Re-analysis of and amendments to the epidemiological study of whole-body vibration (BIA Project 4050)

Status:

completed 06/2009

Aims:

The findings of an earlier epidemiological study into the hazard presented to the spine by whole-body vibrations on various mobile machines had to be reconsidered owing to to changes to measurement and assessment in the course of European harmonization. The changes concern: consideration in the previous project of the vertical vibration axis (in the direction of the spine) alone; the extension of the considered frequency range; the frequency weighting; and the calling into question of the dose method. To this are added efforts to consider not only the root mean square value of the weighted acceleration, but also other parameters which more strongly reflect the shock component of the vibration load and which include a force weighting. The re-analysis, funded with a research focus upon vibration, of the earlier project was to examine these changes and additions and to ascertain whether they led to fundamental changes in or additions to the project results.

Activities/Methods:

In a sub-project, the results of the epidemiological study were examined; the study was to give consideration to the horizontal axes of vibration. The vibration exposure values determined in the previous project were adjusted to the new frequency weighting and the extended frequency range by means of correction factors. Known existing shock weighting methods and various dose methods were also to be considered. In a second sub-project, a force weighting was determined which considered in the first instance the conditions of the original epidemiological study, and then the impact of the changes arising through the present study. The background to this phased procedure was that each phase must involve uncertainties the effects of which could be predicted more effectively by this means. The task of the BGIA - Institute for Occupational Safety and Health was to review the data records obtained in the previous project, to add to them where appropriate, and to provide expert supervision of the re-analysis.

Results:

In sub-project A, the new frequency weighting was shown to have only a minor influence upon the statistical description of a risk of lumbar spine syndrome (low-back pain). Accordingly, the essential results of the previous assessment remain valid. For example, age is once again the most important parameter for the risk of suffering lumber spine syndrome. In addition, only minor differences were found between the parameters studied. The vibration exposure can therefore also be described well by the parameter provided for in the German OHS regulation governing noise and vibration: the daily vibration exposure value A(8). This value also takes horizontal vibration axes into account. In addition, sub-project B presented a force-related parameter which describes the exposure caused by whole-body vibration.

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