Exposure-response relationship between hand-arm vibration exposure and vibrotactile thresholds among rock drill operators: a 4-year cohort study.

OBJECTIVES: The risk of developing hand-arm vibration syndrome (HAVS) from occupational hand-arm vibration (HAV) exposure is traditionally determined by the onset of vascular symptoms (white fingers). However, changes in tactile sensibility at the fingertips is a clinical sign of HAVS which in most cases precedes vascular signs. We aimed to assess relationships between occupational HAV exposure and HAVS-related signs including vibration perception thresholds (VPT) and pegboard score on an individual level, using a longitudinal study design with follow-up tests. METHODS: We followed-up 148 workers exposed to different HAV levels for 4 years, with health examinations including VPT tests and pegboard tests carried out at baseline, 2 years and 4 years. VPT testing included seven frequencies, from 8 to 500 Hz. Second and fifth finger on both hands were tested, thus a total of 28 tests on each subject. We investigated associations using linear mixed models and significance level at p≤0.05. RESULTS: There was a significant exposure-response relationship on an individual level between HAV exposure from rock drills and VPT for 16 of 28 test frequencies. The highest rise (worsening) in VPT was found at the 500 Hz test frequency with 1.54 dB increased VPT per 10-fold increase in cumulative exposure. We found no deterioration in pegboard performance associated with HAV exposure among the participants. CONCLUSIONS: Risk predictions of HAVS may be based on exposure-response relationships between HAV exposure and VPT. The 500 Hz test frequency should be included in the VPT test protocols for early detection of signs related to reduced tactile sensibility.

Hand-Arm Vibration Exposure in Rock Drill Workers: A Comparison between Measurements with Hand-Attached and Tool-Attached Accelerometers.

OBJECTIVES: To assess the hazard of tool vibrations, we need valid exposure measurements. The use of hand-attached accelerometers (vibration sensors) to measure hand-arm vibrations (HAVs) has become a popular approach. However, according to International Standard ISO 5349-2, the preferred attachment of accelerometers is at the tool handle. We compared measures of HAV between hand- and tool-attached accelerometers in rock drilling. METHODS: We measured HAV in five rock drillers using jackleg drills in normal working operations with simultaneous measures of both hand-attached and tool-attached accelerometers. Five to seven measurement cycles of 15 s were executed on each worker, resulting in a total of 29 measurement cycles. To identify possible differences in working technique, we recorded videos of tool handle handgrips during drilling. RESULTS: There was a significant difference (9.5 m s-2; P ≤ 0.05) in vibration magnitudes measured by the tool-attached accelerometers compared with the hand-attached accelerometers. The hand-attached accelerometer showed a lower vibration magnitude for all workers (range of difference: 2.3-14.6). The variation between the two accelerometer attachments was larger between workers than within workers (ICC = 0.68). CONCLUSIONS: For measurements of HAV from jackleg drills, the use of hand-attached accelerometers may cause a lower recorded vibration level compared with tool-attached accelerometers. This difference is likely to vary depending on how workers grip the tool handle, and a misclassification of exposure will occur if workers grip the tool handle in a way that makes the accelerometer lose contact with the vibrating surface. Individual differences in how workers grip the tool handles should be considered when assessing HAV.

Pulmonary function and high-resolution computed tomography in outdoor rock drillers exposed to crystalline silica.

OBJECTIVES: Chronic obstructive pulmonary disease and silicosis are associated with exposure to crystalline silica. We determined the exposure to respirable crystalline silica and estimated exposure-response relationships between cumulative exposure and pulmonary function in outdoor rock drillers. METHODS: 136 rock drillers and 48 referents were recruited from three heavy construction companies. 98 air samples were collected by personal sampling for determination of respirable particulate matter and crystalline silica. Information about individual job tasks, type of drilling equipment and years of exposure in different job categories was obtained by interview. Cumulative exposure to crystalline silica was calculated for all workers. Pulmonary function was assessed by spirometry. A subgroup of 39 subjects with high cumulative exposure to crystalline silica underwent high-resolution computed tomography (HRCT). RESULTS: Cumulative exposure (mean (min-max)) to crystalline silica was 0.69 mgÙ years m-3 (0.01-5.89) in the exposed group. Mean time of exposure among rock drillers was 10.7 years (1-42). Compared with referents, the rock drillers had a lower forced expiratory volume in one second/forced vital capacity ratio (79.4 vs 81.4, p<0.05) and maximal mid-expiratory flow% (85.6 vs 93.9, p<0.05). Further, by stratifying the exposed workers into three equally large groups, a dose-response relationship was demonstrated in the highest exposed group, also in never smokers, at a mean cumulative exposure of 21.7 years at 0.08 mgÙ m-3/years. Silicosis was not detected in HRCT, but other patterns of fibrosis and emphysema were seen. CONCLUSIONS: Outdoor rock drillers exposed to crystalline silica had significantly lower pulmonary function than referents, and signs of airflow obstruction. Silicosis was not detected.

Dose-response relationship between hand-arm vibration exposure and vibrotactile thresholds among roadworkers.

BACKGROUND: Testing of vibration perception threshold (VPT) at the fingertips as a quantitative measure of tactile sensitivity is a commonly used tool in diagnosing hand-arm vibration syndrome. There is limited research on dose-response relationships between hand-arm vibration (HAV) exposure and VPT on an individual level. AIMS: Assess possible dose-response relationships on an individual level between HAV exposure and VPT at the fingertips. METHODS: We assessed average daily vibration exposure (m/s2A8) and cumulative lifetime HAV exposure for 104 participants from different departments in a road maintenance company based on vibration measurements and questionnaires. VPT was measured based on the technical method described in ISO 13091-1:2005 using octave frequencies 8-500 Hz. We investigated associations using linear regression models with significance level p≤0.05. RESULTS: The participants were either exposed to rock drills (n=33), impact wrenches (n=52) or none of these tools (n=19). Exposure to rock drills and impact wrenches was associated with elevated VPT for all seven test frequencies in the second and fifth fingers of both hands. A dose-response with the daily exposure measure m/s2(A8) was found based on 1.2 m/s2(A8) for impact wrenches, and 5.4 m/s2(A8) for rock drills. A stronger association was found with the cumulative exposure for rock drills compared with impact wrenches, and for the second finger compared with the fifth finger. CONCLUSIONS: HAV exposure was associated with elevated VPT, also at exposure levels below the common exposure action value of 2.5 m/s2(A8). Lowering the HAV exposure can contribute to prevent increasing VPTs in these workers.

Impact of technical variations on the ring-finger test for carpal tunnel syndrome.

OBJECTIVE: To assess if recording the sensory latencies of the median and ulnar nerves one-by-one (consecutive) or at the same time (simultaneous) in the ring-finger test for carpal tunnel syndrome (CTS) will show equivalent results or if it will lead to a different clinical classification of patients. METHODS: We assessed the limits of agreement between the simultaneous and the consecutive method based on the median- ulnar sensory latency difference derived by both methods in 80 subjects and compared the number of minimal CTS cases identified by the two methods. RESULTS: Limits of agreement ranged from -0.23 to 0.29 ms. A significantly higher proportion of subjects with minimal CTS (only detectable by using the comparison test) was found using the simultaneous method (n = 8 and 2, respectively; p = 0.03). CONCLUSION: The two methods have a poor to moderate agreement as indicated by the range of the limits of agreement (0.5 ms). SIGNIFICANCE: Even small methodological changes to the ring-finger test can lead to results with different clinical meaning in the same individual and one should be aware of which method was used when interpreting results.

The Effect of a Leisure Time Physical Activity Intervention Delivered via a Workplace: 15-Month Follow-Up Study.

In line with recommendations from both the World Health Organization and the European Union some employers encourage workplace health promotion through physical activity (PA) facilities and leisure time PA-initiatives. The current study describes a 15-month follow-up after an 8-week workplace delivered PA-initiative, investigates if improvements in cardiovascular risk status are sustainable, and elucidates differences according to educational level. One hundred and twenty one employees (43 women) were examined before and after the 8-week PA-initiative and 94 at the 15-month follow-up. PA-levels, blood pressure, resting heart rate, lipids, glycosylated hemoglobin (HbA1c), C-reactive protein (CRP), and selected markers of inflammation were registered at baseline, immediately after the 8-week PA-initiative, and 15 months after baseline. At the end of follow-up (15-month), PA-levels-increased during the 8-week intervention-had returned to baseline values. None of the five improvements in cardiovascular markers (total cholesterol, low density lipoprotein (LDL), P-selectin, CD40Ligand (CD40L) and Monocyte chemoattractant protein-1 (MCP-1)) seen at the 8-week follow-up were sustained. At the 15-month follow-up as compared to baseline HbA1c, CRP (log) and interleukin-6 (IL-6) were reduced by 0.06 mmol/L (95% CI -0.11,-0.01), 0.25 mg/L (95% CI -0.46,-0.04) and 0.39 pg/mL (95% CI -0.75, -0.04), respectively. At baseline, there were differences in cardiovascular risk factors comparing men with low versus high levels of education. No differences in changes in outcomes between these groups of men were found during follow-up. In this study highly educated men generally have lower levels of cardiovascular risk factors, but the effect of PA on such markers in this group do not differ from the effects seen in less educated men.

Tremor and hand-arm vibration syndrome (HAVS) in road maintenance workers.

OBJECTIVES: The aim of this study was to evaluate postural and rest tremor among workers using vibrating hand tools, taking into account the possible effects of toxicants such as alcohol and tobacco. A further aim was to study workers diagnosed with hand-arm vibration syndrome (HAVS) at the time of examination. METHODS: This study comprises 103 road maintenance workers, 55 exposed to vibrating hand tools (age 41.0 years; range 21-62) and 48 referents (age 38.5 years; range 19-64). They were examined with the CATSYS Tremor Pen®. Exposure to vibrating tools and serum biomarkers of alcohol and tobacco consumption were measured. RESULTS: Cumulative exposure to vibrating tools was associated with increased postural (p < 0.01) and rest tremor (p < 0.05) and with a higher Center Frequency of postural tremor (p < 0.01) among smokers and users of smokeless tobacco. Rest tremor Center Frequency was higher than postural tremor frequency (p < 0.001). CONCLUSIONS: The main findings indicate an association between cumulative exposure to hand-held vibrating tools, tremor parameters and consumption of tobacco products. The hand position is important when testing for tremor. Rest tremor had a higher Center Frequency. Postural tremor was more strongly associated with exposure than rest tremor. The finding of increased tremor among the HAVS subjects indicated that tremor might be a part of the clinical picture of a HAVS diagnosis. As with all cross-sectional studies, inferences should be made with caution when drawing conclusions about associations between exposure and possible effects. Future research using longitudinal design is required to validate the findings of the present study.