A study on the vibration-dose limit for Japanese workers exposed to hand-arm vibration

To obtain a vibration-dose limit for Japanese workers exposed to hand-arm vibration, the prevalences of vibration-induced white finger (VWF) and numbness of the hand were studied in 5 different groups of workers exposed to segmental vibration. In addition, the prevalence of primary Raynaud's phenomenon (PRP) in the general population without occupational vibration exposure was computed. The vibration levels in the exposed groups (except chain saw operators) ranged from 124.1-129.2 dB (reference value, 10(-6) m/s2). The prevalence of VWF in these groups was 2.2-4.8%. This value was not statistically significant (p greater than 0.05) when compared to the prevalence of PRP in the general Japanese population (2.7-2.9% in our study and 0.5-4.6% in other surveys in Japan). Although the prevalence of numbness of the hands fluctuated among the groups, no significant differences could be demonstrated. Our results were then compared to those of previous reports by literature study [319 papers on hand-arm vibration syndrome (HAVS) and 25 reports on PRP]. At a glance the Japanese population showed a lower prevalence for PRP compared to other countries, which suggested that exposure to cold and biological abilities should also be considered to assess vibration syndrome. A comparison of the vibration characteristics of different tools and the occurrence of VWF in the hands of workers in the literature with those of our data suggested that a daily hand-arm vibration exposure at a level lower than 2.5 m/s2 (128 dB, reference value 10(-6) m/s2) could possibly decrease the risk of VWF among workers exposed to segmental vibration.