Full text of DOI:10.1093/oxfordjournals.rpd.a006688

Radiation Protection Dosimetry
Vol. 97, No 4, pp. 355–358 (2001)
Nuclear Technology Publishing
POPULATION EXPOSURE TO ELECTROMAGNETIC FIELDS
GENERATED BY RADIO BASE STATIONS: EVALUATION
OF THE URBAN BACKGROUND BY USING PROVISIONAL
MODEL AND INSTRUMENTAL MEASUREMENTS
L. Anglesio, A. Benedetto, A. Bonino, D. Colla, F. Martire, S. Saudino Fusette and G. d’Amore
Regional Environmental Protection Agency, ARPA Piemonte, Department of Ivrea
Via Jervis 30, 10015 Ivrea (TO), Italy
Abstract — Electromagnetic radiation, which is used by broadcasting and mobile telephone systems to transmit information,
permeates the city environment. In order to properly evaluate population exposure to electromagnetic fields, knowledge of their
intensity and spectral components is necessary. In this study the results of radiofrequency field monitoring carried out in Torino,
a large town located in the north-west of Italy are shown: the variation of the electromagnetic field strength is evaluated as a
function of the height from the ground, the location in the urban area and the frequency, separating the contributions of the
different sources (broadcasting antennas and radio base stations for mobile phones). Furthermore, the contribution of the radio
base stations is theoretically evaluated, adding the emissions off all installations situated in Torino and examining the field
strength maps calculated, considering the orography, for different heights. The theoretical values are also compared with those
measured in the frequency range of mobile telephony emissions.
RADIOFREQUENCY URBAN
ELECTROMAGNETIC BACKGROUND SURVEY
field sensor type 8 s.n. K 0035, which works in the
frequency range 100 kHz–3 GHz.
(2) Spectrum analyser HP8594E or HP8562A with
antenna TES1000 for frequencies from 100 kHz to
1GHz.
Radiofrequency electromagnetic background monitoring
was carried out by using the following methodology.
(1) The town of Torino was divided into ten districts. In
each district a grid of 38 points was fixed (see
Figure 1), chosen to be representative of the investi-
gated area (their number depends on the dimensions,
and on the number of the district inhabitants(1)). At
these points, measurements at three different heights
were made: lower floors (ground floor, 1st floor),
intermediate floors (2–5 floors) and higher floors (5–
10 floors), in order to evaluate the trend of field
strength with the height from the ground.
(2) In each site, a wide-band electric field series of
measurements was made in order to determine the
higher exposure areas where a field spectral analysis
was made by narrow-band measurements. So, each
spectral component at a measurement point and its
contribution to the global level of radiofrequency
Wide-band measurements were made with the isotropic
sensor placed on a dielectric support at height of 1.5 m.
The surveyed data represented the global field level in
the frequency range 100 kHz–3GHz.
For spectral analysis a Tes1000 antenna was used,
which is directional with a radiation pattern like a dipole.
This antenna was placed on a dielectric support with the
electrical centre at 1.5 m from the ground and was pos-
itioned in three orthogonal directions, in order to determine
the global electric field vector by considering signals com-
ing from every direction and with different polarisation.
MEASUREMENTS RESULTS
Table 1 presents a summary of data collected at the 38
electromagnetic field was determined to underline measurement points. The table shows measured data, sur-
the sources emitting the strongest signals in differ- veyed with narrow-band measurements, split into different
ent areas of the town.
signals (radio-TV and telephony) and as a function of
(3) The results of the spectral analysis were compared with height from the ground. For each height, mean and stan-
the values measured by a wide-band survey meter.
dard deviation of the radio-television field, of the tel-
ephony field and of the global electric field are reported.
The table shows a growth of electric field mean level
with increasing height from the ground. The mean value
for the whole town is included between 0.41 0.28
V.m−1 and 0.84 0.59 V.m−1.
The telephony per cent standard deviation is bigger.
This is due to the temporal variability of this type of signal
and to the local contribution of the radio base stations.
Figure 2, which represents the data shown in Table 1,
shows the growth of the mean exposure level with the
INSTRUMENTS AND SURVEY CRITERIA
The instruments used were:
(1) Wide-band electric and magnetic field meter Wan-
del & Goltermann EMR-300; with isotropic electric
Contact author E-mail: l.anglesioȰarpa.piemonte.it.
355

L. ANGLESIO, A. BENEDETTO, A. BONINO, D. COLLA, F. MARTIRE, S. SAUDINO FUSETTE and G. D’AMORE
height from the ground and the higher contribution of ation of the exposure levels to electromagnetic fields.
the radio-television signal to the global field.
There are 330 sites for 1440 antennae, with a mean
Comparison among narrow-band measurements and value of 4.4 antennae each.
wide-band data is reported in Figure 3. To show that the
The theoretical model used is based on the far-field
two series of measurements belong to the same popu- zone approximation; that is, the obtained values
lation, that is, there is no difference between the two adequately describe the electric field (E) distribution in
measurement methodologies, a confidence test based on the far-field zone (distance Ͼ2D2/␭, where
the standardised variable Z = (X1
−
X2)/(␴1/N
−
D = maximum dimension of the sources and ␭ = wave-
␴2/N2)1/2 was used. The calculated value of Z was equal length). The model is based on the relation:
to 0.4, corresponding to a significance level equal to
√
P ϫ G(␪,␸) ϫ 30
1%, which means that there is a probability of 1% to
make a wrong hypothesis assuming that two measure-
ment series belong to different populations.
The most significant differences between the two
methodologies were detected in measurement points
where the highest contribution to the global field is
given by mobile-telephony emissions. This is due to the
intrinsic variability of the mobile-telephony electromag-
netic signal and to the lack of DCS signal (frequencies
higher than 1 GHz) in the narrow-band measurements.
E =
d
Table 1. Measured data, surveyed with narrow-band
measurements, split into different signals (radio-TV and
telephony) and as a function of height from the ground.
Lower
Interm.
Higher
floors
floors
floors
(V.m−1
)
(V.m−1
)
(V.m−1
)
EradioTV
Etelephony
Eglobal
Mean
Std dev.
Mean
Std dev.
Mean
0.38
0.29
0.11
0.10
0.41
0.28
0.59
0.44
0.32
0.31
0.71
0.44
0.69
0.54
0.34
0.42
0.84
0.59
RADIO BASE STATIONS: GEOREFERENCING
AND THEORETICAL EVALUATION OF THE
ELECTRIC FIELD
Std dev.
All radio base station sites for mobile phones in town
were georeferred in order to make a theoretical evalu-
6
5
4
1
7
3
2
8
9
10
Figure 1. Distribution of measurement points (b) in the town’s districts.
356

BACKGROUND RF ELECTRIC FIELD IN AN URBAN ENVIRONMENT
where P is the antenna connector power measured in In order to make the evaluation at constant altitude,
watts, d is the distance in metres and G the antenna gain it was necessary to reconstruct the model of urban terri-
in the ␪, ␸ direction, evaluated by radiation pattern. In tory surface, starting from about 500 known altitude
order to evaluate the global RF electromagnetic field points uniformly distributed on the urban area. This
due to mobile telephone systems, a global calculation reconstruction was made using an interpolation algor-
was made of the emissions of all 330 installations, ithm based on the Kriging variogram.
located in Torino, considering at every point the sum of
each radio base station contribution.
For each surface about 120,000 points were calculated
and the electric field calculation interval used was 30 m.
By analysing the maps of electromagnetic field The field strength maps obtained were superimposed to a
strength, obtained for 1.5 m, 7.5 m and 16.5 m heights, numerical map-making, using GIS (geographical
a
it is also possible to identify critical urban areas for informatic system) system, to make easier the identifi-
population exposure in relation to the radio base cation of more critical situations for human exposure.
station locations.
The field strength map for 1.5 m altitude, relevant to
The evaluation was cautiously made, supposing all radio base station emissions is reported, as an example,
installation channels were active and working with on Figure 4, where the different electromagnetic field
maximum possible power.
levels are represented by different colours.
THEORETICAL RESULTS SHOWED BY
INFORMATIC MAPS
COMPARISON BETWEEN THEORETICAL
VALUES AND MEASURED DATA
The electromagnetic field theoretical levels are shown
The theoretical model, based on far-field propagation,
by maps representing field values on orographics sur- used to evaluate the telephony electromagnetic field
faces at 1.5 m, 7.5 m and 16.5 m of altitude.
intensity is approximate, because it does not consider
the attenuation and the reflection caused by buildings.
This model is precautionary, the result is an over-
estimate evaluation of population exposure to electro-
magnetic radiation, due to mobile telephony systems.
Table 2 shows the mean per cent of telephony emission
levels measured with a narrow-band instruments chain
versus theoretically valued levels for each height. It can
be seen that calculated values are always greater than
measured ones. In fact, the theoretical evaluation was
cautiously made supposing that all base station channels
are active and working at maximum power.
The table also shows that the mean differences
between the calculated and measured values become
smaller with the increase in the height. This trend was
a foreseeable result due to the reduction buildings inter-
cepted by radiation and, consequently, of attenuation
and reflection phenomena with the increasing of height
from the ground. In fact, the model used is cautious
because it is based on free-space propagation.
0.9
0.7
0.5
0.3
0.1
Lower floors
Higher floors
Intermediate floors
Figure 2. Electric field as a function of the height and signal
typology. ᭜ TV + Radio, Telephony (BTS), ̆ Total.
3.0
2.5
2.0
1.5
1.0
0.5
0
CONCLUSIONS
Results of our survey allow the creation of a cognitive
instrument for complex RF electromagnetic field
exposure in an urban environment.
Table 2. Percentage of telephony emission levels measured
with narrow-band instruments chain versus theoretically
valued levels for each height.
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70
Measurement points
Lower floors Interm. floors Higher floors
Emis/Ecalc
␴
0.10 0.10 0.25 0.32 0.30 0.23
Figure 3. Comparison between narrow-band (᭜) and wide-
band measurements (᭿).
357

L. ANGLESIO, A. BENEDETTO, A. BONINO, D. COLLA, F. MARTIRE, S. SAUDINO FUSETTE and G. D’AMORE
The arithmetic mean of the electric field found in the
The comparison between mobile telephony narrow-
whole town of Torino was: 0.38 V.m−1 for lower floors; band measured data and values calculated with the
0.59 for intermediate floors; 0.69 for higher floors. So, theoretical model based on the far-field propagation,
it can be concluded that the population is exposed to a indicates that the model used is cautionary. The meas-
mean electric field level which is lower than the caution- ured radio-base signals, in fact, always proved lower
ary level of 6 V.m−1 fixed by Italian law(2)
.
than calculated values and the mean per cent of those
Results obtained with narrow-band instruments show versus theoretical values are: 10% for lower floors; 25%
that the greatest contribution to a global RF electromag- for intermediate floors; 30% for higher floors.
netic field comes from broadcasting sources, apart from
It can be concluded that the methodology used in
the areas that are inside the irradiation cone of the cellu- forecast evaluations of radio-base emissions is always
lar radio-base station.
Measurement points
an over-estimation of the real population exposure level.
Calculated values at 1.5 m (V.m-1)
0.75–1.5
1.5–2.25
2.25–3
3–3.03
N
W
E
S
Figure 4. Representation of electric field levels with different grey levels for 1.5 m altitude.
REFERENCES
1. d’Amore, G., Anglesio, L., Tasso, M., Benedetto, A. and Roletti, S. Outdoor Background ELF Magnetic Fields in an Urban
Environment. Radiat. Prot. Dosim., 94(4), 375–380 (2001).
2. D.M. 381/98 Regolamento recante norme per la determinazione dei tetti di radiofrequenza compatibili con la salute umana.
Gazzetta Ufficiale della Repubblica Italiana, serie generale, no 257 (3 Nov 1998).
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