Health Hazards Associated With Visual Display Units: Part II

Facial rash/dermatitis

There are several reports concerning facial rashes amongst VDU operators. The complaints varied from itching of the skin to reddening with occasional minor desquamation and small papules. It usually occurs after a couple of hours at work and disappears a few hours after leaving work.

All VDUs generate a positively charged electrostatic field which extends 2-3m in front of the VDU. This field is generated by the interaction of the election beam with the VDU screen and attracts particles of smoke, pollen, and duct, etc. These particles are then drawn to the nearest negative charge or ground which may be the face or hands of the operator. Negatively charged particles will also be drawn to the screen, forming the commonly seen 'dusty' layer.

Various experiments have been carried out to prevent skin reactions amongst known cases. One method tried was to place a glass sheet between the operator and the screen. The results have been conflicting. One case reported the method to be successful whilst another found it of no use in preventing the facial rash. The most successful method appears to be the elimination of build-up of static electricity by replacing normal floor carpets with anti-static carpets and by the grounding of the display terminals.

It is believed that the contact dermatitis is caused by irritating submicron dust particles precipitating on the skin of the VDU operator because they are accumulating static electricity. Manufacturers should try to design the unit so that the outside screen potential is as near to 0V as possible. Periodic cleaning of the VDU screen with anti-static solution will control the dust accumulation and maintaining a constant relative humidity of 50-70 percent should also help.

Epilepsy

There has been concern in the past about people who suffer from epilepsy operating VDUs. In fact, VDU work does not cause epilepsy and a person who suffers from this disorder should not be prevented from being a VDU operator. However, some people suffer from a relatively rare form of epilepsy, known as photosensitive epilepsy. In these people a seizure may be triggered after stimulation by a flickering light source or after viewing striped patterns. The incidence of epilepsy in the population is estimated to be about 2 percent, of whom approximately 4 percent suffer from photosensitive epilepsy. Most of the people who are likely to suffer from an attack will have done so before the age of 20 years and it will probably occur whilst watching television.

The possibility of a striped pattern triggered a seizure depends on various stimulus parameters, such as: area of retina, the number of cycles of the pattern per degree, luminance, and pattern stability.

The epileptogenic foctors of a television or VDU can be reduced by:

1. Using a small screen to reduce the area of retina stimulated.
2. Using white alphanumeric on a black background.
3. Limiting the amount of text on the screen.
4. Avoiding scrolling of the text.
5. Reducing the luminance of the display, either by the operator wearing tinted spectacles or by covering the screen with tinted Perspex.

Recommended: Your Computer and Your Eyes

Despite this information it is still difficult to give an accurate assessment of the risk of a photosensitive epileptic suffering a seizure when operating a VDU. Thus it would be wise for a known photosensitive epileptic to seek medical advice before using VDUs.

Radiation

There has been a great deal of concern about dangerous radiation emissions from VDUs. Radiation may be given off by:

1. The screen (vision, UV, and IR, depending on the phosphor);
2. The cathode tube or electronic damper circuit (X-rays);
3. The electronic components or circuit (microwave, UV, radio frequency).

A number of surveys have been carried out to determine the level of electromagnetic radiation emitted by the VDU. These surveys concluded that the measured values of electromagnetic radiation were at levels substantially below existing limits. The national and international limits for continuous exposure were not exceeded and, hence, the radiation emitted from VDUs is not considered to be a health hazard.

Back To: Part I

Photo Credit: physioclinic.sg