Reliable exposure assessment strategies for physical ergonomics stressors in construction and other non-routinized work

Abstract

The objective of this research was to provide guidelines for the reliable assessment of ergonomics exposures in non-routinized work. Using a discrete-interval observational sampling approach, two or three observers collected a total of 5852 observations on tasks performed by three construction trades (iron workers, carpenters and labourers) for periods of several weeks. For each observation, nine exposure variables associated with awkward body postures, tool use and load handling were recorded. The frequency of exposure to each variable was calculated for each worker during each of the tasks on each of the days. ANOVA was used to assess the importance of task in explaining between-worker and within-worker variability in exposures across days. A statistical re-sampling method (bootstrap) was used to evaluate the reliability of exposure estimates for groups of workers performing the same task for different sampling periods. Most exposures were found to vary significantly across construction tasks within trade, and between-worker exposure variability was generally smaller than within-worker exposure variability within task. Bootstrapping showed that the reliability of the group estimates exposure for the most variable exposures within task tended to improve as the assessment periods approached 5 – 6 d, with marginal improvements for longer assessment periods. Reliable group estimates of exposure for the least variable exposures within task were obtained with 1 or 2 d of observation. The results of this study demonstrate that an initial estimate of the important environmental or task sources of exposure variability can be used to develop an efficient sampling strategy that provides reliable estimates of ergonomics exposures during non-routinized work.

Keywords:

• Exposure assessment
• Work sampling
• Physical ergonomics stressors
• Posture
• Construction work
• Bootstrap

Acknowledgements

This work was supported by the National Institute for Occupational Safety and Health (NIOSH) through the Center to Protect Workers' Rights (CPWR) (Grant Nos: UO2/CCU308771 and U02/CCU312014). Gary Davis, Ted DesMarais, Joel Garrett, Mike Grasso, Diane Lee, Bill Rodwell, Trevor Schell and Helen Wellman assisted with data collection. The authors are grateful to Alex Burdorf, PhD, and Svend Erik Mathiassen, PhD for providing valuable advice about some of the statistical considerations of this study. The authors thank International Association of Bridge, Structural and Ornamental Ironworkers (Local 7), United Brotherhood of Carpenters and Jointers of North America (Local 218) and the Labourers' International Union of North America (Local 223) for their cooperation.