Programmreport 2012 - DORIS - Bundesamt für Strahlenschutz

Based on an extensive literature study, measurement and computation methods were developed within the
study “Exposure to non-ionising radiation with frequencies in the terahertz range - development and
application of methods (3610S80001)“ in order to determine the human exposure in the THz frequency
range. To measure the exposure caused by THz systems a two-stage method was proposed: First, using a
lens-coupled THz CMOS camera a hotspot is determined at the point of exposure, respectively the propagation
direction of the beam, and is followed by the measurement of the power density distribution in the beams
cross-section at the exposure location. Therefore, either a direct beam sampling with a THz CMOS direct detector
of small aperture was used or alternatively (in case of a Gaussian-shaped power density distribution)
the knife-edge beam-profiling method. For the numerical dosimetry detailed models of the human skin as well
as of the eye, and field excitation models, e.g. for a Gaussian beam excitation, were generated. The dielectric
material parameters in THz frequency range - required for the calculation of the internal body field and SAR
distributions, but not sufficiently described in the literature - were determined by the "effective medium theory".
Moreover, for the exposure assessment the THz-related temperature increases, based on the SAR as heat
source, were considered.
The aim of the research project “Determination of general public exposure to novel cellular mobile
radio technologies (3611S80002)“ is primarily the measurement and analysis of the general public’s exposure
in the vicinity of LTE and TETRA BOS base stations. Concerning LTE measurements at 102 systematically
and 75 randomly chosen measurement points, exposures extrapolated to the maximal operational
state of the station were found to be between 0.002 and 7.28% of the ICNIRP 1998 field strength reference
levels (median 0.70%). The instantaneous exposure in terms of field strength was smaller by factors between
3.1 and 17.2. TETRA BOS exposure measurements at 40 systematically and 40 randomly chosen points resulted
in extrapolated exposures between 0.03 and 4.63% of the field strength limit (median 0.46%). The instantaneous
exposure was smaller by factors between 2.1 and 4.4 with respect to field strength. The LTE and
TETRA BOS exposure is very similar to the exposure around GSM and UMTS base stations with regard to
order of magnitude and spatial distribution.
It can be concluded, that the base stations of the novel cellular mobile radio techniques LTE and TETRA BOS
cause an exposure increase to the general public. The overall exposure to fixed radio transmitters, however,
is still low (median smaller than 2% of the field strength limit). At the investigated base stations the power related
mobile phone exposure increase was 37% for LTE and 47% for TETRA BOS, both related to maximal
operational state of the station. On average a 22% contribution of LTE and 30% of TETRA BOS to the overall
RF exposure was measured. These values are representative primarily for the direct vicinity of the selected
stations and should not be interpreted as area or population averaged exposure increase.
SUBJECT AREA 09 - GERMAN MOBILE TELECOMMUNICATION RESEARCH PROGRAMME
Within the project “Age dependent effects of high-frequency electromagnetic fields on the development
and differentiation of the CNS of juvenile laboratory rodents“, female Wistar-rats, from an age of 14 days
to 19 months, were exposed for 2 hours per day, 5 days per week in the head reagion to mobile phone electromagnetic
fields (900 MHz GSM). The SAR values were 0, 0.7, 2.5, and 10 W/kg. The primary exposure of
the head region was done by fixating the animals in restraining tubes of different sizes. During the experiment,
three blocks of behavioral and learning tests were performed in juvenile, adult, and pre-senile animals (RotaRod,
Morris-water maze, 8-arm maze, and open field). Between the groups of the exposed and the
sham-exposed animals no profound differences could be identified. A histopathological analysis revealed no
higher tumor incidence in the central nervous system due to exposure. The body weights of the exposed /
sham-exposed animals were not different during the first year, and thereafter only marginally different from
those of the the cage controls, so that the effect of stress as confounder was probably negligible.
XXV