Developing Reliable Ergonomic Exposure Assessment Strategies for Construction Work

Abstract

The objective of this research was to provide guidelines for the reliable assessment of ergonomic exposures in construction work. Using a modified work-sampling approach, two or three observers collected a total of 4852 observations on tasks performed by three trades (iron workers, carpenters and laborers) for periods of several weeks. At each observation, recorded exposure variables included non-neutral trunk posture, trunk flexion, lateral bending or torsion, arm(s) at or above shoulder height, kneeling, squatting or leg bending, load handling, manual materials handling, hand-tool use and power-tool use. The frequency of exposure was calculated for each worker during each of the tasks on each of the days. ANOVA was used to assess the importance of task, between-worker variability and within-worker variability on exposures across days. A statistical resampling method (bootstrap) was then used to evaluate the reliability of exposure estimates for groups of workers performing the same task for different sampling periods. Most ergonomic exposures were found to vary significantly among construction tasks. In most cases, the between-worker component of variance within task was overshadowed by a large within-worker component of variance*** thought to consist largely of day-to-day differences in exposure and measurement error. When the average frequency of the ergonomic exposures was bootstrapped, the reliability of the most variable exposures tended to improve as the assessment periods approached 5 to 6 days, with marginal improvements for assessment periods longer than 6 days. Reliable estimates for the least variable exposures were obtained with 1or 2 days of observation. Based on this study, a task-based approach for classifying ergonomic exposures may benefit epidemiologic research and the evaluation of controls in construction work. A preliminary analysis of exposure variability is recommended when determining sampling strategies, and when multiple exposures are assessed simultaneously, sampling periods exceeding 6 days may be required for reliable measures.