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- Burström, Lage, 1954-, et al.
(författare)
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Vibrotactile perception and effects of short-term exposure to hand-arm vibration
- 2009
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Ingår i: The Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 1475-3162 .- 0003-4878. ; 53:5, s. 539-47
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Tidskriftsartikel (refereegranskat)abstract
- This study clarifies whether the established frequency weighting procedure for evaluating exposure to hand-transmitted vibration can effectively evaluate the temporary changes in vibrotactile perception thresholds due to pre-exposure to vibration. In addition, this study investigates the relationship between changes of the vibrotactile perception thresholds and the normalized energy-equivalent frequency-weighted acceleration. The fingers of 10 healthy subjects, five male and five female, were exposed to vibration under 16 conditions with a combination of different frequencies, intensities, and exposure times. The vibration frequencies were 31.5 and 125 Hz and exposure lasted between 2 and 16 min. According to International Organization for Standardization (ISO) 5349-1, the energy-equivalent frequency-weighted acceleration for the experimental time of 16 min is 2.5 or 5.0 m s(-2) root-mean-square, corresponding to a 8-h equivalent acceleration, A(8), of approximately 0.5 and 0.9 m s(-2), respectively. A measure of the vibrotactile perception thresholds was conducted before the different exposures to vibration. Immediately after the vibration exposure, the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures every minute for a maximum of 10 min. If the subject's thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. Pre-exposure to vibration significantly influenced vibrotactile thresholds. This study concludes that the influence on the thresholds depends on the frequency of the vibration stimuli. Increased equivalent frequency-weighted acceleration resulted in a significant change in threshold, but the thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency-weighted acceleration or the unweighted acceleration. Moreover, the frequency of the pre-vibration exposure significantly influenced (up to 25 min after exposure) recovery time of the vibrotactile thresholds. This study shows that the frequency weighting procedure in ISO 5349-1 is unable to predict the produced acute changes in the vibrotactile perception. Moreover, the results imply that the calculation of the 'energy-equivalent' frequency-weighted acceleration does not reflect the acute changes of the vibration perception thresholds due to pre-exposure to vibration. Furthermore, when testing for the vibrotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained, the previous practice of 3 h avoidance of vibration exposure before assessment is recommended.
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| 2. |
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| 3. |
- Bylund, Sonya H, et al.
(författare)
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A descriptive study of women injured by hand-arm vibration
- 2002
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Ingår i: Annals of Occupational Hygiene. - 0003-4878 .- 1475-3162. ; 46:3, s. 299-307
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to describe the symptoms and the prognosis of vibration injuries in women. The investigation was based on a study of 374 women who had reported an injury due to hand-arm vibration to the Social Insurance Office or had received financial compensation from the Swedish Labor Market Insurance scheme during 1988-1997. Information on, for example, self-rated health symptoms and vibration exposure was collected by means of a questionnaire. On average, the first symptoms started after 7 yr of exposure and the first visit to a doctor took place after 11 yr. Neurological symptoms developed after a shorter period of exposure compared to vascular symptoms, 6.8 and 9.2 yr, respectively. The prevalence of numbness at the time of reporting the injury was 91% and the prevalence of white fingers was reported by 54%. The occupational group with the highest prevalence of vibration injuries was dental technicians. Two thirds of the women had stopped using vibrating machines in their work. Among the women who suffered from white fingers when they reported the injury, 50% declared impairment or no improvement of the symptoms. One woman in five was retired and the same number of women had retrained due to the occupational injury.
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| 4. |
- Liljelind, Ingrid, et al.
(författare)
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Determinants Explaining the Variability of Hand-Transmitted Vibration Emissions From Two Different Work Tasks : Grinding and Cutting Using Angle Grinders
- 2013
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press. - 0003-4878 .- 1475-3162. ; 57:8, s. 1065-1077
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Tidskriftsartikel (refereegranskat)abstract
- Background: There are numerous factors including physical, biomechanical, and individual that influence exposure to hand-transmitted vibration (HTV) and cause variability in the exposure measurements. Knowledge of exposure variability and determinants of exposure could be used to improve working conditions. We performed a quasi-experimental study, where operators performed routine work tasks in order to obtain estimates of the variance components and to evaluate the effect of determinants, such as machine–wheel combinations and individual operator characteristics.Methods: Two pre-defined simulated work tasks were performed by 11 operators: removal of a weld puddle of mild steel and cutting of a square steel pipe. In both tasks, four angle grinders were used, two running on compressed air and two electrically driven. Two brands of both grinding and cutting wheels were used. Each operator performed both tasks twice in a random order with each grinder and wheel and the time to complete each task was recorded. Vibration emission values were collected and the wheel wear was measured as loss of weight. Operators’ characteristics collected were as follows: age, body height and weight, length and volume of their hands, maximum hand grip force, and length of work experience with grinding machines (years). The tasks were also performed by one operator who used four machines of the same brand. Mixed and random effects models were used in the statistical evaluation.Results: The statistical evaluation was performed for grinding and cutting separately and we used a measure referring to the sum of the 1-s r.m.s. average frequency-weighted acceleration over time for completing the work task (a sa). Within each work task, there was a significant effect as a result of the determinants ‘the machine used’, ‘wheel wear’, and ‘time taken to complete the task’. For cutting, ‘the brand of wheel’ used also had a significant effect. More than 90% of the inherent variability in the data was explained by the determinants. The two electrically powered machines had a mean a sa that was 2.6 times higher than the two air-driven machines. For cutting, the effect of the brand of wheel on a sa was ~0.1 times. The a sa increased both with increasing wheel wear and with time taken to complete the work task. However, there were also a number of interaction effects which, to a minor extent, modified the a sa. Only a minor part (1%) of the total variability was attributed to the operator: for cutting, the volume of the hands, maximum grip force, and body weight were significant, while for grinding, it was the maximum grip force. There was no clear difference in a sa between the four copies of the same brand of each machine.Conclusions: By including determinants that were attributed to the brand of both machine and wheel used as well as the time taken to complete the work task, we were able to explain >90% of the variability. The dominating determinant was the brand of the machine. Little variability was found between operators, indicating that the overall effect as due to the operator was small.
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| 5. |
- Liljelind, Ingrid, 1968-, et al.
(författare)
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Variability in Hand-Arm Vibration During Grinding Operations
- 2011
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Ingår i: Annals of Occupational Hygiene. - : Oxford Journals. - 0003-4878 .- 1475-3162. ; 55:3, s. 296-304
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Tidskriftsartikel (refereegranskat)abstract
- Background: Measurements of exposure to vibrations from hand-held tools are often conducted on a single occasion. However, repeated measurements may be crucial for estimating the actual dose with good precision. In addition, knowledge of determinants of exposure could be used to improve working conditions. The aim of this study was to assess hand–arm vibration (HAV) exposure during different grinding operations, in order to obtain estimates of the variance components and to evaluate the effect of work postures. Methods: Ten experienced operators used two compressed air-driven angle grinders of the same make in a simulated work task at a workplace. One part of the study consisted of using a grinder while assuming two different working postures: at a standard work bench (low) and on a wall with arms elevated and the work area adjusted to each operator’s height (high). The workers repeated the task three times. In another part of the study, investigating the wheel wear, for each grinder, the operators used two new grinding wheels and with each wheel the operator performed two consecutive 1-min grinding tasks. Both grinding tasks were conducted on weld puddles of mild steel on a piece of mild steel. Measurements were taken according to ISO-standard 5349 [the equivalent hand–arm-weighted acceleration (m s−2) averaged over 1 min]. Mixed- and random-effects models were used to investigate the influence of the fixed variables and to estimate variance components. Results: The equivalent hand–arm-weighted acceleration assessed when the task was performed on the bench and at the wall was 3.2 and 3.3 m s−2, respectively. In the mixed-effects model, work posture was not a significant variable. The variables ‘operator’ and ‘grinder’ together explained only 12% of the exposure variability and ‘grinding wheel’ explained 47%; the residual variability of 41% remained unexplained. When the effect of grinding wheel wear was investigated in the random-effects model, 37% of the variability was associated with the wheel while minimal variability was associated with the operator or the grinder and 37% was unexplained. The interaction effect of grinder and operator explained 18% of the variability. In the wheel wear test, the equivalent hand–arm-weighted accelerations for Grinder 1 during the first and second grinding minutes were 3.4 and 2.9 m s−2, respectively, and for Grinder 2, they were 3.1 and 2.9 m s−2, respectively. For Grinder 1, the equivalent hand–arm-weighted acceleration during the first grinding minute was significantly higher (P = 0.04) than during the second minute. Conclusions: Work posture during grinding operations does not appear to affect the level of HAV. Grinding wheels explained much of the variability in this study, but almost 40% of the variance remained unexplained. The considerable variability in the equivalent hand–arm-weighted acceleration has an impact on the risk assessment at both the group and the individual level.
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