Work-related Low Back Pain(LBP) is one of tire most important issues in the field of industrial safety and health. Particularly, manual lifting is known as a major cause of work-related LBP and impairment.
Total number of 163 manual lifting tasks in motor assembly processes were investigated. The 1981 and the 1994 equations developed by National Institute for Occupational Safety and Health(NIOSH) were applied to evaluate potential hazards of lifting-related LBP. Comparisons between the 1981 and 1994 NIOSH criteria were made. The relationships between the NIOSH criteria and lifting-related LBP were also analyzed.
The results of this study are as foLIows :
1. The values of Action Limit(AL) by the NIOSH 1981 lifting equation. Recommended Weight Limit(RWL) by the 1994 equation and the weight of the load handled at each manual lifting task were shown log-normal distributions.
2. LI´(the weight of the load/AL) and LI(the weight of the load/RWL) were calculated to estimate the physical stress imposed by each individual lifting tank. As a result, 76.7 % of the total LI´ values exceeded 1 and 12.9 % exceeded 3, and 84.7 % of the total LI values exceeded 1 and 20.9 % exceeded 3.
3. Bus 2 Department showed the highest rate of LI´$gt;1 and LI$gt;1 and Bus 1 Department showed the highest rate of LI´$gt;3 and LI$gt;3
4. In general, the RWLs by the 1994 equation were found lower than the ALs by the 1981 equation. It is assumed to be resulted from the fact that the 1994 equation includes methods evaluating asymmetrical lifting tasks and lifts of objects with less then optimal hand-container couplings, and also covers a larger range of work durations and lifting frequencies than the 1981 equation.
5. Significant correlations were found between LI´ and incidence of LBP (R=0.734, p$lt;0.05), LI and incidence of LBP(R=0.671, p$lt;0.10) and load-weights and incidence of LBP(R=0.797, p$lt;0.05).
6. Control measures are required to achieve the value of LI less than 1 for some tasks having high LI values. Engineering control is highly recommended for some tasks having the value of LI above 3.
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