Controlling Ergonomics Risk Factors

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.

A "hierarchy of controls" is widely accepted as an intervention strategy for controlling workplace hazards, including ergonomic hazards:

• Elimination
• Substitution
• Engineering controls
• Work Practice controls
• Personal Protective Equipment
• Interim Measures

Controlling MSDs through elimination, substitution and engineering controls

The preferred approach to prevent and control MSDs is to design the job including:

• the workstation layout
• selection and use of tools
• work methods to take account of the capabilities and limitations of the work force

A good match, meaning that the job demands pose no undue stress and strain to the person doing the job, helps ensure a safe work situation.

Engineering control strategies to reduce ergonomic risk factors include the following:

• Changing the way materials, parts, and products can be transported . For example, using mechanical assist devices to relieve heavy load lifting and carrying tasks or using handles or slotted hand holes in packages requiring manual handling
• Changing the process or product to reduce worker exposures to risk factors. Examples include maintaining the fit of plastic molds to reduce the need for manual removal of flashing, or using easy-connect electrical terminals to reduce manual forces Modifying containers and parts presentation, such as height-adjustable material bins.
• Changing workstation layout. Examples might include using height-adjustable workbenches or locating tools and materials within short reaching distances.
• Changing the way parts, tools, machinery and materials are to be manipulated. Examples include using fixtures (clamps, vise-grips, etc.) to hold work pieces to relieve the need for awkward hand and arm positions or suspending tools to reduce weight and allow easier access.
• Changing tool designs. For example, pistol handle grips for knives to reduce wrist bending postures required by straight-handle knives or squeeze-grip-actuated screwdrivers to replace finger-trigger-actuated screwdrivers.
• Changes in materials and fasteners. For example, lighter-weight packaging materials to reduce lifting loads.
• Changing assembly access and sequence. For example, removing physical and visual obstructions when assembling components to reduce awkward postures or static exertions.

Controlling MSDs through work-practice and administrative controls

Work practice and administrative controls are closely related attempts to change behaviors. They are management-dictated work practices and policies to reduce or prevent exposures to ergonomic risk factors. Work practice and administrative control strategies include:

• changes in job rules and procedures such as scheduling more rest breaks
• rotating workers through jobs that are physically tiring
• training workers to recognize ergonomic risk factors and to learn techniques for reducing the stress and strain while performing their work tasks

Although engineering controls are preferred, work practice and administrative controls can be helpful as temporary measures until engineering controls can be implemented or when engineering controls are not technically feasible. Since work practice and administrative controls do not eliminate hazards, management must assure that the practices and policies are followed.

Common examples of administrative control strategies for reducing the risk of MSDs are as follows:

• Reducing shift length or curtailing the amount of overtime
• Rotating workers through several jobs with different physical demands to reduce the stress on limbs and body regions
• Scheduling more breaks to allow for rest and recovery
• Broadening or varying the job content to offset certain risk factors (e.g., repetitive motions, static and awkward postures)
• Adjusting the work pace to relieve repetitive motion risks and give the worker more control of the work process
• Training in the recognition of risk factors for MSDs and instruction in work practices that can ease the task demands or burden

Personal Protective Equipment

One of the most controversial questions in the prevention of MSDs is whether the use of personal equipment worn or used by the employee (such as wrist supports, back belts, or vibration attenuation gloves) are effective. Some consider these devices to be personal protective equipment (PPE).

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 question.

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 manual handling job tasks [NIOSH 1994].

A recent epidemiological study credits mandatory use of back belts in a chain of large retail hardware stores in 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.

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?

Source: OSHA

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