Safe Workload Ergonomic Exposure Project

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Safe Workload Ergonomic Exposure Project

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Abstract Background: In 2016, there were 2,384,600 people employed as janitors. Their work, involving a reportedly high physical workload, appeared to place them at risk for days away from work with a rate 2.7 times higher than all other occupations. A Minnesota union identified to researchers at the University of Minnesota a concern relevant to a possible relation between the daily workload and adverse occupational outcomes among a population of janitors. Objective: To determine if there is a relation between exposures of ergonomic workload, mental workload, job satisfaction, stress, physical fitness, and the outcome of injuries in janitors, and to assess the relations between exposures of physical (ergonomic) and mental workload and the outcome of stress in a population of janitors. Methods: Following an initial focus-group discussion among janitors, which identified common and hazardous tasks potentially leading to occupational injuries, a specially designed self-administered questionnaire was developed, pre-tested, and distributed to the janitors. Questions addressed various exposures, including workload, and comprehensive information regarding injury occurrence over two six-month sequential periods (May 2016-October, 2016; November 2016-April 2017). Quantitative ergonomic analyses were performed on a sub-group of janitors (n=30); these included data collection to identify Borg Perceived Exertion (Borg) and Rapid Entire Body Assessment (REBA) scores. Descriptive, multivariable with bias adjustment analyses were conducted on the resulting data Results: Eight tasks were found to be common for janitors. All average REBA scores for the tasks were identified in the high-risk category. The task of repeatedly emptying small trash cans (<25 pounds) was significantly related to injuries. Average Borg scores fell between the very light perceived exertion and somewhat difficult perceived exertion categories. Multivariable regression analyses indicated that age-sex-standardized ergonomic workload, measured by task frequencies and REBA or Borg scores, were positively related to injury occurrence. A decreased risk of injury was associated with both increased job satisfaction and increased physical fitness. A highly suggestive increased risk of injury was associated with increased mental workload. Multivariable regression identified a relation between ergonomic workload and stress. A risk of stress was identified for mental workload. Conclusions: This research increases understanding of the relations between occupational exposures and the outcomes of injury and stress among janitors.


University of Minnesota Ph.D. dissertation. August 2018. Major: Environmental Health. Advisor: Susan Gerberich. 1 computer file (PDF); vii, 275 pages.

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Schwartz, Adam. (2018). Safe Workload Ergonomic Exposure Project. Retrieved from the University Digital Conservancy,

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