750 Introduction to Industrial Hygiene

Risk Factors Inherent in the Task

In addition to considering the worker attributes that may increase the risk of injury, we must also analyze the risk factors the work task itself brings to the job.

Industrial hygienists look at the task variables in the workplace that may increase or decrease the risk of WMSDs depending on its design and location. In large measure, the following task-related risk factors influence the probability and severity of ergonomic injuries when completing work processes.

• Contact Trauma: When any part of your body presses against an external object, the resulting sustained force may cause too much mechanical stress on tissues. It is also possible for excessive mechanical stress to be produced from the impact shock of an object against a part of the body.
• Lifting/Lowering: The impact of improper lifting techniques on the compressive forces exerted on the L5/S1 discs in the lower back when lifting a 50 lb box while bent over forces the employee to rely on the back, substantially increasing the risk of injury. Moreover, if the employee were to twist while lifting the heavy load, the likelihood of sustaining an injury would increase even further.

• Pushing/Pulling: Pushing and pulling tasks place stress on the body because they often require high levels of force, awkward postures, and repetitive movements. These actions increase the risk of injury, especially to the back, shoulders, and arms. The level of risk depends on the weight of the object, the distance it must be moved, the height of the force applied, and the surface conditions.
• High force requirements: Heavy loads or objects that resist movement require greater force, leading to strain and fatigue.
  Control: Use carts, dollies, or powered equipment to reduce manual force.
• Awkward body positions: Pulling behind the body or pushing with bent wrists increases stress on muscles and joints.
  Control: Train workers to keep their backs straight, bend at the knees, and push with the whole body rather than just the arms.
• Distance and frequency: Moving loads over long distances or repeating pushes and pulls many times increases risk.
  Control: Minimize travel distances, reorganize the workspace, and rotate tasks among workers.
• Handle height: Pushing or pulling loads at heights above the shoulders or below the knees increases strain.
  Control: Adjust handle heights to be between waist and chest level whenever possible.
• Surface conditions: Slippery, uneven, or rough surfaces increase the force required to push or pull safely.
  Control: Maintain clean, smooth floors and ensure wheels on carts or dollies roll easily.
• Vibration: Depending on the type and duration of exposure, vibration can impact different parts of the body, or the whole body.
• Segmental Vibration: When handling vibrating tools for a prolonged duration, vascular insufficiency in the hand and fingers can also result in interference with sensory receptor feedback. If a worker can't "feel" the grip properly, he or she may compensate by applying more force than is necessary to hold and handle an object. Segmental vibration has also been linked to carpal tunnel syndrome.
• Whole Body Vibration: When the whole body is subjected to vibration, as most commonly experienced by truck drivers, there is an enhanced risk of injury, especially to the lower back. The most common whole-body vibration forces are not sudden, but rather occur over a period of time. For example, this type of vibration is usually created by large vehicles as they travel over highways and especially terrain.

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