CAB - Agricultural Safety Resource Guide: 6 - VIDEO DISPLAY TERMINALS (VDT's)

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Agricultural Safety Resource Guide

6 - VIDEO DISPLAY TERMINALS (VDT's)

Introduction

There are many health concerns associated with video display terminals (VDT's). Some of these are high-voltage electricity, ergonomics, and noise. The greatest concern is whether extremely low frequency radiation fields or higher frequency fields emitted by VDT's pose a problem, particularly to pregnant women. Tests conducted by the NIOSH show that emission levels for all types of radiation are below those allowed in current standards. However, the possible effects of radiation continue to be a concern to employees and remain an unresolved issue.

Most ergonomic concerns regarding VDT's have to do with wrist and eye strain. Eye strain is by far the most common computer related health problem, accounting for more than 10 million cases a year. A person who uses computers heavily can reduce eye strain by adjusting room lighting to reduce glare. Work stations and lighting should be arranged to avoid reflections from the screen or surrounding surfaces. The top-most line of the display should not be higher than the user's eye. The screen and document holder should be the same distance from the eye to avoid constant changes of focus.

Another problem related to the use of computer keyboards is carpel tunnel syndrome. This condition occurs when inflamed tissues in the wrist swell, putting pressure on nerves that pass from the arm to the hand. Many ergonomically designed keyboards are on the market. A moveable keyboard is a plus.

In addition to overall adjustability of equipment, some general guidelines for minimizing fatigue include these:

Posture support: The seat and backrest of the chair should support a comfortable posture permitting occasional variations in sitting position. Chair heights and backrest angle should be easily adjustable.

Arms: When the operator's hands are resting on the keyboard, the upper arm and forearm should form a right angle. The hands should be in a reasonably straight line with the forearm.

Legs and feet: The chair height is correct when the entire sole of the foot can rest on the floor or footrest and the back of the knee is slightly higher than the seat of the chair.

Screen position: Screens that swivel horizontally and tilt or elevate vertically enable the operator to select an optimum viewing angle. If you are planning to buy a new monitor, choose one that conforms to the low-radiation MPR 2 emissions standards set by the Swedish Board for Measurement and Testing. Many new monitors made by IBM, NEC, and Sony meet this standard. LCD displays, like those in notebook PC's, emit no ELF radiation at all.

Laws and regulations

OSHA has no standards that apply specifically to video display terminals or extremely low frequency fields. However, OSHA does have standards that protect employees against overexposure to radiation, noise, and electrical hazards.

Model programs

CAL/OSHA: Four-Step Ergonomics Program for Employers with Video Display Terminal (VDT) Operators.

Suggested articles/brochures

OSHA currently publishes literature on ergonomic factors surrounding video display terminals and carpel tunnel syndrome.

Lewin, I. David. "Small business computing: There are ways to help computer users avoid eyestrain and repetitive-stress injuries." Nation's Business. March 1995.

"How to optimize your computer workplace." Compute. March 1993.

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