Vibration - Occupational - Hand Arm Vibration Syndrome [HAVS]

Workers whose hands and arms are regularly exposed to high vibration levels may experience injury to the hands and arm; these injuries include damage to the blood circulation system and to the nerves and muscles; one of the symptoms can be finger blanching and numbness which gives the condition its other name of Vibration White Finger or VWF. However, the correct term for the collection of injuries is "Hand Arm Vibration Syndrome".

Typically exposed workers will be using powered tools, such as jack-hammers and chain-saws; however, harmful exposure to vibration could occur to employees guiding work-pieces through vibrating machinery, for example using pedestal grinders.

Assessment of Damage
Draft for Development DD43 published by BSI in 1975, has now been superseded by BS. 6842:1987 "Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand". This document details methods of measuring and assessing the vibration. In the appendix to the Standard, the probability of causing vibration damage symptoms is expressed as follows:

1. The daily exposure time required to produce symptoms is inversely proportional to the square of the vibration level; i.e. 8 hours/day exposure at any given level is equivalent to 2 hours/day at twice the vibration level.
2. In terms of years of exposure, the probability of developing finger blanching [Taylor Pelmear Stage I symptoms] is inversely proportional to the level of the vibration. Consequently, if the vibration level is halved, the time before the onset of symptoms will tend to be doubled; i.e. 3 years' exposure at any given vibration level, is a likely to produce the same degree of finger blanching as 6 years exposure at half that vibration level.
3. It appears that with normal tool usage, symptoms do not usually occur if the frequency weighted acceleration is below about 1.0 m/s² [certain frequencies are more damaging than others and therefore are given more weight]. Thus for a low-vibration tool [below 1.0 m/s²], it is unlikely that any damage will occur no matter how long the exposure.

It can be seen that the relationship between daily exposure, years at any given exposure and vibration magnitude are complex. The equivalent exposures are produced in Table 5 of BS.6842:1987. This table reproduced below gives the equivalent exposures at which would produce finger blanching symptoms in 10% of an exposed population:

In an investigation of a employee’s vibration history, the first factor looked for, is use of a tool which would give rise to a frequency weighted acceleration in excess of 1.0 m/s²; then, if the vibration dosage, to which he was exposed, would have caused finger blanching [or worse] in more than 10% of an exposed population.

Preventative Measures
At Appendix B of BS. 6842:1987, various methods of reducing the risk of vibration white finger damage are recommended:

1. Measure the vibration.
2. Where appropriate and reasonably practicable, choose a process to minimise the vibration exposure.
3. Maintain equipment carefully in accordance with the manufacturer's instructions.
4. Arrange for medical screening of employees prior to employment in this type of work, and at regular intervals thereafter for as long as the worker continues to be exposed to vibration.
5. Encourage employees to report and demonstrate finger blanching when it first occurs and if there is a deterioration.
6. All individuals who use vibrating equipment should be advised of the risk of exposure to hand arm vibration.
7. Work schedules with rest breaks are recommended.

There is an extensive on-line directory of Hand Arm Vibration measurements available elsewhere.  Hand Arm Vibration Syndrome [HAVS] used to be known as Vibration White Finger [VWF], therefore, for our purposes they are the same thing. 

<<< Back to Vibration Occupational Introduction