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A review of the state of the art on hand-arm and whole-body vibration
G. Miccoli
Earth-Moving Machinery and Off-Road Vehicles Institute, CEMOTER National Research Council, CNR, 44044 Cassana (FE), Italy
[email protected] A review is presented of the state of the art on hand-arm and whole-body vibration. Attention is paid on the evaluation of exposures to this kind of vibration, dose-effect relationships, diagnostic tests, improved methods and measurement techniques for vibration injuries, testing of protective equipment. Applicability and limitations are taken into account of relevant current standards methods and their development. Reference is made to the up-to-date European projects dealing with hand-arm and whole-body vibration subject.
INTRODUCTION Over the last ten years, great attention has been devoted to the situation regarding European normative studies in the human transmitted vibration field. Studies concerning this subject are entrusted to CEN/TC 231 [1] for the standardization in the field of mechanical vibration and shock, including: methods for measuring mechanical vibration and shock, methods for assessing exposure to mechanical vibration and shock, methods for reducing risks resulting from exposure to mechanical vibration and shock by machine design, methods for measuring and assessing the vibration and shock reduction characteristics of personal protective equipment, e.g. gloves, vibration isolators, e.g. handles, and suspension systems, e.g. seats. Occupational exposure to mechanical vibration can cause injury to the hands and arms and to the spinal system. Vibration transmitted to the hands and fingers from powered hand tools causes neurological, vascular (e.g. ‘vibration-induced white finger’), bone and joint disorders in the upper limbs. Vibration transmitted to whole-body through seats is associated with musculo-skeletal disorders of the spinal system, such as low back pain, early degeneration of the spine and herniated discs. The main reference is given by ISO standard 5349: 2001 as far as hand-arm vibration measurement and professional exposure risk evaluation are concerned. Standard ISO 2631-1:1997 (actually to be revised) represents the parallel technical reference for whole-body vibration. Although precise standards exist in order to evaluate human exposure to both hand-arm and whole-body vibration, the assumed dose-effect relationships are not
fully substantiated and do not take account of the many confounding factors that influence the hazards to workers. Moreover, there are no harmonized methods for regular health surveillance, protocols of which need to be supported by objective diagnostic tests, hazard surveillance and methods for protecting workers against hazards. Up-to-date European projects can be ascribed, proposing new and improved vibration measurement and analysis techniques or dealing with detection and prevention of injuries due to occupational vibration exposures. It is author’s mind not to summarize all the details and specifications, considered well acquired, of the relevant standards dealing with hand-arm and whole-body vibration. Simply their applicability, limitations and development are taken into account.
HAND-ARM VIBRATION Vibration transmitted to the hand-arm system is dealt with by ISO 5349-1 [2], presenting measurement and evaluation general methods, and by ISO 5349-2 [3], giving application guidelines. These two ISO standards can be considered good normative documents, in comparison with ISO 2631-1:1997 [4], dealing with whole-body vibration. Vibration transmitted to the hand-arm system, indeed, covers a more limited field, inside which greater knowledge and experience have been achieved.
ISO standards 5349-1 and 5349-2 consider periodic, casual and impulsive (repeated shocks) vibrations.
Vibrations transmitted to the hand-arm system can be generated by hand held machines and hand guided
tools and vehicles, generally speaking, and also by industrial, agricultural and working machine components, as control and driving levers, steering wheels and similar ones. A coordinate system is defined referring to the operator’hand exposed to vibration (biodynamic system), adjusted to match the grasped tool. Vibrations are acquired along three normal axes. Attention has to be paid on the simultaneity of the acquisitions. Dimensions and position of the accelerometer(s) represent really a limitation to the measurement. The accelerometer, indeed, has to be small enough to locate the measurement point, has to be rigidly fixed on the vibrating (curved) surface, guarantee a normal grasp by the operator, not interfere with operating levers. Undoubtedly, it represents an intrusive element for the measurement. Accelerometer frequency response has to be flat within the measurement frequency range (6.3 Hz to 1.25 kHz). On this purpose, resonance frequencies of the transducer alone and of the transducer installed on the vibrating surface have to be carefully considered. DC-shift phenomenon has to be avoided referring to piezoelectric transducers. The integrating meter, defined in ISO 8041 [5], has to be used for vibration acquisition/measurement. A proper frequency weighting filter is applied, in order to evaluate the equivalent acceleration, this filter being the same for all the three axes and considered suitable for all vibration effects and every kind of disorder and tool. A spectrum analyser can be equally used for vibration acquisition/measurement, as suggested by ISO 5349-2, this way allowing the identification of measurement errors and spectral components useful for vibration reduction. The total vibration value, relevant to a daily exposure definite duration, has to be referred to 8 hours by adopting the ‘equal energy’ principle, such a way allowing a comparison among different duration exposures. As a consequence, under the same effects, the daily exposure duration turns out to be inversely proportional to the acceleration squared value. It has to be noted that the exposure evaluation regards vascular disorders only, the dose-effect relationship being not known yet as far as neurological and musculo-skeletal disorders are concerned. In order to carry out a correct analysis procedure, referring to the measurement time, ISO 5349-2 proposes four possibilities, depending on tool use and working continuity, by defining a suitable exposure duration and allowing an acceleration value average for different tool types and application periods. Testing of vibrating hand-held tools is needed in order to qualify these products and to assess their
compliance to Directive 98/37 [6]. In fact the Directive imposes to each producer of tools to declare the level of vibration that the tool transmits to the user, because vibration has a significant impact on safety and health of habitual users. At present, as for ISO standards, existing EN type B and C norms are dealing with how tests have to be carried out [7]. These norms highlight several needs, but lack operative suggestions on how to measure the interaction between human and tool. According to all these norms, tests are carried out with tool operating in standard conditions. These tests require accurate and reproducible measurements, but their results are strongly operator dependent, because of inevitable variability which arises when the hands and arms of human beings become part of the equipment support and guidance system. On the other hand, the hand-source coupling can also modify tool vibration amplitude. The knowledge of gripping and pushing force exerted by the operator during tests could improve repeatability of results, so that new methods of investigation turn out to be necessary and must be developed. CEN/TC 231 points out, by its vibration guidelines, safety standards draftings for other Technical Committees dealing with vibration, as CEN/TC 144 (Tractors and Machinery for Agriculture and Forestry), CEN/TC 255 (Hand-Held Non Electric Power Tools – Safety), CEN/TC 151 (Construction Equipment and Building Material Machines - Safety). In each of these documents, the need is expressed of measuring the contact pressure and pushing force applied by the operator to the tool handles during tests. CEN Report 12349:1996 [8], dealing with health effects of vibration on human body, emphasizes this need by showing the existence of a strong relation between contact pressure and damages. At present, different ISO working document proposals exist dealing with this subject (ISO/PWI 15230 [9], ISO 8662-n – 1988-1999 [10]), but till now no practical and operative solution is really available in order to measure contact pressure distribution during tool tests. The DOPTEST EU funded research project [11], concluded in November 2000, showed a strong correlation between grasp force, tool vibration, hand-arm vibration and the onset of vascular disorders in fingers. The contact force measurement has been carried out by capacitive sensor matrices applied on the handle of the vibrating tool. Contact force spatial distribution has been correlated to hand surface vibration spatial distribution by the application of a laser vibrometer. At present, as DOPTEST project result exploitation, a CEN proposal has been submitted to
develop sensing element matrices in order to meet the demand for hand-held tool testing [12]. The development will have to address to measurement system performance, particularly dynamic response and long term stability, as well as ergonomic aspects. The aim being the use of sensor matrices for tests with minimum intrusivity and effectively applicable for pre-normative purposes or in support to future directives and/or standards. Main up-to-date research and development themes, relevant to the hand-arm vibration field, can be summarized as: evaluation of vibration perception thresholds and effects of contact area/location to be included in models of the sensory mechanisms, vascular disorders to be associated with hand-held tools and vibration levels, disorders and vibration exposure association, development of antivibration gloves, standards and legislation applicability and updating, methods and procedures for evaluating the hand-arm system/tool interaction.
WHOLE-BODY VIBRATION Vibration transmitted to whole-body, to be referred to self-propelled machines and means of transportation, covers a more important role, from the health point of view, in comparison with that generated by steady machines. It concerns, indeed, an extremely larger number of people and is characterized by a higher amplitude (10-100 times). The paper refers to this kind of whole-body vibration. ISO 2631-1, 1997 [4] defines measurement and evaluation methods for whole-body vibration. This standard allows the evaluation of vibration in terms of health and comfort effects, perception and motion sickness. ISO 2631-1 does not represent a good normative document, being not univocal and presenting numerous gaps, omissions and contradictions. ISO 2631-1 considers periodic, casual and transient vibrations. The vibrations have to be acquired along three normal axes, defined by a coordinate system relevant to human body, with the origin corresponding to subject/vibrating surface contact point. The accelerometer(s) has to be fixed inside a rigid or semi-rigid support [13], in case of a vibrating surface capable to be deformed (e.g. cuscion and seat back). The parameter to be considered, from the health point of view, is represented by the frequency weighted acceleration. ISO 2631-1 prescribes different frequency weighted filters according to vibration axis,
measurement position and evaluation method applied (health, comfort, perception, motion sickness). The frequency weighted acceleration average value can be determined as a summation of different contributions, in case of acquisitions carried out for periods of different duration and referring to various vibration conditions. The advantage, in comparison with an only and not interrupted measurement, consists on the possibility of evaluating the periods characterized by the highest vibration values (essential in terms of health) and determining new operator exposure levels for periods of different duration (risk evaluation). The frequency weighted acceleration average squared value, i.e. the equivalent acceleration, is measured for the evaluation of vibration in terms of effects on health, comfort and motion sickness. ISO 2631-1 refers to this parameter also in case of perception. Really, the perception threshold evaluation is based on the acceleration peak value. The integrating meter, defined in ISO 8041 [5], has to be used for vibration acquisition/measurement. A spectrum analyser can be equally used, allowing the identification of dominant spectral components. ISO 2631-1 introduces two additional measurement methods, besides the base one, in order not to under estimate vibration effects. The frequency weighted acceleration transient highest values are taken into account, in parallel with the acceleration squared ones, as they have effect on health and comfort. The first method (running rms) considers mainly the frequency weighted acceleration highest effective value, within the all measurement period, by means of the time constant Slow. In such a way, it neglects time vibration trend. That is, two vibration phenomena characterized by the same maximum value, are considered analogous, from the health point of view, leaving transient number out of consideration. The second additional method is based on the time integration of the frequency weighted acceleration value raised to the fourth power, from which the Vibration Dose Value is obtained. This method points out the highest values, i.e. vibration transients, in comparison with the base method founded on the integration of the acceleration squared values. ISO 2631-1 reports suggestions on matching the results achieved by the three methods, in order to carry out the best measurement. In terms of health considerations, the highest acceleration value acquired during a test should be emphasized, taking into account the vibrations along the three axes and all the measurement positions. The vector summation of the frequency weighted
acceleration values can be also considered for comfort and health effect evaluation. As far as health is concerned, the evaluation method defined by ISO 2631-1 refers to different pathologies produced by vibration. Health effects depend on the absorbed vibration dose. The dose is determined by the product of the daily exposure duration by the frequency weighted acceleration average value. It seems that, in order to have the same effects, it is necessary doubling the acceleration value raised to the fourth power, not squared, by halving the exposure duration. At present, health effects are not completely documented and/or objectively observed, and can be given indications only on risks effectively remarkable. Comfort evaluation method refers to means of transportation. Acceleration value vector and global summations are computed, referring to the vibrations along the three axes and different areas. Human activities/vibration interference has still to be well understood. Discomfort can be influenced by transient vibration and so it can be probably under estimated by the base method. ISO 2631-1 reports a comfort/ discomfort evaluation table, its values referring to acceleration global summation and limits leaving exposure duration out of consideration. ISO 2631-1 reports also vibration perception threshold values referred to the frequency weighted vertical acceleration peak value. This threshold values show great variability among individuals. The Commission of the European Union supported a research network (known as the Vibration Injury Network) under the BIOMED2 concerted action program [14]. The collaborative research involves nine laboratories in eight European countries. Objective of the network consists on establishing uniform methods and procedures for the detection and prevention of injuries due to occupational hand-arm and whole body vibration exposure. This is to be achieved by: (i) development of common procedures for health surveillance, including improved methods for the detection and diagnosis of disorders; (ii) collaborative epidemiological research to investigate dose-response relationship between vibration exposures and injury; (iii) collaborative laboratory investigations of the interaction between vibration and other environmental, ergonomic and individual risk factors; (iv) consideration of methods for preventing disorders, including the applicability of current standard methods for hazard surveillance and for testing the protection provided by gloves and seats. With the involvement of network partners in national, ISO and CEN working groups, the results of the EU project will be available for the development of future standards concerned with: (i) the evaluation of
exposure to hand-transmitted vibration and whole-body vibration; (ii) guidance on dose-effect relationships for hand-transmitted vibration and whole-body vibration; (iii) diagnostic tests for vibration injuries; (iv) testing of protective equipment. The main up-to-date research and development themes, relevant to the whole-body vibration field, can be considered summarized by the tasks and objectives described in the EU project Vibration Injury Network.
REFERENCES 1. CEN/TC 231, 2000, Mechanical Vibration and
Shock 2. INTERNATIONAL STANDARD ISO 5349-1, 2001,
Mechanical Vibration – Measurement and Evaluation of Human Exposure to Hand-Transmitted Vibration – Part 1: General Guidelines
3. INTERNATIONAL STANDARD ISO 5349-2, 2001 Mechanical Vibration – Measurement and Assessment of Human Exposure to Hand-Transmitted Vibration – Part 2: Practical Guidance for Measurement in the Workplace
4. INTERNATIONAL STANDARD ISO 2631-1, 1997, Mechanical Vibration and Shock – Evaluation of Human Exposure to Whole-Body Vibration – Part 1: General Requirements
5. INTERNATIONAL STANDARD ISO 8041, 1990, Human Response to Vibration – Measuring Instrumentation
6. Directive 98/37/EC, Safety of Machinery 7. EN 28662-1: 1992, Hand-Held Portable Power Tools –
Measurement of Vibration at the Handle – Part 1: General
8. CEN Report 12349, 1996, Mechanical Vibration – Guide to the Health Effects of Vibration on the Human Body
9. ISO/PWI 15230, Mechanical Vibration – Definition and Guidelines for the Measurement of the Coupling Forces for Operators exposed to Hand-Arm Vibration
10. INTERNATIONAL STANDARDS ISO 8662-n, 1988-1999, Hand-Held Portable Power Tools – Measurement of Vibrations at the Handle
11. DOPTEST EU Project, SMT4-CT97-2181, Frame- work Programme IV
12. CEN/STAR Proposal, TC 231, 2000, Development of Measurement Technique of Contact Pressure Distribution for Hand-Held Vibrating Tools Testing
13. INTERNATIONAL STANDARD ISO 10326-1, 1992, Mechanical Vibration – Laboratory Method for Evaluating Vehicle Seat Vibration – Part 1: Basic Requirements
14. Griffin, M.J., Lewis C.H., ‘European Vibration Injury Network’, Proceedings of the INTER-NOISE 99 Conference, 1999, Vol. 2, pp. 943-948
New measurement procedure of Hand-Arm Vibration from the DOPTEST Research Project
P. Christa, A. Cristallia, R. Debolib, G. Di Giulioc, M. Geudera
G. Miccolid, N. Paonec, G.L. Rossie
aNovel GmbH, Munich, Germany bInstitute for Agricultural Mechanization, IMA, CNR, Torino, Italy
cUniversity of Ancona, Dpt. of Mechanics, Ancona, Italy dEarth-Moving Machinery and Off-Road Vehicles Institute, CEMOTER, CNR, Ferrara, Italy
eUniversity of Perugia, Dpt. of Industrial Engineering, Perugia, Italy
A review is presented of the research activity carried out during the DOPTEST EU Project. The paper summarizes the application of an innovative technique in order to better quantify and analyse vibration emission by hand-handle vibrating tools. Laser vibrometer and capacitive sensor matrix are used to measure hand transmitted vibration and grip force/pressure distribution at the hand-handle interface. Results achieved showed a strong correlation between grasp force, tool vibration, hand-arm vibration and the onset of vascular disorders in fingers.
INTRODUCTION Testing of vibrating hand-held tools is needed in order to declare the levels of vibration that tools transmit to the operator. That has a significant impact on user safety and health. Recent studies from CEN point out the large uncertainty, low repeatability and low reproducibility of vibration measurement, with particular reference to hand-held tools. Test results are strongly operator dependent. That limits their applicability, invalidates comparison and concurrence, does not guarantee product safety and harmlessness. Various Technical Committees, as CEN/TC 231, 144, 255, 151 working on Standard and Pre-standard Projects related to hand-held tool vibration testing, also pointed out the need of measuring grip force and contact pressure between hand and handle, together with the total force applied by the operator. The EU funded research Project DOPTEST [1], within the Standards, Measurements & Testing Programme, proposed a new measurement technique in order to better quantify and analyse vibration emission by hand-held tools. The Project research activity has been carried out mainly on a hydraulic breaker. The innovative sensing technique is a combination of scanning laser Doppler vibrometer (LDV) and capacitive sensor matrixes. The LDV application has been suggested as a no-contact technique for measuring vertical vibrations on operator’s hand during working cycles. It overcomes a problem relevant to the use of conventional three-axis accelerometer applied on the vibrating handle, that
causes user discomfort, thus contributing to decrease test repeatability. In addition, the application of capacitive sensor matrixes has been suggested in order to measure contact pressure distribution and grip force at the hand-handle interface.
LASER VIBROMETER AND SENSOR MATRIX
A LDV employing He-Ne laser radiation has been used. From the results obtained, it appears that the laser vibrometer can measure skeleton motion of the hand. Where the skin is very thin and near to the bone, the data are representative of the bone vibration. Cosmetics application reduces laser light penetration and enhances (30%) laser signal amplitude. Tests on subjects, in different points of the hand and with typical skin cosmetics, have been performed by a single point laser vibrometer to determine the uncertainty related to the laser beam-skin interaction. Vibrometer 40 MHz frequency modulated Doppler output signal has been acquired using a long memory (8 Msamples) high sampling rate (1 GHz) digital oscilloscope. A laser beam-skin surface angle up to 40° still guarantees a LDV measurement with an acceptable uncertainty. In order to measure the grip force and the pressure distribution at the hand-handle interface, a capacitive elastic sensor matrix has been developed and tested. A calibration device has been set up and a series of single sensors (1 cm² sensitive area) tested to define
measuring pressure range and sensor static characteristics. In particular, an on purpose developed cylindrical device has been used to calibrate the matrix. The calibration process allows also adjusting for possible transducer non-linearities. A test-bench based on an electrodynamic shaker has been developed for the sensor dynamic characterisation. Single sensor frequency response functions have been measured within 2 Hz to 500 Hz frequency range. All sensors show a signal attenuation by increasing frequency. Depending on sensor type, on polymer material as dielectric and sandwich structure, a useful range up to 200 Hz has been validated. The final elastic matrix developed and applied on the breaker handle consists of 256 sensor elements. The matrix has been calibrated up to 12 N/cm² and shows an hysteresis < 5% within this pressure range.
RESULTS AND CONCLUSIONS A test bench has been developed according to the European Standard 8662-5 in order to evaluate the vibration level of the hydraulic hammer. To support the LDV head over the breaker, a rigid structure has been built up and isolated from the vibration transmitted by the soil. One breaker handle has been instrumented by the sensor matrix and an accelerometer mounted in compliance with European Standards. Tests have been carried out on 10 young healthy volunteers. They were required to control and apply a total vertical force of about 200 N while they operated the breaker with a different grip force. The following informations were acquired during each test: knuckle vibration velocity time history by LDV; handle acceleration time history by accelerometer and LDV; mean pressure values and total grip force by the capacitive matrix; vertical load force exerted by the operator; vascular effects by photoplethismography and finger skin temperature by thermocouples. Results (Fig.1) show that at 27.5 Hz (main hammer frequency) the subject holding the breaker with a low grip force presents the higher vibration velocity values on all the knuckles. This means that the grip force influences the results of the vibration tests. The capacitive matrix describes the distribution of local pressure applied by the palm and the fingers (Fig. 2). A comparison of pressure maps of different subjects shows that even if a constant vertical load is applied to the handle, the grasp turns out to be rather different. Furthermore the subject is not really able to keep the same grip force. Velocity vibration maps recorded by the LDV over
FIGURE 1. Vibration velocity spectra of index finger knuckle of 3 subjects.
FIGURE 2. Capacitive matrix pressure distribution map. a grid of 19 points on the hand surface show that the hand moves as a rigid body at the fundamental frequency of the breaker. Vibration velocity amplitude varies remarkably across hand surface at higher frequencies. Again this measurement validates the spatial correlation between regions of large local contact pressure and low vibration. A fairly good correlation of data has been also obtained referring to medical tests. A higher vasoconstriction has been observed when a weak grip is applied (high vibration levels). On conclusion, it has been emphasized the relevance of no-contact LDV measurements for studying hand-arm vibration. The capacitive sensor revealed the big influence of the grip force on the vibration level measurement. Monitoring the vertical load and the grip force together could improve the low repeatability and reduce the very large dispersion of data of the actual vibration tests. Furthermore the distribution of the force applied by the operator to the tool handles during a working cycle can provide the designer with remarkable informations aimed at tool performance improvement as far as vibrations are concerned.
REFERENCES 1. DOPTEST EU Project, SMT4-CT97-2181, Frame-
work Programme IV
New Perspectives on Hand-Arm Vibrationfrom the VINET Research Project
P. Lenzunia Italian National Institute for Occupational Prevention and Safety (ISPESL), Department of Florence, 50121
Florence, Italy. E-mail [email protected]
Despite many decades of investigations of individuals exposed to hand-arm vibration (HAV), our knowledge of themechanisms leading to impairments, disabilities, and possibly injuries, is still very incomplete. The advancement of ourunderstanding of hand-transmitted vibration has been the objective of the Vibration Injury Network (VINET), where researchprojects from nine individual partners from eight different countries have been coordinated under the auspices and the financialsupport of the EU. The network has recently finalized its activities after a three-year collaborative action. This paper provides a broad overview of some of the results of the network which shed new light on issues such as theappropriateness of the existing frequency weighting curve to predict different physiological responses, the reliability of existingdose-response relationship, the role of alternative descriptors of exposure. A short discussion of the main results is included andsome suggestions for future studies are presented.
INTRODUCTION
Exposure to hand-transmitted vibration is a re-cognized cause of vascular, neurological and bone andjoint disorders in the upper limbs. These disorders havestrong economical as well as legal implications, butabove all their existence should be of ethical concernfor a modern society. Although standards exist for evaluating humanexposure to vibration, current criteria are often basedon a very limited scientific evidence, and do not takeinto account many factors which influence themagnitude of the hazards posed to workers. This contribution outlines the results of the VibrationInjury Network (VINET), a EU-sponsored concertedaction involving nine partners from eight differentcountries. The primary aim of the network was toadvance methods for the detection and prevention ofinjury due to vibration exposure at work, alone or incombination with other risk factors. The work wasdivided into four main work packages, dealing withboth medical and technical aspects of vibration. A widerange of issues was investigated ranging from theassessment of injuries, to the establishment of dose-response relations, and to the development of improvedmethods for preventing disorders.
WORK PACKAGES
Wp1h
The objective of this work package was to develop aprotocol for the health surveillance of workers exposed
to hand-transmitted vibration. The protocol comprisesguidelines for the initial assessment and periodicclinical examinations at regular intervals, astandardised questionnaire and a physical examinationprocedure for the clinical assessment of the peripheralneurological and vascular systems. Two separatequestionnaires were developed for initial assessmentand periodic follow-up, for administration byoccupational health physicians. Translations have beenmade in many of the national languages of thenetwork partners. The Italian version has beenpublished in the context of the Italian NationalGuidelines for the assessment of vibration hazards atthe workplace [1]. The self-administered initialassessment questionnaire has been implemented by aspart of a Microsoft Access� database.
Wp2h
A document was prepared with recommendationsfor epidemiological studies. The document summarizesways and methods for collecting data about medicalhistory, past exposure, personal characteristics andpsycosocial environment. Three options are providedfor assessment of present exposure: “observation”(large populations), “analysis” (medium sizepopulation) and “expertise” (small samples). The reanalysis of data from a few recent studiesshowed that a poorer prediction of the occurrence ofVibration-induced White Finger was found when usingthe ISO 5349-1 [2] frequency weighting, indicating theneed for substantial revision. Improvements were alsofound desirable in the time-dependence of cumulativevibration dose.
Wp3h
The main objective of this work package was toinvestigate the changes in the vascular andsensorineural functions of the human finger and hand,as well as in the biodynamic response of the hand-armsystem, caused by exposure to hand-transmittedvibration of different magnitudes, frequencies anddurations. A multi-centre experimental study wascarried out at various European centres. This study wasdesigned to acquire elements from vascular,neurological and biomechanical investigations, wasperformed under the same experimental conditions andwith a common methodology of investigation. Studiesof vascular and neurological effects provided newevidence of the inadequacy of both the existingfrequency weighting and the “equal energy principle”on which the current vibration assessment procedure isbased. Experimental studies of the power absorbedduring exposure to hand-transmitted vibration was alsoused to improve the current knowledge of themechanical interaction between the hand-arm systemand the vibrating tool, for possible exploitation byfuture modelling work. The ability of the frequencyweighting curve to correctly predict the amount ofabsorbed power was found to depend significantly onthe vibration magnitude.
Wp4h
The main objective of this work package was toimprove the evaluation of exposure to hand-transmittedvibration, and to develop methods of protectingoperators against hazards associated to hand-transmitted vibration. Different evaluation methods were surveyed andcompared, focusing on possible ways to improve thefrequency weighting curve and the estimate of theexposure duration. Laboratory and field measurementsof the attenuation effectiveness of commerciallyavailable anti-vibration gloves were carried out.
Deliverables
A substantial number of scientific papers, appearingboth in refereed journals and in conferenceproceedings, has been contributed to the scientificliterature on hand-transmitted vibration. In the longrun, the evaluation, assessment, and ultimately theprevention of the HAV sydrome will undoubtedlybenefit from this pool of knowledge. The Vibration Injury Network has also resulted intwo items of more direct exploitation:
� The leaflet “Hand-arm vibration. The hand indanger”, prepared to assist employers to bettermanage the prevention of occupational hazardsassociated with exposure to hand-transmittedvibration. The document includes sections onspecific hazards, causes, technical solutions andmedical surveillance. Edited by INRS, it isavailable in English and French.
� An internet database of acceleration valuesmeasured on hand-held vibrating tools was set up.The database currently stores data on more than3000 tools, and is accessible at the addresshttp://umetech.niwl.se. It includes bothmanifacturer-declared emission values, measuredaccording to the appropriate documents of theISO 8662-X series, and values measured duringnormal operation, measured in accordance withISO 5349.
ACKNOWLEDGEMENTS
The Vibration Injury Network is the EC BIOMED 2concerted action – project BMH4-CT98-3251. Thefollowing partners participated:� The Institute of Sound and Vibration Research,
University of Southampton (United Kingdom)� The Federal Institute for Occupational Safety and
Health (Germany)� The Coronel Institute, University of Amsterdam
(The Netherlands)� The Hygiene and Work Physiology Unit of the
Catholic University of Louvain (Belgium)� The National Institute for Research on Safety
(France)� The National Institute for Occupational
Prevention and Safety (Italy)� The National Institute for Working Life (Sweden)� The Studium of Mechanics of the University of
Patras (Greece)� The Institute of Occupational Medicine of the
University of Trieste (Italy)
REFERENCES
1. Italian National Guidelines for Risk Assessment ofVibration at the Workplace, edited by the ItalianNational Institute for Occupational Prevention andSafety (ISPESL), 2000 (in Italian).
2. ISO Standard 5349-1, 2001, Measurement andevaluation of human exposure to hand-transmittedvibration, International Standard Organisation
New Perspectives on Whole-Body Vibration from theVINET Research Project
P. Nataletti
Department of Occupational Hygiene, National Institute for Prevention and Safety at Workplace, Rome, Italy
This paper summarises the results of the VINET (Vibration Injury Network) research project for the detection and prevention ofinjuries due to occupational vibration exposures transmitted to the whole body. This research network has been supported bythe Commission of the European Union under the BIOMED2 concerted action, and involved in collaborative research nineresearch laboratories in eight European countries. The main results of the project were the following: development of commonmethods for health surveillance; improved knowledge of dose-response retationships between whole-body vibration exposuresand injuriy; investigation of the interaction between whole-body vibration and other environmental, ergonomic and individualfactors; improvement of methods for preventing disorders.
INTRODUCTION
Million of workers throughout Europe are exposed tomechanical vibration transmitted to the whole bodymainly through the seats of industrial vehicles, and thisexposure can result in musculo-skeletal disorders ofthe spinal system, including low back pain, earlydegeneration of the spine and herniated discs [1, 2, 3].These effects are believed to be evident in drivers ofindustrial vehicles [4], and in several Europeancountries are compensated. The Commission of theEuropean Union has supported a three yearscollaborative research network known as VINET(Vibration Injury Network) under the BIOMED2concerted action program. The research projectinvolved nine research laboratories in eight Europeancountries:Institute of Sound and Vibration Research (ISVR,project leader), University of Southampton, UK;Federal Institute for Occupational Safety and Health(FIOSH), Berlin, Germany;Coronel Institute, University of Amsterdam,Netherlands;Occupational Hygiene & Work Physiology Unit,Université Catholique de Louvain, Belgium;Institut National de Reserche et de Securité (INRS),Vandoeuvre, France;National Institute for Prevention and Safety atWorkplace (ISPESL), Rome, Italy;National Institute for Working Life (NIWL), Umeå,Sweden;University of Patras, Stadium of Mechanics, Greece;University of Trieste, Institute of OccupationalMedicine, Italy.
RESULTS
The main objective of the Vibration Injury Networkwas to advance methods for the detection andprevention of injury due to whole-body vibrationexposures at work. This is being achieved throughcollaboration among leading European researchers intovibration transmitted to the human body in thefollowing five main areas of work described below:
1. Development of common methods forhealth surveillance, including thedevelopment of improved methods for thedetection and diagnosis of disorders.
A standardised guide and a questionnaire have beencompleted for the health surveillance of workersexposed to whole-body vibration. The documents,accessible on the internet at the addresshttp://www.human-vibration.com , describe physicalexamination procedures for clinical assessment,guidelines for pre-employment medical control andperiodic clinical examinations, and common criteriafor medical contra-indications and for evaluation ofclaims for compensation.
2. Establishment of dose-responserelationships between vibration exposuresand injury, through collaborativeepidemiological research.
A protocol has been developed for multi-nationalepidemiological study of injuries caused by exposure
to whole-body vibration. The document provide guidefor researchers embarking on research in this area anda foundation for future epidemiological work. Thedevelopment of the protocols was assisted bycollaborative re-analysis of data previously collectedby the partners and by new pilot studies [5]. Databaseare being developed to store data from epidemiologicalstudies that are being planned.
3. Investigation of the interaction betweenvibration and other environmental,ergonomic and individual factors,thorough collaborative laboratoryexperiments.
The design for a multi-centre experimental study waselaborated by the three principal laboratories thatperform human experiments with whole-bodyvibration within the European Union (FIOSH, ISVRand NIWL), and a database has been developed.Analytical finite element model for the invertebral diskL5/S1 as well for the group L5/S1 and in-between diskL5/S1 has been developed by Patras group. The modelwill be used to predict the strain of the invertebral diskL5/S1 and to develop a video simulation of an entirecycle of disk deformation under vibration loading withvertical, oblique, rotational and shear forces. Adatabase of biodynamic data will be available for thesharing of experimental results between Europeanlaboratories involved in biodynamic modeling work.
4. Improvement of methods for preventingdisorders, including consideration ofcurrent standard methods for hazardsurveillance and for testing of theprotection provided by seats.
A database containing whole body vibration datameasured on more than 60 off-road vehicles has beenmade available on the internet, at the address of theSwedesh National Institute for Working Lifehttp://umetech.niwl.se. The database contains CEdeclared values as well as measurements made duringnormal operation at work sites in accordance with thestandard ISO 2631. These data provide a valuableresource for the determination of vibration exposuresof workers, and for reducing exposures by selection ofvehicles with lower emission. The database will soonbe complemented with vibration levels measured inother categories of vehicles (e.g. buses, lorries, fork-lift trucks, forestry machines, etc.). An informativebooklet is being published by the French InstitutNational de Reserche et de Securité for employers ofworkers exposed to whole-body transmitted vibration.
The booklet is based on guidelines developed by thenetwork partners, and is intended to provideinformation appropriate for most European countries.
5. Dissemination of results.
One International Conference and one InternationalWorkshop were organized by participants in theVibration Injury Network and financially supported bythe project: the 2nd International Conference onWhole-Body Vibration Injuries [6], held in Siena inNovember 2000, organized by the Italian NationalInstitute for Prevention and Safety at Workplace incollaboration with the University of Trieste; theInternational Workshop “Modelling of Spinal LoadsAssociated with Vibration and Shock – State of theArt, Critical Assessment, Application and ResearchNeeds”, organized by FIOSH in Berlin, in October1999 [7].
ACKNOWLEDGMENTS
The research has been supported under the BIOMED2concerted action program, contract No. BMH4-CT98-3251.
REFERENCES
1. M.J. Griffin, Handbook of Human Vibration, London.Academic Press, 1990.
2. M.H. Pope and T.H. Hansson, Clinical Orthopaedics andRelated Research, 279, 49-59 (1992).
3. H. Seidel and R. Heide, International Archives ofOccupational and Environmental Health, 58, 1-26(1986).
4. C.T.J. Hulshof and B.V. Zanten, International Archivesof Occupational and Environmental Health, 59, 205-220(1987).
5. M. Bovenzi and C.T.J. Hulshof, International Archivesof Occupational and Environmental Health, 72, 351-365(1999).
6. M. Bovenzi, I. Pinto and N. Stacchini, Proceedings ofthe 2nd Int. Conference on Whole Body VibrationInjuries, Siena, November 2000, submitted forpublication in Journal of Sound and Vibration.
7. Proceedings of the 1st Int. Workshop on Modelling ofSpinal Loads associated with Vibration and Shock,Clinical Biomechanics, 16, Suppl. 1.
Occupational Exposure Limit for Hand-arm Vibrationin Japan
N. Harada, T. Sakuraia, T. Fukuda, S. Takahashi, S. Shirono, T. Fujimura,H. Morita, J. Inagaki and K. Suizu
Department of Hygiene, Yamaguchi University School of Medicine, Ube 755-8505, Japana Department of Health Science, Nippon Sport Science University, Tokyo 158-8508, Japan
The 8 hours energy equivalent value of 2.8 m/s2 rms by frequency weighted vibration acceleration in three axes is recommendedas the exposure limit for hand-arm vibration of the Japan Society for Occupational Health. The exposure limit is based on therelation between the prevalence of white finger (WF) and the magnitude of hand-arm vibration exposure among worker groups.When the magnitude of vibration exposure is under the recommended limit, the prevalence of WF is expected not to exceed thatof the general population in Japan after 10 years' exposure.
There are various guidelines of occupationalexposure to hand-arm vibration [1]; however we didnot have general exposure limit for hand-arm vibrationin Japan. The 8 hours energy equivalent value of 2.8m/s2 rms by frequency weighted vibration accelerationin three axes is recommended as the exposure limit forhand-arm vibration of the Japan Society forOccupational Health in 2001. When the magnitude ofvibration exposure is under the limit, the prevalence ofWF is expected not to exceed 3%, its upper limitexcluding that of vibration origin in the male generalpopulation in Japan, after 10 years' exposure.
WHITE FINGER IN JAPANESEGENERAL POPULATION
Table 1 shows the prevalence of WF excluding thatof vibration origin in the Japanese general populationaged 20 years or more [2-4]. The epidemiological dataused for the analysis are limited to studies of Japanesesubjects. The reason is that the prevalence of WF in theJapanese general population is lower than that inCaucasians [2]. It was considered that theprevalence ofWF in the Japanese general population is roughly 1 to3 % for males and 1 to 4 % for females.
WHITE FINGER AND LOWMAGNITUDE OF VIBRATION
Table 2 shows the prevalence of WF among maleworkers exposed to low magnitude of hand-armvibration in Japan [4-7]. There are not enough dataamong female workers to permit analysis. The data byFutatsuka et al [7] are estimated values from the reportof the Committee on Hand-arm Vibration Syndrome ofJapan Society for Occupational Health in 1980, whichanalyzed numerous studies in Japan.
WHITE FINGER AND MAGNITUDE OFHAND-ARM VIBRATION
The relations among prevalence of WF, magnitudeof hand-arm vibration exposure and the duration ofexposure were analyzed [8]. For the relation betweenprevalence of WF and the duration of exposure tohand-arm vibration, nine studies were available[5,9,10-12]; however data for vibration magnitudewere available from only five of these [5,9,12] amongthem. Remarkable dose-response relationships amongthe duration of exposure, the magnitude of vibrationand the prevalence of WF were observed.
Table 1 Prevalence of WF excluding that of vibration origin in general population in Japan (over 20 years of age
---------------------------------------------------------------------------------------------------------------------------------------- ref number of subjects range of age prevalence of WF
male female male female male female ---------------------------------------------------------------------------------------------------------------------------------------- Harada et al, 1991 1875 1998 20-69 20-69 1.4% 1.9% Inaba et al, 1989 149 262 20-89 20-89 1.3% 1.5% Mirbod et al, 1994 1027 1301 30-59 30-59 2.7% 3.4% ---------------------------------------------------------------------------------------------------------------------------------------- average and 95%CI: male:1.9% (1.4-2.3%), female:2.4% (1.9-2.9%)
Table 2 Prevalence of WF among male workers exposed to low magnitude of hand-arm vibration in Japan ------------------------------------------------------------------------------------------------------------------------------------- ref tools/ weighted average prevalence
machines acceleration exposure of WF(single axis) hrs/day years
------------------------------------------------------------------------------------------------------------------------------------- Mirbod et al, 1994 digginga) 1.6-2.1m/s2 5 22 2.5% Mirbod et al, 1994 aircraftb) 2.3-2.5m/s2 4 17 2.3% Mirbod et al, 1994 chain-saw 2.7-5.1m/s2 3 19 9.8% Tominaga, 1995 motor-cycle 1-2m/s2 c) 4 c) 12 1.8% Tominaga, 1995 motor-cycle 2-3m/s2 c) 4 c) 12 3.0% Matsumoto et al, 1981 motor-cycle 1.6m/s2 2.5 9.7 2.7% Futatsuka et al, 1984 various 3.2m/s2 c) 4 c) 10 5.0% d)
Futatsuka et al, 1984 various 3.2m/s2 c) 4 c) 16 12.8% d)
------------------------------------------------------------------------------------------------------------------------------------- a):job, b):factory, c):equivalent value for 4 hrs, d):estimated value theoretically.
RECOMMENDED OCCUPATIONALEXPOSURE LIMIT
From the above results, the 8 hours energyequivalent value of 2.8 m/s2 rms by frequencyweighted vibration acceleration in three axes isrecommended as the occupational exposure limit of theJapan Society for Occupational Health (Table 3).When the magnitude of vibration exposure is underthis value, the prevalence of WF is expected not toexceed 3%, its upper limit excluding that of vibrationorigin in the male general population in Japan, after 10years' exposure.
REQUIRING FUTURE WORK
After 10 years' exposure, the prevalence of WF stillincreases because of additional exposure to hand-armvibration. As the base of prevalence of WF in the malegeneral population in Japan, 3% is considered to be themaximum value. Epidemiological data for theinvestigation are not necessarily enough. Particularly,an occupational exposure limit for female workerscannot be investigated because of lack ofepidemiological data. Vibration induced healthdisturbances other than WF, such as the neurologicaland musculo-skeletal disturbances also remain to beinvestigated in future.
REFERENCES1. International Organization for Standardization, ISO 5349-1 (2001). 2. Harada N et al, J C1in Epidemiol, 44, 649-55 (1991). 3. Inaba R et al, Jpn J Health Human Ecol, 6, 281-5 (1989). 4. Mirbod SM et a1, Int Arch Occup EnvironHealth, 66, 13-22 (1994). 5. Tominaga Y, Proc StockholmWorkshop 94, Solna, National Inst Occup Health, 153-6(1995). 6. Matsumoto T et al, Jpn J Ind Health, 23, 485-95(1981). 7. Futatsuka M et al, Int Arch Occup Environ Health,
54, 201-21(1984). 8. Harada N et al, Proc 9th Int Con Hand-arm Vibration, Nancy, INRS, (2001, in press). 9. MatsumotoT et al, Arh hig rada Toksikol, 30 suppl,.701-7 (1979). 10.Wakisaka I et al, Arch Med Univ Kagoshima, 17, 1-6 (1975).11. Futatsuka M et al, Jpn J Ind Health, 18, 3-10 (1976). 12.Futatsuka M, Int Arch Occup Environ Health, 54, 251-60(1984).
Table 3 Recommend of occupational exposure limit for hand-arm vibration of the Japan Society for Occupational Health ------------------------------------------------------------------- exposure time frequency weighted vibration (min/day) acceleration in three axes (m/s2 rms) ------------------------------------------------------------------- 6 or less 25.0 10 19.4 15 15.8 30 11.2 60 7.92 90 6.47 120 5.60 150 5.01 180 4.57 210 4.23 240 3.96 270 3.73 300 3.54 330 3.38 360 3.23 390 3.11 420 2.99 450 2.89 480 2.80 -------------------------------------------------------------------
Vibration exposure of the hand-arm system: simultaneousmeasurement of hand contact pressure, acceleration and
digital haemodynamic effects
M. Valentino a, V. Rapisarda a, N. Paone b, G. DiGiulio b, G.L. Rossi c
a Clinic of Occupational Medicine, University of Ancona, 60020 Ancona, Italy b Department of Mechanics, University of Ancona, University of Ancona, 60100 Ancona, Italy,
c Department of Industrial Engineering, University of Perugia, 06125 Perugia, Italy
The finger blood flow variations induced by the vibration generated by a hydraulic breaker held with a weak or a strong gripwere studied in 10 healthy men. Blood flow was measured in the four fingers of both hands with a photoplethysmographicapparatus before and after testing. Grip force at the palm and the acceleration transmitted to the hand were measuredsimultaneously using a polymeric capacitive sensor matrix placed between hand and handlebar and a Doppler laser vibrometer,respectively. Results show that: 1) the vibration transmitted to the hand caused a temporary reduction in finger blood flow; 2) thisreduction was greater when the tool was held with the weak grip; 3) the looser grip caused increased transmission of accelerationto the hands.
INTRODUCTION
Hand-arm vibration syndrome (HAVS) is anoccupational disease affecting the musculo-skeletal,peripheral nervous and vascular arm structures [3].Current research aims at establishing the limits ofexposure [2], the physical parameters [4], and theindividual and general factors that may influence thesyndrome’s onset [5]. A new method that allows to measuresimultaneously hand-handlebar contact pressure andthe acceleration transmitted to the hand was used inthis study. The haemodynamic effects induced byvibration on the digital arterioles was studied in twodifferent testing conditions: weak and strong grip.
MATERIAL AND METHODS
Ten male, non-smoking, Italian students (height180 + 9 cm, weight 78.5 + 4.2 kg, age less than 30years) volunteered for this study. None had a historyof cardiovascular, connective tissue or dysmetabolicdisease, significant upper limb trauma, professionalexposure to vibration or family history for Raynaud’sphenomenon. Before performing the tests, subjects, who werewearing light clothing, remained sitting for 20 min toadapt to an ambient temperature of 20-24°C. Subjects were asked to hold a new hydraulicbreaker (Lifton, Denmark) operating in a metalcylinder filled with oil and steel balls to simulate thesurface on which these tools are normally used. The
bench complied with ISO-EN 28662-5 on the testingof hydraulic and pneumatic hydraulic breakers. Testslasted 5 min and took place on two different days. Onthe first, the breaker was held using a weak grip andon the second using a strong grip. Tool conditionsand operator posture were in line with EN 709. The measurement apparatus used in this study hasbeen developed jointly by Ancona University (Italy),the Italian National Research Council (CNR), LiftonBreakers and Novel GmbH (Germany) in theframework of the DOPTEST project (contract SMT4-CT97-2181) financed by the European Union. Itconsists of a polymeric capacitive sensor matrix(Novel) able to detect the spatial distribution of thecontact pressure between the hand surface and thehandlebar, and of a laser Doppler system for themeasurement of the vibration transmitted to the hand(laser vibrometer) aimed at the operator’s hand. Theanalysis of acceleration was performed along thehorizontal (X) and vertical (Z) axes. The data werecollected and processed with a support software thatcan acquire the vibratory signals in the time domainand process them into frequency data at each sensingpoint. Measurements of the overall vibration levelwere performed on the basis of accelerometric dataweighted for frequency in line with the applicableregulations. The haemodynamic analysis consisted of themeasurement of blood flow in the distal phalanxes ofthe four fingers of both hands from the end of the testto the return to baseline values using aphotoplethysmograph equipped with a single
photoreceptor (ULP 85 Gutman, Germany) and setat the recording speed of 25 mm/s. Statistical analysis was performed with the SSPC-PC programme (SPSS, Italy) using one-way varianceanalysis. Significance was established at P < 0.001.
RESULTS
The mean pressure and acceleration values werecalculated for each subject. A statistically significantinverse relationship (r=-0.60) was evidenced betweenacceleration and grip forces as the amplitude of thevibration transmitted to the hand’s surface decreasedwith increasing grip strength and vice versa (see Fig.1).The amplitude of the photoplethysmographic wavesin basal conditions was always in the normal range[6]. As the baseline values did not show significantdifferences (P> 0.01), they were pooled into a singlereference value. Baseline and values after the twotests for each subject are reported in Table 1. In all subjects, mean wave amplitude decreasedafter the tests: in 9 subjects it decreased more afterthe weak grip test, whereas in subject no. 5 the datawere reversed because on the first day (weak grip) heexerted a pressure of 774.3 N, and on the second(strong grip) a pressure of 729.7 N (Table 1).Consistently significant amplitude differences (p<0.01)were observed between baseline and both sets ofpost-testing values as well as between these (Table1).
CONCLUSIONS
The study of the haemodynamic changes in fingerblood flow is the first step to understand thephysiopathological changes that lead to Raynaud’sphenomenon [1,4].
Table 1. Mean amplitude value of photoplethysmographicwaves (SD) measured in the long fingers of both hands in10 volunteersNo. Baseline Weak grip Strong grip1 14.75(1.90) 7.12(2.90) 9.87(2.53)2 17.21(2.47) 9.12(4.05) 10.00(2.50)3 17.00(4.34) 6.75(3.57) 9.87(2.74)4 15.62(2.44) 7.37(1.92) 12.50(4.10)5 20.25(3.49) 10.50(3.16) 8.50(2.72)6 16.50(2.26) 8.50(1.41) 9.00(4.14)7 15.62(2.82) 5.50(2.32) 9.37(2.66)8 14.00(2.72) 7.37(2.38) 8.25(3.91)9 13.75(2.49) 3.62(0.91) 6.00(1.60)10 19.75(4.65) 12.62(1.59) 15.25(5.31)
p<0.01 (one-way variance analysis).
0
500
1000
1500
0 5 10 15 20Acceleration (m/s2)
Forc
e (N
)
FIGURE 1. Correlation between acceleration magnitudeand grip force applied to the handlebar of the vibrating tool.
The flow modifications induced by vibrating toolsare influenced by a range of factors: physical -frequency, acceleration, direction of vibration;individual - age, sex, race; occupational – dailyexposure, years of regular daily use, tool type,working environment; postural – position of the bodyin relation to the tool, type and strength of the grip,etc. These factors may have a different relativeweight in different workers and induce differentvasospastic reactions [2,5]. The present data show that the reduction in bloodflow was greatest when the tool was held with theweaker grip: in this case, acceleration is greater dueto looser hand-handlebar contact and to the lighterstatic load of the hand-arm system applied on thehandlebar. The data obtained with the new apparatus used inthis study could find an application in the design ofimproved industrial hand-held tools with reducedvibration.
REFERENCES
1. Bovenzi, M., and Griffin, M.J., Haemodynamicchanges in ipsilateral and contralateral fingers causedby acute exposure to hand transmitted vibration. OccupEnviron Med, 54, 566-576 (1997).
2. Bovenzi, M., Exposure-response relationship in thehand-arm vibration syndrome: an overview of currentepidemiology research. Int Arch Occup Environ Health,71, 509-519, (1998).
3. Bovenzi, M., La sindrome da vibrazioni mano-braccio:(i) quadri clinici, relazione esposizione-risposta, limitidi esposizione. Med Lav, 90, 547-555, (1999).
4. Bovenzi, M., Lindsell, CJ., and Griffin, M.J., Acutevascular responses to the frequency of vibrationtransmitted to the hand. Occup Environ Med, 57, 422-430, (2000).
5. Burstrom, L., and Bylund, S., Relationship betweenvibration dose and the absorption of mechanical powerin the hand. Scand J Work Environ Health, 26, 32-36,(2000).
6. Franzinelli, A., and Angotzi, A., Validità e limiti dellafotopletismografia nella diagnosi dell'angioneurosi dauso di strumenti vibranti, Med Lav, 67, 268-277,(1976).
