This material is for training purposes only. Its purpose is to inform Oregon employers of best practices in occupational safety and health and general Oregon OSHA compliance requirements. This material is not a substitute for any provision of the Oregon Safety Employment Act or any standards issued by Oregon OSHA. For more information on this online course and other OR-OSHA online training, visit the Online Course Catalog.

MODULE 5: CONTROLLING RISK FACTORS

Rid the job of risk factors

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.

Types of Controls

The following control measures are widely accepted as intervention strategies for controlling workplace ergonomic hazards:

Engineering Controls. Reduce or eliminate potentially hazardous conditions through design, redesign, substitution, and replacement.
Management Controls. Change work procedures and scheduling to reduce exposure to the hazard.
Interim Measures Temporary use of engineering and/or management controls until permanent controls are in place.

Engineering Controls

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.

Workstation design

Aspects of workstations you can change with engineering controls include:

workspace layout,
work surfaces,
standing and walking surfaces,
seating,
storage,
work fixtures,
work environment.

Computer workstations

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.

Work Surfaces

Surface needs to be deep enough to allow proper keyboard positioning and to accommodate a monitor viewing distance of 18-24”.
Surface needs to be wide enough to accommodate keyboard, mouse and reference material.
Surface height (or keyboard height independent of the main surface) should be adjusted for the user or adjustable for multiple users.
Avoid resting your wrists on a hard or sharp surface (use a wrist rest if necessary).
Leave enough leg room to allow your legs to move freely.

Keyboards

Should be thin and detachable. Must be positioned low enough to keep wrists straight, shoulders relaxed, and elbows angled between 90 and 120 degrees. (A wrist rest can help you maintain straight wrists.) Alternative keyboards now on the market provide additional options which may alleviate discomfort.

Mouse or Trackball

Should be within easy reach and at the same height as the keyboard. Trackballs may be a better alternative because they eliminate some arm movement required by the mouse.

Monitors

Should be positioned so that the top of the screen is slightly below eye level, for a viewing angle of about 30 degrees. The viewing distance should be 18-24”.

Chairs

Should have adjustable back support that presses firmly against your lower back and extends at least up to mid-back. Should have an easily adjustable seat height to permit your feet to rest flat on the ground with a knee angle of roughly 90 degrees. (some people might need a foot rest to achieve this angle.) Should have a rolling, five-pronged base for stability and to prevent unnecessary twisting. Should have adjustable padded arm rests to support the weight of the shoulders and the arm. Should have an adjustable seat pan to allow the computer user to work comfortably in a forward or reclined position.

Workspace layout

Workspace layout and arrangement should be carefully designed so that it meets the following requirements:

The workspace should be adjustable to fit each worker's size.
The worker should be able to maintain the neutral position and avoid awkward or extended reaches and jerky movements while performing the task.
A full range of motion with adequate leg room, as well as a variety of working positions to avoid static postures should be provided.
The worker should have adequate space for access to all necessary tools and equipment, and frequently used tools should be within easy reach.

Work surfaces

Work surfaces should be at the proper height and angle for the individual worker's size and tools and equipment used.
They should permit neutral postures and be adjustable, especially where different kinds of tasks are performed or the workstation is shared.

For example, where workers inspect or assemble small parts, or perform other visually intensive task, work surfaces could be tilted to reduce neck, shoulder and arm strain.

Walking and standing surfaces

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.

Seating

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:

Adequately support the back and legs.
Have padded seats.
Have separately adjustable back and seat cushions.
Permit feet to be supported either on the floor or with a foot rest.
Be easily adjustable while seated.
Be able to swivel for most tasks.
Isolate the worker from whole-body vibration.
Have adjustable arm support when appropriate.

Storage

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 and frequently used items close to the worker.

Work fixtures

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, these guidelines should be followed:

Select tools that allow the wrist to be held straight and that minimize twisting of the arm and wrist. Good working posture can be maintained when properly designed tools are used.

Select tools that allow the operator to use a power grip, not a pinch grip. Minimal muscle force is required to hold objects in a power grip posture. The pinch grip requires excessive fingertip pressure, and can lead to a CTD.

Avoid tools that put excessive pressure on any one spot of the hand (i.e., sides of fingers, palm of the hand).

For power or pneumatic tools, select tools with vibration dampening built in whenever possible. Provide personal protective equipment such as gel-padded gloves to reduce exposure to vibration.

Work environment

Workplace environmental factors interact with those the worker and the task bring to the job, and deserves careful consideration. Methods to minimize work-environment hazards include:

Isolating equipment or operations that produce loud or distracting noise.
Making lights bright enough without causing glare.
Isolating hands and feet from cold.
Reducing whole-body vibration while riding in vehicles or standing near equipment.
Isolating workers from excessive heat by providing adequate cooling and ventilation.

Management Controls

Management controls are management-dictated procedural and scheduling changes designed to reduce or prevent exposures to ergonomic risk factors. Although engineering controls are preferred, management 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 management controls do not eliminate hazards, managers must continually ensure safe procedures and policies are followed to make sure exposure to hazards is minimized.

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

Safe procedures that maintain workers in neutral postures, and reduce frequency, duration, and severity of exposure to risk factors. Lifting, carrying, pushing or pulling objects can strain the back, arms and shoulders. Strength and lifting limits should not be exceeded; extreme muscular exertion can cause injury. Effective lifting techniques should always be used.
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.
Requiring the use of Personal Protective Equipment (PPE) while performing tasks.
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.

Work rates

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.

Job Enrichment

Tasks involving repetitive motion are major contributors to CTDs. You can minimize repetition by:

Using automation, such as in stapling, sorting, labeling or filling operations.
Changing the job to include tasks that don't use the same muscle groups.

For example, in a check-sorting operation, instead of having one person open mail, another take stamp them and yet another record the figures, each worker could do each of those tasks.

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. More on backbelts Still more!.

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?

Safety System Improvements

An effective ergonomics program operates within a larger safety management system that is composed of many interrelated programs. Each program or "subsystem" includes specific processes that may not interrelate directly to ergonomics. 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 follows:

Design root causes. Inadequate design of the safety management system. The development of written safety plans, policies, processes, procedures and practices is very important to make sure appropriate conditions, activities, behaviors, and practices occur.
Implementation root causes. Failure to carry out the plan as designed. Failure to effectively implement the safety management system is critical to the success of the system. You can develop a wonderfully designed system, yet if it's not implemented correctly, it won't work.

A missing or inadequate component in any one of these subsystem processes might negatively impact on ergonomics. Examples of safety subsystems include:

Safety training
Safety accountability
Hazard identification and control
Employee involvement

Incident/Accident investigation
Safety communications
Evaluation and improvement

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.

Making safety system improvements might include some of the following:

Including "safety" in a mission statement.
Improving safety policy so that it clearly establishes responsibility and accountability.
Changing a work process so that checklists are used that include safety checks.
Revising purchasing policy to include safety considerations as well as cost.
Changing the safety inspection process to include all supervisors and employees.

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.

Last words

Almost everything you need to know about ergonomic control strategies, right? Well, not quite, but you do have a good introduction to them. Remember, ergonomics control strategies may not be immediately obvious. If you can't figure out an effective solution, don't forget to take advantage of an outside expert (my pitch for our Oregon OSHA ergonomist). Participating in the consultation process with an ergonomist is a real win-win for your company and an excellent education for you. Time to take the module review quiz, so let's go. Answer each question as best you can. Scroll up the page to review if you like.

Module Quiz

21. Which of the three ergonomics control strategies is most effective?

a. Technical Controls
b. Engineering Controls
c. Management Controls
d. Interim Measures

22. Which of the three ergonomics control strategies limits exposure to the hazard?

a. Technical Controls
b. Engineering Controls
c. Management Controls
d. Interim Measures

23. Which of the following is not listed as a component of proper computer workstation design you must address to maintain proper posture?

a. the printer
b. the work surface
c. the keyboard
d. the chair

24. According to the text, effective and safe procedures should incorporate each of the following ergonomics goals, except:

a. decrease recovery time
b. maintain neutral postures
c. reduce duration of exposure
d. reduce frequency of exposure

25. According to the text, inadequately developed written safety plans, policies, processes, procedures and practices is describes this safety management system failure:

a. system implementation failure
b. system design failure
c. system personal failure
d. system management failure

Good work on Module 5! Remember, if you can get rid of the hazard, you don't have to manage behavior. That's smart business. Continue on to Module 6 to learn more about how to implement engineering and management controls. If you have any questions or comments, just drop me an email at monique.e.schmidt@state.or.us.

Please take a brief survey to tell us what you think of the Oregon OSHA Web site.

Adobe Reader is required to view PDF files. Click the "Get Adobe Reader" image to get a free download of the reader from Adobe. Available for Macintosh or Windows.