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RR479 - Temporary threshold shifts as indicators of hand-arm vibration exposure

Current methods of assessing vibration exposure are based on measurements of exposure time and vibration magnitude that are weighted according to their frequency (International Standard ISO5349-1). However, whether this approach is valid for both vascular and sensory hand-arm vibration syndrome (HAVS) is unknown. In addition, other factors such as grip and posture are also important in determining the energy absorbed.

Vibration and thermal perception thresholds are commonly used as indicators of damage to the peripheral neurosensory systems and are used to aid diagnosis of HAVS. Temporary changes in perception of vibrotactile and thermal sensitivity occur following vibration exposure. In this study we wished to investigate:

  1. the duration of vibration exposure required to reliably elicit a temporary threshold shift (TTS);
  2. the relationship between these changes and acceleration level of vibration;
  3. establish how these changes are related to the frequency of vibration.

It was found that the duration of vibration exposure made very little difference to the extent of the TTS, and consequently an exposure period of 15 minutes was chosen as the standard exposure. The TTS in vibrotactile perception measured at 125Hz increased with increasing acceleration level of vibration and was also related to the frequency of vibration, with lower frequencies having the greatest TTS.

The pattern of change in TTS at 125Hz with the frequency of vibration exposure was similar to the frequency –weighting published in ISO5349-1. However, ISO5349-1 may underestimate the effects of frequencies in the range of 16 to 250Hz when compared to this study.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

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Updated 2010-03-19