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Abstract
Objectives To determine the extent of hand transmitted vibration exposure problems, particularly hand-arm vibration syndrome (HAVS), among construction workers in Malaysia.
Methods A cross-sectional study was conducted on a construction site in Kuala Lumpur, Malaysia. 243 workers were recruited. Questionnaire interviews and hand examinations were administered to 194 respondents. Vibration magnitudes for concrete breakers, drills and grinders were measured using a 3-axis accelerometer. Clinical outcomes were compared and analysed according to vibration exposure status.
Results Vibration total values for concrete breakers, impact drills and grinders were 10.02 ms−2, 7.72 ms−2 and 5.29 ms−2, respectively. The mean 8 h time-weighted hand transmitted vibration exposure, A(8), among subjects on current and previous construction sites was 7.52 (SD 2.68) ms−2 and 9.21 (SD 2.48) ms−2, respectively. Finger tingling, finger numbness, musculoskeletal problems of the neck, finger coldness, abnormal Phalen's test and abnormal light touch sensation were significantly more common in the high vibration exposure group (n=139) than the low–moderate vibration exposure group (n=54). Mean total lifetime vibration dose among exposed subjects was 15.2 (SD 3.2) m2 h3 s−4 (ln scale). HAVS prevalence was 18% and the prevalence ratio of stage 1 and higher disease in the high vibration exposure group versus the low–moderate vibration exposure group was 4.86 (95% CI 1.19 to 19.80).
Conclusions Hand transmitted vibration is a recognisable problem in tropical countries including Malaysia. The current study has identified clinical symptoms and signs suggesting HAVS among construction workers exposed to hand transmitted vibration in a warm environment.
- Hand arm vibration syndrome
- tropical
- prevalence
- construction workers
- construction
- vibration
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What this paper adds
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Large numbers of industrial workers in tropical countries are at risk of exposure to hand transmitted vibration.
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However, the prevalence of HAVS and its typical clinical manifestations in warm environments have not been properly established.
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This study shows that HAVS is a recognisable condition in warm environments but manifests with different clinical signs and symptoms compared to cold environments.
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The findings of this first study on HAVS in Malaysia will serve as a baseline for further research and may stimulate local authorities to tackle the problem of hand transmitted vibration.
Introduction
Hand-arm vibration syndrome (HAVS) is a disabling clinical condition characterised by a complex of signs and symptoms in the vascular, neurological and musculoskeletal systems of the upper limbs due to prolonged exposure to hand transmitted vibration. The prevalence of HAVS ranged from 5% to more than 80% globally depending on the types of tools, extent of vibration exposure and climatic factors.1–7 The condition is widely recognised in temperate zones due to the presence of its well-known clinical feature—vibration white finger (VWF)—which is now known to be provoked by low ambient temperature.8–12 Its prevalence in warm countries is not well established because VWF13–16 does not typically occur and the available literature on HAVS in tropical countries is limited.13–18 Recent data from South Africa5 showed that the prevalence of HAVS among gold miners exposed to hand transmitted vibration from rock drills in warm environments was 15%.
An overview of epidemiological studies shows that sensorineural disorders tend to appear earlier than vascular disorders and that these disorders develop independently of each other at different rates.19 Neurological and musculoskeletal signs of HAVS are more common than vascular symptoms in tropical countries because the critical ambient temperature for the provocation of VWF is around 15°C.20 The low rate of VWF could explain the low disease prevalence in tropical countries since the classical diagnosis of HAVS includes VWF.
No information on HAVS is available to date for Malaysia. Information from the Department of Statistics, Malaysia shows that about 2.3 million workers were employed in agriculture, forestry, construction, mining and quarrying in 2005.21 Despite so many being employed in industries where hand transmitted vibration hazards are common, only 15 workers applied to the Social Security Organization (SOCSO), Malaysia for compensation claims under the item ‘diseases caused by vibration (disorders of muscles, tendons, bones, joints, peripheral blood vessels or peripheral nerves)’ in 2006.22
This study was conducted to determine the prevalence of HAVS and its clinical manifestations among a group of construction workers in a warm environment. The results of this study will also add to the existing literature on the characteristics of HAVS in tropical countries.
Methods
This is a cross-sectional study. A large construction site covering 13 acres in Kuala Lumpur city centre was selected for this study. Average ambient temperature is above 25°C throughout the year, varying from 24°C at night to 33°C during the day. Average relative humidity is 85% throughout the year. All construction work on the project was carried out by one main subcontractor.
All plant operators working for the main subcontracting company were recruited into the study. The plant operators were involved in general operations and construction of the building including assisting with or laying bricks, concrete finishing, non-specialised woodwork, demolition and repairing, and area cleaning. Some of the plant operators worked at drilling, concrete breaking, steel cutting and metal grinding, and hence were exposed to hand transmitted vibration. Administrative officers and non-manual support staff were not included in the study as their work was very different from that of plant operators. Female subjects and those with a history of injury or surgery with residual complications involving muscles, nerves and bony structures of the hands, forearms and arms were excluded. A total of 243 eligible plant operators worked on the construction site during the data collection period of 3 January 2007 to 24 April 2007.
All respondents were interviewed using a modified questionnaire with Malay translation based on the Hand-Transmitted Vibration Health Surveillance - Initial Questionnaire and Clinical Assessment, created by the Research Network on Detection and Prevention of Injuries due to Occupational Vibration Exposures (Vibration Injury Network). The questionnaire was pretested and pilot tested using a subsample of the study population and found to be reliable and suitable for use in the current study.23
The interview included questions on basic demographic information, occupational, social and medical histories, detailed vibration exposure information including employment duration, duration of employment at the current construction site, type of vibratory tools used and daily duration of operation for each vibratory tool, yearly exposure and total number of years of exposure in both current and previous construction sites. Subjects were asked specifically to recall and report as accurately as possible the daily duration of operation for each vibratory tool after excluding all work breaks including all rest periods, lunch hours, tea breaks and dinner time.
Information on HAVS symptoms was obtained from the interview and from physical examination of the hand, with specific hand function assessment using the Purdue Pegboard, the Rolyan Hot and Cold Discrimination Kit, Semmes Weinstein monofilaments, the Touch-Test Two-Point Discriminator and a tuning fork. All hand function assessments were carried out at room temperature at 27°C. For the Purdue Pegboard test, the discriminating threshold for abnormal findings was 1 SD below the normative population means for male maintenance and service employee data (means 13.61 and 13.45 for the right and left hands, respectively) as provided in the operator's manual. The discriminating temperatures for cold and hot sensation using the Rolyan aluminium temperature probes were 25°C and 37°C, respectively. The Semmes Weinstein monofilaments test was recorded as abnormal if the subject's threshold of response was monofilament 3.61 and above (based on the Touch-Test Sensory Evaluator Chart). The upper limit for normal static two-point discrimination was set at 6 mm. Vibration sensation was considered abnormal if the subject perceived no vibration at the distal interphalangeal joints of the index and little fingers following application of a 128 Hz tuning fork. The interview and physical examination were conducted by two different researchers who were blinded to each other's results.
Assessment of workplace tool use revealed that vibratory tools of the same type and model were used in both current and previous construction sites as equipment was procured in bulk for use throughout the company. The most common vibratory tools used by subjects in any construction project were concrete breakers, impact drills and grinders. The most frequent tasks using these tools were demolishing concrete structures, hole drilling and steel cutting. Hence, the vibrations produced by these three tools were measured using a VI-400Pro 3-axial human vibration monitor (Quest Technologies, Oconomowoc, Wisconsin, USA) under actual operating conditions. Measurements were conducted by a qualified technician according to ISO 5439-2:2001. The accelerometer was firmly attached to an adaptor (HAV Sensor Mounting Block and Clamp Assembly, part no. 072-005, Quest Technologies) and clamped to the tool handle according to ISO 5439-2:2001. The signal cables were taped to the vibrating surface as near to the mounted accelerometer as possible to avoid the triboelectric effect. A mechanical filter constructed of butyl rubber sheeting was placed between the adaptor and the tool handle to avoid overloading and DC-shift caused by percussive tools. A minimum of three readings were taken for each tool and each reading was taken at least 1 min. The measurements and information on daily vibration exposure duration obtained from the questionnaire were used to calculate the daily 8 h time weighted average vibration exposure level, A(8), of each subject.
The majority of the workers used more than one tool. The A(8) of each subject was calculated based on the following mathematical formula:
where ahνi
is the vibration total value for each tool and Ti
is the duration of exposure for each tool. The vibration total value, ahν
, is the square root of the sum of the squares of the acceleration magnitudes of each tool in three orthogonal axes and is given by the mathematical formula:
where ahwx
, ahwy
and ahwz
are the frequency weighted root mean square accelerations in the x-axis, y-axis and z-axis, respectively. The personal life time vibration dose (LVD) was also calculated based on formula suggested by Griffin24 ,25 as follows:
where thi is the daily vibration exposure duration of each tool (hours/day), tdi is the number of working days per year for each tool and tyi is the total number of years use for each tool.
Plant operators whose A(8) in current or previous construction sites was equal to or exceeded the American Conference of Governmental Industrial Hygienist (ACGIH) recommended threshold limit value (TLV) of 4 ms−2 were categorised as the high exposure group. Those whose A(8) was less than 4 ms−2 or who had not used any vibratory tools were categorised as the low–moderate exposure group. The TLV recommended by the ACGIH was used as the cut-off value because it is used by the Malaysian Department of Occupational Safety and Health as a guide for hand transmitted vibration exposure. The outcome variables were compared and tested between the two groups of workers.
This study obtained written approval from the main contractor prior to conduct of the study. Informed consent was obtained from each subject before interview and physical examination. An explanation was provided to subjects concerning the purpose of the study which was also stated on the subject information sheet. This was followed by written consent once the subjects understood the purpose and conduct of the study. Subjects were given assurance that all reported symptoms or physical examination findings were confidential and the information would not be revealed to their employer, to prevent any possibility of employment discrimination. Subjects were also informed that any information provided or obtained in the study could not be used for the purpose of compensation.
Data entry was validated using the double entry method. Analysis was carried out using SPSS V.15.0. Categorical data from the different exposure groups were compared using χ2 analysis with relevant Yates correction or Fisher's exact test. Student t tests and ANOVA were used to compare the means of two and more than two groups of data, respectively. The corresponding non-parametric tests such as the Mann–Whitney test and Kruskal–Wallis test were used where data were not normally distributed. Crude and adjusted prevalence ratios were calculated for all outcome variables by the log binomial regression method with SAS V.9.1 using the procedure PROC GENMOD with dist=bin and link=log. The significance level for all statistical tests was set at 0.05 unless specified.
Results
A total of 194 eligible plant operators responded to the study (response rate 80%). All subjects were foreigners, with 95% being from Indonesia and the rest from Bangladesh. The mean age of subjects was 29.9 (SD 6.4) years. Most of the workers (96%) had achieved at least primary education, while the majority (66%) had achieved secondary education. All were fluent in Malay and understood the questionnaire except for one whose data were excluded from subsequent analysis. All subjects were of medium build (average BMI 20.9) with a dominant right hand. Median duration of employment and mean duration of working at the current construction site were 24.0 (range 0.1–174.0) and 9.5 (range 0.1–36.0) months, respectively. Seventy per cent of the subjects were current smokers, but very few had a history of tobacco chewing, alcohol consumption or chemical exposure at work. None of the subjects had a second job or history of vibration exposure during their spare time. There were 139 (72%) workers in the high exposure group. Table 1 compares the basic characteristics of subjects between the two groups.
Characteristics of the study subjects
The main sources of hand transmitted vibration exposure in the current study were concrete breakers, grinders and impact drills. The frequency weighted vibration magnitudes of the three vibratory tools are shown in table 2. The mean A(8) for hand transmitted vibration for the high exposure group in current and previous construction sites were 7.52 (SD 2.68) ms−2 and 9.21 (SD 2.48) ms−2, respectively.
Average frequency weighted vibration acceleration magnitudes for vibratory tools
Neurological and musculoskeletal symptoms were more prevalent than vascular symptoms. Finger tingling and numbness were experienced by 16% and 14% of all subjects, respectively. Only three subjects reported finger colour change at least once in their lifetime. Other reported symptoms related to HAVS were musculoskeletal problems of the upper limbs (19%), musculoskeletal problems of the neck (14%), hand grip weakness (18%), finger coldness (13%), difficulty handling small objects (2%) and difficulty opening tight jars (4%). Physical examination revealed no digital pallor or cyanosis in any subject. Tinel's and Phalen's tests were positive in at least one hand in 15% and 13% of subjects, respectively, with 11% having both tests positive and 6% only one test positive. There was no significant difference in the distribution of positive tests between right and left hands. Neurological assessment of the hands showed abnormal findings only in light touch, temperature sensation and hand dexterity. There was no muscle wasting and the mean hand grip strengths of the left and right hands were 40.1 (SD 6.0) and 41.5 (SD 6.1) kg, respectively.
The prevalence of finger tingling, finger numbness, musculoskeletal problems of the neck, finger coldness, abnormal Phalen's test and abnormal light touch sensation was significantly higher in the high exposure group than in the low–moderate exposure group. Although the prevalence of abnormal symptoms and signs was also higher in the high exposure group, the findings are not statistically significant. The results are shown in table 3.
Prevalence ratio (PR) of symptoms and signs of hand-arm vibration syndrome among subjects with high versus low–moderate vibration exposure
The mean total LVD among the high exposure group was 15.2 (3.2) m2 h3 s−4 (ln scale). Simple regression analysis of total LVD and prevalence of HAVS related symptoms showed that finger tingling, finger numbness, hand grip weakness, finger coldness and abnormal Tinel's and Phalen's test were related to the trend of total LVD. Table 4 shows the prevalence ratio of HAVS related symptoms and signs for each unit increase in the logarithmic scale of total LVD.
Prevalence ratio (PR) of symptoms and signs of hand-arm vibration syndrome for each unit increase in the logarithmic scale of total lifetime vibration dose
Subjects were also classified according to their neurological symptoms (tingling and numbness) and hand assessment findings (Semmes Weinstein monofilament test, Purdue Pegboard test and two-point discrimination test) into different stages based on the Stockholm Workshop Scales (table 5). The prevalence of HAVS among subjects with high vibration exposure was 18%. The prevalence ratio of stage 1 and higher disease among subjects in the high vibration group versus the low–moderate group was 4.86 (95% CI 1.19 to 19.80).
Prevalence of neurological outcomes based on the Stockholm Workshop Scales among study subjects
Discussion
The exact prevalence of HAVS in this study is undetermined. If we restrict our definition of HAVS to the occurrence of symptoms in all three components of the hand (vascular, neurological and musculoskeletal), the prevalence of HAVS in this study was zero. The absence of vascular symptoms alone does not conclusively exclude pathology caused by hand transmitted vibration. Since 72% of subjects were exposed to hand transmitted vibration exceeding the recommended TLV and the prevalence of neurological and musculoskeletal symptoms was significantly higher among exposed subjects, it is very likely that these abnormal outcomes are due to hand transmitted vibration. Based on the Stockholm Workshop Scales for classification of neurological symptoms, the prevalence of HAVS was found to be 18% in this study. This result corresponds with the prevalence of HAVS among gold miners working in a warm environment in South Africa.5
There were three cases of finger colour changes in the current study. However, review of clinical descriptions and exposure information suggested only one (0.5%) possible case of VWF, although 18% of the vibration exposed subjects complained of finger coldness. Previous studies in warm countries such as Papua New Guinea, Indonesia,14 India13 and Vietnam15 did not report VWF among vibration exposed workers. The current subject reported finger whiteness over the distal phalanges of the right index to little fingers and left middle fingers several times per week, with the longest colour change (which occurred early in the morning) lasting about 7 min. While this subject might be more susceptible to early morning cold weather, other affected individuals might not have been exposed to colder environments triggering VWF, and hence the low reporting of finger whiteness in this study.
The prevalence of neurological symptoms was much higher in this study, being 20% and 18% for finger tingling and finger numbness, respectively. In previous studies on HAVS5 ,13–15 among tropical rain forestry workers and rock drillers in a warm climate, the prevalence of neurological symptoms, particularly finger tingling, numbness and paraesthesia, varied from 13% to 18%. In this study, the prevalence of musculoskeletal problems in the upper limbs, in the neck and hand grip weakness was 23%, 17% and 21%, respectively. The most common upper limb and neck symptoms included pain and stiffness of the elbow, shoulder and neck. Other studies13 ,15 reported different types of symptoms as proxy for upper limb and neck musculoskeletal disorders; the prevalence of musculoskeletal problems in other studies ranged from 7% to 30% and commonly reported symptoms were upper limb pain and stiffness. Current findings on the prevalence of HAVS related symptoms correspond to those in other studies from other tropical countries.
The mean total LVD found in this study was lower than those from other studies which ranged from 19.1 to 21.4 m2h3s−4 (ln scale).26–28 The reason for the lower LVD is that the year of exposure to vibration among subjects in this study was relatively short compared to other studies. Despite the low LVD, increasing HAVS prevalence with increasing LVD is still apparent. A cross-sectional study design is not appropriate for determining dose–response relationships due to recall bias and lack of a temporal cause–effect relationship. Although a significant association was found between total LVD and some HAVS symptoms in this study, the results are subject to study design limitations and bias in data collection. A more appropriate research design would be a cohort study or a case–control study, both of which, however, are difficult; case–control studies require case finding and cohort studies are very labour extensive and long follow-up.
Since the study population consisted of construction workers on a Kuala Lumpur construction site, the result cannot be generalised to all construction workers in Malaysia. Besides, as the study subjects were all foreigners, mainly from Indonesia, the results do not reflect the health outcomes of the local population. However, the study does raise issues regarding the health of the large number of migrant workers employed in civil construction in Malaysia and other newly industrialised countries.
Risk factors which could effect the prevalence of HAVS symptoms in this study were smoking, tobacco chewing, alcohol consumption, chemical exposure at work, non-work exposure to hand transmitted vibration, past medical and surgical history involving the upper limbs, vascular and neurological disease with residual organ dysfunction, and medication with neurotoxic side effects. In this study, few of these risk factors were present and differences were not significant between exposed and unexposed subjects (table 2). Hence, the effects of these risk factors on the outcome are negligible.
A cross-sectional study is of limited use for ascertaining the cause–effect relationship between exposure and outcome. Despite significant findings, this study can only detect the association between vibration exposure level and the occurrence of signs and symptoms related to HAVS.
This study is subject to recall bias because most of the information on duration and frequency of vibration exposure was obtained from a questionnaire. A previous history of vibration exposure requires subjects to recall prior use of vibratory tools and duration and frequency of use, and is liable to bias especially if the subject is aware of the study hypothesis. This will give rise to differential misclassification bias and may cause a false positive association. Recall bias was minimised as far as practicable by using visual aids to identify vibratory tools and concealing the study hypothesis from participants. It is thus assumed that by concealing the study hypothesis, the chances of incorrect recall regarding vibratory tool usage are similar across exposed and unexposed workers thus reducing differential misclassification bias. Although there may still be non-differential misclassification bias, this is of less importance as it shifts the result towards the null.
This study was considered to have interviewer bias because only one interviewer conducted interviews and collected information on exposure and outcome for all subjects. This limitation was minimised by the use of standardised questions on vibration exposure and outcome variables.23 The use of a single interviewer also prevented inter-observer bias during the clinical examination of study subjects. Measurement bias may occur if different techniques or operators or inaccurate equipment is used for vibration measurement. In this study, all measurement was carried out by one trained technician according to ISO 5439-2:2001. The accelerometer used was calibrated annually according to the standard requirement. Hence, inter-observer bias was eliminated and measuring equipment error was minimised.
This study used the ACGIH recommended TLV of 4 ms−2 for 8 h TWA hand transmitted vibration exposure as the cut-point for dividing subjects into high and low–moderate vibration exposure groups. This value is one unit lower than the upper limit recommended by the European Directive, which however agreed on a daily hand arm vibration exposure limit value (ELV) of 5 ms−2. In the current study, the five subjects exposed to daily vibration of between 4 ms−2 and 5 ms−2 all reported negative symptoms (data not shown). Hence, it is of little significant whether the European Directive or ACGIH standard is used in this study because the number of subjects falling between the two values was too small, and shifting negative responses towards the low–moderate exposure group only increases the strength of association in the high exposure group. In practice, the ACGIH standard seems to be more stringent and for a country such as Malaysia without local data to justify either standard, selecting the lower limit is appropriate for prevention.
Further research with a larger sample and wider coverage should be conducted to establish the actual prevalence of HAVS in common industries such as construction, logging, mining and manufacturing in tropical countries as well as to determine to what extent common vibratory tools are used in these industries. The data collected could then be used to establish the TLV for an Asian population working with vibratory tools in a tropical climate as compared to Western countries. Further research should also be directed towards determining dose–response relationships and the prognosis of HAVS in tropical countries.
Conclusion
HAVS is a recognisable problem in Malaysia. The current study has identified clinical symptoms and signs suggesting a diagnosis of HAVS among a group of construction workers exposed to hand transmitted vibration in a warm environment. These findings are comparable to those from studies in other countries with similar climates. Since this study was conducted in a limited group of construction workers, further research with a larger sample and wider coverage is required to better understand the actual prevalence and extent of HAVS in common local industries such as construction, logging, mining and manufacturing.
Acknowledgments
We would like to thank Mr Mohd Rosdi for helping with vibration measurements, and the Malaysia Construction Industry Development Board (CIDB) for their supporting letter to enter the selected construction site.
References
Footnotes
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Funding This study was partially funded by a Postgraduate Research Fund from the Institute of Research and Consultancy Management, University of Malaya. The funding source had no involvement in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.
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Competing interests None.
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Provenance and peer review Not commissioned; externally peer reviewed.