[A study on the vibration hazards due to using bush cutters (author's transl)]

Bush cutters were introduced into Japanese forestry for cutting bush in 1957 or thereabout. Thereafter, they have been used widely not only in forestry but also in agriculture, public engineering, etc. In spite of the fact that vibration acceleration levels of the bush cutters are high, vibration hazards due to using these tools have not been studied. The reason lies in few professions using bush cutters exclusively. Moreover, the tool is only used seasonally from June to September. The author examined 641 bush cutters users in the State Forestry in southern Kyushu and compared the results with a sample of chain saw users matched by age, duration of use, and district. The prevalence rate of Raynaud's phenomenon is 0.4% at 4 years after beginning the use of bush cutters, 4.0% after 10 years and 9.2% after 18 years. The prevalence of Raynaud's phenomenon in chain saw users is twice as great as that in bush cutter users. Bush cutter users are attacked by Raynaud's phenomenon after about 1,000 hours' use of the tool. The difference is regarded to depend on the difference in the density of use and the difference in the levels of vibration acceleration. The vibration hazards due to using bush cutters were characterized by relatively mild complaints in the upper extremities, together with disturbances of peripheral circulation but not always with peripheral neuropathy.