A Cohort Study on Raynaud's Phenomenon in Workers Exposed to Low Level Hand-Arm Vibration

Abstract

Abstract: A Cohort Study on Raynaud's Phenomenon in Workers Exposed to Low Level Hand-Arm Vibration: Kotaro TOMIDA, et al. Department of Hygiene, School of Medicine, Wakayama Medical University-To clarify the incidence of Raynaud's phenomenon among workers exposed to low level hand-arm vibration for a long time, a sample cohort of workers mainly operating a bush cleaner (the vibration level was 2-4 m/s 2 rms) were followed up for a period of 20 yr. The sample cohort consisted of 331 male workers mainly working at maintaining public roads or afforesting and gardening on a farm. The examination was based on questionnaires used in special medical examinations for vibration syndrome from 1977 to 1996. Raynaud's phenomenon was observed in 11 subjects. The accumulative occurrence rate increased linearly in the case of more than 11 operating years. The mean number of operating years at the occurrence of Raynaud's phenomenon was 11.7 ± 7.1 yr. The mean total operating time at the occurrence of Raynaud's phenomenon was 3,756 h on the geometric average. Stockholm Workshop scale classified 1 subject as Stage 1 (mild), 4 subjects Stage 2 (moderate) and 6 subjects Stage 3 (severe). By the person-year method, the incidence of Raynaud's phenomenon was 4.48 per 1000 person-year. These findings show that the number of operating years for a bush cleaner should be considered to prevent Raynaud's phenomenon, even though the hand-arm vibration level is low. In recent years, the work control against exposure to hand-arm vibration has well been established and thereby Received Feb 7, 2000; Accepted Aug 6, 2000 Correspondence to: K. Tomida, Department of Hygiene, School of Medicine, Wakayama Medical University, 811-1 Kimiidera, Wakayama 641-8509, Japan exposure time to hand-arm vibration has been decreased. Vibrating tools have been improved and the exposure level has been decreasing 1) , but exposure to low level hand-arm vibration has induced long-term exposure to hand-arm vibration in workers operating vibrating tools. Under such conditions of the long-term exposure to low level hand-arm vibration, the occurrence of Raynaud's phenomenon has not yet been examined sufficiently. We have given special medical examinations for vibration syndrome for a long time to workers mainly operating bush cleaners. The exposure level of a bush cleaner seemed to be much lower than that of a chain saw, but a bush cleaner can also cause Raynaud's phenomenon in operators. In this study, a sample cohort of workers mainly operating bush cleaners were followed up for a period of 20 yr to clarify the occurrence of Raynaud's phenomenon in workers exposed to low level hand-arm vibration for a long time