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The latest studies of computer monitors show a definite link between radiation exposure and miscarriage or birth defects

The latest studies of computer monitors show a definite link between radiation exposure and miscarriage or birth defects.

On 27 July, the Health & Safety Executive announced that pregnant women who use computers with video display units (VDUs) are not at increased risk of miscarrying. Their good cheer was based on a study published in July's British Journal of Industrial Medicine (Vol 49 No 7). The study, which examined 450 pregnant women, was the first to be carried out in a UK working population. According to Dr Eve Roman, as quoted in the press release, "We found it made no difference whether a woman worked on aVDU as part of her general day, whether she just used it occasionally or whether her only contact with a VDU was that it happened to be in the same room." The study concluded: "For the many women who use VDUs in their jobs, this finding provides reassurance."

In fact, Britain may be a lone wolf in decrying what it views as scaremongering. Mounting evidence shows a definite relationship between exposure and adverse pregnancy outcome, prompting many other countries to adopt safety regulations or exempt pregnant women from having to work on screens. WDDTY commissioned Simon Best, editor and publisher of Electromagnetic News, and something of a walking encyclopaedia on the subject, for the latest studies of hazards.

Considerable ongoing controversy surrounds the claims of health hazards from using VDUs. Claims of increased headaches, tiredness, skin and some eye problems in operators have been increasingly accepted by occupational medicine specialists and preventive practices recommended. The growing problem of repetitive strain injury (RSI) has recently been highlighted by successful court action by journalists and other operators. However, claims of increased malformations and miscarriage in pregnant women have generally been disputed by those authorities charged with recommending safety guidelines, relying on the inconclusive and contradictory results of studies to date, despite clusters of adverse pregnancy outcomes and increasingly strict guidelines on exposure by certain countries. As for the claim of adverse effects from the electromagnetic fields(EMF) emitted by VDUs, opponents cite the low general level of fields generated, uncontrolled ergonomic factors, and general stress or auto suggestion to dismiss such possibility. However, some very recent research may force them to revise their views.

VDUs emit up to eight different types of radiation, from (ionising) X-rays, almost all of which are absorbed by the glass of the cathode ray tube (although this may not be the case with older or damaged models); to ultra-violet: infra-red; radio-frequency; microwave; ELF; pulsed and static fields. A significant proportion of these consist of pulsed 50Hz and 15-20 kHz fields. (See box for definition of terms.) Other laboratory research suggests that pulsed fields may be the most potentially damaging to animals and humans because of their greater penetrative effects.

Claims of clusters of miscarriages and other problems began to emerge in the late Seventies, primarily in North America. In a recent book entitled VDU Terminal Sickness: Computer Health Risks and How to Protect Yourself (Merlin Press, 1991), journalist Peggy Bentham lists over 20 clusters or studies of adverse pregnancy outcome in various countries between 1979 and 1989.

In 1982, Dr Bernard Lee conducted a survey, on behalf of the British Civil Service Medical Advisory Service, of 803 women at the Department of Employment in Runcorn, Cheshire. These women worked at least 10 hours per week with VDUs in the three months prior to and the three months after conception. Their pregnancy outcomes were compared to a control group of women of the same age who worked in the same office complex but who were not regularly using VDUs. According to Bentham, Dr Lee found that over 43 per cent of the pregnancies in women who worked at VDUs ended unsuccessfully. Among the VDU operators, out of 55 pregnancies there were 14.5 per cent miscarriages, 6.7 per cent stillbirths and 22 per cent malformations, compared to a 16 per cent adverse pregnancy outcome in the control group of 114 pregnancies. Dr Lee concluded: 'The figures . . . indicate that there is more than a 95 per cent chance of there being a connection between VDUs and miscarriage."

In a Swedish study of birth malformations reported at the first International Conference on Work with VDUs, held in Stockholm in 1986, 4,117 female clerks at Social Security Bureaus were split into five groups, from those with no VDU exposure to those who had been exposed to VDUs for a maximum of 15 hours a week. In group B, 412 women who used VDUs for not more than three hours a day, there was a 100 per cent increase in significant birth malformations over that expected. The incidence of birth defects in group A, 2,748 women using VDUs more than two hours a day, was four times higher than would be expected for non users in the general population. (Work with Display Units, by B. Knave and P Wideback, eds, Elsevier, Amsterdam, 1987.)

In 1986 the Japanese General Council of Trade Unions surveyed 13,000 VDU workers, including 4,500 women of whom 250 became pregnant or gave birth during the time of the survey. The researchers observed that the number of miscarriages, premature births and stillbirths correlated to the amount of time spent using or working near a switched on VDU. Of those pregnant women who used the VDU for one hour daily, 25 per cent had a combination of miscarriage, deformed babies and stillbirths. Of those who had spent six hours daily at a VDU, 66 per cent had adverse outcomes. ("Japanese Miscarriages Blamed on Computer Terminals," New Scientist, 23 May 1985.)

In one of the first studies to link miscarriage and birth deformities with actual radiation from VDUs, a Polish team, led by Dr Mijolajczck, reported their findings at the above mentioned international conference in 1986. They found a significantly greater rate, varying from 25 per cent to 66 per cent, of spontaneous miscarriage (mainly in the early stages of pregnancy), malformed offspring and still births in pregnant VDU operators than in pregnant women working as clerks with no exposure to VDUs.

Two factors were found to be significant. First, the increased number of hours worked at a VDU correlated with a significantly higher number of adverse pregnancy outcomes.

Secondly, radiation and static levels were found to be much higher around some makes of VDU than others. Specifically, the EMF levels were much higher around the Raytheon and Mera VDUs than around the Westinghouse models. And the static electricity measured above the keyboards (1 metre above the ground and 40cm from the screen) varied between 160V and 180V on different models of Raytheon VDUs, between 100V and 600V on different Mera models, while it was reduced to between 0 and 60V around different Westinghouse VDUs.

Besides such differences in emitted radiation, the team also found that problems affecting the reproductive system were significantly higher among both men and women users, including incidence of fertility and various menstrual problems.

A study by Goldhaber, Polen and Hiatt at the health organisation Kaiser-Permanente, in Oakland, California, found that women who used VDUs more than 20 hours a week had more than twice as many miscarriages as women doing other types of work. Their survey of 1,583 pregnant women showed that the risk of both early (less than 12 weeks) and late (12 weeks or more) miscarriage increased approximately 80 per cent for all women who worked on VDUs for more than 20 hours a week, compared to those doing similar work without VDUs. A 100 per cent increase in miscarriage was found when VDU operators were compared to non working women. The results also showed a 40 per cent increase in birth defects for both moderate (5-20 hrs/week) and heavy (over 20 hrs/week) use, but the number was too small to support a statistically significant link. (American Journal of Industrial Medicine, 1988; 13:695-706.)

The Kaiser study was important because it pointed out that the highest EMFs actually occur at the sides and rear of monitors not at the front. This means that the number of hours at a terminal may not be a reliable index of exposure. In fact, it will tend to underestimate an operator's exposure, depending on office seating and co-workers' use of machines, so that, if there is a risk to pregnancy outcome from the EMFs, it is likely to be greater than suggested in the study.

Corroborating this view and that different makes of VDUs can emit vastly differing levels of radiation, the July 1990 issue of MacWorld, the US based Macintosh users' monthly, reported a study it had conducted of 10 different types of Macintosh compatible monitors manufactured by six companies, including Apple. Tests measuring ELF EMFs disclosed "worrisome" levels from 10 of the monitors as high as 70 mG (7nT) four inches from the sides and back of some, especially colour, models. Levels of 22 mG (2.2 uT) were found at four inches from the front. At 28 inches (arm's length, fingers extended) the emissions from the front fell to below 1 mG, approximating background levels. The authors advise that users wishing to reduce their exposure to pulsed EMFs should sit with monitors at arm's length and more than four feet from the sides and back of nearby monitors.

As a result of these well publicized findings, two of the US companies involved, MegaGraphics and Sigma Designs, said they intended to modify their monitors so as to reduce VLF (very low frequency) emissions, while Apple has been joining with other manufacturers, such as IBM, Hewlett Packard and Compaq, to fund more research and set up a working group to address the ELF health issue.

In a more recent study, which looked at magnetic field exposures as an integral part of the study, Finnish workers found that women using VDUs emitting strong magnetic fields may be at greater risk than those using low field monitors. Reporting their preliminary results at a conference in Brussels in January, Dr Maila Hietanen, a physicist at the Institute of Occupational Health in Helsinki, Finland, found that VDU operators who were exposed to ELF magnetic fields greater than 9 mG had a miscarriage risk nearly three and a half times greater than those operators with ELF exposures of less than 4 mG, an increase that was statistically significant. Women exposed to 4 to 9mG ELF magnetic fields had almost twice as many miscarriages as those exposed to less than 4 mG, and there appeared to be a dose response relationship between magnetic fields and miscarriages, although not a statistically significant one.

Hietanen also reported a significant increase in the number of miscarriages among women exposed to strong VLF magnetic fields. Interestingly, the study did not reveal a miscarriage risk when the women were classified according to the number of hours they worked at a VDU the method that has been used in most past pregnancy studies only when they were classified according to actual magnetic field exposure.

Commenting on her results, Hietanen felt that those using new VDUs should not be too worried since most new models have much lower fields than the older models did. If a VDU meets the new SWEDAC guidelines for emissions (see below) she believes that a user need not be concerned.

If subsequent studies confirm the Finnish results, the change of focus of concern should move from looking at hours of exposure at a VDU to actual emission levels of different frequencies. And that may then require a very large amount of testing of individual machines, or the even more expensive cost of upgrading hardware.

At present there is no specific legislation regarding work with a VDU in the UK. The Health & Safety Executive bases its guidance on the National Radiological Protection Board's present assessment of the scientific literature on the hazards of the various frequencies emitted.

Not all countries agree with this view. The Swedish Board for Technical Accreditation (SWEDAC) brought in the following guidelines as of January 1, 1991. Measured at 10cm from the screen, AC electric fields should be less than 25V/m for VDUs with frequencies between 5Hz and 2 kHz, and less than 2.5 V/m for those between 2-400 kHz. The associated magnetic field should be less than 250 nT for the first category and less than 25 nT for the second.

In the US the first ever emissions guidelines for VDU EMFs were proposed in April 1991 by the ad hoc industry panel developing US measurement protocols. Working under the auspices of the Institute of Electrical and Electronic Engineers, the panel recommended the same magnetic field values as SWEDAC but lower electric fields. For the latter, the proposed guideline is 10 V/m at 50cm.

Britain will also soon have to comply with the requirements of the EC Directive on Working with Display Screen Equipment, which comes into effect on 1 January 1993. The HSE has issued a consultative document on proposals for complying with the directive and should be issuing final guidelines in November.

Under radiation, the document states: "All radiation, with the exception of the visible part of the electromagnetic spectrum, shall be reduced to negligible levels from the point of view of the protection of workers' safety and health." The latest study appears to have reinforced the HSE's blinkered position.

If it does the EC Directive also requires employers to keep employees informed "on all aspects of safety and health relating to their workstations". So if you keep yourself up to date on research results, you will be a position to bring pressure to bear on the HSE (and employers) for better guidelines and conditions.

Simon Best is editor of Electromagnetic News, which carries news of VDU research or developments. For details write to EM News, PO Box 25 Liphook, Hants GU30 7SE.

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