EH&S News

Environmental Health and Safety

University of Massachusetts at Amherst

Editor: Robert DiCarlo Summer 1996 Vol. 2 No. 2

Inside This Issue

Radiation

Video Display Terminals

Pregnancy

Vision

Ergonomics

Work Rest Regimens

References

Work Station Design Features

VDT Radiation

Testing by numerous private and governmental organizations, including the National Institute for Occupational Safety and Health (NIOSH) and the Food and Drug Administration's Bureau of Radiological Health (BRH), has so far failed to show any radiation hazard from VDTs. For example, detectable emissions of X-ray and radio-frequency radiation have been found to be well below the public exposure standards for electronic equipment which produces radiation. (1)

Some researchers have suggested that chronic exposure to extremely low frequency (ELF) radiation may be associated with certain types of cancer. However, virtually all scientific and medical organizations have rejected these claims on the basis that such effects are biologically implausible. (2) Research thus far has failed to show any association between health problems and ELF fields generated by VDTs.

NIOSH has concluded: "The radiation shielding that is already an integral part of the VDT equipment is adequate in protecting the worker against the radiation produced by the machine." (1)

Video Display Terminals

The use of video display terminals (VDTs) on campus has increased dramatically over the past decade. Many people now spend a large portion of their work time in front of a terminal. Prolonged VDT work without adequate breaks can lead to eye strain and musculoskeletal problems. In addition to these health concerns, questions have arisen about the safety of VDTs as a potential source of electromagnetic radiation. This newsletter provides an update on VDTs and offers suggestions to alleviate problems commonly associated with VDT use.

Pregnancy

Thus far epidemiological studies have largely failed to show any association between reproductive problems and VDT use. In a detailed study conducted in March of 1991, federal government researchers found that pregnant women working all day at VDTs do not have a higher risk of miscarriage than pregnant women working at jobs not involving VDTs. The six-year study was conducted on 730 telephone operators in eight southeastern states. (3) Seven other large studies conducted in the U.S. and elsewhere, also have concluded that VDT use does not predispose the worker to reproductive problems. The one exception was a 1988 study by Kaiser-Permanente Medical Care Program in Oakland, CA, which found a higher than expected rate of miscarriages among women working with VDTs for more than 20 hours per week. (2) The study's authors could not explain the cause of the elevated miscarriage rate, but several reasons have been postulated, including constrained posture and job stress.

NIOSH and other scientific organizations have concluded that VDTs do not present a

radiation hazard to the pregnant VDT operator or to the developing fetus. In an article, a representative for the American College of Obstetricians and Gynecologists stated, "In reviewing all the studies and all that we know about VDT radiation, there is nothing in the machine itself that would have any effect on pregnancies." (2)

Vision

Vision problems can usually be traced to improper area lighting, screen glare, and incorrect eyeglass prescriptions. Most eyeglasses are designed for distances of 12 inches (reading) or 20 feet (distance). Since the VDT screen is generally set at 20 inches from the eyes, the operator may need "music glasses," in which the distance for reading is set at 20 inches (the usual distance from a musician's eyes to the sheet music).

General room illumination should be as low as possible, depending upon the demands of other tasks performed in the same area. The screen should be positioned so that lighting (windows or artificial) is not in front of the operator. Ideally, the light source should be behind and off to the side of the operator. Drapes or window shades can help reduce glare from windows. Special screens, glare shields, hoods, and tinted spectacle lenses may also help reduce glare.

Additional visual comfort depends on the units themselves. If possible, check out the equipment prior to purchase. Look for units that are easy to read and have large letters (for better spatial integration). These features should be considered:

1) The rate of decay of the phosphor (the flicker rate) should be relatively slow (less than 30 times per second) to reduce flicker

2) The Dot Matrix - VDTs have a wide assortment of type styles. Those with more space inside letters such as "O" and "R" are easier on the eyes

3) Units with adjustable brightness and contrast controls are preferred

4) Swivel screens or screens that can be tilted slightly down will help reduce glare

Vision Testing

Persons who wear corrective lenses should be tested both with and without them. General eye exams should be conducted annually. The test should include the following:

a) Central visual acuity (sharpness of vision) at distance (ability to see test targets well at 20 feet)

b) Central visual acuity at near point (ability to see test targets well at 13-20 inches)

c) Muscle balance and eye coordination

d) Depth perception

e) Color discrimination

Illumination

Appropriate task lighting should be focused directly on reading materials and work surfaces to avoid eye strain. General room lighting should be set up at relatively low levels, approximately 500-700 lux (45-65 ft-c). Lighting should be increased or decreased to meet individual needs.

Glare Control

· Drapes, shades or blinds over windows should be closed

· The terminals should be properly positioned with respect to windows and overhead lighting. The operator should not face an unshaded window.

· The terminal should be positioned at a 90 degree angle from an unshaded window to prevent direct sunlight from shining on the screen.

· Anti-glare filters may be installed on the VDT screen.

· Direct lighting fixtures may need to be recessed; and baffles may be used to cover fluorescent fixtures.

Ergonomics

Musculoskeletal Effects

Ergonomics is the study of the interaction between the work environment and the body's musculoskeletal system. Many physical problems associated with VDT use can be traced to poorly designed work stations. Conditions such as poor furniture design, incorrect equipment position, and inadequate work breaks may cause or aggravate neck and shoulder problems.

Operating a VDT may involve maintaining a single posture for a long period of time (such as holding one's arms in an upright position). Such static work can create high physical strain. One potentially disabling disease associated with extreme wrist strain is carpal tunnel syndrome. This condition is an inflammation of the wrist's carpal tunnel, the channel through which the hand's arteries, nerves and tendons pass. Maintaining a horizontal line from elbows to fingers and following appropriate work-rest regimens are important measures in preventing this condition. Proper positioning of the screen and the seat may help to alleviate back, neck, or shoulder problems.

Suggestions for improving the ergonomic aspects of VDT use focus on correct work station design and establishment of work-rest regimens.

Seating Position

· Chair should have adjustable seat pan height, backrest height and tension.

· Feet should be slightly elevated so that the seat cushion does not press against thighs.

· Backs should be firmly supported.

· The line from elbow to fingers should be horizontal.

Keyboard and Screen Position

· Keyboard height, screen height and position should be independently adjustable.

· Screen brightness and contrast should be adjustable by operator.

· The top of the screen should be at eye level.

To achieve the proper position, some additional equipment may be needed, such as, a foot stool (a cardboard box will do), a palm or wrist rest, or a forearm pad. In addition, the copy holder should be directly in front of the operator at eye level - this eliminates the need to twist the head constantly while looking from document to VDT screen.

Work Rest Regimens

A 15-minute work-rest break* should be taken after 2 hours of continuous VDT work for operators under moderate visual demand and/or moderate work load. (Moderate visual demand involves working on VDTs for less than 60% of total work time.)

A 15-minute work-rest break should be taken after 1 hour of continuous VDT work for operators under high visual demand or high workload, and those engaged in repetitive tasks. (High visual demand tasks are those which require the operator to work in front of the terminal for 60% or more of their work time.)

Many short breaks are better than a single long break, for better recovery of visual acuity.

*The 15-minute work-rest break can be accomplished by switching to another non-VDT task. It does not imply that an additional work break is required.

References

1) NIOSH Publications on Video Display Terminals, May 1987,

(U.S. Department of Health and Human Services).

(2) Minter, S.G. "Do VDTs Cause Reproductive Harm?"

Occupational Hazards, October 1989 (pp.136-140).

(3) Schnorr, T.M. et al, "Video Display Terminals and the Risk of Spontaneous Abortion,"

The New England Journal of Medicine, March 14, 1991 (p.727).

(4) Potential Health Hazards of Video Display Terminals, NIOSH Research Report,

Publication No. 81-129. June 1981, (U.S. Department of Health and Human Services).

(5) An Evaluation of Radiation Emissions from Video Display Terminals, Publication No. 81-8153, February 1981,

Bureau of Radiological Health, Food and Drug Administration, (U.S. Department of Health and Human Services).

NOTE: This newsletter was developed by staff members of the Division of Environmental Health and Safety (EH&S).

Dr. Frederick H. Bloom, Director of eye care at University Health Services, reviewed the section on vision.

For further information on VDTs or to have an ergonomic assessment of your work area,

contact EH&S, N-414 Morrill Science Center at 545-2682.

Environmental Health and Safety News

is a publication of Environmental

Health and Safety at the University of Massachusetts, Amherst, Massachusetts 01003

Telephone: 1- 413-545-2682

fax: 1- 413-545-2600

e-mail: safety@admin.umass.edu

http://www-unix.oit.umass.edu/~safety

Director: Donald Robinson