Hand-arm vibration in snowmobile drivers.

Hand-arm vibration was measured on the handlebars of snowmobiles (N = 29) and a postal inquiry was made among reindeer herders, N = 2,705. Since many subjects had used also other vibrating tools a snowmobile group proper (N = 334) was established, and in this group 18% of the subjects reported that they had experienced white finger attacks and 48% numbness of the hands. The age-adjusted prevalence of the white finger syndrome was more than three times higher in the snowmobile group than in the controls. The frequency-weighted acceleration of snowmobile vibration was 3.5 m/s2, and risk evaluation based on the annex of the ISO 5349 standard predicted the prevalence of the white finger syndrome well in the snowmobile group. The most critical points for damping the vibration were the motor mounting and resonance in the steering yoke. There is a need for health care, technical improvements, changes in working habits and other protection means to reduce the symptoms of vibration associated with driving terrain vehicles.