Hand-arm vibration exposure and the development of vibration syndrome.

To evaluate the circulatory disturbances, sensory disturbances and damage to muscles and joints by chain saw vibration exposure, the process of the deterioration of the symptoms with chain saw operating time was studied. Subjects were classified into eight groups according to TOT (Total Operating Time): Group 0, 46 controls; Group A, 39 operators (< 2,000 hours); Group B, 53 operators (2,000-4,000 hours); Group C, 45 operators (4,000-6,000 hours); Group D, 29 operators (6,000-8,000 hours); Group E, 31 operators (8,000-10,000 hours); Group F, 35 operators (10,000-15,000 hours); and Group G, 34 operators (> 15,000 hours). The subjective symptoms and clinical findings due to operating chain saws were divided into three main categories of peripheral circulatory disturbances, sensory disturbances and damage to muscles and joints. According to the criteria, the total score of each disturbance was calculated per individual in Group 0 and Groups A through G, respectively. The scores for the three (circulatory, sensory, muscles and joints) disturbances increased significantly with the increase of TOT. The scores for circulatory disturbances increased significantly in Group A and B, as compared with those in its previous Group, respectively. The scores for sensory disturbances increased significantly in Groups A, B, and F. The scores for damage to muscles and joints increased significantly in Group B.