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Back Injuries in Heavy Industries: Risk Factor Exposure Assessment (Part B)
RS2002/03-013 (Part B)
Final Report Date: January 2008
| Principal Investigators: | Mieke Koehoorn and Kay Teschke (UBC) |
| Co-Investigators: | Hugh Davies, Paul Demers, Murray Hodgson (UBC); Peter Johnson (University of Washington) |
For more information about this project, please contact Dr. Kay Teschke or Dr. Mieke Koehoorn, or visit the UBC Back Study website.
Issue
Many British Columbians employed in heavy industries will suffer from back injuries over the course of their careers. Although many related studies have been done, the research community has not yet reached a consensus on what the occupational causes of back injuries are. In part, this is because exposures to risk factors for back injuries are very difficult to measure. This project contributes to this area by testing approaches that could make measuring exposures easier and more effective in future studies.
Key findings
- Observations by trained observers throughout a workshift, and interviews with employees at the end of the shift were found to be successful and cost-effective methods for measuring risk factors for back injuries.
- The inclinometer was the most successful of the three measurement instruments, and provided detailed and precise data.
- Data collected through the cost effective methods of observations and interviews can predict the data collected through the more expensive approach of using measurement instruments. The observation data results in good predictions while the interview data results in fair predictions.
Objectives
- To identify successful and cost-effective exposure measurement techniques for use by health researchers studying the causes of back disorders
Methods
Participants were selected in two different ways. First, a random sample of workers with a back-related compensation claim, from the five industries of interest (forestry, wood and paper products, warehousing, transportation, construction) was selected using WorkSafeBC data. The WorkSafeBC Research Secretariat made the initial contact with each potential participant, then those who gave permission were contacted by the research team. A total of 54 participants were selected in this manner. The second stage of participant selection was to randomly select 1 to 3 co-workers of each injured worker participant. This resulted in another 72 participants. In total, the study included 126 individual participants from 50 different workplaces.
The research team took measurements between September 2004 and March 2006 using the following exposure assessment methods:
- Observations by trained observers throughout a workshift, using an observation form (Back Exposure Sampling Tool) developed through a four month process including a literature review, comparison with a biomechanical model, feasibility testing, and inter-observer reliability testing. Work factors observed included tasks, items or power tools held, items worn (e.g., tool belt), general body posture, trunk angles, trunk supports, lateral bending, manual materials handling, and any additional pertinent comments. When workers were in vehicles, additional observations were made of the vehicle type, terrain, slope, speed, driving style, vehicle load, and vehicle information.
- Interviews were conducted with employees at the end of the shift, using a structured questionnaire based on the same work factors as the observation form.
- Three measurement instruments were used:
- An inclinometer to measure posture
- EMG to measure muscle activity
- A vibration monitor to measure vibrations on vehicle seats.
The data were analyzed to answer the following questions:
- How successfully could each of the five exposure assessment techniques be used in diverse work settings, and how much did each cost to use?
- What were the exposure levels, as measured via the three instruments (inclinometer, EMG, vibration monitor), by industry and by job?
- Could the data collected using the observation form and the interview be used to predict the exposures as measured by the three instruments?
Results
Observations by trained observers throughout a workshift, and interviews of employees at the end of the shift were successful and cost-effective methods for measuring risk factors for back disorders. They could be conducted in the challenging and dynamic worksite environments typical of heavy industry. Observations and interviews did not require the significant capital expenditures associated with measurement instruments, although they did require significant personnel resources.
Of the three measurement instruments used, the inclinometer was most successful in the heavy industry worksites, and was able to collect a range of measurements in a cost-effective manner. It provided detailed and precise data that was a useful complement to the more general data collected through observations and interviews.
Statistical equations were developed to determine if the most successful and cost-effective methods, observations and interviews, could be used to predict the data measured by the more expensive instruments. Overall, the observation data did a good job of predicting the measurements that were taken with the various instruments, while the interview data did a fair job of predicting the measurements.
A number of factors associated with gathering exposure measurement data influenced the success and cost of the various methods. Workers in BC’s heavy industries operate in a wide range of settings, many of which are affected by extreme and unusual conditions, tasks, and postures. Many of these variables limited the effectiveness of the measurement instruments used. For example, the seats in log boom boats are sometimes fully immersed in water. This made it impossible to use the electric vibration monitoring instrument. Hot and humid conditions in paper mills cause workers to sweat, making it uncomfortable and difficult to wear measurement instruments. The final report provides more detail on the types of challenges that were encountered.
Conclusions
This study showed that observations and interviews are two cost-effective methods that did a fair to good job of predicting the data that was collected using the measurement instruments. The results of this study will improve the research community’s capacity to conduct robust measurements of exposure in occupational environments. The ability to predict exposure levels using data collected cheaply and reliably will be useful for future studies.
Future directions
This study was a part of Phase One of a research program to study the causes of back injuries in heavy industries and to test ways to reduce them. Phase One, which included this study as well as the study entitled Back Injuries in Heavy Industries: Defining Back Injury Outcomes for Research Purposes, addressed two persistent methodological problems in back injury epidemiology: the difficulty of defining and identifying new back cases of injury, and the difficulty of measuring exposures for large scale epidemiological studies. Phase Two will investigate the relative importance of many different risk factors and their interactions in the development and progression of new onset and chronic back injuries in heavy industry. Phase Three will be a randomized workplace trial of the effectiveness of various control measures to reduce the risk of work-related back injuries.
Publications and Presentations
Publications
Trask C, Teschke K, Village J, Chow Y, Johnson P, Luong N, Koehoorn M. Measuring low back injury risk factors in challenging work environments: an evaluation of cost and feasibility. American Journal of Industrial Medicine 2007;50(9):687-96.
Trask CM, Teschke K, Morrison J, Johnson PW, Village J, Koehoorn M. How long is long enough? Evaluating sampling durations for low back EMG assessment.
Journal of Occupational and Environmental Hygiene 2008 Oct;5(10):664-70.
Village J, Trask C, Luong N, Chow Y, Johnson P, Koehoorn M, Teschke K. Development and evaluation of an observational back exposure sampling tool (Back-EST) for work-related back injuries. Applied Ergonomics 2008 Oct 16. [Epub ahead of print]
Luu T, Li D, Hodgson M. Literature review – Active and passive vehicle seat suspension systems. (2004)
Presentations
Trask, C, Teschke, K, Koehoorn, M. (2008) Back pain and disability reporting by workers in heavy industry: implications for case-control studies. Association of Canadian Ergonomists 39th Annual Conference. October 5-8 Alymer, Canada.
Trask, C, Teschke, K, Koehoorn, M. (2008) Mean, Peak, and Cumulative Spinal Compression Estimates in Five Heavy Industries Association of Canadian Ergonomists 39th Annual Conference. October 5-8 Alymer, Canada. Finalist: Best PhD Student Paper Award.
Trask C, Koehoorn M, Village J, Johnson P, Chow Y, Teschke K. Evaluating the efficiency of exposure assessment methods: cost, feasibility, and overcoming challenges in the field. PREMUS2007: Sixth International Conference on Prevention of Work-related Musculoskeletal Disorders. Boston, USA; August 27-30, 2007.
Trask C, Koehoorn M, Village J, Johnson P, Chow Y, Teschke K. Modeling determinants of low back exposures in construction, forestry, transportation, warehousing and wood products industries. PREMUS2007: Sixth International Conference on Prevention of Work-related Musculoskeletal Disorders. Boston, USA; August 27-30, 2007.
Johnson P, Ploger J, Trask C, Village J, Chow Y, Koehoorn M, Teschke K.
Longitudinal exposure assessments of low back posture in five heavy industries in British Columbia. PREMUS2007: Sixth International Conference on Prevention of Work-related Musculoskeletal Disorders. Boston, USA; August 27-30, 2007.
Teschke K, Johnson P, Trask C, Chow Y, Village J, Koehoorn M. Measuring Posture for Epidemiology: Comparing Inclinometry, Observations, and Self- Reports. EPICOH2007: 19th International Conference on Epidemiology in Occupational Health. Banff, Canada: October 9-12, 2007.
Trask C. BC Back Study: Evaluating ergonomic assessment methods for occupational field studies. School of Occupational and Environmental Hygiene Seminar Series. Vancouver, January 12, 2007.
Village J, Trask C, Morrison J, Johnson P, Teschke K, Koehoorn M. Whole-body vibration measurements in the BC forestry and transportation industries. Association of Canadian Ergonomists (ACE) 37th Annual Conference, Banff Alberta, October 22-25, 2006.
Trask C, Village J, Morrison J, Johnson P, Teschke K, Koehoorn M. How long is long enough? Physical exposure estimates and sampling duration. Association of Canadian Ergonomists (ACE) 37th Annual Conference, Banff Alberta, October 22-25, 2006
Trask C, Cooper J, Teschke K, Luong N, Koehoorn M. Direct recruitment of workers and worksites in heavy industry for occupational field studies. Canadian Association for Research on Work and Health, St. John’s, Nfld, June 2006
Trask C, Koehoorn M, Village J, Morrison J, Teschke K, Ploger J, Johnson PW. Evaluating full-shift low back EMG and posture measurement for epidemiological studies. IEA2006, 16th World Conference on Ergonomics. Maastricht, the Netherlands. July, 2006
Trask C, Koehoorn M, Village J, Teschke K, Johnson PW. Modeling determinants of working exposures and exposure variability. IEA2006, 16th World Conference on Ergonomics. Maastricht, the Netherlands. July, 2006
Trask C, Luong N, Koehoorn M. Development and testing of an observation tool for occupational ergonomic exposure assessment in heavy industry. (2005) Canadian Association of Research on Work and Health Conference, Vancouver, BC, Canada.
Trask C, Morrison J, Village J. Comparing EMG calibration methods for occupational field studies. (2005) Association of Canadian Ergonomists Annual Conference, Halifax, NS, Canada