Journal Articles

Bovenzi M, Apostoli P, Allessandro G, et al. Changes over a workshift in aesthesiometric and vibrotactile perception thresholds of workers exposed to intermittent hand transmitted vibration from impact wrenches. Occ and Envir Med 1997; 54:577-587.

The use of impact wrenches can cause a deterioration of tactile perception in the fingers, according to this study from the Institute of Occupational Medicine at the University of Trieste in Italy. The deterioration can occur even when the worker’s daily exposure to the impact wrench’s vibration is at a level generally considered to pose little risk.

An impact wrench is a power tool that delivers significant amounts of vibration to the worker’s hands. Occupational exposure to vibration from hand tools is associated with an increased risk of neurological, vascular, and musculoskeletal disorders of the upper arms. Early symptoms include intermittent tingling and numbness in the fingers and hands. Workers may have reduced tactile function, meaning they have reduced senses of touch, temperature, pain, and dexterity.

The researchers studied 30 workers who used impact wrenches in their daily work, plus 25 controls who performed manual labor but did not use impact wrenches or other tools that deliver substantial vibration to the hands. The tactile function of the workers’ hands was measured before and after work, and the results showed that those using impact wrenches lost tactile function.

"A significant temporary threshold shift in vibration perception at all test frequencies was found in the workers exposed to vibration but not in the controls," the researchers report. "A significant increase in depth sense perception thresholds was found in the men exposed to vibration."

The degree to which the tactile function was impaired was directly related to the amount of vibration received from the impact wrench over a workshift. Tactile function can be diminished even when the worker is not exposed to what is considered an excessive degree of vibration.

"The loss of tactile sense can also disturb the manual control of power tools, increasing the risk of accidents at the workplace," the researchers say.