Vibration containing multiple shocks - an occupational health perspective regarding ISO 2631 Part 5 (2004) and an alternative risk assessment

The ISO 2631- 5(2004) proposes a method to evaluate vibration exposure containing multiple shocks “in relation to human health”. However, the experimental basis and the soundness of the underlying model has been questioned and epidemiological studies confirming the validity of this model are lacking. Based on a review of the available literature the basis and application of the proposed standard and alternatives will be critically examined regarding occupational health applications. The algorithm utilized in ISO2631-5(2004) is based on military experiments and standard development. In the experiments military volunteers were chosen to study their pain threshold and other health parameters. A small number of healthy subjects (n=54), ages 19-40y, participated in a series of short and long-duration motion exposures. Long-duration experiments assessed fatigue and recovery to repeated shocks (up to 7 hours per day, or 4 hours per day for 5 days). ISO 2631- 5(2004)/ANSI method attempts to calculate vibration shocks for possible fatigue failure effects on the “vertebral bony endplate” (lumbar spine), for a subject in "normal health”, typically ahead of 20-25 years of exposure. Such specific findings are rare clinical endpoints in occupational medicine. No EU compensation system utilizes ISO 2631-5 at this time. An alternative risk assessment model has been proposed ("VibRisks") in which different posture- and body-mass-index (BMI)-dependent internal compressive and shear forces of the spine are considered. A comparison of occupational vibration data appears to indicate different risk projections utilizing both of these models, with the VibRisk model being more sensitive for occupational vibrations and conditions.