INTERNATIONAL COMMISSION ON NON‐IONIZING RADIATION PROTECTION
ICNIRP PUBLICATION – 2012 ICNIRP STATEMENT
ON HEALTH ISSUES ASSOCIATED WITH MILLIMETER
WAVE WHOLE BODY IMAGING TECHNOLOGY PUBLISHED IN: HEALTH PHYSICS 102(1):81‐82; 2012
ICNIRP Guidelines
ICNIRP STATEMENT—HEALTH ISSUES ASSOCIATED WITH
MILLIMETER WAVE WHOLE BODY IMAGING TECHNOLOGY
International Commission on Non-Ionizing Radiation Protection*
INTRODUCTION
A NEW generation of whole-body image scanners has
been installed in many airports and other security
checkpoints worldwide. They are capable of detecting
weapons or objects made of any type of material that
are being worn or are concealed by clothing at a short
range or at distances of a few meters, within a defined
scanning zone.
Active scanners emit electromagnetic waves at fre-
quencies in the tens of gigahertz (GHz or 109
Hz) or the
microwave region and form an image by processing the
waves scattered by the object or person being scanned. It
is noteworthy that scanners designed to passively detect
the broadband microwave radiation emitted by the hu-
man body do not expose the body to electromagnetic
waves.
At the frequencies used by these scanners, the
energy per photon (quantum energy of GHz radiation) is
not sufficient to break chemical bonds or to ionize atoms
or molecules. Thus, the scanners use non-ionizing radi-
ation, unlike traditional x-ray backscatter machines,
which use ionizing radiation.
The typical parameters of the active scanners in-
volve 10 to 100 mW of total output power from antennas
operating at 30 to 100 GHz. They take about 2 to 5 s to
complete a multi-directional scan of the subject. These
scanners are also referred to as millimeter wave (mm
wave) body scanners because at this frequency the
wavelength is between 3 and 10 mm in air.
These scanners can image through a subject’s cloth-
ing and detect concealed weapons, explosives, or suspi-
cious articles and display them along with detailed
images of the surface anatomy. For the general public,
the scans involve a brief exposure time. However, for
occupational situations during manufacturing, testing and
installation, repeated exposures or extended exposure
durations may occur. The scientific data on possible
effects and health implications of mm waves are sparse.
Aside from thermal interactions, little is known about
mm wave interactions with biological systems or the
mechanisms that may govern any direct interaction.
The objective of this statement is to address the
possible adverse health effects from exposure to mm
waves used in whole body electronic security scanners.
The statement includes an assessment of the applicability
of currently available exposure guidelines.
INDUCED FIELDS AND ENERGY DEPOSITION
At the frequencies of mm waves, the induced fields
and energy deposition in biological media can be deter-
mined in much the same manner as for other non-
ionizing spectra if the permittivity of relevant tissues at
these frequencies is known. Between 30 to 100 GHz, the
behavior of relative permittivity follows those of the
lower frequencies. Specifically, the real and imaginary
parts of the complex relative permittivity for skin tissues
decrease from 20 to 6 and 20 to 12, respectively.
However, the skin tissue is not homogeneous but
consists of a multilayer of stratum corneum (SC), epi-
dermis, and dermis and varies according to body loca-
tion; for example, forearm and palm skin have thin and
thick SC, respectively. In general, at mm wave frequency
the permittivity of skin is governed by cutaneous free
water contents.
The specific absorption rate (SAR) of the mm wave
energy increases with frequency. Calculations of mm
wave transmission for skin on the forearm showed an
increase from 55% to 65% between 30 and 90 GHz
(Alexseev and Ziskin 2007; Alexseev et al. 2008). It is
noteworthy that a thick SC in the palm causes an increase
in transmission as a result of the layer matching phenom-
enon at higher mm wave frequencies. Power transmis-
sion coefficient for skin on the forearm showed an
* ICNIRP Secretariat, c/o Gunde Ziegelberger, c/o Bundesamt fu ̈rStrahlenschutz, Ingolstaedter Landstrasse 1, 85764 Oberschleissheim,
Germany.
The authors declare no conflict of interest.
For correspondence or reprints contact info@icnirp.org.
0017-9078120
Copyright © 2011 Health Physics Society
DOI: 10.1097/HP.0b013e31823a1278
www.health-physics.com 81
increase from 55% to 65%. However, at the highest
frequencies the SAR in the deeper regions of the skin
may become lower because of the reduced penetration
depth at these frequencies. For example, the penetration
depth of a plane-wave field decreases from 0.8 to 0.4 mm
and 1.2 to 0.7 mm for skin on the forearm and palm,
respectively.
GUIDELINES FOR LIMITING EXPOSURE
The ICNIRP recommends guidelines for limiting
human exposure that pertain to frequencies over the
entire non-ionizing radiation spectrum (ICNIRP 1998,
2009). For radio frequency electromagnetic fields be-
tween 10 to 300 GHz, the existing guideline for the
general public is 10 W mϪ2
averaged over a certain time
interval that decreases with increasing frequency (6 min
at 10 GHz and 10 s at 300 GHz). In addition, for pulsed
fields, the peak incident power density averaged over the
pulse width may not exceed 10 kW mϪ2
. The correspond-
ing values are 50 W mϪ2
and 50 kW mϪ2
, respectively,
for occupational exposures. These values are based on
the avoidance of adverse effects caused by mild whole-
body heat stress and/or tissue damage caused by exces-
sive localized heating.
It is noted that mm wave body scanners operate in
pulse modes. The power levels employed by these mm
wave body scanners are low but can generate power
densities up to 1.0 kW mϪ2
for a pulsed field averaged
over the pulse width. The resulting human exposures are
about a tenth of currently recommended guidelines for
the general public.
Acknowledgments—The support received by ICNIRP from the Australian
Radiation Protection and Nuclear Safety Agency, the International Radia-
tion Protection Association, the European Commission, and the German
Federal Ministry for the Environment, Nature Conservation and Nuclear
Safety is gratefully acknowledged.
During the preparation of this statement, drafted under the leadership
of the ICNIRP SC3 Chair, James C. Lin, the composition of the Interna-
tional Commission on Non-Ionizing Radiation Protection was as follows:
P. Vecchia, Chairman (Italy), R. Matthes, Vice-Chairman (Germany), M.
Feychting (Sweden), A. Green (Australia), K. Jokela (Finland), J. Lin
(United States of America), K. Schulmeister (Austria), Z. Sienkiewicz
(United Kingdom), A. Peralta (The Philippines), P. So
̈derberg (Sweden),
B. Stuck (United States of America), A. Swerdlow (United Kingdom), E.
Van Rongen (The Netherlands), B. Veyret (France), G. Ziegelberger,
Scientific Secretary (Austria).
All ICNIRP members are requested to fill in and update as
necessary a declaration of personal interests. Those documents are
available online at www.icnirp.org/cv.htm.
REFERENCES
Alekseev SI, Ziskin MC. Human skin permittivity determined
by millimeter wave reflection measurements. Bioelectro-
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Alekseev SI, Radzievsky AA, Logani MK, Ziskin MC. Milli-
meter wave dosimetry of human skin. Bioelectromagnetics
29:65–70; 2008.
ICNIRP. Guidelines for limiting exposure to time-varying
electric, magnetic, and electromagnetic fields (up to 300
GHz). Health Phys 74:494–522; 1998.
ICNIRP. Statement on the "Guidelines for limiting exposure to
time-varying electric, magnetic and electromagnetic fields
(up to 300 GHz)." Health Phys 97:257–259; 2009.f f82 Health Physics January 2012, Volume 102, Number 1
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