Introduction
The increasing use of computers has affected virtually every office on campus. To take maximum advantage of computers without compromising the health of workers, it is important that the computer workstation, the work environment, and work practices be adapted to the needs of the worker. Ergonomics is the adaptation of machines to people. The University of North Carolina at Chapel Hill is committed to providing a safe and healthful environment for all workers. Application of ergonomic principles to computer workstations is a priority for the office work environment.
There are ways to solve, or at least alleviate, most of the problems associated with computers. Solutions include adjusting and controlling the physical environment, the design of the desk and chair, the placement of the screen and keyboard, the position of the document, and the placement and intensity of office lighting. Alleviation of health problems utilizes ergonomic principles, which entail the planning and adapting of equipment, tasks and office procedures to promote well-being and efficiency of workers.
The following guidelines are intended to provide specific examples of how workers can adapt their workstation and work practices to minimize stress and potential adverse effects of computer usage.

Applicability of the Guidelines
Guidelines regarding office furnishings and computer equipment must be followed when making new purchases. Priority should be given to replacing existing furniture and equipment of workstation users meeting the definition of "heavy" workload (as defined in Section 2-13) and furniture and equipment used by the public, such as in computer laboratories. Guidelines regarding work practices are to be followed by all workstation users.

Computer Workstation Guidelines

Visual
Visual problems are the most frequently reported problems by computer workers. Complaints include eye discomfort, eyestrain, burning, itching, irritation, and aching. Other less frequent symptoms include blurred vision, color fringes, and reported deterioration of visual acuity. Severe optical discomforts (eye irritations, soreness, and tiredness) may not go away within a short period of time following work and may even be present at the start of the next day's shift. Data suggest that some types of computer work produce greater levels of visual complaints than traditional office or visually demanding inside work.
Prolonged attention to visual detail with reduced eye movement in a restricted visual field can cause eyestrain and other problems. In addition, eyestrain is caused by high light levels and glare from outside light sources and/or reflections from surfaces in the environment. Finally, air temperature and humidity can lead to sore eyes.
Lighting: Large contrasts with the general environment should be avoided. Computer users are generally more comfortable when the room lighting is reduced below that associated with normal office lighting. A luminance in the range of 200 lux to 500 lux is recommended for workplaces with visual display terminals (ANSI/HFS 100-1988).
The contrast ratio between screen and source document should not exceed 1:10. Some experts argue that the ratio should not exceed 1:3. Some studies suggest that the contrast between screen characters and the source document is more important than the contrast between the screen background and the source document. Users should try different screen configurations to find the one most comfortable for the individual user. Use of directional lamps for hard copy are beneficial where both the computer and paper copy are necessary for normal work activities.
Positioning of the eyes and the screen with respect to light sources is also important for the comfort of the operator. Avoid having lights (or windows) in the visual field of the operator. Avoid having lights (or windows) behind the operator that will reflect on the screen. Ideally, fluorescent lights should not be directly overhead and should be perpendicular to the screen. Other ways of minimizing glare include use of window shades or curtains, taping a piece of cardboard across the top of the monitor to act as a visor or placing a glare proof filter on the screen. Although filters may be necessary to avoid glare on the screen, they also increase the contrast ratio and thus should only be used in situations where other means of reducing glare are not feasible. Other effective glare control can be maintained through one or more of the following measures:

• Use recessed, indirect and baffled lighting
• Provide windows with curtains or blinds
• Design workstations to allow monitor orientation to avoid harsh light sources
• If a workstation is located near a window, place the monitor at a right angle to the window
• Locate the worker so that light comes from the side or behind the worker to avoid shining directly onto the screen and into the worker's eyes
• Provide screen hoods at worker's request to block angular reflections and glare sources
• Provide detachable anti-glare filters at worker's request
• Use full spectrum lighting
• Use furnishings with a matte, non-reflective finish
• Paint walls in a matte, non-reflective coating
• Insure room and task lighting is free of flicker

Musculoskeletal Issues
Musculoskeletal problems are common to many sedentary jobs. Because the body is designed for movement, a fixed position is more tiring than a dynamic one. Computer worker complaints are most often related to the neck, shoulders, back and wrists. Complaints mentioned less often involve the arms, hands, and legs. Researchers indicate musculoskeletal symptoms are more frequently reported by computer workers than workers in traditional office jobs.
Posture: Good posture while using a computer is the primary defense against fatigue and stress. The back should be kept straight and the arms and shoulders relaxed. Avoid placing the body in awkward positions. Examples include lifting with the arms above shoulder height; making long, extended reaches; using one shoulder as a telephone rest; and working with elbows outstretched.
According to scientific and medical information, serious musculoskeletal health symptoms are most often associated with computer jobs requiring constrained working positions for an entire work shift. In a seated position, the computer worker is subject to continuous stress on almost all postural muscles. The amount of stress is dependent upon the position of various parts of the worker's body. Holding the head to the side or forward may lead to neck and shoulder fatigue and pain. Other neck and shoulder complaints result from the use or position of the worker's arms. For example, elevation of the arms will add to neck and shoulder strain. Prolonged, constrained postures required by the job will make this condition worse.
There are several common characteristics of computer jobs that have been related to increased musculoskeletal complaints. These include the design of the computer and workstation equipment, the nature of the task, work pace, repetitiveness of the job, work and rest break schedules, and personal attributes of workers. In order to provide a workstation which takes ergonomic principles into consideration, the worker must have flexible equipment which allows each individual to perform his or her work in a manner which alleviates musculoskeletal problems.
Keyboard: Display screen and keyboard should be positioned in front of the worker to avoid placing the body in a position where the back and neck must be twisted in order to use the keyboard. The position of the hands and wrists relative to the keyboard is an important consideration given the prevalence of wrist disorders such as carpal tunnel syndrome, tendonitis, etc. Factors which may also contribute to the disorders are repetitive motion and external trauma, as related to keyboard and mouse use. The keyboard in combination with the seating and work surface should be adjustable so that the user, while seated in a normal, upright position, is able to operate the keyboard with his/her forearm, wrists and hands in a neutral position approximately parallel to the floor. The keyboard should be at the fingertips with the arms and hands in a slightly downward slope. The use of keyboard shelves and under-the-desk trays should not be used if they interfere with leg placement or cause a bending of the wrists.
Wrists should be kept straight. Wrists should not be rested on sharp edges, such as a desk edge. The space in front of the keyboard should be sufficient to provide support for the hands and arms of the user. Palm, hand, wrists, or arm supports may be useful to help keep wrists flat. A rolled up towel can be used to provide a simple wrist support.
Monitor: Display screens should be placed at a height appropriate to and determined by the worker. The top of the screen should be no higher than worker's eye level and the bottom of the screen no lower than forty degrees below the worker's eye level. Worker distance from the screen should be a matter of worker preference.
Monitors should be placed directly in front of the user with an eye-to-screen distance of 12 to 30 inches. The top of the screen should be at eye level so that the screen work area is slightly below the horizontal plane. Users who wear bifocals may find that a lower monitor height will avoid the necessity to tilt the head back to view the screen. Monitor pedestals, swivel arms, or phone books may be used to adjust monitor height. If too high, do not put the monitor on top of the disk drive unit.
While there are differences of opinion with regard to the best color combinations for legibility and comfort, dark letters on a light background is a reasonable choice. Choose colors that are pleasing to the user. Green, blue and orange are generally found to be more soothing than red, yellow, and other bright colors.
A properly designed chair is essential for computer users. It affects posture, circulation, pressure on the spine, and comfort. Poor chair design can be one of the most significant causes of musculoskeletal stresses and strains.
A good backrest is an important feature of the chair. It should adjust up, down, backward, and forward. The height of the backrest should be adjusted so that it supports the inward curve of the lower spine (lumbar). If the lumbar support is inadequate, a back support pillow or rolled-up towel may be used. The backward/forward adjustment is to be used to maximize the support of the thighs without pressing against the back of the knees which may cut off circulation. Ideally, the angle between the trunk and thighs should be greater than 90 degrees. Backrests should allow for the worker to lean back to a comfortable resting position.
The seat surface should be a reasonable composition so that the user does not suffer pressure from a hard seat or become engulfed in a soft seat. The cushion should have minimum contouring and ridges. Chair stability and mobility are critical for ease of movement while in the chair. There should be five legs and the casters must be matched to the surface, i.e., for carpet or hard surface. Seats should be gently rounded on the front to avoid interference with blood flow to the lower legs. The height of the seat pan should be adjustable so that the user's feet are firmly rested on the floor or a footrest. The thighs should be approximately horizontal and the lower legs vertical.
Arm rests, if provided, should be at least 18-inches apart and allow the upper arm to hang naturally from the shoulder when the forearm is on the arm rest. Arm rests should be removed from the chair if they interfere with the furniture and prevent normal positioning with the keyboard and monitor.
Tables should be adjustable when needed for proper screen and keyboard heights and adequate leg room.
Footrests should be provided at worker's request to ensure that the worker's thighs are parallel to the floor. A stack of old telephone books taped together makes an inexpensive footrest. Improper seat height and design can restrict blood circulation.
Document holders should be provided and should be adjustable to the height, distance, and angle of the screen to avoid possible glare and unnecessary worker movement which can cause neck, shoulder or back aches.
Furniture should be arranged to provide adequate amount of leg room to allow freedom of motion.
An adequate work area for paper work, etc., should be provided on one side of the computer. The side this work area will be on should be determined by the worker.

Figure 1 - Areas of Adjustability

Stress
Job stress as reported by computer workers is often described in terms of psychological and physical strains such as frustration, anxiety, irritability, anger, depression, stomach or gastrointestinal disturbances, muscle and physiological tension. As is true with visual and musculoskeletal health complaints, the primary cause of job stress is lack of consideration of the relationship between the worker and the work environment, including eyestrain and musculoskeletal problems. Some of the factors which can contribute to job stress include poor working conditions, excessive noise, excessive job demands and work pace, lack of control, and lack of participation in the implementation of computer use.
In order to alleviate stress, attention should be addressed to those areas which contribute to stressful conditions. Excessive and/or annoying noise creates stress which can have an adverse effect upon workers' health, safety, and productivity. Acoustic pads should be installed under keyboards and printers at worker's request. Impact printers should be provided with acoustic covers where necessary to reduce sound levels to 65 dBA as measured at the workstations. All noise sources in the surrounding environment should be controlled to ensure that the total sound level measured at the workstation does not exceed 70 dBA.
Because of the heat generated by computers and other concerns which affect stress, the following are recommended: Every effort should be made to locate workstations at a reasonable distance from heating and cooling vents. Vents should be ducted and shielded to divert airflow away from computer workers. Because of the heat generated by some machines and the effect of heat on eyestrain and working conditions, office temperatures should be kept between 68 and 78 degrees F.

Combined Health Effects
Prolonged and continuous use of computers affects stress level, eyestrain and musculoskeletal problems. Occasional changes in any work will provide an opportunity to flex the body, adjust eyes to different sight conditions, and relieve the tedium of repetitious work. Breaks, therefore, alleviate or prevent visual, muscular and psychological fatigue and may improve overall performance.
Rest Breaks: To the extent practicable, managers should provide a variation in the tasks to be performed to minimize eyestrain, musculoskeletal problems and stress. Breaks from the computer should include movements to stretch, limber, and relax muscles. Short, frequent breaks are more beneficial than longer, less frequent ones. It is important to remember that no single position is appropriate for long periods of time; shift or vary the manner of sitting. Break up the sitting period by standing, stretching, or walking.
Managers should take into account the following in working out a schedule:

• The National Institute for Occupational Safety and Health recommends breaks of fifteen minutes for every hour for jobs that require more than two (2) hours of constant viewing time, constant rapid muscular action, fixed positions for extended periods of time, or for jobs that are highly repetitive and boring.
• To alleviate eyestrain and musculoskeletal problems, computer workers need to be given an opportunity to relax the eyes by looking at distant objects and to move the body. This will require alternative work assignments during some part of the day for heavy and moderate users.
• Workers whose workstations do not substantially comply with these guidelines may require additional non-computer work to alleviate the problems caused by non-compliance.

Electrical Safety
All electrical cords and cables shall be installed and routed in accordance with National Electric Codes.

Electromagnetic Radiation (EMR)
In the past some concerns have been raised about possible adverse health effects from exposure to electromagnetic radiation associated with computer use. Most frequently these concerns have centered around female computer users who have experienced problem pregnancies such as spontaneous abortion, still birth, premature birth, low birth weight and congenital defects.
A study recently completed by NIOSH and published in the New England Journal of Medicine concluded: "The use of video display terminals and exposure to the accompanying electromagnetic fields were not associated with an increased risk of spontaneous abortion." The findings of this major study should be considered the most important to date in addressing concerns related to the potential for adverse reproductive outcomes as a result of working with computers.
These guidelines will be revised from time-to-time as more data are available regarding environment, health and safety and computer use.

Assistance
Environment, Health and Safety Office staff are available for consultation on workstation design and work practices. Environment, Health and Safety also has a software package that is available upon request that guides the user through a self-inspection of his/her workstation. Call 962-5507 and ask for computer ergonomics assistance.