AN EPIDEMIOLOGICAL STUDY ON RAYNAUD'S PHENOMENON AMONG WORKERS USING AN IMPACT WRENCH

摘要

The purpose of this study was to clarify the occurrence of Raynaud's phenomenon among workers using an impact wrench for a long time. The subjects were 704 workers regularly using an impact wrench and taking special medical examinations for vibration syndrome from 1981 to 2008. Raynaud's phenomenon was observed in 39 subjects during the observation period. The mean operating years at the occurrence of Raynaud's phenomenon was 25.5±8.3 (standard deviation) years. The mean total operating time (geometric average) at the occurrence of Raynaud's phenomenon was 11,689 hours. By the person-year method, the incidence rate of Raynaud's phenomenon was around 4 persons per 1000 person-years. This rate did not increase until 15 years after beginning of the observation, but increased linearly after that. The vibration level of an impact wrench (from 4.9 m/s~2 to 22.6 m/s~2) exceeded the occupational exposure limit value (4.9 m/s~2). Various countermeasures, such as introducing automatically apparatus and keeping the working environments warm to protect from cold exposure, were taken in the factory. The incidence rate of Raynaud's phenomenon was not high, although the vibration level of the impact wrench was high. This may result from various countermeasures. However, a long period of exposure to vibration had the potential to lead to the occurrence of Raynaud's phenomenon even under various countermeasures.