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Objectives: The effect of anthropometric factors on the fingertip vibrotactile perception threshold (VPT) of industrial vibrating tool operators (IVTOs) is not well known. The purpose of this study was to investigate the associations between anthropometric factors and fingertip VPT., Methods: We included for analysis two groups of IVTOs: Group 1, predominantly forestry workers (n=325); and Group 2, public servants (n=68). These IVTOs regularly received medical examinations to evaluate hand-arm vibration syndrome. In the examination, measurements of their fingertip VPTs were taken before and after cold-water immersion (10 minutes at 10°C for Group 1 and 5 minutes at 12°C for Group 2). Their body height and weight were measured to calculate the body mass index (BMI). The presence of peripheral neuropathy (PN) was defined as a VPT ≥17.5 dB at 10 minutes after finishing immersion., Results: In the univariate analysis, weight and BMI were associated with a decreased risk of PN in both Groups 1 and 2. The negative association between BMI and PN remained in the multivariate analysis consistently, but weight reached marginal significance only in the multivariate analysis without BMI in both the groups. Age was positively associated with PN consistently in Group 1 but not in Group 2. Years exposed to vibration showed positive association with PN only in the univariate analysis of Group 1., Conclusions: Among IVTOs, factors reflecting body heat production, such as weight and BMI, were associated with a decreased risk of VPT-defined PN, regardless of the task engaged.

Objectives: The purpose of this study was to clarify the occurrence of Raynaud's phenomenon among workers using an impact wrench for a long time., Methods: The subjects were 704 workers regularly using an impact wrench and taking special medical examinations for vibration syndrome from 1981 to 2008. Raynaud's phenomenon was observed in 39 subjects during the observation period., Results: The mean operating years at the occurrence of Raynaud's phenomenon was 25.5 ± 8.3 (standard deviation) yr. The mean total operating time (geometric average) at the occurrence of Raynaud's phenomenon was 11,689 h. By the person-year method, the incidence rate of Raynaud's phenomenon was 6.27 persons per 1,000 person-years. The estimated risk of developing Raynaud's phenomenon did not increase until 12 years after starting to operate an impact wrench but increased exponentially after that. The vibration level of an impact wrench (from 4.9 m/s(2) to 22.6 m/s(2)) exceeded the occupational exposure limit value (4.9 m/s(2)). Various countermeasures, such as introducing automatically apparatus and keeping the working environment warm to protect from cold exposure, were taken at the factory., Conclusions: These findings showed that the rate of occurrence of Raynaud's phenomenon was not high, although the vibration level of the impact wrench was high. This may result from various countermeasures to prevent the occurrence of Raynaud's phenomenon. A long period of exposure to vibration had the potential to lead to the occurrence of Raynaud's phenomenon even under various countermeasures.

Measurements of changes in finger skin blood flow with laser Doppler perfusion imaging (LDPI) in response to cold provocation test (10 degrees C, 10 min) were performed in 12 men suffering from vibration induced white finger (VWF) and 13 exposed controls. The mean perfusion values in both groups reduced markedly as a result of immersion of the hand in cold water. In the controls, however, the mean value increased gradually until the end of the cold provocation, while that in the VWF subjects remained at the lowest level. After removal of the hand from the cold water, the skin blood perfusion in the controls recovered rapidly and nearly reached the baseline value. In the VWF subjects, it had a slight increase immediately following the cold immersion but no tendency to rise as the time span increased. Analysis of covariance controlling for possible confounders revealed that the VWF subjects had significantly lower perfusion values compared to the controls in the last several minutes of the cold provocation and the following recovery. These findings suggest that the LDPI technique enables visualizing and quantifying the peripheral vascular effects of cold water immersion on the finger skin blood perfusion and thus has the potential of providing more detailed and a&curate information that may help detect the peripheral circulatory impairment in the fingers of vibration-exposed workers.

The aims of this study were (1) to measure frequency-weighted vibration acceleration and (2) to study the effects of introducing a vibration-proof impact wrench on VWF in workers. The subject pool was 383 male workers who were regularly using an impact wrench and taking special medical examinations for vibration syndrome in a factory from 1982 to 1999. The prevalence of workers with VWF increased gradually after 1982, reached a peak value (4.8%) in 1986, gradually decreased after 1987, and disappeared in 1994. Sixteen subjects who had had VWF at least one time during the observation period were selected for this study. The stages of VWF were at stage I on the Stockholm Workshop scale in all subjects. After the vibration-proof impact wrench was introduced in 1986, the vibration acceleration of the impact wrench measured on the handle decreased from 8.6-11.1 m/s2 to 5.1-7.1 m/s2. The actual time per day that subjects were assumed to use the impact wrench was 108 minutes. The subjects actually used an impact wrench more than the occupational exposure limit allowed. However, VWF disappeared after the introduction of a vibration-proof impact wrench. This might have resulted from the combined effect of introducing the vibration-proof impact wrench and certain countermeasures that were taken against cold working environments.

Objectives: This study was aimed to assess the peripheral circulatory functions of forestry workers exposed to hand-arm vibration, using simultaneous measurements of finger skin temperature (FST) and finger blood flow (FBF)., Methods: The subjects were five men with vibration-induced white finger (VWF), four subjects with numbness in their hands and five exposed controls without any signs or symptoms related to vibration syndrome. Simultaneous measurements of FST and laser-Doppler FBF were performed before, during and following a 10-min recovery period after the hand was immersed in cold water (10 degrees C, 10 min). Partitional measurements of finger blood flows could be made between the capillaries and deeply located vessels using two laser-Doppler flow probes having narrower and wider optic fiber separations., Results: The FST as well as the FBF of the capillary and deeply located vessels during and following the cold immersion test in those with VWF and in the subjects with numbness had a slight increase immediately following the cold immersion and no tendency to be augmented as the time span increased. After the cold immersion test, the control group had significantly greater FST and FBF compared to other groups. Particularly, from the 5th to the 10th min after the cold provocation, the values of FBF of the deeply located vessels in those with VWF were significantly lower than the controls. During the course of observation, the FST had significantly linear relationship with the recorded capillary and deep FBF values, and that was much closely correlated with the deep FBF (i.e., P < 0.01 in each selected condition). The slope of the regression lines in the capillary were steeper and shallow in the deep FBF., Conclusions: In addition to the measurement of capillary FBF, more detailed and accurate information on the peripheral circulatory functions of vibration-exposed subjects can be obtained by including the assessment of the deep FBF.

To clarify the trends in the number and the severity of vibration syndrome in Wakayama for these 23 years, the records of the medical examinations for vibration syndrome were analyzed with 4,652 (a total of 9,920) private forestry workers exposed to hand-arm vibration. The number of the subjects who took the medical examinations reached a maximum of 1,242 in 1978. After that, it decreased year by year, but remained at about 300 or less from 1988. There was a corresponding increase in age and the number of years of operating chain saws among the subjects examined. The compensated cases reached a maximum number of 393 cases in 1977, and then a drastic decrease was noted. Year by year there was an increase in the number of cases whose medical examinations revealed no abnormality. The regional occupational health care system including the surveillance card, which has been active since 1975, has probably contributed to the decrease or prevention of occurrence of vibration syndrome in Wakayama.

Clinical data of workers (40-69 yrs) operating chain saws for a ten-year period from 1986 to 1995 were analyzed to assess the evaluation standard of finger skin temperature for a cold provocation test (10 degrees C 10 min). Screening points of finger skin temperature for screening 191 workers with a vibration induced white finger (VWF) were obtained from receiver operating characteristic (ROC) curves. The screening points at 5 min and 10 min after a cold provocation were approximately equal to 50th percentiles of 217 workers with no symptoms (NS group). The screening points of recovery rates at 5 min and 10 min after a cold provocation almost agreed with 50th percentiles in NS group. A new evaluation standard was prepared in reference to these screening points and finger skin temperatures by fraction in NS group. The new one will be useful for the health care of workers operating vibrating tools under present working conditions.

This study was designed to clarify the age variation of the indices in the accelerated plethysmography (APG) for fingers and set the standard ageing curve. The indices of APG of workers with exposure to vibration were compared with those of the standard ageing curves. The subjects were 815 male workers, ranging in age from 18 to 66, without exposure to vibration and without history of hypertension, circulatory diseases or diabetes. Their indices of APG are used establishing the standard ageing curves. The workers occupationally exposed to hand-arm vibration were also the subjects to evaluate peripheral circulation of hand. The APG was measured on the index finger tip of his dominant side by an accelerated plethysmometer. The subjects were divided into age groups at intervals of 5 years. In all age groups from 18 to 64 years, each index of APG showed an approximately normal distribution in a logarithmic scale. The mode of the distribution shifted to a lower value with increasing age. The standard ageing curves were drawn by calculating 25th, 50th and 75th percentiles by a nonparametric method for each group. Each index of the standard ageing curves dropped with increasing age. The significant age effect was slightly marked below 30 years, but marked between 30 and 50 years. The indices of APG of workers with exposure to vibration were also compared with those of the standard ageing curve. The indices of -b/a and a/d of workers with exposure to vibration were deteriorated beyond physiological change. We established the standard ageing curves for APG for male men. The technique is good for the evaluation of peripheral circulation disorder of aged workers with occupational exposure to vibration.

To evaluate the circulatory disturbances, sensory disturbances and damage to muscles and joints by chain saw vibration exposure, the process of the deterioration of the symptoms with chain saw operating time was studied. Subjects were classified into eight groups according to TOT (Total Operating Time): Group 0, 46 controls; Group A, 39 operators (< 2,000 hours); Group B, 53 operators (2,000-4,000 hours); Group C, 45 operators (4,000-6,000 hours); Group D, 29 operators (6,000-8,000 hours); Group E, 31 operators (8,000-10,000 hours); Group F, 35 operators (10,000-15,000 hours); and Group G, 34 operators (> 15,000 hours). The subjective symptoms and clinical findings due to operating chain saws were divided into three main categories of peripheral circulatory disturbances, sensory disturbances and damage to muscles and joints. According to the criteria, the total score of each disturbance was calculated per individual in Group 0 and Groups A through G, respectively. The scores for the three (circulatory, sensory, muscles and joints) disturbances increased significantly with the increase of TOT. The scores for circulatory disturbances increased significantly in Group A and B, as compared with those in its previous Group, respectively. The scores for sensory disturbances increased significantly in Groups A, B, and F. The scores for damage to muscles and joints increased significantly in Group B.

In eight groups of subjects operating various hand-held vibrating tools and aged from 30 to 59 years, the prevalence rates of vibration-induced white finger (VWF) and numbness, pain, or stiffness in the upper and lower extremities were investigated. Hand-transmitted vibration levels (HTVLs) were measured on the back of the hand, by means of unidirectional (x-axis) vibration dosimeters, and the frequency-weighted acceleration levels [(Lh,w)eq,t] were determined as the vibration levels. The prevalence rates of VWF and numbness of the hands in these subjects were compared to the prevalence rates of Raynaud's phenomenon (RP) and numbness of the hands in 1027 males and 1301 females not occupationally exposed to vibration (age range: 30-59 years). It was observed that in subjects exposed to HTVLs of between 1.1 and 2.5 m/s2, the prevalence of VWF was between 0.0% and 4.8%. The prevalence of VWF reached 9.6% in a group of workers exposed to HTVLs of 2.7-5.1 m/s2. The latter group showed a significant difference (P < 0.05) in the prevalence of VWF compared to the 2.7% prevalence of RP in male subjects of the general population. The prevalence of VWF in female subjects exposed to vibration (4.3%) was not significantly different from the prevalence of RP in females of the general population (3.4%). The prevalence rates of numbness of the hands were in the range of 6.5%-30.4% in the exposed groups and in the range of 13.4%-29.5% in the general population. Among the subjective symptoms, only VWF showed a significant positive correlation with HTVLs (R2 = 0.5, P < 0.05). It was concluded that in decisions concerning quantitative recommendations for vibration exposure, the prevalence of VWF should be employed. With a view to decreasing the risk of developing VWF, estimated vibration safety values for 4 h and 2 h daily exposures are discussed.

To study the effects of construction machinery operation on subjective symptoms, a questionnaire survey was carried out among construction machinery operators by a self-reporting method. Subjects were 184 power shovel operators, 127 bulldozer operators, 44 forklift operators as operator groups, and 44 office workers as a control. Their ages were in a range of 30-49 years. The questionnaire contained 20 symptoms referring to fatigue, digestive problems, and upper or lower limbs or back problems. The prevalence rate and symptom characteristics were examined. The dominant symptoms of the operator groups were stiff shoulder, low back pain, and stomach symptoms. The prevalence rate of low back pain was significantly different between forklift operators and controls. No significant differences were found in the symptoms of upper limbs and fingers between operator groups and controls. The prevalence of Raynaud's phenomenon was 0.5%-2.3% in the operator groups and 2.3% in the control group.

Vibration hazards which arise after exposure to mechanical vibration comprise various types of disorders, the most common of which are peripheral circulatory disturbances. It is now well recognized that aging effects all organ systems of the human body. The present study was therefore performed to assess the effects of aging on finger skin temperature and on hyperemia time after pressing the nail, both of which reflect peripheral circulatory functions. The subjects were 88 farmers and 86 chain saw operators ranging in age from 30 to 69 years, and 27 healthy persons aged 21 to 37 years as controls. Data were evaluated before and after cold water immersion tests in which the hand was immersed in 10 degrees C water for 10 minutes. The results obtained were as follows: 1) Before the test, skin temperature was negatively correlated with age, and hyperemia time was positively correlated with age in both farmers and chain saw operators but not in the case of the control subjects. 2)The skin temperature became lower, and hyperemia time grew longer with advancing age in both farmers and chain saw operators before and after the immersion tests. In comparison of the average skin temperature and hyperemia time between farmers and chain saw operators classified by age, the average skin temperature in chain saw operators was significantly lower than that in farmers, and the average hyperemia time in chain saw operators was significantly longer than that in farmers of every age group after the immersion test. The results suggest that we should take age-related changes into consideration to some degree when we evaluate the finger skin temperature and hyperemia time in diagnosing peripheral circulatory disturbances.

Among the vibration hazards resulting from the use of vibrating tools, Raynaud's phenomenon, the peripheral nervous disturbances and the bone-joint abnormalities have been well known. Especially, Raynaud's phenomenon, which is explained as a spasm of the peripheral vascular vessels caused by disorders of the peripheral nerves or abnormalities of the arteriolae, represents the peripheral circulatory disturbance. In the worker with such a disorder of the peripheral circulatory function, it is likely that the mechanism of the cold pressor response would have been changed. The authors examined the relationship between the peripheral circulatory function and the cold pressor response in 51 chain saw operators. The following examinations were carried out: skin temperature, nail-press test and cold pressor test by 10-minute-immersion in 10 degrees C water. There was statistically an inverse correlation (r=-0.316, P < 0.025) between the increase in systolic blood pressure at the second minute during immersion and the mean skin temperature of the finger-tip during the latter half of 10-minute-immersion. It would be surmised from this result that the worker with lower peripheral circulatory function tends to increase the excitability in the sympathetic nervous system.

The correlation between the severity of vibration syndrome and hand-tool operating time in chain saw workers has been studied. The total chain saw operating time was calculated by using the equation: chain saw operating hours/day X days/year X years, and 266 chain saw operators were classified into four groups (0-2000 h, 2000-5000 h, 5000-8000 h, over 8000 h). Forty-six forestry workers not using chain saws were used as controls. The prevalence rates of symptoms were checked and statistically compared in each group. In the group with under 2000 hours' experience, symptoms were generally confined to tingling, numbness, or pain; with 2000-5000 hours peripheral nerve and circulatory disturbances, including Raynaud's phenomenon, and muscle and general body conditions were influenced to some degree; with 5000-8000 hours' functional changes were noted; while with over 8000 hours about half the operators suffered severely from functional or organic changes due to vibration.

Urinary hydroxyproline excretion was measured in 130 chain saw operators aged 28-59 and in 31 normal control subjects aged 26-59 with no occupational exposure to vibration. The results measured were expressed as a ratio of hydroxyproline to creatinine. (1) No significant correlation between hydroxyproline/creatinine ratio and age was observed among normal subjects. (2) In chain saw operators grip and pinch strength decreased gradually with an increase of the total chain saw operating time, while the prevalence of pain in the hands or motility disturbance in the elbow joints showed a tendency to become greater as total operating time increased. Hydroxyproline/creatinine ratio in the group with over 9000 hours' experience was significantly higher than that in the group with under 3000 hours (p less than 0.05). By comparison with controls, the ratio in the group with over 3000 hours was significantly higher at the 5% level. (3) Hydroxyproline/creatinine ratio in the group with pain in the hands or with motility disturbance in the elbow joints was significantly higher than that in the group without them (p less than 0.05). (4) Hydroxyproline/creatinine ratio was inversely correlated with grip and pinch strength in operators ranging in age from 40 to 49 (p less than 0.01). (5) All individual ratios for operators with lower grip strength showed a higher increment than the mean values obtained from controls. These results indicate that increased urinary hydroxyproline excretion in chain saw operators may occur in association with damage to the musculoskeletal system caused by the prolonged use of vibrating tools.

Vibration hazards caused by using vibrating tools include such disorders as peripheral circulatory disturbances, peripheral nervous disturbances and abnormalities of the bones and joints. It is generally acknowledged that the effect of physiological aging on the nervous system gradually increases with age. In this paper, therefore to assess the effect of aging on the peripheral nervous function as evaluated by pain and vibratory sense thresholds of fingers, 135 farmers and 130 chain saw operators ranging in age from 30 to 69 years were examined. Moreover, 27 normal persons aged between 21 and 37 years served as the control for comparison. The results obtained were as follows: 1) In the control subjects, there was no age-related change in the pain threshold. However, the vibratory sense threshold at a frequency of 125 Hz or 250 Hz showed a tendency to increase with advancing age. 2) In both farmers and chain saw operators, thresholds in the pain and the vibratory sense at a frequency of 125 Hz or 250 Hz showed a tendency to increase with advancing age. 3) The pain thresholds in chain saw operators seemed to be slightly higher than those in farmers in all age groups, but the differences were not statistically significant. On the other hand, the vibratory sense thresholds at a frequency of 125 Hz or 250 Hz in chain saw operators were significantly higher by 5 dB than those in farmers in all age groups. From these results it is suggested that we have to use age-adjusted standard criteria in evaluating thresholds of the pain and the vibratory sense at a frequency of 125 Hz or 250 Hz.

To investigate the dose-response relationship and the relationships among symptoms related to the vibration syndrome, 266 chain saw operators were examined. The subjects were classified into four groups according to total operating time (TOT): Group E1 (below 2,000 hrs, n = 39), Group E2 (2,000-5,000 hrs, n = 76), Group E3 (5,000-8,000 hrs, n = 51), and Group E4 (over 8,000 hrs, n = 100). The control group (Group O) consisted of 46 healthy subjects with very brief employment period as bush cleaners. The subjective symptoms and clinical findings were divided into four major symptom categories: circulatory disturbances, sensory disturbances, damage to muscles and joints, and general symptoms such as autonomic nerve disturbances. Each major symptom category was rated from 0 to 25 according to the severity of the symptoms observed (Table 2). The mean scores in the four major symptom categories were compared for the four TOT groups in order to study the dose-response relationship. The relationship among symptoms was investigated by cluster analysis for the four major symptom categories of all operators in each group and inferred from the significance of partial correlation coefficients between the two of the four major symptom categories calculated for each group. The mean scores in the four major categories showed a significant elevation with the increase in TOT. A dose-response relationship of the vibration syndrome was proved. Each major symptom category was aggravated, not independently, but in close correlation with the symptoms. The inter-symptom relationships of the vibration syndrome were confirmed. That is, very close correlations between circulatory disturbances and sensory disturbances and between sensory disturbances and damages to muscles and joints were demonstrated.