ABSTRACT
In the U.S. alone, there are some 8 million to 10 million workers who daily are exposed to occupational vibration (Wasserman et al, 1974). These vibration exposures are usually categorized into two groups (Wasserman, 1987). Whole body vibration (WBV), or headto-toe exposure, affects such employees as truck, bus, heavy equipment, farm vehicle, forklift, and overhead-crane operators. The second group is hand-arm vibration (HAV), or localized vibration exposure, mainly, but not exclusively, affecting employees who use all manner of vibrating pneumatic, electrical, hydraulic, and gasoline-powered hand tools. Rarely does one speak of “crossover exposures” between WBV and HAV except in the case of certain hand-tool usage such as road rippers or jackhammer-type tools, where the worker can choose either to grasp the tool with the hands, extending the tool away from the torso (HAV exposure), or to let the tool rest against the torso (WBV exposure) in an attempt to damp the vibration (Shields and Chase, 1988; Wasserman, 1989). Sometimes both can occur simultaneously, such as in motorcycling or mountain bike use. The medical effects of HAV and WBV are distinctly very different, as are their vibration exposure patterns and physical characteristics such as acceleration levels, vibration frequencies, and pathways into the human body. Thus it is common practice to discuss HAV and WBV separately because, although they share a common physics, they do not share a common physiology, nor do they share the same safety and health effects.
