex-coalminers had exceeded £100 million in payments by 2004.
The European Union passed Directive 2002/44/EC in 2002 on the minimum health and safety requirements for workers exposed to vibrations, to be ratified by July 2005.
Good practice in industrial health and safety management requires that worker vibration exposure is assessed in terms of acceleration amplitude and duration. Using a tool that vibrates slightly for a long time can be as damaging as using a heavily vibrating tool for a short time. The duration of use of the tool is measured as trigger time, the period when the worker actually has their finger on the trigger to make the tool run, and is typically quoted in hours per day. Vibration amplitude is quoted in metres per second squared, and can be measured by an accelerometer on the tool, or guessed by reference to comparable measurements. Amplitudes can vary significantly with tool design, condition and style of use, even for the same type of tool. The UK HSE gives the example of a hammer drill which can vary from 6 m/s² to 25 m/s². HSE publishes a list of typically observed vibration levels for various tools, and graphs of how long each day a worker can be exposed to particular vibration levels. This makes managing the risk relatively straightforward. HSE gives two figures for exposure duration, a limit to the daily trigger time for everyday use, and a limit for the trigger time in one day for a one-off exposure. At 6 m/s² these are 1 hour and 6 hours. At 25 m/s² these are zero and 15 minutes.
The effect of legislation on worker vibration limits is intended to drive employers to provide better-designed, better-maintained tools, and to train workers appropriately. It also drives tool designers to innovate to reduce vibration. One example is the suspension mechanism designed into chainsaws.
