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Data compression expands
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Impasse in V D U hazard research Very low frequency radiation could yet pose a hazard to VDU operators, according to the Canadian Centre of Occupational Health and Safety. Its controversial report comes from task fomes set up by the Canadian government to investigate allegations that birth defects and miscarriages are linked to VDU use. Explanations put forward so far, following the cases in 1980 of workers on the Toronto Star newspaper, include stress, chance, ergonomic factors and radiation (see, for example, article by E.A. Cox in Displays 4 (1983) 7). A scientific impasse has now been reached on this question, says the CCOHS. In December 1982, staff of CCOHS met to review the state of the scientific knowledge relating to VDUs as a possible cause of birth defects and spontaneous miscarriages. They agreed that the present state of scientific knowledge is incomplete on the question. The weight of the scientific evidence is against x-rays as the culprit, they say. Measurements published show the degree of ionizing radiation exposure associated with VDUs to be negligible. Non-ionizing radiations, particularly ultra-violet and visible light, infra-red, and microwaves, are not produced in quantities such as to be harmful to humans. The scientific evidence does, however, show that certain VDUs produce pulsemodulated, very low frequency electromagnetic fields. Whether these are a cause for concern is not yet clear, says the CCOHS, but reports indicate that their strength sometimes exceeds exposure limits set for other parts of the electromagnetic spectrum which are close in frequency to these fields. There is some scientific evidence to suggest that pulse-modulated fields could be biologically more harmful
DISPLAYS. APRIL 1983
than non-pulse-modulated fields, though this is still a matter for debate. The hypothesis is that pulse-modulated electromagnetic fields may be able to induce potential gradients which could be high enough in parts of surfaces of living cells to cause damage. Whether this hypothesis is consistent with any link between VDUs and birth defects and miscarriages can only be discovered after investigations have been carried out. The CCOHS suggests that animal testing and mathematical modelling would show whether pulse-modulated electromagnetic fields comparable to those emitted from VDUs are capable of inducing harmful potential gradients at key points of cells in the human body. S~Jch investigations would take a number of years to complete.
manufacturers and other affected parties, on the feasibility of shielding all sources of pulsed electromagnetic fields in new equipment and existing VDUs. CCOHS is setting an example by seeking advice from the manufacturers on the effective shielding of its own VDUs. As an interim measure, standards that exist for slightly higher frequencies should be extended to cover frequencies down to 10 kHz, a principle which has been recognized by the American Conference of Governmental Industrial Hygienists. Under this recommendation, exposure measured at a distance of 300 mm from the nearest surface of a unit would not exceed a maximum intensity of 60 V m -1 .
Canadian Centre for Occupational Health and Safety, 250 Main S~reet E, Hamilton, Ontario L8N 1H6, Canada
New display techniques Meanwhile, studies of a different nature are either under way or being planned. These involve epidemiological tests in which the rate of birth defects and miscarriages would be explored for women who have worked with VDUs, and for those who have not. The CCOHS scientists say that action is needed now. It should not be deferred until enough evidence has been accumulated to provide a definitive answer to the question. They believe that a =cautious approach should be adopted and all reasonable steps taken to reduce or eliminate this pulse-modulated electromagnetic radiation, even though its potential for harm is unconfirmed. Research should be accelerated into finding ways of eliminating emissions of pulsed electromagnetic fields, for example through shielding of equipment or the development of new display techniques. The scientists also recommend that the appropriate government regulatory bodies begin discussions now with equipment
Data compression e x p a n d s Data compression products, currently commanding a market estimated at $52 million annually, have the potential to rocket to $1.2 billion by 1986, in constant 1981 dollars, according to a study by Frost and Sullivan. The report gives two reasons for this boom. First, the cost of data transmission leapt by about 70 per cent during 1981, after certain bulk rate tariffs for major communications users were abolished. Second, although the cost of on-line storage on a per-character basis has fallen with the introduction of double and quadruple density recording discs, demand for storage has grown so rapidly that overall costs for most computer users have increased sharply. The report expects growth to be greatest in data processing.
Frost and Sullivan Inc, 106 Fulton Street, New York, NY, 10038, USA
121
Impasse in V D U hazard research Very low frequency radiation could yet pose a hazard to VDU operators, according to the Canadian Centre of Occupational Health and Safety. Its controversial report comes from task fomes set up by the Canadian government to investigate allegations that birth defects and miscarriages are linked to VDU use. Explanations put forward so far, following the cases in 1980 of workers on the Toronto Star newspaper, include stress, chance, ergonomic factors and radiation (see, for example, article by E.A. Cox in Displays 4 (1983) 7). A scientific impasse has now been reached on this question, says the CCOHS. In December 1982, staff of CCOHS met to review the state of the scientific knowledge relating to VDUs as a possible cause of birth defects and spontaneous miscarriages. They agreed that the present state of scientific knowledge is incomplete on the question. The weight of the scientific evidence is against x-rays as the culprit, they say. Measurements published show the degree of ionizing radiation exposure associated with VDUs to be negligible. Non-ionizing radiations, particularly ultra-violet and visible light, infra-red, and microwaves, are not produced in quantities such as to be harmful to humans. The scientific evidence does, however, show that certain VDUs produce pulsemodulated, very low frequency electromagnetic fields. Whether these are a cause for concern is not yet clear, says the CCOHS, but reports indicate that their strength sometimes exceeds exposure limits set for other parts of the electromagnetic spectrum which are close in frequency to these fields. There is some scientific evidence to suggest that pulse-modulated fields could be biologically more harmful
DISPLAYS. APRIL 1983
than non-pulse-modulated fields, though this is still a matter for debate. The hypothesis is that pulse-modulated electromagnetic fields may be able to induce potential gradients which could be high enough in parts of surfaces of living cells to cause damage. Whether this hypothesis is consistent with any link between VDUs and birth defects and miscarriages can only be discovered after investigations have been carried out. The CCOHS suggests that animal testing and mathematical modelling would show whether pulse-modulated electromagnetic fields comparable to those emitted from VDUs are capable of inducing harmful potential gradients at key points of cells in the human body. S~Jch investigations would take a number of years to complete.
manufacturers and other affected parties, on the feasibility of shielding all sources of pulsed electromagnetic fields in new equipment and existing VDUs. CCOHS is setting an example by seeking advice from the manufacturers on the effective shielding of its own VDUs. As an interim measure, standards that exist for slightly higher frequencies should be extended to cover frequencies down to 10 kHz, a principle which has been recognized by the American Conference of Governmental Industrial Hygienists. Under this recommendation, exposure measured at a distance of 300 mm from the nearest surface of a unit would not exceed a maximum intensity of 60 V m -1 .
Canadian Centre for Occupational Health and Safety, 250 Main S~reet E, Hamilton, Ontario L8N 1H6, Canada
New display techniques Meanwhile, studies of a different nature are either under way or being planned. These involve epidemiological tests in which the rate of birth defects and miscarriages would be explored for women who have worked with VDUs, and for those who have not. The CCOHS scientists say that action is needed now. It should not be deferred until enough evidence has been accumulated to provide a definitive answer to the question. They believe that a =cautious approach should be adopted and all reasonable steps taken to reduce or eliminate this pulse-modulated electromagnetic radiation, even though its potential for harm is unconfirmed. Research should be accelerated into finding ways of eliminating emissions of pulsed electromagnetic fields, for example through shielding of equipment or the development of new display techniques. The scientists also recommend that the appropriate government regulatory bodies begin discussions now with equipment
Data compression e x p a n d s Data compression products, currently commanding a market estimated at $52 million annually, have the potential to rocket to $1.2 billion by 1986, in constant 1981 dollars, according to a study by Frost and Sullivan. The report gives two reasons for this boom. First, the cost of data transmission leapt by about 70 per cent during 1981, after certain bulk rate tariffs for major communications users were abolished. Second, although the cost of on-line storage on a per-character basis has fallen with the introduction of double and quadruple density recording discs, demand for storage has grown so rapidly that overall costs for most computer users have increased sharply. The report expects growth to be greatest in data processing.
Frost and Sullivan Inc, 106 Fulton Street, New York, NY, 10038, USA
121