The following is a complete transcript of the Summary and Appendix 2: Some Questions and Answers from Visual Display Units: Radiation Protection Guidance (Occupational Safety and Health Series No. 70).

This document has been prepared by the International Non-Ionizing Radiation Committee of the International Radiation Protection Association in collaboration with the International Labour Organization.

It has been provided for the information of staff. The book is available for loan or for perusal at the Risk Management Unit, Personnel Services, T.C. Lamble Administration Building.

Summary

The visual display unit (VDU) has become a major element in the modern work environment as an interface between operator and computer. The discussion as to whether work at VDUs can affect human health has been centred on different types of effect such as eye changes or discomfort, musculoskeletal problems, adverse reproductive outcomes, skin disorders and stress reactions.

Ergonomic and organisational concerns pertaining to eye discomfort, stress reactions or pain in the neck or the wrists and other musculoskeletal disorders, motivate a number of preventive or remedial actions. Such actions should be directed towards the VDU entity, the workplace, the work environment, the design of the work task and work organisation. A large number of national and international provisions, studies, documents and recommendations have been published.

A number of careful studies have measured the electromagnetic radiation or fields from different types of VDUs. Until recently most screens have been based on the cathode ray tube (CRT) technique. Liquid crystal (LCD), plasma and electroluminance (ELD) displays are more recent advantageous alternatives because of low weight (easy to carry around) and lower electromagnetic fields. Their disadvantages are poor visual ergonomics (low contrast and small usable viewing angles) and long change-over times. However, LCD screens have, during the last years, reached a more acceptable stage of development. This guide focuses on radiation issues of CRT-based VDUs, which may be summarised as follows:

X-ray radiation: This is produced within the CRT. The glass material of the tube, however, effectively prevents any leakage of X-ray radiation outside the tube. Thus, X-ray emission from VDUs is not detectable.

Ultraviolet radiation (UVR): UVA (long wavelength UVR) radiation can be detected from certain VDUs. The levels are, however, insignificant compared to present IRPA/INIRC general population and occupational standards, and also insignificant compared to emission from other sources (e.g. sunlight through windows).

Light: Visible radiation is emitted and is necessary in order to perform the intended function of the VDUto provide a visual display. Luminance levels are adjustable to the comfort of the operators and are far below current exposure limits.

Infrared radiation (IR): IR is emitted from all bodies. Since all surfaces of the VDU are at room temperature or slightly above, IR can be detected, although at levels far below any limits of concern for health.

Low-frequency electromagnetic fields: In the radiofrequency (very low frequency, VLF) range and extremely low frequency (LEF) field range, electric and magnetic fields can be measured. The dominant sources are the power supply (at 50/60 Hz) and the horizontal and vertical sweep generators (at frequencies of 15-35 kHz and 50-80 Hz, respectively). These fields do not represent any risk factor when compared with current IRPA/INIRC general population or occupational guidelines. Epidemiological studies have generally failed to show an association between the use of VDUs emitting those fields and various health problems that have been suggested as due to those fields. Attempts to relate health hazards to explicitly measured fields emanating from VDUs have also been unsuccessful.

Electrostatic fields, air ions: Electrostatic fields at VDU workplaces have been suggested as a possible cause of skin disorders. The magnitudes of electrostatic fields are greater in the environment of VDU operators than for office workers without VDU work. This may, in turn, cause changes in light air ion concentrations. No correlations between electrostatic fields from the VDUs or air ions at operator positions and skin problems have, however, been found.

Ultrasound: Airborne ultrasonic (acoustic) radiation is produced in CRTs as a result of mechanical vibrations generated in the core of the flyback transformer (responsible for the horizontal sweep of 15-35 kHz). The sound pressure levels found are considerably below existing general public and occupational limits of exposure levels. Some individuals may detect this or a subharmonic in the higher noise frequency region as an annoying factor.

Health effects which have been suggested as caused by exposure to electromagnetic radiation or fields include adverse pregnancy outcome, skin disorders and cataracts of the eyes. Comparison of the occurrence of cataracts and of adverse pregnancy outcomes among VDU operators to those of the reference group have failed to show an excess occurrence due to VDU work. In some countries, a number of VDU operators have experienced skin complaints. The relationship of these to specific factors of VDU work is not known.

Based on current biomedical knowledge, it can be concluded that there are no health hazards associated with radiation or fields from VDUs. Thus there is no scientific basis to justify shielding or radiation monitoring, nor eye examinations to search for ocular pathology due to radiations in VDU operators. However, since a large number of people are involved in VDU work, it is important that further knowledge is gained on certain areas where our knowledge must be regarded as incomplete:

(a) further investigations should be undertaken to determine the possibility that skin complaints may be related to VDU work;

(b) the possibility of interactions between low-frequency magnetic fields and biological systems requiresin generalfurther work. Consideration should be given to magnetic fields in various situations, and should not be restricted to VDU work situations.

Appendix 2: Some questions and answers

Do VDUs emit radiation?

Yes. VDUs emit radiation, particularly visible light which allows the characters on screen to be seen. Weak electromagnetic fields and very low levels of other radiation, not visible to the human eye, can be detected by sensitive instruments. Similar emissions are produced by television receivers.

Can radiation from VDUs be harmful to health?

The levels of most radiations and electromagnetic fields emitted from VDUs are much less than those from natural sources. such as the sun or even the human body, and all are well below levels considered harmful by expert bodies such as the International Radiation Protection Association and the World Health Organisation. Radiation emissions from VDUs are not considered to be harmful to health.

Are any protective devices needed against radiation from VDUs?

Fear of possible radiation effects has sometimes caused VDU operators to consider protective devices such as special aprons or radiation shields. These are of no value, because they are designed either to shield radiographers from X-rays, which VDUs do not emit, or to minimize low-level electromagnetic fields which are not regarded as hazardous in any case.

How should the workplace be organized if several VDUs are located together?

The weak electromagnetic fields produced by television receivers and VDUs extend in all directions, but their intensity decreases very quickly with distance from the source. A workplace should be organised to ensure that VDU operators are no closer to other VDUs than they are to their own.

Does radiation increase as a VDU ages or is repaired?

There are no components in a VDU which could fail and cause an increase in emission levels while continuing to produce a clear usable image. Because of the nature of their electronic circuits, VDUs will show acceptable displays only if their currents and voltages are within design tolerances, and so an older or repaired VDU will not emit radiation significantly different from a new one of the same model.

Is there any benefit from testing VDUs for radiation emission while they are in service in the workplace?

No. When VDUs first become common, many workers are worried about the new technology. In-service testing in some workplaces may have allayed some worker concerns about radiation from VDUs, but since there is no increase in radiation emissions from VDUs as they age or are repaired, continued in-service testing is unnecessary.

Could radiation from a VDU harm an unborn child?

Given that the levels of radiation from VDUs are much lower than recommended limits, and that these limits themselves incorporate significant safety factors, there is no evidence to suggest that any harm to an unborn child would result from exposure to the radiation emissions from a VDU. Much research has already been done, and more is under way, to resolve this question. The weight of evidence so far indicates strongly that the answer is "no".

How do other types of display screens compare with VDUs?

Flat screen displays, such as the liquid-crystal or gas-plasma displays used in some laptop computers, produce even small amounts of radiation than those which use television-type tubes. It may be sensible to use the new types for special purposes, such as to increase portability or battery life, but concern about radiation emissions should not be a factor in their choice.

Can you reduce the strength of the static and low-frequency electric fields?

It has been shown that these electric fields are very low and have no effect on health. However, if it is found necessary to reduce the glare from the monitor it is possible to use a low-cost plastic screen which has a conductive coating. If the coating is grounded, the electric fields will be reduced to extremely low levels.