Back injuries in heavy industries, Part B : risk factor exposure assessment Teschke, Kay; Trask, Catherine; Village, Judy; Chow, Yat; Cooper, James; Davies, Hugh; Demers, Paul; Hodgson, Murray; Hong, Kevin; Hurrell, Christie; Johnson, Peter W.; Knott, Melissa; Luong, Nancy; Morrison, Jim; Wright, Geoff; Xu, Fan; Koehoorn, Mieke
Many British Columbians employed in heavy industries will suffer from back injuries over the course of their careers. Occupational back injuries are very common in this province, and they are also very costly due to lost workdays, compensation claims, and health care costs. Although many studies have investigated back injuries and their risk factors, the research community has not reached a consensus on the occupational causes. In part, this is because exposures are difficult to measure in large numbers of people in real work settings. We tested five approaches to measuring exposures in the following heavy industries: forestry; wood and wood products; construction; transportation; and warehousing. Three methods used measurement instruments: • an “inclinometer” to measure posture for the full work shift; • “electromyography” (EMG) to measure back muscle activity for the full shift; • a vibration meter to measure “whole body vibration” on vehicle seats when the participant was in the vehicle. Of these methods, the inclinometer was most feasible to use in the challenging work environments typical of heavy industry (e.g., being out in the weather, changing work tasks and body positions). It collected several measurements (forward and backward bending angles, side-to-side bending angles, and speed of trunk movements). Two methods did not use instruments: • observations by trained observers of postures, lifting, vehicle use, and tasks for the full shift; • end-of-shift interviews of employees about postures, lifting, and vehicle use during the shift. Both were feasible to use. Interviews were the least costly of all the methods tested. We also tested to see whether statistical models could be derived to estimate the exposures measured by the instruments, using information collected via the less expensive interview and observation techniques. Overall, the observation data did a reasonable job of predicting the measurements that were taken with the various instruments. In most cases, the interview data did not predict the instrument measurements as well. Depending on the aims, locations, and budget, studies of back injuries could be best served by using a combination of exposure assessment techniques. The following combination could work well in heavy industry settings: observations to collect information about lifting, vehicle use, and tasks; and inclinometry to measure postures and movement speeds in detail. This study also provided data about exposures to back injury risk factors in British Columbia across many different jobs in the five heavy industries. Floor layers, construction labourers, bricklayers, bus cleaners, and fallers had consistently high posture and muscle activity exposures. Heavy equipment operators had the highest vibration exposures.
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