HEALTH: WHO Gives Computer Screens a Clean Slate

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Jul 27 1998 (IPS) - The bad name earned by computer screens for alleged negative health effects was improved greatly Monday following feedback from studies by UN specialist agencies.

Research from the World Health Organisation (WHO) detracted from claims that electromagnetic fields emitted by the screens were behind the health problems suffered by Video Display Unit (VDU) users.

The WHO counter-claimed the complaints could be caused by other elements of the working environment: interior air quality, tension and ergonomic aspects, like posture in the seat in front of the screen.

Computers have proliferated in the last 30 years, meaning massive increases in the use of visual terminals in both workplaces and homes in the industrialised countries.

Estimates from the WHO indicate there will be some 150 million units in operation world-wide. By this time, 60 percent of the workforce in the US and Canada will be using these terminals.

The WHO said Monday these conclusions on the apparent innocuousness of the screens agrees with the findings of the International Commission of Protection on Non-Ionising Radiation Protection, a constituent body of the International Labour Office (ILO).

It also criticised the effectiveness of most of the products available on the market to protect against the electromagnetic fields and radiation, like screens and other radiation “absorbing” devices.

“These articles do not offer even the least protecting effect against emissions from the visual screens,” declared the WHO.

When VDUs were first introduced into the workplace they earned a terrible reputation as the causes of a whole series of health complaints: headaches, dizziness, tiredness, cataracts, adverse pregnancy outcomes and skin rashes.

Toward the end of the seventies the notion arose that working with computer screens could affect the outcome of a pregnancy, stated the WHO.

Examples quoted at the time referred to clusters of pregnant mothers working with these terminals who had suffered an unusually high number of miscarriages and malformed children.

These claims, noted the WHO, led to a great many epidemiological studies being carried out, along with experimentation in Europe and North America, where the alleged cases had taken place.

Taken as a whole, these studies have failed to demonstrate any effects on reproductive processes due to the elecromagnetic fields emitted by the VDUs, stressed the WHO.

On the contrary, the studies suggested the possible effects on reproduction could be due to other professional factors, like the stress related to this sort of job.

The WHO study also stated there was no proof found of cataracts and other eye diseases being linked to working with the screens.

In extreme situations, it did say, glare and reflection from VDU screens have been identified as a source of eye strain and headaches in extreme circumstances.

The visual terminals are similar to television screens, the only difference being that they display information from the computer rather than a television signal.

Classic terminals produce images on a big Cathode Ray Tube (CRT) by firing a beam of high-energy electrons from the cathode onto a special phosphorous-coated glass screen. This coating emits light when struck by the fast-moving electrons.

The electron beam creates the image from the electronic signals sent by the computer, which are controlled by coils at the back of the CRT, sweeping the electrons in vertical and horizontal directions.

The electronic circuit used to create the image produces static electric and magnetic fields along with high and low frequency electromagnetic fields.

Data from the WHO study said the range of the electrical and magnetic fields, and optical radiation produced by the VDUs cover almost the entire electromagnetic spectrum.

Optical radiation emitted includes ultraviolet, visible and infrared – for while visible light forms the image the screen should produce, the infrared appears as heat dissipated by the unit.

The ultraviolet radiation is produced only in tiny quantities, lower than the level coming in a window on a winter’s day, claimed the WHO.

Meanwhile, the electrical and magnetic fields have emissions of three different ranges of frequencies.

The horizontal deflection coils emit fields of between 15 and 35 kilocycles per second. The lower frequency fields, from 50 to 60 Hertz, are generated by the energy source, transformers and vertical deflection coils.

The third range refers to weak signals registered on higher radiofrequencies, coming from the electronic circuitry within the VDU and signals generated by the computer.

Then there are the static electrical fields, said the WHO, especially on damp days, produced by the accumulation of an electrical charge due to the bombardment of electrons on the screen.

Finally, the cathode tube produces very low energy X-rays, but the glass screen is thick enough to completely absorb these before they can get out of the video terminal.