ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

 

Introduction

The widespread use of VDTs has been accompanied, however, by expressions of concern from VDT operators, trade unions, and the media about possible adverse health effects associated with VDT use. Adverse pregnancy outcomes, eye problems and skin disorders have been blamed on the electromagnetic radiation emissions from VDTs.

Radiation and the VDT

Some VDTs currently in use are based on cathode-ray tube (CRT) technology and the information in this bulletin applies only to this type of VDT. The VDT is designed to emit visible radiation (light) with a brightness that is adjustable by the operator. In creating the display, however, other types of electromagnetic radiation are also generated, in particular, extremely low frequency, radiofrequency, infrared, ultraviolet and X- ray emissions.

The CRT is an evacuated glass tube which has a source of electrons at one end and a screen, which is coated on the inside with a phosphor, at the other. When a sufficiently high voltage is applied to the CRT, a focussed beam of electrons is produced which is then scanned across the screen. The beam is switched on and off in order to generate the display. The interaction of these electrons with the phosphor causes the emission of visible radiation, plus a small amount of ultraviolet radiation, from the screen. This interaction also produces low energy X-rays which are absorbed by the thick glass envelope. Some infrared radiation is emitted as a result of heat generated within the electronic circuitry during VDT operation.

Radiofrequency radiation is emitted by the horizontal deflection coil which moves the beam across the screen, by the CRT itself and by the extra high voltage transformer which supplies the voltage necessary to accelerate the electron beam in the CRT. Extremely low frequency electromagnetic fields (EMF) surround the AC power connection and the vertical deflection coil. Radiofrequency emissions and extremely low frequency EMF's are not confined to the VDT screen - they occur in all directions from the VDT.

Alleged Health Effects

Eye problems

Many surveys have shown that VDT operators suffer from eye strain, nausea, headaches and blurred vision more often than other office workers. These subjective complaints are also described by people performing other close-visual tasks and indicate that either the display needs adjusting, the screen should be relocated, or the operator's eyesight needs correcting. VDT emission levels of radiation known to cause cataracts are either not detectable or are very low. Indeed, no survey has shown that VDT use causes cataracts.

Skin disorders

Almost all cases of skin disorders among VDT operators have occurred in northern Europe. There, the typically dry atmosphere may be an important factor. The build-up of electrostatic charges on the operator's body, the presence of atmospheric aerosols in off ice environments and the susceptibility of the operator to skin problems may all be contributing factors. The VDT's electrostatic field is not considered to be involved, although further studies are being undertaken. The humidity in Australian offices is somewhat higher, which could explain the lack of reports of local incidence. Ultraviolet radiation emissions from VDTs are not considered to cause skin disorders either.

Adverse pregnancy outcomes

Allegations that adverse pregnancy outcomes among VDT operators are due to radiation emissions are tested by two types of study. The results of animal studies, where chicken eggs or pregnant mice are exposed to radiation similar to that from a VDT, are inconclusive. In any event, they cannot predict human experience. Reliable epidemiological studies conclude that the incidence of adverse pregnancy outcomes among VDT operators and women who do not operate a VDT are not significantly different. So there is no firm evidence to support the above allegations.

Summary of ARPANSA Measurements

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has measured the radiofrequency, microwave, ultraviolet and X-ray emissions from 70 different models of monochrome and colour VDTs. These measurements were made at ARPANSA using very sensitive and accurate equipment, generally with the VDT screen filled with "M"s and set at maximum brightness. The results have been published in the Clinical & Experimental Optometry 69:2 March 1986 journal (PDF 1,072kb) as "Electromagnetic radiation emissions from video display terminals (VDT's)", where the emission levels are compared with exposure limits recommended by the International Radiation Protection Association (IRPA) and the Standards Association of Australia. This Report also reviews the studies into the alleged adverse health effects.

The above measurements showed that -

• radiofrequency radiation was detected, but at levels which were low compared to recommended exposure limits,
• no microwave radiation was detected,
• ultraviolet radiation was detected, but at levels which were very much lower than recommended exposure limits, and
• no X-ray emission was detected.

The levels of infrared radiation emitted from nine VDTs have also been measured at ARPANSA and found to be less than that emitted from a human hand.

Extremely low frequency (ELF) electromagnetic fields were not measured at ARPANSA as they were not considered to be a hazard. Other studies have reported that these VDT fields are less than the 50/60 Hz IRPA exposure limits. Still, concerns about the health implications of long-term exposure to ELF magnetic fields have recently been expressed. Current scientific opinion about these implications is in dispute by minority groups and further studies are in progress.

Conclusion

The electromagnetic radiation emissions from VDTs that were measured by ARPANSA are alleged to be responsible for adverse health effects among VDT operators. These allegations are not supported by either animal studies or reliable epidemiological studies. Furthermore, the emission levels from VDTs used in Australia are less (and, in most cases, very much less) than the relevant recommended exposure limit. It is therefore concluded that these emissions are not a hazard to the health of VDT operators or to the foetuses of pregnant operators.

 

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