whole-body vibration exposures in a developing country: a pilot study in south africa amongst...

Author Details Author name: Darren Mark JOUBERT

Position: Lecturer

Organisation: Central Queensland University

Postal Address: School of Health and Human Performance, University of Central

Queensland, Bruce Highway, Rockhampton, 4703, Queensland, Australia.

Telephone: +09 617 4930 6905

Fax: +09 617 4930 9871

Email: [email protected]

Bibliography: Darren has an MSc (Med) Public Health from the University of

Cape Town, South Africa. He currently teaches and researches in the field of

occupational health and safety at Central Queensland University in Australia, and

has a special interest in occupational hygiene issues in developing countries and

whole-body vibration exposure in the workplace (forklift drivers particularly).

© CybErg’2002 Paper Phy009

Whole-body vibration exposures in a developing country: a pilot study in South Africa amongst forklift drivers at

the port of Durban.

Darren Mark JOUBERT

Central Queensland University, School of Health and Human Performance, Bruce Highway, Rockhampton, 4703, Queensland, Australia.

[email protected] ____________________________________________________________________________ Abstract

Many economic, social and political factors in developing countries play a

significant role in increasing the effects of occupational ergonomic hazards and the resulting

occupational diseases and disorders. Whole-body vibration is one such hazard, which has

received little attention in South Africa due to the fact that it is difficult to evaluate, quantify

and control. Whole-body vibration hazards are associated with the use of industrial vehicles

that are often outdated, inadequately maintained, and have operational lives long past the

norm for modern industrialized first world countries. This paper reports on a pilot study

conducted at the largest harbour in Africa the Port of Durban on the east coast of South

Africa, and whole-body vibration exposures experienced by drivers of forklift trucks under

various test operational conditions. Factors both economic and environmental that

contribute to high vibration exposures and subsequent adverse musculo-skeletal disorders

and complaints that have lead to an increase in sick leave and medical treatment amongst

this cohort are highlighted. Whole-body vibration was measured using the ISO 2631/1-1997

methodology on a small cohort of forklift trucks, and the majority of vibration results

exceeded the European Union Machinery Directive and ISO 2631/1-1997 root mean

squared exposure values of 0.5 ms-2 for 8 hours. Some of the forklifts exceeded the EEC

machinery directive vibration exposure limit of 0.7 ms-2 by up to four fold. Perceived

comfort levels as per ISO 2631/1-1997 for the recorded results are also reported.

Key Words: Whole-body vibration, Forklift drivers, Developing countries, Port.

© CybErg’2002 Paper Phy009 ___________________________________________________________________________________________

1. Introduction

Whole-body vibration exposure has been around since the advent of vehicles and other

mechanical industrial equipment and many studies have shown the probable link between

exposure and related adverse effects to the musculo-skeletal system of exposed workers in

various occupations (Bovenzi and Hulshof 1998, Bongers and Boshuisen 1990, Bongers,

Boshuisen and Hulshof 1990, Riihimaki, Tola, Videman and Hanninnen 1989, and Brendstrup

and Biering-Sorensen 1989). The multifactorial nature of vibration exposure requires a more

holistic approach to the evaluation of the problem, and consideration of various important

factors in order to allow adequate assessment. Various factors in addition to vibration levels

need to be considered and developing countries often have additional factors that can directly

and indirectly influence the operational conditions, vibration levels and associated exposures of

professional drivers. These factors need to be acknowledged and assessed in order to allow for

the correct and adequate control of a complex and multi-factorial problem.

2. The Study Environment

This study was conducted at the port of Durban, in response to the number of complaints

from forklift drivers with ongoing chronic problems of lower back pain and other musculo-

skeletal injuries. A further need for this study was to find ways reduce the excessive number of

days being lost by the organisation due to increased sick leave and driver back injuries.

The Port of Durban consists of three main operational areas under the control of the main

port authority, and for this study a selection of forklifts from each area was selected and

included in the sample cohort.

Drivers in the three areas operate on an eight hour revolving shift cycle; first shift 6am to

2pm, second shift 2pm to 10 pm, and third shift 10pm to 6am. At the port even though the

normal shift period is 8 hours, with a mid-shift half hour break for meals, the drivers often

have extended exposure periods of up to 12 hours, with overtime work included. This results

not only in longer periods of exposure, with increased vibrational dose, but also reduced time

for physical recovery, repair and recuperation.

In addition the drivers work on an unofficial piece-work system, where drivers can go off shift


early if they complete the work allocated for the day in a shorter time period. This questionably

increases productivity, but is acceptable to the drivers, and is also an influencing factor that increases

vibration exposure levels and associated health effects, with the increase in driving speeds,

vibrational shock loads and reduced rest periods experienced in the rush to complete the job. The

forklift drivers do no manual lifting work and are employed only to drive forklifts.

Forklifts are usually parked open to the elements on the wharf side, with exposure to humid salt

laden air, rain and wind. It is common to find that corrosion of the seats is quite severe, and due to

lack of maintenance and lack of use, the seat adjusters for both weight-damping and fore-aft

adjustments are often corroded and stuck in one position. When the study was conducted the survey

results indicating the seats were very seldom or never adjusted by the drivers for vibration

attenuation according to driver weight as per the manufacturers instructions.

Many different types, makes and models of forklifts are used at the port over a range of different

load capacities, from 3 tons to 40 tons. Due to the increasing costs of forklifts they are often kept in

service for extended periods of time. Many of these older types of forklifts are still in daily use at the

port and have inadequate seating, with poor ergonomic design and almost no vibration damping

capabilities. The seat is bolted directly to the floor or chassis of the forklift in some cases and offers

no adjustment for weight for vibration damping, but relies on the foam rubber cushioning of the seat

to offer attenuation and protection (figure 1). These older types are fortunately being phased out as

more modern forklifts are being added to the fleet.

© Darren Joubert

© CybErg’2002 Paper Phy009 Figure 1. Seat with foam rubber cushioning for vibration protection.

Many of the driving surfaces found in areas of the port, especially on the wharf sides, where the

traffic and volumes of work and cargo handled has increased over the years, has resulted in badly

damaged surfaces that in some places have not been resurfaced in over 20 years (figure 2).

© Darren Joubert

Figure 2. Shows typical wharf side driving conditions with debris, holes and rough uneven driving surfaces. 3. Basic Vibration Concepts and Terminology Vibration intensity or magnitude is usually specified as the change of position of a body, usually

measured from its resting position. Displacement levels can be measured in inches or millimetres.

The primary quantity used to describe the intensity of a vibration environment, irrespective of the

type of transducer used in the actual measurements is acceleration, which is normally expressed in

metres per second squared (m/s -2). The acceleration of a body is the time rate of change of the

velocity or speed, and for occupational vibration, the acceleration is the most important quantity

since it is proportional to the forces applied to the body of the exposed worker, and it is believed that

the forces are the source of damage and harm (DiNardi 1997:469).


This can be further expressed as root mean squared (rms), and is useful in vibration measurement

as workplace vibration exposures are complex and contain many vibration frequencies (figure 3).

The average can be obtained by summing the squares of the acceleration values measured over

time, dividing by the measuring time, and then taking the square root of the resulting value.

(DiNardi 1997:469)

Peak

Average

RMS Amplitude

Peak to Peak

Figure 3. Amplitude Relationships and Root Mean Squared (rms) values for vibration.

4. Vibration evaluation and assessment methods

ISO 2631-1997 Mechanical Vibration and Shock - Evaluation of Human Exposure to Whole-

Body Vibration, requires that the evaluation includes measurement of the weighted root-mean-

square (r.m.s) acceleration. It is expressed in metres per

second squared (m/s -2) for translational vibration and is

calculated as:

where:

aw(t) weighted acceleration [m/s²]

t duration of the measurement [s].


ISO 2631-1997 makes allowance for health guidance caution zones, which allow the application of a

rough assessment of likely health effects taking into account the vibration (rms) values and exposure

periods (figure 4). Griffin (1998) argues that the dependent variable in this type of assessment could

be the probability or severity of a specified disorder or the cumulative exposure duration before the

occurrence of a specified disorder in a specified percentage of the exposed population. However the

standard does not offer a definite means for predicting such effects. For exposures below the zone,

the ISO 2631-1997 standard warns that, health effects have not been clearly documented and/or

objectively observed. Caution with respect to potential health effects is indicated and above the zone

health risks are likely.

Figure 4. Health guidance zones (ISO 2631-1, 1997).

The European Union Machinery Directive (1994) poses a threshold level for vibration, i.e.: the © CybErg’2002 Paper Phy009

exposure value below which no adverse effect on health and safety is expected at an 8-hour exposure

of < 0.25ms-2. The action level (i.e.: the value above which technical, administrative, and medical

provisions must be undertaken) is 0.5ms-2, and the exposure limit (i.e.: the exposure value above

which an unprotected worker is exposed to unacceptable risks) is set at 0.7ms-2.

In situations where vibration is transient, i.e. is of short duration caused by shocks, the rms value

tends to underestimates the vibration and therefore the crest factor (maximum peak value divided by

rms) best describes the vibration. When the crest factor is more than 9 (i.e. the high shock loadings),

it is recommended to use additional evaluation methods like the running r.m.s or the fourth power

vibration dose method which is more sensitive to peaks than the basic method because it uses a forth

power instead of a second power of acceleration time history. The fourth-power vibration dose value

is expressed in m/s 1.75 . If the crest factor is below or equal to 9, the basic evaluation method is

normally sufficient.

Griffin (1998) however, maintains that some confusion prevails as to which method would be

the best to use as the standard does not obviously indicate which results are to be used to reach a

conclusion as to what exposure is acceptable, and in fact two different health guidance caution

zones are given, leading to confusion as they can both lead to opposing results.

5. Expected comfort reactions to vibration environments

ISO 2361/1-1997, does not give specific limits of vibration magnitude as related to comfort due to

the many factors which, vary with each type of environment and application. The standard however

does give values which, give an approximate indication of likely reactions from exposed drivers to

various magnitudes of overall vibration values. These potential reactions are shown in table 1 below.

Table 1. Expected comfort reactions to vibration environments (ISO 2631/1-1997).

Less than 0.315 m/s2 not uncomfortable

0.315 m/s2 to 0.63 m/s2 A little uncomfortable

0.5 m/s2 to 1 m/s2 fairly uncomfortable

0.8 m/s2 to 1.6 m/s2 uncomfortable

1.25 m/s2 to 2.5 m/s2 very uncomfortable

Greater than 2 m/s2 extremely uncomfortable


McPhee, Foster and Long (2001) point out that the vibration dose value is a also a sensitive

indicator of ride roughness and has been found to correlate very well with drivers subjective

opinion. For example a driver who complains that the ride is very rough could be exposed to

vibration in the “likely” health risk zone.

The calculation of exposure limit, FDPB (Fatigue-decreased proficiency boundary) and reduced

comfort boundary when analysing WBV has been made obsolete with the replacement of ISO

2631/1-1985 with ISO 2631/1-1997 so these measures will not be discussed in this paper.

6. Methods 6.1 The Measurement Procedure

Thirty-three different exposure configurations were tested. The driver carried out four separate

test runs for each exposure scenario (rough vs smooth), to obtain a mean value. This was done firstly

with the seat unadjusted to its lowest unadjusted setting (ie: no theoretical vibration damping

provided), and then adjusted for the driver’s specific weight according to manufacturer

specifications. Seat effective transmissibility values (SEAT %) will not be reported for individual

forklifts in this paper. Each forklift, with an adjustable seat, had to be tested over 16 different test

runs, to take into account the different operational variables as shown in table 2 below:

Table 2. Shows test variables (operational condition) under which the forklifts were tested during the different test runs.

Test variable Explanation of term

Rough adjusted Rough driving terrain + Seat adjusted for driver weight

Smooth adjusted Smooth driving terrain + Seat adjusted for drivers weight

Rough unadjusted Rough driving terrain + Seat not adjusted for driver weight

Smooth unadjusted Smooth driving terrain + Seat not adjusted for driver weight

Two of the forklifts of the older type, had seats that were not adjustable, and one additional test run

was carried out on a loaded forklift to ascertain the effects of loads on the vibration characteristics.

Each run took approximately 80 - 90 seconds.


6.2 The Test Vehicles

A total of nine forklifts from the three areas were selected by convenience sampling (details

shown in table 3 below). Only vehicles of between 3 to 5 tons (that fell within the study protocol)

were included.

Table 3. Characteristics of the forklifts on which vibration measurements were conducted Forklift

Manufacturer & model

Capacity (load)

Driver weight

Seat weight adjustable?

Area 1 A

Mitsubishi 30 (diesel)

3 000 kg

74 Kg

No

B

Mitsubishi 45 (diesel)

4 500 kg

74 Kg

Yes

C

Mitsubishi 35 (gas)

3 500 kg

74 Kg

Yes

D

TCM FD40 (diesel)

4 000 kg

74 Kg

Yes

Area 2 E

TCM FD50 (diesel)

5 000 kg

94 kg

Yes

F

Hyster (diesel)

5 000 kg

94 kg

Yes

Area 3 G

Linde H40 (diesel)

4000kg

85 kg

Yes

H

Mitsubishi PFD510 (diesel)

3 000kg

85 kg

No

I

TCM FD40 (diesel)

4 000kg

85 kg

Yes

NOTE: all vehicles except the Linde H40 had pneumatic tyres. :Sample included 8 diesel powered forklifts and one powered by L.P.G gas.

For the analysis and measurement of whole-body vibration in this study the ISO-2631/1-1997

standard was used: Mechanical Vibration and Shock - Evaluation of Human Exposure to Whole-

Body Vibration which, was at the time of the study adopted as a draft South African standard.

Measurement of vibration was conducted by using a Bruel & Kjaer (B&K) tri-axial piezo-electric

accelerometer (Model 4322) mounted on the forklift seat in a deformable rubber disc shaped pad © CybErg’2002 Paper Phy009

which followed the seat contour (see figure 5). In addition to the measurements on top of the seat

surface an additional measurement was conducted by placing an accelerometer underneath the seat

on the forklift chassis to capture data in the z-axis (vertical) plane in order to determine the transfer

function of the seat (SEAT % value). Tri-axial accelerometers measure vibration intensities and

frequencies in the X (fore and aft), Y(sideways) and Z (up and down) directions and the

accelerometer charge outputs produced by the vibrational energy during the test drives were

amplified using PCB model 424A accelerometer charge amplifiers, sent over a Johne and Reilholfer

PCM telemetry system (figure 6), and captured and stored on a remote PC station.

© Darren Joubert

Figure 5. Placement of seat accelerometer.


© Darren Joubert

Figure 6. Radio telemetry system and aerial connected to accellerometer.

All equipment was assembled as per ISO 2631/1-1997 requirements and as specified in the South

African Bureau of Standards Code of Practice, S.A.B.S- 0259 for accredited laboratories, calibrated

on an annual basis. This was done at the National Metrology Laboratory of the Council for Scientific

and Industrial research (C.S.I.R) in Pretoria, South Africa. Secondary calibration was carried out on

site (before and after each set of measurements were conducted). To do this a signal generator was

used to send a known electronic signal into the measurement train, and the attenuation of the signal

or signal drop was then measured using a Gould calibrator oscilloscope. Appropriate adjustments

were then made if necessary to ensure accurate and reliable results.

6.3 The Test Drivers

In each of the three areas one driver was used to drive all forklifts that were to be tested in that

particular area. Each driver was fully briefed as to the aims and objectives of the measurements and

were instructed to drive at a normal speed and manner, as they would on any normal work day. Four

test runs per vehicle per surface, and per seat adjustment were carried out for the calculation of a

mean value under each test condition. Driver’s participated in the study on the basis of informed © CybErg’2002 Paper Phy009

consent with the option to withdraw at any stage.

6.4 The Test Areas and Driving Surfaces

Vibration measurements were conducted over two days in the three areas in the study. In each of

these three areas two separate representative driving environments were selected to include both

rough (wharf side) (figure 7) and smooth (shed) (figure 8) operating conditions to ascertain the

effects that driving surface would have on vibration levels. Sheds used for storing break bulk items,

i.e. not in large steel shipping containers, were chosen as most representative of a smooth operating

surface, whilst the area outside the sheds, on the wharf side were chosen as representative of the

rough operating conditions, with its poorly maintained often damaged surface crossed by railway

lines.

© Darren Joubert

Figure 7. Wharf side driving conditions with railway lines and pitted tarmacadam surface.


© Darren Joubert

Figure 8. Smooth test driving surface inside the wharf storage sheds. 6.5 Vibration Data Capture and Frequency Analysis

The raw vibration data electronic signal from the accelerometer was passed through a series of

charge amplifiers and sent via the custom-built telemetry system and aerial for real time capture on a

nearby personal computer. After the measurement the vibration data was imported from the personal

computer based logging system into a custom analysis software package for frequency analysis and

evaluation.

The vibration results from the three groups of forklifts tested (from the three areas) are presented

individually and then combined as one group after comparisons for differences between them were

made, and this combined group was then compared to the overall EEC Machinery Directive (1994)

exposure standard of 0.5 ms-2 as well as ISO 2631/1-1997 vibration health guidance (rms) zone and

the expected comfort reactions to vibration environments. The mean effects of driving surface and

seat adjustment on vibration levels are also presented.


7. Results 7.1 Profile of vibration results Table 4. Mean vibration rms values for individual forklifts (ms-2) Forklift Rough

a djusted Rough nadjusted u

Smooth a djusted

Smooth u nadjusted

Rough adjusted ( loaded)

A - 3.05 - 2.04 - B 1.91 2.88 1.45 1.58 - C 1.18 1.19 0.82 0.82 - D 1.31 1.17 1.07 0.83 - E 1.33 1.54 0.48 0.47 - F 1.51 1.36 0.75 0.97 - G 0.82 1.36 0.64 0.84 - H - 1.06 - 0.74 - I 0.78 0.74 0.58 0.57 0.54 Bold indicates result exceeds EEC machinery Directive and the ISO 2631/1 guidance level of 0.5 ms-2 .

00.5

11.5

22.5

33.5

Multi axis rms values

A B C D E F G H IForklift

Rough Adjusted

Rough Unadjusted

Smooth Adjusted

Smooth Unadjusted

Rough Adjusted Loaded

Graph 1. Graphical representation of multi-axis root mean squared vibration levels (ms –2) for each forklift under different seat and terrain test conditions. Driving surfaces as well as the seat adjustment for optimum vibration attenuation are two aspects of

the vehicle factors and driving environment that play a large role in the vibration exposure of the

driver. In table 4 (shown graphically in Graph 1) above, the vibration root mean squared values are

presented stratified by driving surface of the various test areas (rough and smooth) as well as seat


adjustment settings (unadjusted or adjusted for weight). All results (bar three) exceeded the EEC

machinery directive (rms) action level of 0.5 ms-2 and in 82% of the test conditions exceeded the

exposure limit of 0.7 ms-2 . The ISO 2631/1-1997, guidance level was also exceeded in all but three

results. The loaded condition in one test run for forklift ( I ) reduced the vibration levels from 0.78 to

0.54 ms-2 , due to the stabilising nature of the load carried.

7.2 Driving surfaces Table 5. Effects of driving surface on vibration levels. Combined multi-axis vibration root mean squared values by driving surface

Test condition

Vibration rms values (ms -2)

Mean

SD

Rough driving surface

1.4

0.63

Smooth driving surface

0.92

0.43

Bold denotes RMS values that exceed 0.5 ms -2

The effects of driving surfaces on the mean root mean squared (rms) vibration values are shown in

table 5 above, for combined results of all forklifts. Rough driving surfaces in each test area were

higher than the corresponding smooth driving surfaces. Smooth driving surfaces (rms = 0.92 ms -2 ;

SD: 0.43) when compared to rough conditions; rms = 1.4 ms -2 ;SD: 0.63) had lower mean rms values

as would be expected. (P = 0.01). 7.3 Seat adjustment Table 6. Shows vibration root mean squared values for combined seat adjustment setting.

Test condition

Vibration rms values (ms -2)

Mean

SD

Seat adjusted

1.0

0.32

Seat unadjusted

1.2

0.54

Bold denotes rms values that exceed 0.5 ms -2 The effects of seat adjustment on vibration rms values is shown in table 6 above and although mean

vibration (rms) values were slightly higher in unadjusted seats than in the adjusted seats the difference


was not statistically significant (p = 0.2). The seat effective amplitude transmissibility factors (SEAT

%) are however a better indication of seat effectiveness in vibration attenuation, as the transmission of

vibration and energy loss (or gain) is compared across the seat mechanism by comparison of chassis

vibration values and seat top vibration values, giving a value that will indicate either attenuation of

vibrational energy or amplification. The results of the SEAT % values in the forklifts tested above

indicated no significant difference overall in the average SEAT % values between the seats adjusted

(110.4 SD 43.9) and unadjusted (121.6, SD: 42.1) seats (p = 0.6). Individual SEAT % values are not

reported.

7.4 Perceived comfort levels Table 7. Perceived (expected) comfort levels. Forklift Rough

A djusted Rough nadjusted u

Smooth a djusted

Smooth U nadjusted

A - ● - ● B ○ ● ○ ○ C ○ ○ ◊ ◊ D ○ ○ ◊ ◊ E ○ ○ - - F ○ ○ - ◊ G ◊ ○ - ◊ H - ◊ - - I - - - - Note: Categories overlap and table excludes fairly uncomfortable, a little uncomfortable and not uncomfortable. Key: ● = extremely uncomfortable (above 2 m/s-2), ○ = very uncomfortable (1.25 m/s-2 – 2.5 m/s-2) , ◊ = uncomfortable (0.8 m/s-2 – 1.6 m/s-2).

From the perceived comfort levels (table 7 above) as per ISO 2631/1-1997, it can be seen that the

expected reaction (from a driver comfort perspective) in most cases (70% of driving conditions tested)

would cause some degree of discomfort to drivers. The reaction from drivers in this study was

supported from the results of an adapted standardised questionnaire administered (Kuorinka, Jonsson,

Kilborn, Vinterburg, Biering-Sorenson, Andersson and Jorgensen , 1987) which, indicated that 89%

of drivers suffered from chronic lower back pain and other musculo-skeletal disorders. Perceived

comfort reactions are thus a useful measure of overall subjective reactions to vibration levels as well as

the driving environment and the forklifts.


8. Discussion

Mean whole-body vibration values (rms) in all 9 forklifts tested exceeded the threshold level for

vibration set out in the EU machinery directive(1994) of 0.2 ms-2 , and the majority of the forklifts in

the sample exceeded the action level (0.5 ms-2 ) which is also laid down in the ISO 2361/1-1997

standard. Some of the forklifts tested also exceeded the exposure limit of 0.7 ms-2 by up to four fold,

thereby exposing drivers to unacceptable vibration risks. The vibration exposure at the port under

some of the operational test conditions exceeded the mean vibration levels of other studies that have

been conducted in developed countries in Europe, such as studies by Bongers and Boshuisen (1990)

which reported vibration levels of 0.8ms-2 on forklifts, or 1.4ms-2 in another study on wheeloaders

(Bongers et al 1990), and in another study by Bovenzi (1998) a range of 0.24-0.71ms-2 was reported

on buses, and 0.89-1.41ms -2 on tractors.

At the port many additional risk factors other than direct vibration exposure that directly or

indirectly influence the vibration levels are also present and in combination increase the driver

exposures. These include the condition of the driving surfaces which had a significant effect on the

vibration levels experienced. The condition of the vehicles and the vibration seat adjustments

mechanism on all the forklifts tested (when present) were shown to generally not offer adequate

vibration protection to the driver even when adjusted correctly for the drivers weight according to the

manufacturers specifications. The organisational factors such as he long shift hours, inadequate rest

breaks, the use of a piece- work system also increased exposures and associated effects.

These factors were somewhat echoed in the perceived reaction results that indicated most drivers

would find the conditions ranging from uncomfortable to extremely uncomfortable. These results

were supported by the high prevalence of lower back pain (89%) reported by the drivers as well as

with anecdotal comments made by drivers during interviews.

9. Limitations of Vibration Results

The results of the vibration measurements were however, limited in their application due to

logistical problems, which precluded the measurement of vibration under full operational conditions.

The number of forklifts tested was low and the selection of the forklifts included in the study was not

fully randomised. The vibration data cannot be applied with any degree of certainty to the entire


population of forklifts or exposure conditions existing in the different areas at the port. The results do

however, give an indication of the vibration exposure levels that could be experienced by drivers of

these vehicles and the effects of other factors such as driving surface and seat adjustment on those

levels. These limitations need to be borne in mind when interpreting these results and caution

exercised when applying them to other working conditions. Nonetheless, some inferences can

tentatively be made as to the probable exposure conditions and the implications for assessing the

effectiveness of the seats of the forklifts as well as driving conditions. Overall indications of probable

exposures can be ascertained when the average mean vibration levels in the three areas are compared

to the EEC machinery directive and the ISO vibration exposure limits and guidelines. A more

rigorous investigation into whole-body vibration associated with vehicular use would have required a

larger randomly selected sample from each area with one driver and multiple exposure conditions.

This was unfortunately not possible for this study but may be warranted for future investigations.

10. Conclusion

Many aspects need to be considered when assessing a particular hazard that is as complex as

whole-body vibration exposure, especially when other indirect factors within the organisation have an

influence on the exposure characteristics. None of the factors can be evaluated alone and because

whole-body vibration is a complex occupational hazard it requires a holistic approach to its

measurement and evaluation in order to allow correct assessment within context. Various methods of

assessing the vibration exposures and expected reactions can be used but caution must be considered

when using different measures or methodologies as these can have an influence on the overall

interpretation of the data and findings.

In developing countries many aspects need to be considered in addition to the vibration exposure,

such as the fact that forklifts trucks are often still in use long after their operational life is over in more

developed countries. Cultural and organizational differences and norms may also play a part in

increased vibration exposures, and existing controls such as seat adjustment mechanisms to attenuate

vibration may not be used at all or because of lack of maintenance may be on a whole ineffective in

providing adequate and anticipated protection. All of these risk factors cannot be addressed or

controlled for with one control measure and care must be exercised that a holistic approach to

vibration control is striven for rather than the quest for a panacea. © CybErg’2002 Paper Phy009

Acknowledgements

The author would like to acknowledge the financial support of the National Research Foundation

of South Africa, the Ernest Oppenheimer Memorial Trust, and the research committee of Mangosuthu

Technikon, as well as individual acknowledgement to Dr Leslie London (University of Cape Town)

and Portnet for their involvement and access to conduct this research.

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