Whole-body vibration and back pain-related work absence among heavy equipment vehicle mining operators.

OBJECTIVE: To determine the association between several whole-body vibration (WBV) exposure estimates and back pain-related work absence. METHODS: Exposures (based on the weighted daily root mean square acceleration, A(8); the daily vibration dose value, VDV(8); and the daily equivalent static compression dose, Sed(8)) of 2302 workers during 4 years were estimated using each worker's monthly vehicle operation records and WBV measurements from 11 different types of heavy equipment vehicles in a large coal mine. Company payroll data provided work absence during the concurrent 4 years of exposure. Cox regression models estimated the associations between the different WBV metrics and time to first work absence related to back pain. An adjusted R2 statistic provided a measure of model fit. RESULTS: All estimated metrics of WBV exposures were positively and significantly associated with back pain-related absence. HRs varied from 2.03 to 12.39 for every 0.21 m/s2 increase in the A(8)-based exposures; from 1.03 to 1.18 for every 1.72 m/s1.75 increase in VDV(8)-based exposures; and from 1.04 to 1.07 for every 0.06 MPa increase in Sed(8)-based exposures. Models using the estimated VDV(8) metric for the z axis fit the data best as measured by the R2 statistic. CONCLUSION: Higher WBV exposures were associated with back pain-related absences in this population, which appears after a few years of follow-up. Introducing controls to lower exposure levels may help reduce back pain-related work absences.

Assessment of Whole-Body Vibration Exposure in Mining Earth-moving Equipment and Other Vehicles Used in Surface Mining.

This study characterized whole-body vibration exposures in a set of vehicles that operate in open-pit mines and compared three different daily exposure parameters based on the ISO 2631-1:1997 and ISO 2631-5:2004 standards. Full-shift, 6 to 12-hour, continuous whole-body vibration measurements were collected from 11 representative types of vehicles in terms of hours of operation and number of vehicles used. For each type of vehicle, the exposure parameters (A(8), VDV(8), and Sed(8)) were calculated for each axis (x, y, and z), and in addition, shear or horizontal (∑xy) and vector sum (∑xyx) whole-body vibration exposure. Findings showed that: (i) substantially higher shear and vector sum whole-body vibration exposures indicated relatively high levels of exposure on the non-predominant axis; (ii) the predominant axis of exposure varied across the different type of vehicles; (iii) there were differences in whole-body vibration exposure parameters regarding the standards-based predictions of potentially adverse health outcomes (the impulsive exposure parameters VDV(8) and Sed(8) were higher and reduced acceptable vehicle operation times by one-half to two-thirds relative to A(8) exposures); and (iv) based on the predominant exposures and the time to reach daily vibration action limits, the operation of most mining vehicles would be limited to less than 8 hours a day. Differences in whole-body vibration exposure parameters impact the prediction of potentially adverse health outcomes and may introduce some uncertainty regarding how to best characterize a vehicle operator's actual exposure.

Effect of local leg cooling on upper limb trajectories and muscle function and whole body dynamic balance.

This study was designed to find out if local leg cooling affects muscle function and trajectories of the upper limb during repetitive light work as well as capability to maintain dynamic balance. Nine healthy female subjects performed repetitive lifting task with right hand for 60 min while standing in front of a table with six target angles (30 degrees -220 degrees ) and with the legs inside a container with 15 degrees C cold water (Cold condition, C) or without water (Normal condition, N). Muscle temperature of the medial aspect of the gastrocnemius, rectal, and skin temperatures were measured continuously. The trajectories of the right upper limb were recorded with a 3D motion analysis system. Muscular strain (averaged EMG, a-EMG) and EMG gaps in eight muscles of the right upper limb were measured. End point excursion depicting the ability to maintain dynamic balance was measured before and after each experiment. Leg cooling decreased significantly (P < 0.05) the muscle and the mean skin temperature in C compared with N (6.7 and 2.2 degrees C, respectively). No marked changes in the trajectories or EMG activity were observed between the different environmental conditions. The end point excursion was significantly (P < 0.05) reduced in C compared with N and a positive correlation between excursion and muscle temperature was found at the end of the working period in C. In conclusion, local leg cooling did not affect upper limb muscle function or trajectories, but ability to maintain dynamic balance was reduced.

Health problems related to working in extreme cold conditions indoors.

OBJECTIVES: To identify health problems among workers performing cleaning, maintenance and machine operation tasks inside cold storage rooms with temperatures between -43 degrees C and -62 degrees C in a freeze drying coffee company. STUDY DESIGN: Descriptive study. METHODS: All 24 workers working inside the cold stores participated in the study. A questionnaire about cold-related health problems and the standardized Nordic questionnaire assessing muscle complaints were completed by all exposed workers. A physical examination was performed on each worker. RESULTS: The most relevant cold-related health problem was episodic finger symptoms (50%), followed by respiratory symptoms (21%), peripheral circulation symptoms (20%), and repeated pain in the musculoskeletal system (12%). Two subjects had a previous diagnosis of Raynaud's phenomenon (RP). The prevalence of musculoskeletal complains in the neck and low back was 21% in each. CONCLUSIONS: The prevalence found for various complaints among the freeze drying coffee workers implies that the cold conditions inside cold stores may present a real risk of cold-related health problems and, due to lowered concentration level, for injuries, too. Greater efforts should be made to minimize the cold exposure by designing automation processes to prevent continuous exposure to cold during freeze drying process. In addition, improving the cold-protective clothing and guaranteeing its appropriate use will reduce health risks.

Effects of cooling and clothing on vertical trajectories of the upper arm and muscle functions during repetitive light work.

The present study was designed to find out if cooling and/or clothing affect the vertical trajectories and muscle function of the upper arm during repetitive light work. Twelve female subjects performed a one-handed lifting task for 60 min while standing in front of a table with six target angles (30 degrees to 220 degrees ). The experiment was carried out in a climatic chamber in three different conditions: at 10 degrees C (C), at 25 degrees C (TN), and at 10 degrees C dressed in cold-protective clothing (C(p)). Skin and rectal temperatures were measured continuously. The vertical trajectories of the head, shoulder, elbow, and wrist on the right side of the body were recorded. Muscular strain (averaged EMG, a-EMG) and EMG gaps in eight muscles on the right upper arm were measured. The variation of the vertical trajectory amplitude of the upper arm measured from the elbow was significantly higher (at 200 degrees ) both at C and C(p) (50 and 25% respectively) and in shoulder (at 220 degrees angle) at C (33%) compared with TN (P < 0.05). Both C and C(p) increased a-EMG and reduced the number and duration of EMG gaps significantly in all muscles studied. In conclusion, in repetitive tasks the high mean vertical trajectory and changes in the amplitude of the trajectory of the upper arm at C and C(p) compared with TN were associated with increased muscular strain and reduced number of EMG gaps (more continuous activation of given muscle fibers). The changes in trajectories may serve as indicator of a risk for local muscle fatigue.

Costs of work-related musculoskeletal disorders (MSDs) in developing countries: Colombia case.

The real burden of occupational diseases, specifically work-related musculoskeletal disorders (MSDs), and its impact on workers' productivity is not known. The situation is critical in developing countries where only cases that cause workers' disability are recorded. In this study, the incidence of MSDs in Colombia was estimated by using the age and gender specific double incidence rate of repetitive strain injuries diseases in Finland for 2002. The results showed that the estimated number of MSDs recorded in Colombia during 2005 was 23,477 cases at the rate of 11.6 cases per 10,000 workers. The estimated total cost of these MSD cases relative to workers' productivity was 171.7 million US Dollars, representing around 0.2% of Colombia's Gross Domestic Product for 2005. The systematic appraisal of the incidence of MSDs and their associated cost on workers' productivity are necessary in developing countries to reduce the costly impact on productivity and to increase workers' well-being.