The recent Conformity Update on a possible new SAR standard stated:
"The existing standard, say the manufacturers, is interpreted differently in
different countries and may not measure what it is purported to measure, that
is, the conversion of radiated energy into heat by biological tissue."
I was reminded of an explanation of RF radiation matters I sent to a non-layman
colleague several years ago. My knowledge was based on my participation in the
development of a digital RF personal communicator that preceded cellphones.
This system is currently used by IBM Customer Engineers for dispatch and service
call reporting. Here is my old note that may be of interest to some subscribers
to this forum:
Electromagnetic radiation (I will use ER henceforth) was present in nature
before the advent of man-made devices. Sunlight, lightning, and the earth's
magnetic fields are examples of natural ER. Virtually all electric equipment
emits ER, e.g. vacuum cleaners, arc welders, and ITE. For purposes of
protecting wireless (RF) communications, the ER of ITE is legislated in most
major countries. Specifically, digital electronic equipment employing clock
rates of 10kHz or more is required to meet these established EMI limits.
Given the interference limits placed on ITE equipment, the resulting ER is well
within the "safe" limits established by most world health organizations. For
example, the American Conference of Governmental and Industrial Hygienists
(ACGIH) publishes Threshold Value Limits (TLVs) and Biological Exposure Indexes
(BEIs) for chemicals, physical agents, and various forms of "radiation". The
most severe limit for "radiofrequency/microwave radiation" is 1mW/cm2 for
frequencies between 30mHz and 100mHz. ITE equipment ER is well below this level
(measured at the body). In other words, the body of existing scientific
evidence does not find health hazards at the low levels of ER common for ITE.
However, here is the problem. Even the word "radiation" (of any kind) produces
fear. This goes back to our initial understanding of nuclear radiation and the
atomic bomb. The treatment of cancer with "radiation" therapy furthers this
fear. As a result, all forms of ER have become suspect. The most recent trend
is to question the 60Hz fields from transmission lines, and from routine
household appliances, e.g. hair dryers and electric blankets. These are partly
based on a study where it appearred that young lukemia victims in a subdivision
all lived within short distances from power distribution lines.
I could go on and on, however, here are the "facts":
1. ER is present in nature and in all electrical appliances.
2. The EMI limits imposed on ITE allow only low levels of ER to exist in
ITE.
3. The ER typical of ITE is believed to be well below those with health
consequences.
4. But,.....it is obvious that some day it may be determined that even
continued exposure to low levels of ER from lowly household appliances
can contribute to subtle health problems.
5. This issue is sure to be debated and studied for many years to come.
6. The issue may not be the "facts", but what the public believes. Some
electric blanket manufacturers have already modified their design to
reduce 60Hz fields, although nothing has been conclusively "proven".
Year 2000 Update on above discussion:
Cellular phones bring a new aspect to this discussion. As "intentional"
radiators, their output power is relatively low. However, this "low" power
is being radiated from a source (antenna) that is all but touching the user's
body, i.e. at the point of maximum field strength.
I do not know how the radiated immission (measured at the receiving surface)
energy compares to the long accepted limit of 1mW/cm2. However, Russia has
long declared an upper limit that is an order of magnitude lower (0.1mW/cm2)
because of their belief in possible biological effects to long term exposure
to low level radiation that is not based on radiated energy converted to heat
within biological tissue.
During the "cold war", the U.S. took great issue with the fact that the Russians
seemed to be bombarding the U.S. embassy in Moscow with RF
"radiation". The U.S. took steps to shield the entire building, and sent
many dependents back to the states. Oddly, the levels of radiation reported
were under the accepted Western level of 1mW/cm2, but over the Russian level
of 0.1mW/cm2.
In other words, SARs based on the "heating" aspect of RF radiation may or may
not be the proper parameter to predict long term health effects. Personally,
I use my cellphone as little as possible.
[All of the above is either personal opinion, or "facts" as reported in various
sources.]
George Alspaugh
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