محتوای کار و عوامل خطر ارگونومیک فیزیکی در اهن الات ساخت و ساز

Construction ironwork (CI) has been identified as a trade wherein the exposures to ergonomic risk factors are high. In this study, quantitative exposure assessments for seven specific ironwork tasks selected from the four main specialties of CI—machinery moving/rigging, ornamental, reinforcing, structural—were performed. A total of 13,821 observations were made using the work-sampling, specialty-task-activity-based analysis method called PATH (posture, activity, tools, and handling) and a taxonomy developed specifically for CI. The PATH data provided specialty-task-activity estimates of the percentage of time ironworkers spent in specified postures of the trunk, arms, and legs, and also gave estimated frequencies of manual materials handling activities as well as 11 other predefined activities. Depending on the specialty-task-activity performed, results showed that ironworkers spent anywhere from 13% to 48% of their work time in non-neutral trunk postures; worked with one or both arms at or above shoulder level 6–21% of the time; and stood on uneven/unstable work surfaces 3–53% of the time. The type of activity performed was consistently found to be a major predictor of the frequency of work time spent in non-neutral postures for the trunk, legs, and arms. Relevance to industry These results can be used to target hazardous activities in CI such as rebar and structural ironwork and confirms the need for specialty-task-activity-specific information within each construction trade on exposures and worker activities so that the most appropriate ergonomic interventions can be designed and implemented.

Recent studies and statistics have shown that the rates of musculoskeletal injuries and disorders among workers in the construction trades are much higher when compared to those working in other industries (Schneider, 1997; CPWR, 1996). According to the US Bureau of Labor Statistics, construction workers suffer work-related injuries and illnesses at a rate of 7.9 cases per 100 equivalent workers compared to the all-industry average of 5.7 (BLS, 2001). Construction workers had the highest rate of injuries of 7.8 versus that all industry average of 5.4 (BLS, 2001). In general, construction workers are at a high risk of developing work-related musculoskeletal disorders (WRMSDs) that are associated with exposure factors in this work environment (Holstrom et al., 1993; Guo et al., 1995; Kisner and Fosbroke, 1994; Schneider and Susi, 1994). Despite the high prevalence of ergonomic risk factors in construction work (Schneider and Susi, 1994; Schneider, 1997; Kisner and Frosbroke, 1994), research has been limited in this industry. This can be attributed mainly to logistical reasons. Specifically, some of the main problems faced by researchers seeking to design studies for this segment of the working population are high task variability, highly irregular work periods, constantly evolving work environments, and high worker mobility. As a result, systematic and comprehensive trade- and task-specific investigations of the relationship between ergonomic exposures and WRMSDs have been undertaken for only a limited number of trades (e.g., Lindstrom et al., 1974; Wickstrom, 1978; CPWR, 1994; Riihimaki, 1985; Cook et al., 1996). Just as office- or factory-based exposure information is often inapplicable to the dynamic construction work environment, so to, each construction trade and the major tasks associated with it often present different and unique ergonomic challenges to the worker. Trade- and task-specific information on tools, exposures, worker tasks and work conditions is likely to prove most useful in designing and selecting the most appropriate prevention measures to minimize the incidence of WRMSDs among construction workers. The term ‘construction’ ironwork (CI) (also commonly referred to as ‘outside’ ironwork) is used to distinguish this type of ironwork from ‘shop’ or ‘fabricating’ ironwork which, unlike CI, tends to take place indoors in more structured, factory-like settings. In general, CI involves the erection of structural steel, placement of reinforcing bars in concrete structures, moving heavy machinery, rigging and erection of equipment and scaffolding, installation of fabricated building components, and welding and cutting. In the United States, CI is sub-classified around four main specialties (Robertson, 1975): (1) structural ironwork (SIW), (2) reinforcing ironwork (RIW), also know as rod or rebar work or concrete reinforcement work, (3) ornamental ironwork (OIW), and (4) machinery moving/rigging ironwork (MMRIW). Each CI specialty consists of key tasks and activities that are specific to that specialty (Table 1). Those entering the ironwork trade are required to undertake a 3-year apprenticeship training program wherein they are taught and exposed to all four ironwork specialties (Robertson, 1975). On completion of the training program, the ironworker gains “journeyman” status and begins to specialize in one or two of the above CI specialties. Journeymen can, however, and do regularly change their specialty based on job requirements and current job market demands. A few studies that have specifically collected ergonomic exposure data on CI (e.g., Forde, 2000a,b; Lindstrom et al., 1974; Hart and Link, 1991). These studies have found that typical of CI is that it requires the ironworkers to lift, carry, and manipulate heavy loads; work in severely cramped spaces or sustained awkward postures; work with their arms overhead; use heavy, vibrating pneumatic tools to which they must apply large forces and hold in static positions; and work at great heights while constantly exposed to the elements such as rain, snow, ice, wind, and temperature extremes. In other studies, the focus has been mainly on RIW as it relates to low back pain/disorder outcomes (e.g., Lindstrom et al., 1974; Nummi et al., 1978; Saari and Wickstrom, 1978; Wickstrom, 1978; Riihimaki et al., 1990; Riihimaki et al., 1989; Riihimaki, 1985; Nurminen, 1997; Buchholz et al., 2003). It appears that no published studies have examined the ergonomic exposure profiles for other CI specialties. In general, it is clear that construction ironworkers are exposed to many ergonomic hazards. What is not clear, however, is whether these hazards remain the same across CI specialties (or even within a particular CI specialty, across activities) in terms of frequency, intensity, and duration. Given the paucity of information on the ergonomic exposures profiles for each CI specialty, the goal of this research study was to provide specialty-task-activity-based ergonomic exposure estimates for each of the four main specialties of CI. These exposure profiles could then be used to (i) target those CI specialty-task-activities that pose the greatest risk to ironworkers, and (ii) inform the development of workable and cost-effective interventions, including training materials.

This study, as well as others (e.g., Lindstrom et al., 1974; Nummi et al., 1978; Saari and Wickstrom, 1978; Wickstrom, 1978; Riihimaki et al., 1990; Riihimaki, 1985; Buchholz et al., 2003), clearly identify CI as a construction trade wherein exposures to ergonomic risk factors such as awkward postures, heavy lifting, and forceful exertions are significant. As is typically true of most trades, however, the ergonomic risk profiles can and do vary depending on the specific specialty, task, and activity being performed. In CI, there are four main specialties—MMRIW, OIW, RIW, and SIW—each with multiple, unique tasks and activities. There therefore exists a need for studies which clearly quantify and define the shape of these profiles by CI specialty, tasks, and activities. This study is a first step towards establishing a task-based database on ergonomic exposures common to CI. Once task-specific ergonomic exposure profiles are determined for each CI specialty, then their association with adverse musculoskeletal health outcomes can be determined in future epidemiologic studies. Furthermore, researchers can then be better able to propose and develop preventive ergonomic interventions that are targeted on the most hazardous tasks and activities of each CI specialty. The results of this research can be used in developing improved tools and work methods. For example, changes in the tools and work methods used in RIW(RW) and SIW(B) have the potential to reduce the frequency of non-neutral trunk and arm postures for these two CI tasks (Schneider, 1994; Li, 2002). Tools that reduce the amount of below knee level and above shoulder level work can be designed and used for these tasks (Sillanpää et al., 1999). Additionally, materials engineering and layout strategies can be implemented that minimize the maximum weight lifted or MMH activity required. The effectiveness of any changes made in work methods or tools used can be analyzed using the analytic method employed in this study. Employing such a specialty-task-activity-based, work-sampling based technique which associates specific work postures with specific work activities will enable researchers and others to develop work interventions that have been proven to actually decrease exposures to adverse ergonomic risk factors.