AAWSAP DIRD, Anomalous Acute and Subacute Field Effects on Human Biological Tissues, March 2010

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the "hotspot" range which lies between 400 MHz and 2 GHz. The heating is highly
nonuniform with typical ratios between spatial peaks and whole body average specific
absorption rates of the order of 150: 1 to 200: 1.' {above and Figure One adapted from
[ 1]}
Figure One
I
Subresonance
Resonance range
,
Hot spot
Surface
absorption
range
range
Whole body
:Partial :
range
: body :
:theadl :
I
I
30
300
400
2000 f(MHz)
Variation ofnormalistd specific absorption ratt wirhfrrqumcy and rtlattd absorption
characrerisrics in living organisms: reproduced wirh rht pe,,ni.ssion qf WHO from :
Electromagnetic fidds (300 Hz w 300 Ghz) 1993: 76. (Emnronmental Htalrh
Criuria 137.)
A. THE EFFECTS THAT BURN
From the perspective of aerospace applications, the millimeter wave length of emitters
has been of greatest interest for human effects, and there have been extensive reviews
documenting effects at both low and high levels of incident energy [20,21]. For our
purposes, the most basic biophysical information that pertains is clear: with dry
clothing, 90-95 % of the energy is efficiently absorbed with or without an air gap acting
as an impedance transformer. These millimeter waves (30-300 GHz) penetrate the skin
to a depth of several millimeters. The ANSI (American National Standards Institute)
safety guideline of 5 mW/cm2 for RF /NIEMR equates to a SAR of 65-357 W/kg.
The depth of penetration involves the area of cutaneous receptors, and at and above
these levels will be perceived first, as prickling sensation, then pain and finally
erythema and even second degree burns if exposures last on the order of minutes:
burning can occur in a non-linear dose-effect range above these SAR levels, as
described elsewhere in this paper.
The threshold of heat perception is near 0.7 mW/cm 2, with power densities of about 9.0
mW/cm2 causing sensations of pain within one second of exposure. It is notable, that
the non-liner effects apply; e.g. for 3 GHz {decimeter, not millimeter wave lengths},
the thresholds are on the order of 30 times less. Indeed, especially in the Former Soviet
Union, there is substantial literature on these wavelengths at SARs below 10s of W/kg
(as with Diathermy Machines in the US in the '50s) being exploited for a wide range of
external and internal (gastrointestinal) therapies.
Of interest here, in the context of incident RF that can produce heating injury, are a
series of very early experiments done at Brooks Air Force Base and the Oak Ridge
National Laboratories during the Cold War era intended to study potential weapons and
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