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Vibration - Occupational - Hand Arm Vibration Syndrome [HAVS]

The Control of Vibration at Work Regulations have come into force (see below). 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 is "Hand Arm Vibration Syndrome".  Find out more at the HSE website.

Hand Arm Vibration Syndrome is typically caused by using tools, such as jack-hammers and chain-saws; however, vibration exposure can occur when guiding work-pieces through machinery, e.g. pedestal grinders.

Assessment of Damage
In the appendix to BS. 6842:1987 "Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand" [replaced by BS EN ISO 5349-1:2001] detailed methods of measuring and assessing the vibration, the probability of causing vibration damage symptoms was 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:

Table of Frequency Weighted Vibration Magnitudes [m/s² r.m.s.] which may be expected to produce finger blanching in 10% of population

Daily Exposure Hours

Exposure Duration [years]

½

1

2

4

8

16

8

44.8

22.4

11.2

5.6

2.8

1.4

4

64.0

32.0

16.0

8.0

4.0

2.0

2

89.6

44.8

22.4

11.2

5.6

2.8

1

128.0

64.0

32.0

16.0

8.0

4.0

½

179.2

89.6

44.8

22.4

11.2

5.6

¼

256.0

128.0

64.0

32.0

16.0

8.0

In an investigation of a employee’s vibration history, the first factor looked for, is use of a tool which would produce a frequency weighted acceleration in excess of 1.0 m/s²; then, if the vibration dosage 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 were recommended:

  1. Measure the vibration.
  2. Where appropriate and reasonably practicable, choose a process to minimise and control the vibration exposure.
  3. Maintain equipment carefully in accordance with the manufacturer's instructions.
  4. Arrange for pre-employment medical screening, and at regular intervals for as long as the vibration exposure continues.
  5. Encourage employees to report 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. Control work schedules to include rest breaks.

 

The Control of Vibration at Work Regulations 2005

Further and more comprehensive details of the Control of Vibration at Work Regulations 2005 can be read in the HSE publications INDG175 and L140.  The following is a brief extract of INDG1755.

The Exposure Action Value

The exposure action value (EAV) is a daily amount of vibration exposure above which employers are required to take action to control exposure. The greater the exposure level, the greater the risk and the more control employers will need to install. For hand-arm vibration the EAV is a daily exposure of 2.5 m/s2 A(8).

The Exposure Limit Value

The exposure limit value (ELV) is the maximum amount of vibration an employee may be exposed to on any single day.  For hand-arm vibration the ELV is a daily exposure of 5 m/s2 A(8). It represents a high risk above which employees should not be exposed.

The Regulations allow a transitional period for the limit value until July 2010. This only applies to work equipment already in use before July 2007. The exposure limit value may be exceeded during the transitional period as long as the employer has complied with all the other requirements of the Regulations and taken all reasonably practicable actions to reduce exposure as far as possible.

Requirements

 The Control of Vibration at Work Regulations require employers to

  • assess the vibration risk to employees;

  • decide if they are likely to be exposed above the daily exposure action value (EAV) and if they are:

  • introduce a programme of control to eliminate risk, or reduce exposure to as low a level as is reasonably practicable;

  • provide health surveillance (regular health checks) to those employees who continue to be regularly exposed above the action value or otherwise continue to be at risk;

  • decide if they are likely to be exposed above the daily exposure limit value (ELV) and if they are:

    • take immediate action to reduce their exposure below the limit value

    • provide information and training to employees on health risks and the actions taken to control those risks.

    • consult a trade union safety representative or employee representative on the proposals to control risk and to provide health surveillance;

    • keep a record of the risk assessment and control actions;

    • keep health records for employees under health surveillance

    • review and update risk assessments regularly.

    •  

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