Risks of Occupational
Vibration Exposures
VIBRISKS
EC
FP5 project no. QLK4-2002-02650
Quality of Life and Management of Living Resources Programme
January 2003 to December 2006
Background
Millions of European
workers are exposed to mechanical vibration transmitted to their hands from
powered tools or transmitted to their whole body from the seats of industrial
vehicles. Disorders of the upper limbs caused by hand-transmitted vibration
are among the most compensated industrial diseases in several European states
and exposure to whole-body vibration is associated with disorders of the spinal
system.
The
currently standardised methods of assessing the severity of vibration exposures
are not based primarily on epidemiological evidence or on an understanding of
the relevant mechanisms of injury. They are not sufficient to predict the risks
of injury or define optimum means of preventing injury.
Objectives
The
principal objective of VIBRISKS was to improve understanding of the risks of
injury from exposures to hand-transmitted vibration and whole-body vibration
at work by means of multi-national epidemiological studies, supported by fundamental
laboratory research and biodynamic modelling. Secondary
objectives were:
- To contribute to a scientific
basis for political decisions on the adequacy of current preventive measures
and expenditure on prevention.
- To provide guidance on
health surveillance that can be applied by occupational health workers across
Europe for the minimisation of risk (primary prevention), the screening of
exposed workers, and the management of individuals who have symptoms of hand-transmitted
vibration injuries (secondary prevention).
- To help industry by
reducing the social and economic costs associated with disorders.
Work
Programme
The
studies of hand-transmitted vibration (HTV) and whole-body vibration (WBV) were
designed to be complimentary, since they involve many common tools and procedures.
For both HTV and WBV, the work was divided into three components:
- Coordinated multi-national
epidemiological field studies of dose-response relationships for adverse outcomes
arising from occupational exposures to vibration.
- Laboratory experimental
studies and biodynamic modelling to support the field investigations, including
the definition of alternative means of evaluating vibration exposures and
predicting risk.
- Supporting activities,
including: (i) the definition of methods to be used in the epidemiological
surveys, and (ii) the integration of the findings from the experimental and
biodynamic studies with the results of the epidemiological research so as
to provide occupational health guidance.
Results
and Achievements
Epidemiological studies
of hand-transmitted vibration
In Italy and Sweden, baseline
and follow-up longitudinal epidemiological studies were completed with groups
of workers having different exposures to hand-transmitted vibration. A second
follow-up survey was completed in Italy. The Italian survey provided evidence
of dose-response relationships for sensorineural and vascular symptoms and a
dose-effect relationship for cold-induced digital arterial hyper-responsiveness
and impaired manual dexterity in HTV-exposed workers. The Swedish study group
had only short vibration exposures, but significant associations were found
between indices of peripheral vascular and sensory dysfunction and measures
of daily and cumulative vibration dose. Vibration exposure and awkward neck
postures were associated with neck pain among the workers.
Experimental
and modelling studies
of hand-transmitted vibration
Collaborative experimental
studies on hand-transmitted vibration were carried out in Italy, Sweden, and
the UK to improve understanding of the effects of vibration magnitude, frequency
and duration on acute changes in both vascular function (finger blood flow and
finger systolic blood pressure) and neurological function (vibration perception
thresholds and thermotactile thresholds). The observed changes in vascular and
sensorineural function during and following vibration exposure were not consistent
with the 'energy-equivalent' time-dependency currently used to evaluate occupational
exposures to hand-transmitted vibration. The vascular studies suggest that intermittent
vibration is less hazardous than continuous vibration with the same 'energy'.
Reductions in finger blood flow were not limited to the finger experiencing
force and vibration. Both vibration magnitude and exposure duration influenced
thermotactile thresholds.
Experimental studies in
Italy and the UK suggested that recent exposure to force and moderate levels
of hand-transmitted vibration will not greatly affect finger systolic blood
pressure following cold provocation, as used to identify vibration-induced white
finger. In Sweden, prior exposure to vibration on the day of a test was found
to influence vibrotactile and thermotactile perception thresholds.
In the UK, studies of the
effects of age and gender on vascular function (finger systolic blood pressure
after cooling) and sensory function (thermotactile and vibrotactile thresholds)
provided normal values to assist the interpretation of clinical and epidemiological
studies of the hand-arm vibration syndrome.
In France, a 3-D biodynamic
model of a finger was elaborated to understand how vibration propagates in the
tissues and how to calculate internal mechanical properties, such as strain.
The studies also improved understanding of finite element calculations of visco-hyperelastic
behaviour.
Epidemiological studies
of whole-body vibration
In Italy, Sweden, the Netherlands
and the UK, baseline and follow-up longitudinal epidemiological surveys were
completed with groups of workers occupationally exposed to whole-body vibration.
A further follow-up survey was completed in Italy and an intervention study
in the Netherlands continues to investigate the effects of health surveillance
and other intervention measures. Various physical and psychosocial factors were
found to be associated with an increased risk of low back pain (LBP). The Italian
and the Dutch results were consistent with increased risk of LBP in those with
higher cumulative exposures to whole-body vibration. However, standardised measures
of daily vibration exposure were poorly associated with LBP. Studies in Sweden
and the UK did not find clear relationships between WBV and LBP.
The findings of the case-control
study in the UK suggest that, in the general population, WBV is not an important
cause of LBP that is severe enough to result in referral for MRI imaging of
the lumbar spine.
Experimental
and modelling studies
of whole-body vibration
In Germany, experiments
and modelling of the spinal system led to a new method of predicting spinal
stress from vibration in vehicles. A numerical model of the spinal system was
extended to predict load on the spine from the forces caused by combinations
of driver posture and whole-body vibration. When applied to the vibration measured
in the epidemiological studies, the evaluations indicated an underestimation
of health risks by the exposure limit value in the Physical Agents (Vibration)
Directive.
Supporting
activities
Protocols were developed
for the epidemiological studies of hand-transmitted and whole-body vibration.
These defined measures of vibration dose, means of summarising exposures and
their effects, and self-administered and clinically-administered questionnaires
for the baseline and follow-up studies. The protocol for hand-transmitted vibration
also defined tests for diagnosing the hand-arm vibration syndrome. The protocols
are valuable guides for future research and should also assist clinical studies.
VIBRISKS also produced
health surveillance guidance that will help occupational health workers to minimise
risk, screen exposed individuals, and manage individuals with symptoms of vibration
injuries.
Conclusions
The epidemiological
and experimental studies of hand-transmitted vibration indicate that improvements
are possible to the frequency weighting and the time-dependency currently used
to predict the risks of vibration-induced disorders. The results confirm that
finger systolic blood pressure after cold provocation is related to vibration
exposure, and that both thermal thresholds and vibrotactile thresholds are indicators
of sensorineural damage caused by hand-transmitted vibration.
The studies of whole-body
vibration indicate that improvements are needed to the method of predicting
risks to the low-back. Risks of injury to the low-back due to mechanical forces
are complex and multi-factorial and cannot be predicted solely from measurements
of vibration. Especially important are postural factors that have been shown
to influence spinal forces and the risk of low back pain.
The findings have implications
for the Physical Agents (Vibration) Directive of the EU and the development
of new standards. However, the subject is very complex and there are many implications
associated with any change to current procedures. Further research on hand-transmitted
and whole-body vibration is required before specific changes can be confidently
recommended.
Benefits
and Beneficiaries
VIBRISKS has contributed
to the prevention and control of vibration-induced disorders by disseminating
new methods, new findings, and experience from the project to occupational health
professionals, standards committees (national, European, and International),
and to employers and their workers.
The VIBRISKS Final Report
and all 21 Annexes are publicly available to assist others undertaking relevant
research. The VIBRISKS protocols for diagnosing vibration-induced injuries,
and the VIBRISKS guidelines for the health surveillance of persons exposed to
hand-transmitted vibration or whole-body vibration, are available for application
by occupational health workers across Europe and worldwide.
Two international conferences
and workshops were organised by the VIBRISKS project team to disseminate information
from the project: (i) the 3rd International Conference on Whole-body Vibration
Injuries in Nancy, France (7-9 June 2005) and (ii) the 2nd International Workshop
on HTV Injuries in Gothenburg, Sweden (6-7 September 2006). The results are
also presented in many papers already published or awaiting publication in scientific
journals.
Partners
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UoS
University of Southampton, U.K. (Coordinator)
including
contacts
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UTRS
Institute of Occupational Medicine, University of Trieste, Italy
in association with
- Physical Agents Laboratory, Department of Prevention
(USL7), Siena
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FIOSH
Federal Institute for Occupational Safety and Health, Berlin, Germany
in
association with
- Woelfel Consulting Engineers GmbH, Höchberg
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UMUH
Department of Biomedical Engineering & Informatics, University Hospital
of Northern Sweden
in association with
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AMC
Academic Medical Centre, University of Amsterdam, The Netherlands
contacts
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INRS
Institut National de Recherche et de Sécurité, Nancy, France
contacts
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European Commission
Funded
by the 5th Framework Programme
contacts
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