[The effect of whole-body vibration: an unrecognized medical problem]

Exposure to whole-body vibration is a growing concern in industry, traffic and in other branches of the economy. This harmful physical factor endangers work efficiency and human health not only at work but also in everyday life, in public transportation and even at home. In spite of increasing exposure to vibrations, our medical practice does not pay adequate attention to the health effects of whole-body vibration. The paper deals with the basic characteristics of vibration (frequency, amplitude, velocity and acceleration), its adequate evaluation (effective or weighted average value, peak values, rating and weighting procedure of vibration measurement) and exposure (vibration direction, exposure time, transmission and dissipation). In industry and traffic, vibrations present complex oscillatory motions, characterized by a wide frequency spectrum, variable amplitude and acceleration, and different directions. To assess the harmful effects of vibration, the International Organization for Standardization (ISO) has proposed three standards for acceptable human exposure to whole-body vibration: fatigue-decreased proficiency boundary, exposure limit and reduced comfort boundary. Quantitative parameters of vibration for some vehicles, and for constructional, industrial and agricultural machinery are also given. The most pronounced long-term effect of whole-body vibration is damage to the spine. The spinal region most frequently affected is the lumbar part, where spinal deformation, lumbago and sciatica can develop. The possible cause of spinal damage could be mechanical overload and metabolic changes of the intervertebral disc. Other organ systems, such as peripheral and autonomic nervous, vestibular, vascular, digestive and female reproductive systems are also liable to become affected. Risk assessment of chronic health effects is based on the appropriate evaluation of whole-body vibration exposure and individual response. Health risk increases with the intensity and duration of vibration exposure. The concomitant factors are forced sitting posture and heavy physical work. Human response to whole-body vibration depends on factors promoting the development of degenerative changes such as constitution, previous spine disease and young age. The main problems in diagnosing whole-body vibration syndrome are differentiation of vibration induced disorders from age dependent changes of the spine and lack of a specific diagnostic method for assessing those changes. Therefore, only permanent medical surveillance can guarantee proper assessment of the damage induced by whole-body vibration. For vibration exposed workers preplacement and periodic examinations are recommended. Those should include a basic medical examination and an X-ray of the spine, or at least of its lumbar part.