Comparative Assessment of Manual Material Handling Using the Two Methods of NIOSH Lifting Equation in a Tile Manufacturing Company MAC and Revised

Manual material handling (MMH) can be lead to work-related musculoskeletal disorders and one of the most common disorders due to MMH tasks is low back pain. This study was conducted for determination of musculoskeletal disorders, assessment of MMH tasks by MAC and revised NIOSH lifting equation methods and compares the results of these two methods. This descriptive-analytic study was conducted on 30 workers in a tile manufacturing industry in Hamadan in 2011. Nordic musculoskeletal questionnaire (NMQ) was used for determining the musculoskeletal disorders prevalence and MAC and NIOSH methods were applied for the assessment of manual material handling tasks. Finally, these two methods were compared in terms of the agreement on risk assessment outputs. Lower back, shoulder and knee symptoms were found to be the most prevalent problems among the workers studied with prevalence rate of 66.7%, 40.1% and 40% respectively in recent years. According to NIOSH equation, the loads lifted by workers were exceeding than recommended weight limit. The results showed that for both MAC and NIOSH methods risk levels were high in abrasive grinding, varnishing, furnace and packaging units. Comparison of risk assessment outputs from two applied methods showed 100% agreement. Physical stress imposed on body while lifting the loads were high in all units and one of the main reasons was using fixed load handling trolley that led to high prevalence of musculoskeletal disorders in workers. This study recommends ergonomic measures for improving working conditions.