Comparison of ergonomic risk assessments in a repetitive high-risk sawmill occupation: Saw-filer

AimsThe aims of this study are to: (1) compare the results of 5 ergonomic risk assessment methods calculated with quantified physical exposure information, (2) examine the effect of multiple definitions of the posture and exertion variable on the risk assessment methods, (3) describe the variability in risk assessment scores between workers, (4) examine the ability of risk assessment component scores to differentiate between facilities with significantly different levels of exposure, and (5) examine the association between risk output and recorded incidence rates.ScopeQuantified physical exposure information collected from 15 saw-filers in four sawmill facilities was used to calculate the RULA, REBA, ACGIH TLV, Strain Index and OCRA procedures based on multiple posture and exertion variable definitions.ResultsRecorded incidence of upper extremity musculoskeletal injury in the saw-filer position ranged from 0.12 to 0.86 per person year worked. All risk assessment methodologies examined (with the exception of the ACGIH TLV calculated with %MVC) agreed a level of risk was associated with performance of the saw-filer job. Posture and exertion variable definition was observed to have a significant effect on the component scores and/or risk output of all methods assessed. Meaningful variability in risk assessment scores was observed between workers. Components of all assessments, with the exception of the ACGIH TLV, differentiated between facilities assessed. Average risk index scores of the SI and OCRA procedures were observed to increase as recorded incidence of injury increased; however statistical significance was not demonstrated.ConclusionsSuggestive evidence exists that the components of the strain index and OCRA methods measuring posture and frequency were sensitive to actual differences between facilities and that the combined role of physical exposures in precipitation of musculoskeletal injury was accounted for. Posture and exertion variable definitions were observed to significantly affect the component scores and/or risk output of all methods.Relevance to industryAn understanding of inter subject variability, the effect of variable definition selected, and the sensitivity of risk output to incidence of injury are necessary to correctly apply ergonomic risk assessments in industrial prevention efforts.