Single shocks on hand-arm system caused by machines and tools

Status:

completed 06/2022

Aims:

Aim of the research project was to identify whether single-impact exposures to the hand-arm system can contribute to greater health problems than general hand-arm vibration exposures. It was to work out how relevant this type of exposure may be in a professional context.

As part of the research project (FP415), the health effects of single shocks on the hand-arm system were examined in comparison to vibration exposure. Thereby:

• Exploring of workplaces with single impact exposures
• Modeling of health effects of single-shock exposures
• Assessment of the early health effects of single-shock exposures on the hand-arm system
• Evaluation of relationships between exposure and health effects
• Possible leisure time confounders were investigated in more detail.

Activities/Methods:

In terms of methodology, questionnaire surveys, systematic literature research, modeling, an experimental pilot project, a randomized, controlled experimental study, a standardized device measurement under laboratory conditions and an exposure and effect measurement of non-professional/leisure time activities (on the sports/training grounds ) were carried out. Due to the large number of methods used, reference should be made here to the methodological parts of the various work packages (WP 1 to 4 in the respective appendices of the report).

Results:

Single shock exposures in the low dose range seem to occur in many occupations (WP1). These exposures are epidemiologically associated with health problems (especially in the hand area). The modeling approaches (WP2) show that one reason for the health effects in the hand area can be the entries of low-frequency and high-frequency impact or vibration components. The measurement methodology for physiological effects (WP3) identified from the systematic literature search can be used for both single shock and vibration exposures. Both the pilot study and the main study (WP4) indicate that early neurological effects (vibration perception threshold) are already to be expected below the action values, depending on frequency and dose. Furthermore, a change in finger temperature is associated with single shock exposure, although a dose-dependency cannot be made absolutely probable here. A frequency dependency seems to be emerging. At the selected dose (below the action values), muscular activation but no fatigue of selected muscle groups in the forearm and upper arm can be detected in the EMG. In contrast, an at least frequency-dependent reduction of pinch force of the exposed hand can be seen. A serial use of single shock exposures and spectrum vibrations seems to be able to contribute to an increased perception of health complaints (paraesthesia). The results can also be found in the examined devices/tools (bolt setter, nailer, drill hammer) - especially in the neurological area. Finally, it can be stated that various leisure time activities (e.g. tennis and golf) are suitable for exceeding exposures in the action or limit value range.

Overall, transient physiological effects could already be detected below the currently applicable action values. Since the relationship between transient effects and overt dysfunction has not yet been clarified, it is possible that the current methods for calculating exposure values (ISO standards) do not provide adequate protection for health effects from single shock exposures. Suggestions for preventive programmes are deducted from the study results.

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