Physical exposure assessment in monotonous repetitive work - the PRIM study

Objectives A program called the Project on Research and Intervention in Mon otonous Work (PRIM) was initiated in 1994 as a prospective cohort study of work-related musculoskeletal disorders. The group-based exposure assessment strategy, focusing on task-related exposure and used to obtain baseline me asures of physical exposures, is reported in this paper. Methods Monotonous, repetitive worktasks were evaluated at 19 factories. Ta sks with an estimated similarity in physical exposure were aggregated befor e 103 exposure groups were formed. Subjects from the exposure groups were r andomly sampled for measurements, and task-related exposure levels were qua ntified by 43 single exposure items using a real-time video-based observati on method that allowed computerized estimates of repetitiveness, body postu res, force, and velocity. In combination with questionnaire-based data on t ask distribution, the duration of exposure was calculated at the individual level. Results The video-based observational method and the large number of exposu re variables enabled the establishment of detailed quantitative exposure pr ofiles in 103 task-based exposure groups. However, methodological problems associated with the use of grouped exposure assessment were revealed. Despi te efforts to optimize group homogeneity, the within-group variance was lar ger than the between-group variance for several shoulder postural variables . Conclusions A task-based exposure-assessment strategy can be successful in solving some of the main problems associated with the assessment of physica l workplace exposures. The large within-group variance in exposure to nonne utral shoulder postures may eventually require individual assessment or the inclusion of groups with maximal contrast in exposure or both.