[Evaluation of health risk in machine operators exposed to whole body vibration].

A total of 45 machine operators employed at the same power station were examined with special emphasis put on the musculoskeletal system. A group of 15 bulldozer operators, 19 engine operators and 11 tractor drives were exposed to the whole-body vibration with average vertical equivalent acceleration ranging from 0.2 mg-2 to 0.5 ms-2 r.m.s. The incidence of low back complaints over a period of 12 months was similar to that observed in the occupational study groups. However, back pains combined with other health disorders were most common in bulldozer operators (80%) while the lowest percentage (36%) of such cases was observed among tractor drivers. The analysis of lifetime exposure to the whole body vibration in both groups showed that bulldozer operators worked only 5 years longer, on average, but they spent twice as many hours at work as tractor drivers. The study indicates that individual lifetime exposure to the whole-body vibration may play an important part in the evaluation of health effects.