Ergonomic improvements are changes made to improve the "fit" between a job and the capabilities of the employees performing it. Analyzing jobs to identify factors associated with risks for MSDs lays the groundwork for developing ways to reduce or eliminate ergonomic risk factors for MSDs.
To control ergonomic hazards, a hierarchy of controls has been used as a means of determining how to implement feasible and effective controls. ANSI Z10-2005, Occupational Health and Safety Management Systems, encourages employers to use the hierarchy of hazard control strategies listed below.
The idea behind this hierarchy is that the control methods at the top of the list are potentially more effective and protective than those at the bottom for controlling ergonomic hazards. Following the hierarchy normally leads to the implementation of inherently safer systems, ones where the risk of illness or injury has been substantially reduced. Let's take a closer look at the hierarchy of control strategies.
Elimination and substitution, while most effective at reducing hazards, also tend to be the most difficult to implement in an existing process. If the process is still at the design or development stage, elimination and substitution of hazards may be inexpensive and simple to implement.
For an existing process, major changes in equipment and procedures may be required to eliminate or substitute for a hazard. For example, if you have to work in a space that requires poor work postures, you might eliminate the need to perform the work within that space. If you have to lift a heavy object, you might substitute the heavy object with an object of less weight.
Engineering controls involve making changes to workstations, tools, or equipment used on the job. These controls are preferred over all others because they make permanent changes that can totally eliminate hazards at the source. Although they may be more expensive to implement than other controls, their effect is often more significant.
Let's take a look at some of the various engineering control strategies that may be effectively used to eliminate hazards.
Aspects of workstations you can change with engineering controls include:
Check out this short audio clip by Dan Clark of the theSafetyBrief.com that discusses four detailed reasons why forklifts, conveyors and hoists so workers can avoid sprains, fractures and musculoskeletal injuries.
Computer workstations have special considerations you should be aware of. The monitor and keyboard positions, lighting, and seating are especially important in preventing work-related MSDs and eye discomfort. Shared workstations should be easily adjustable so the screen and keyboard can be at the proper level. Take a look at some specific workstation design considerations and problems/solutions for computer workstations.
There are five components of proper computer workstation design that you must address to maintain proper posture: the work surface; the keyboard; the pointing device or trackball; the monitor; and the chair.
1. Work Surfaces
3. Mouse or Trackball
Workspace layout and arrangement should be carefully designed so that it meets the requirements listed below.
For example, where workers inspect or assemble small parts, or perform other visually intensive tasks, work surfaces could be tilted to reduce neck, shoulder and arm strain.
Surfaces on which people stand for long periods should be designed to prevent slipping and provide adequate traction and comfort. Anti-fatigue floor mats, sit-stand stools, and footrests can help make workers more comfortable.
Seat-height adjustability and lower back support are important for work done for a long time while seated. Some workers may choose to sit part of the time and stand other times to reduce stress on the body from working in one position too long. Chairs or seating should:
Storage areas should be organized so that workers maintain good body positions, reduce muscular forces, and avoid excessive reach. Store heavy items between knee and shoulder height. Frequently used items should be stored close to the worker.
Workers should not have to use their hands or bodies as a vise to hold objects; mechanical devices do this much better. Tooling fixtures and jigs should be set up to avoid awkward postures and excessive forces.
Improper hand tool selection or improper use of tools can cause CTDs. Hand tools should fit the employee's hand; employees with small hands or who are left-handed may need tools designed specifically for these situations. Hand and wrist posture are important because they affect how much force the muscles must produce to hold objects. When selecting and purchasing hand tools, the guidelines listed below should be followed.
Workplace environmental factors interact with those the worker and the task brings to the job, and they deserve careful consideration. Below is a list of methods to minimize work-environment hazards.
Administrative controls are management-dictated procedural and scheduling changes designed to reduce or prevent exposures to ergonomic risk factors. Although engineering controls are preferred, administrative controls may be needed as well, especially when engineering controls can not totally eliminate a hazard or when engineering controls are not technically feasible. Since administrative controls do not eliminate hazards, managers must continually ensure safe procedures and policies are followed to make sure exposure to hazards is minimized.
The capacity of workers should be considered in establishing production goals. Increased work rates, excessive overtime, and incentive programs for piece work can cause fatigue, increasing the chance for injury.
Tasks involving repetitive motion are major contributors to CTDs. You can minimize repetition by:
For example, in a check-sorting operation, instead of having one person open mail, another stamp them and yet another record the figures, each worker could do each of those tasks.
In the field of occupational safety and health, PPE generally provides a barrier between the worker and the hazard source. Respirators, ear plugs, safety goggles, chemical aprons, safety shoes, and "hard hats" are all examples of PPE. Whether braces, wrist splints, back belts, and similar devices can be regarded as offering personal protection against ergonomic hazards remains open to debate.
Although these devices may, in some situations, reduce the duration, frequency, or intensity of exposure, evidence of their effectiveness in injury reduction is inconclusive. In some instances they may decrease one exposure but increase another because the worker has to "fight" the device to perform his or her work. An example is the use of wrist splints while engaged in work that requires wrist bending.
On the basis of a review of the scientific literature completed in 1994, NIOSH concluded that insufficient evidence existed to prove the effectiveness of back belts in preventing back injuries related to manually handling job tasks [NIOSH 1994]. A recent epidemiological study credits mandatory use of back belts in a chain of large retail hardware stores for substantially reducing the rate of low back injuries [Kraus 1996]. Although NIOSH believes this study provides evidence that back belts may be effective in some settings for preventing back injuries, NIOSH still believes that evidence for the effectiveness of back belts is inconclusive.
More on backbelts
Less controversial types of personal equipment are vibration attenuation gloves [NIOSH 1989] and knee pads for carpet layers [Bhattacharya et al. 1985]. But even here, there can be concerns. For example, do the design and fit of the gloves make it harder to grip tools?
Interim measures are nothing more than temporary applications of engineering and/or management controls until more permanent solutions can be applied. For instance, if a computer monitor is too low, placing a phone book under the monitor might be an effective temporary solution. Having two people lift heavy objects until a pneumatic lift can be purchased is another example of a temporary fix to the problem.
An effective ergonomics program operates within a larger safety management system that is composed of many interrelated programs. When hazardous conditions and unsafe behaviors exist, it's usually because the safety management system is failing somehow. These failures represent the root causes for accidents and may be categorized as shown below.
A missing or inadequate component in any one of these subsystem processes might have a negative impact on ergonomics. Listed below are examples of safety subsystems.
Missing or inadequate safety system components may represent the root causes for ergonomic injuries. Hazardous conditions and unsafe behaviors represent the outward symptoms that give clues about the underlying safety system weaknesses. Therefore, every effort should be made to improve system components to ensure long term workplace safety.
Listed below are some examples of safety system improvements.
Notice that in each example we are describing a missing or inadequate process, policy, procedure, plan, or program that may or may not be directly related to ergonomics.
Controlling ergonomic hazards requires a balanced approach of both engineering and management control strategies. It's an ongoing effort that needs the help of everyone in the organization.
Watch this Washington State Dept. of Labor and Industries video that explains the potential causes of back injuries, and discusses ways to prevent back pain. Covers establishing load capabilities and proper positioning. Slides to Video format.
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