In the November 8, 1996 issue of Science (Vol. 274, pg. 910) is an
announcement that the US National Research Council "seemed to deal a
mortal blow to one of the most polarised and long-running environmental
controversies -- whether electromagnetic fields (EMF's) from power lines
or household appliances pose a threat to human health. After an
exhaustive, 3-year study, a 16-member panel said there is 'no conclusive
and consistent evidence' that ordinary exposure to EMF's causes cancer,
neurobehavioral problems, or reproductive and developmental disorders."
For those interested in what this is all about, a brief summary follows.
CRT's (Cathode Ray Tubes) direct a beam of electrons at a thin layer of
phosphor which coats the screen on your monitor. When the electrons
strike the phosphor, shadow mask and other screen components, x-rays are
produced. The amount and energy of the x-rays depends on the
accelerating voltage. The relatively low voltages in CRT's (compared to
commercial x-ray machines) means that relatively low quantities of low
energy x-rays are produced and modern monitors are so well shielded, that
there is no concern of being irradiated over time. Though it is possible
for a damaged monitor to emit x-ray radiation, it is unlikely that
harmful amounts will be released, and most x-rays would be directed
towards the back or sides of the monitor. Any damage to the front of
the CRT severe enough to increase x-ray emission would cause the CRT to
All televisions and computer monitors must comply with various worldwide
standards for ionizing emissions. Information relating to this compliance
is typically included on the product label, or within the users manual.
Recently, concerns about low frequency (LF) and very low frequency (VLF)
electro-magnetic and electro-static emissions have been raised. Many
studies have been established recently to determine if these concerns
are warranted. None of the studies has concluded that there is any
correlation between the radiation and possible health risks. In Sweden,
a large study was undertaken and as a result, the Swedish government,
and the Swedish Workers Union (TCO) both established recommended limits
of radiation for office equipment, including Video Display Terminals
(VDT's). The same limits are applied to monitors; the Swedish Government
standard is referred to as MPR 1992, and the TCO standard is referred
to as TCO. Many new monitors adhere to the Swedish emission regulations.
Epidemiologists have suggested that the risk factors for some childhood
cancers (particularly leukemia) are as high as two for some populations
exposed to low frequency EMI. A risk factor of two means that the odds
of being afflicted with a disease is twice as likely in the exposed
population than in a control population. In general, a risk factor of
less than six is not considered significant (cigarette smoking has a risk
factor of 10-20). As a result, several groups have publicly stated that
there is no significant health risk from EMI radiation levels experienced
by people from home appliances or nearby high voltage lines.
Critics of the Swedish study suggest that it was simply too huge.
According to a television documentary, over 800 comparisons were made
for correlation between exposure and pathologies. Statistics would
suggest that given enough completely random and uncorrelated measures,
the odds are that some of them will display a high correlation. As a
result, any study that is large enough will produce correlations
between _some_ of the measured quantities. Because of this criticism,
and the fact that only correlation, and no causation was proved in the
study, the Swedish government has since reversed their decision to
mandate maximum EMI emissions.
Studies in the U.S. to determine if EMI could cause cancer or other
illness, birth defects or any other health problems in rats have
come up negative. The rats were exposed to 0-10000 mG (milli-Gauss)
magnetic fields (the earth's magnetic field is ~500 mG), and their
skeletal and visceral organs, reproduction, frequency of cancer and
immunology all came up normal. The chronic studies that were
undertaken by the same group will be completed in 1996. Other studies
showed that EMI had no effect on the growth of cancer cells.
So, you have to make your own decisions, but the overwhelming majority
of experts agree that there is no cause for concern.
For more information, contact:
Tel: (800) 363-2383 (in the USA)
In Washington, DC, call: 484-1803