No main differences were observed between the personal characteristics of the three groups. According to the Stockholm scale, the sensorineural symptoms were mainly at stage SN1, with 9% at stage SN2 and none at stage SN3. These symptoms are associated with exposure to vibration, and had a prevalence of 40% in group 1, versus 20% in the two other groups. Furthermore, 25% of the workers exposed to vibration complained of symptoms at least once a week, compared with only 2% in the other groups