Muskuloskeletal disorders in the New Zealand sawmilling industry : prevalence, risk factors and intervention strategies : a thesis in partial fulfillment of the requirements for the degree of MAster of Ergonomics at Massey University
Government injury data indicated that New Zealand's sawmilling industry had a high number of musculoskeletal disorder (MSD) claims of high cost. New Zealand's forestry and wood processing sector is also a growth industry, with 100 new mills likely to be developed by 2010. Required to address the high rate of MSDs is a systematic review of manual handling risk factors and the development of related intervention strategies. Detailed information on the prevalence and nature of MSDs in NZ sawmilling was sought. Available Accident Compensation Corporation injury records provided limited detail on the work tasks causing MSDs in sawmill workers. An industry survey of reported accidents for a 12 month period (September 2000-August 2001) was completed to determine MSD prevalence, and to identify sawmilling operations with high manual handling risks. 56% of MSD reports were from millhands and tablehands, who complete the majority of timber handling tasks. Back injuries accounted for 37% of MSD reports, and upper extremity complaints a further 35%. Tasks creating the largest proportion of MSDs in sawmills were pulling, sorting and stacking of timber from green or dry tables/chains (conveyors moving freshly sawn or kiln-dried timber, from which boards are taken and stacked), filleting tasks (stacking timber with spacer sticks before drying), and grading/sorting on the green table/chain. In case studies of two South Island sawmills, timber handling tasks at green and dry tables were investigated to determine manual handling risk factors. Karsh et al (2001) suggest that multiple intervention applications are the most successful in reducing MSDs. A range of assessment methods was therefore used to identify a range of manual handling risk factors and potential interventions. Assessments included worker interviews, archival data review, environmental assessment, lifting strength testing, force measurement, anthropometry, dimensional assessment, discomfort reporting, exertion scales, Rapid Entire Body Assessment, and application of a manual handling risk assessment. The manual handling risks identified were related to a wide range of aspects of the task (frequency, workplace design), worker (experience, training), load (timber size, chain/table design), environment (temperature, lighting) and management (task rotations, maintenance schedules). The intervention strategies developed to reduce the manual handling risks included workspace geometry (such as the relationship of timber on the table to the packet, and packet spacing), workflow management (such as task rotations, and managing peaks and troughs in production), task technique training (such as board throwing methods, induction training, and the use of protective aprons), table design (such as height, type of chain or conveyor), and glove design. Mill-specific recommendations based on these strategies were presented to the mills. Further work is indicated to evaluate the effectiveness of recommended intervention strategies.