The work setting is characterized by an interaction between the following parameters:
- a worker with attributes of size, strength, range of motion, intellect, education, expectations, and other physical/mental capacities.
- a work setting comprised of parts, tools, furniture, control/display panels and other physical objects.
- a work environment created by climate, lighting, noise, vibration, and other atmospheric qualities.
The interaction of these parameters determines the manner by which a task is performed and the physical demands of the task.
As the physical demands of a task increase, the risk of injury increases. When the physical demands of a task exceed the physiological capabilities of a worker, an injury will likely occur.
Work Risk Factors
Certain characteristics of the work setting have been associated with injury. These work characteristics are called risk factors and include:
Task Physical Characteristics (primarily interaction between the worker and the work setting)
- Posture
- Force
- Velocity/acceleration
- Repetition
- Duration
- Recovery time
- Heavy dynamic exertion
- Segmental vibration.
Environmental Characteristics (primarily interaction between the worker and the work environment)
- Heat stress
- Cold stress
- Whole body vibration
- Lighting
- Noise
Other Workplace Risks
The risk factors addressed by industrial ergonomics are a partial list of hazards present in the work setting. Others include:
- Job stress
- Job invariability
- Job invariability
- Work organization
- Workload
- Working hours (shift work, overtime)
- Displays and control panels
- Slip and falls
- Fire
- Electrical exposures
- Chemical exposures
- Biological exposures
- Ionizing radiation
- Radiofrequency/microwave radiation.
Professionals such as industrial hygienists, human factors analysts, safety engineers, occupational medicine physicians, and occupational nurses evaluate and control these other risks. The ergonomist must recognize the skills and capabilities of these individuals. A working relationship is essential for optimum work site health and safety.
Assessing the Workplace for Ergonomic Risk Conditions
Evaluation of ergonomic risk conditions generally involves two steps:
1. identification of the existence of ergonomic risks
2. quantification of the degree of ergonomic risk.
Identification of ergonomic risk conditions
Several approaches are used to identify the existence of ergonomic risks. The method used depends on the managerial philosophy of the company (getting workers involved through a participatory process versus top/down process), level of analysis (one job versus company wide evaluation), and personal preference. There is no one correct approach.
Quantification of ergonomic risk conditions
Once the presence of risk factors is established, the degree of risk associated with those factors is evaluated. This is done through the application of analytical ergonomic tools and the utilization of specific guidelines. Ergonomic Analytical ToolsThere are a great variety of analytical tools. The tools are frequently orientated to a specific type of work (e.g., manual material handling) or a particular body part (e.g., wrist, low back).
Analytical tools also vary greatly in their style of conclusions. They may provide job prioritization for intervention, quantification of activities associated with increased risk of injury, or recommendation for a load weight limit for lifting. The examiner determines which analytical tool is best for evaluation of the identified risks based on an understanding of the tool's applications, strengths, and weaknesses.
An analytical tool can, at best, provide an approximation of the degree of risk. Variation in individual physiology, history of injury, work methods, and numerous other factors influence whether a person will sustain an injury. Further, many tools have not been tested adequately for reliability and validity. This status reflects the youth of the profession. Despite these shortcomings, tools still offer a standard method of analysis and reasonable assessment of risk.
Examples of analytical tools include:
- RULA - Rapid Upper Limb Assessment - Assesses the risk of cumulative trauma disorder through posture, force, and muscle-use analysis.
- OWAS - Ovako Working Posture Analysis System - Provides intervention prioritization based on posture and loads (Karhu et al., 1977).
- Repetitive Motion Evaluation - Analyzes posture, repetition, and discomfort to reveal the performance of high risk motions (Drury, 1987).
- Observation Analysis of the Hand and Wrist - Quantifies hand exertions associated with risk factors of pinch grip, high force, wrist flexion/extension/ulnar deviation, power tool exertion, and use of hand to strike object (Stetson et al., 1991).
- Utah Back Compressive Force Model - Evaluates the risk of low back injury for a one-time lifting task based on lumbar disc compression.
- Utah Shoulder Moment Model - Evaluates the risk of shoulder injury for a one-time lifting task comparing task moment to an individual's capacity.
- NIOSH Work Practices Guide (1981) - Evaluates the risk of a lifting task based on NIOSH parameters.
- Revised NIOSH Lifting Equation (1994) - Evaluates the risk of a lifting task based on expanded NIOSH parameters.
- Liberty Mutual Tables - Based on psychophysical experimentation, determines the maximum acceptable weight for a lifting/lowering task, push/pulling task, and carrying task given selected job characteristics. Tables are accessible from the Lifting/Manual Material Handling Job Review and Analysis Options.
- AAMA Metabolic Model - Evaluates the risk of physical exertion strain for a task.
- Anthropometry Analysis - Determines proper workplace dimensions for various body sizes.
- Detailed Checklist For Computer (VDT) Workstation Risk Analysis - Presents the recommended characteristics of a VDT workstation.
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