EVALUATION AND CHARACTERIZATION
OF FETAL EXPOSURES TO LOW
FREQUENCY MAGNETIC FIELDS
GENERATED BY LAPTOP COMPUTERS
NICOLA ZOPPETTI (1)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
NICOLA ZOPPETTI (1)
DANIELE ANDREUCCETTI (1)
CARLO BELLIENI (2)
ANDREA BOGI (3)
IOLE PINTO (3)
(1) Cnr - Institute of Applied Physics (IFAC-CNR) Via Madonna del Piano 10, (50019) Sesto Fiorentino (FI), Italy
(2) Department of Paediatrics, Obstetrics and Reproduction Medicine University of SienaSiena, Italy
(3) ASL 7 - Prevention Department Physical Agents Laboratory, Siena, Italy
Introduction
• USL7-Siena and IFAC-CNR are cooperating in a project aimed at
assessing the exposure to electromagnetic fields in occupational
environment. One of the objective of the project is to create and
populate a Database, called “Physical Agent Portal” (PAF), in which
the main sources of occupational exposures are represented. This
Database is intended to be used as source for risk assessment
procedures that Italian employers are obliged to carry on since
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
procedures that Italian employers are obliged to carry on since
January the 1st 2009 also for EMF.
• Pregnant workers were identified as a category to which dedicate
particular attention. In particular, in the frame of the project two
sources, both of low frequency magnetic field, were considered to
which pregnant can be exposed: industrial sewing machines and
laptop in office and domestic environment.
Introduction and summary
• Especially in domestic environment laptop computers
can be used in tight contact with body, and womb in
particular, for pregnant women.
• Laptop computer (LPT) and their
battery chargers (BTC) are
sources of not negligible
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
sources of not negligible
magnetic fields, with frequency
contents that can vary
considerably depending from the
model and the considered zone
of the device . In any case the
magnetic field has complex
(impulsive) waveform.
Introduction and Summary• Five models of LPC & BTC were considered and preliminary magnetic
field measure were carried on to find, for each of them, the points
characterized by the maximum field both under the laptop and close
to the battery charger.
• The field was measured and acquired in those 5+5 points.
• The measured samples were elaborated to apply the weighted
peak (WP) approach and to obtain a set of WP indexes that
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
‘indicate’ exposure standard violation if value 1.0 is exceeded. This
step entails the development of numerical filters that represent the
inverse of the ICNIRP reference levels
• For the models of laptop and battery-charger that generate the
higher WP indexes a ‘worst case’ dosimetric analysis was carried
supposing B field uniform in the volume occupied by the pregnant
digital body model and equal to the field measured close to the
device.
In this presentation ...1. Measurement setup
2. Brief description of the implementation of numerical filters that
represents the inverse of ICNIRP reference levels/basic restrictions
(constrains).
3. Characteristics of the measured field are presented and in particular
summary of the exposure indexes calculated for the 5 models of
LPT and BTC.
4. Basics of a dosimetric method suitable to treat exposures to
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
4. Basics of a dosimetric method suitable to treat exposures to
complex waveform (not sinusoidal) impressed fields with general
polarization and that allows the assessment of the compliance with
ICNIRP basic restrictions that vary with frequency avoiding the
spectral decomposition of the problem (not convenient in case of
several spectral components and in relation to the so called
“spectral leakage” phenomenon).
5. Results of the dosimetric analysis referred to 1 LPC and 1 BTC.
(1) Measurement setup
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
True RMS
(1) Measurement setup
Narda-ELT400
Agilent U2531A
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
Narda-ELT400
Analog outputs
(2) Developement of numerical ICNIRP filters
( )( ) HzbHzaAbsas
sAsH ffc 008282
21025.6
1)(
6
2
⋅=⋅=⋅⋅
=++
= − ππ
B98pop
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
( )cbTjcaTj
fd ebeazbazba
zzKAzH
ππ 22
21
21
1111111
21)(
−−−−
−−==
⋅⋅++−−⋅−⋅⋅=
( )
( ) cTnfjcTnfj
cTnfjcTnfj
f
nc
ebaeba
ee
A
fjH
K
ππ
ππ
π
42
42
11111
21
2
−−
−−
⋅⋅++−−⋅−
=
(2) Analog vs Numerical
Percentage relative
differences
∆% (amplitude) ∆% (phase)
Fs/8 0.0036 % 5.3 %
Fs/4 0.0213 % 21.6 %
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
The phase of the numerical filter
is 0 at Fs/2 (Nyquist limit)
It is necessary to use a sampling frequency ‘sufficiently’higher than the highest significant component of theinput spectrum (this can entail a preliminary acquisition at the maximum
sampling rate and a spectral analysis, when the characteristics of the measured
field are not known before the measurement campaign)
Fs/4 0.0213 % 21.6 %
Fs/2 0.13 % 100 %
(3) Considered LPC
ID Model
A Acer Aspire 5920
B Dell Inspiron 610M
C Dell Precision M4400
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
C Dell Precision M4400
D Sony Vaio vgnz41md
E Macbook Pro
Sampling frequencies: 200 kS/s/ch (LPC)
50 kS/s/ch (BTC)
(3) Characteristics of the measured B field
(LPC)
ALPC
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
BLPC
CLPC
(3) Characteristics of the measured B field (LPC)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
DLPCE
LPC
(3) Characteristics of the measured B field
(BTC)
ABTC
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
BBTC
CBTC
(3) Characteristics of the measured B field
(BTC)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
DBTCE
BTC
LPC
Bmax Brms WP03max WP10max
A 2.113E-06 7.380E-07 0.2208 0.0423
B 5.266E-06 9.314E-07 0.2328 0.0325
C 2.876E-06 1.082E-06 0.1429 0.0150
D 1.791E-06 5.470E-07 0.1413 0.0318
E 2.493E-06 9.911E-07 0.1877 0.0416
1.7- 5.3 µT
(3) Exposure indexes calculated for the 5
models of LPT and BTC
7.8 x
7.9 x
5.3 x
5.6 x
4.2 x
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
BTC
Bmax Brms WP03max WP10max
A 3.019E-05 4.730E-06 1.7528 0.2248
B 1.998E-05 2.735E-06 1.1174 0.1421
C 1.049E-05 2.704E-06 0.8682 0.1651
D 3.608E-06 1.297E-06 0.2918 0.0523
E 6.866E-07 2.805E-07 0.0449 0.0107
5.2 x
7.2 x
9.5 x
4.4 x
4.5 x
0.7- 30 µT
LPC
Bmax Brms WP03max WP10max
A 2.113E-06 7.380E-07 0.2208 0.0423
B 5.266E-06 9.314E-07 0.2328 0.0325
C 2.876E-06 1.082E-06 0.1429 0.0150
D 1.791E-06 5.470E-07 0.1413 0.0318
E 2.493E-06 9.911E-07 0.1877 0.0416
1.7- 5.3 µT
(3) Exposure indexes calculated for the 5
models of LPT and BTC
7.8 x
7.9 x
5.3 x
5.6 x
4.2 x
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
0.7- 30 µT BTC
Bmax Brms WP03max WP10max
A 3.019E-05 4.730E-06 1.7528 0.2248
B 1.998E-05 2.735E-06 1.1174 0.1421
C 1.049E-05 2.704E-06 0.8682 0.1651
D 3.608E-06 1.297E-06 0.2918 0.0523
E 6.866E-07 2.805E-07 0.0449 0.0107
5.2 x
7.2 x
9.5 x
4.4 x
4.5 x
LPC
Bmax Brms WP03max WP10max
A 2.113E-06 7.380E-07 0.2208 0.0423
B 5.266E-06 9.314E-07 0.2328 0.0325
C 2.876E-06 1.082E-06 0.1429 0.0150
D 1.791E-06 5.470E-07 0.1413 0.0318
E 2.493E-06 9.911E-07 0.1877 0.0416
1.7- 5.3 µT
(3) Exposure indexes calculated for the 5
models of LPT and BTC
7.8 x
7.9 x
5.3 x
5.6 x
4.2 x0.001
0.01
0.1
B [
T]
Reference Levels B pop. (1998-2010)
2010-B-pop
1998-B-pop
2x @50Hz
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
0.7- 30 µT BTC
Bmax Brms WP03max WP10max
A 3.019E-05 4.730E-06 1.7528 0.2248
B 1.998E-05 2.735E-06 1.1174 0.1421
C 1.049E-05 2.704E-06 0.8682 0.1651
D 3.608E-06 1.297E-06 0.2918 0.0523
E 6.866E-07 2.805E-07 0.0449 0.0107
5.2 x
7.2 x
9.5 x
4.4 x
4.5 x
1E-06
1E-05
0.0001
B [
T]
f [Hz]
4.32x
16x
Selected LPC & BTC
ALPC
•Complex/impulsive waveform
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
ABTC
•Complex polarization (LPC)
•Almost linear polarization (BTC)
Selected LPC & BTC
ALPC
•Complex/impulsive waveformSuitable to treat exposures to complex waveform (not sinusoidal)
impressed fields with general polarization.
(4) Desired characteristics of the dosimetric
method
Focusing the attention on the time evolution of the exposures and
not to the space distribution of the field.
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
ABTC
•Complex polarization (LPC)
•Almost linear polarization (BTC)
impressed fields with general polarization.
Avoids the spectral decomposition of the problem (not convenient
in case of several spectral components and in relation to the so
called “spectral leakage” phenomenon).
Allows the assessment of the compliance with ICNIRP basic
restrictions that vary with frequency
(4) Weighted peak dosimetry at low frequencies with
linearly polarized impressed field
Separation space-time dependence
),( trB
)()( tf⋅rB
Solution of a quasi static,
space-dependent dosimetric
problems
(linear polarization)
quasi-static conditions
+
Faraday law
)()(
tgtdf =)()(),( tgt ⋅= rJrJ
(*1)
)(rE
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
)(rJ
)(tgdt
=)()(),( tgt ⋅= rErE
Application of
surface/volume average +
RSS
)(rJ
)(rE
Series of first order filters that
represent the inverse of ICNIRP BR for J
and Ein-situ
{ }
{ })()(),(
)()(),(
tgtWPE
tgtWPJ
E
J
Γ⋅=
Γ⋅=
rEr
rJr{ })(tgEΓ
{ })(tgJΓ
)(rE
(4) Weighted peak dosimetry at low frequencies with
homogeneous impressed field
Separation space-time dependence
),( trB
Solution of three quasi static, space-
dependent dosimetric problems
(homogeneous field)
quasi-static conditions
+ Faraday law
)(tdB
∑=
⋅=3
1
)()(),(i
ii tgt rJrJ
( ) ( ) ( )tBztBytBxt zyx ˆˆˆ),( ++=rB
)(3,2,1 rE
zyx ˆ,ˆ,ˆ ( ) ( ) ( )tBtBtB zyx ,,
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
)(3,2,1 rJ)(
)(3,2,1
,,tg
dt
tdB zyx =∑=
=
⋅=3
1
1
)()(),(i
ii
i
tgt rErE
Application of surface/volume
averages (**)
Series of first order filters that
represent the inverse of ICNIRP
Guidelines for J and Ein-situ
)(3,2,1 rE
( ) ( ) ( ){ } ( ) ( ){ } ( ) ( ){ }2
3
1
23
1
23
1
,
Γ+
Γ+
Γ= ∑∑∑=== i
iJiyi
iJiyi
iJix tgjtgjtgjtWPJ rrrr
Averages applied separately on each cartesian component
Linearity of Γ
Pregnant body model• Tomoaki Nagaoka, Toshihiro Togashi, Kazuyuki Saito, Masaharu Takahashi, Koichi
Ito and Soichi Watanabe An anatomically realistic whole-body pregnant-woman
model and specific absorption rates for pregnant-woman exposure to
electromagnetic plane waves from 10 MHz to 2 GHz Physics in Medicine and
Biology, Vol.52, pp.6731-6745, 2007
• S.Gabriel, R.W.Lau and C.Gabriel The dielectric properties of biological tissues:
III. Parametric models for the dielectric spectrum of tissues, Physics in Medicine
and Biology, Vol.41, N.11, November 1996, pp.2271-2293.
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
and Biology, Vol.41, N.11, November 1996, pp.2271-2293.
• A. Christ, W. Kainz, E.G. Hahn, K. Honegger, M. Zefferer, E. Neufeld, W. Rascher, R.
Janka, W. Bautz, J. Chen, B. Kiefer, P. Schmitt, H.-P. Hollenbach, J. Shen, M. Oberle,
D. Szezerba, A. Kam, J.W. Guag, and N. Kuster. The Virtual Family Development of
surface-based anatomical models of two adults and two children for dosimetric
simulations. Physics in Medicine and Biology, 55 N23-N38, January 2010, online
December 2009, http://dx.doi.org/10.1088/0031-9155/55/2/N01.
• R Cech , N Leitgeb and M Pediaditis Fetal exposure to low frequency electric
and magnetic fields Physics in Medicine and Biology, Vol 32, N. 4, 2007
J Ein(5) Results (A, LPC)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
WPJ WPE
WPE in skin (A,LPC)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
WPE-PNS battery charger
TISSUE MAX 99%-ile
Skin 0.631 0.039
WP10=0.225
WPE in skin (MRI)
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
WPE-PNS battery charger
TISSUE MAX 99%-ile
Skin 27.0413 5.32045
WP10=0.42
(5) Results (A, BTC)
5.2 x
Tissue WP03 WP10WPJ
max
WPE
CNS
99%
WPJ /
WPE
Brain Grey Matter 1.21 0.033 37
Brain White Matter 0.64 0.028 23
Cerebellum 0.87 0.019 47
7.2 x38 x
avg.
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
1.75 0.225
Cerebellum 0.87 0.019 47
Pons 0.43 0.009 47
Fetal Brain 0.17 0.020 8
Fetal Eye 0.27 0.005 55
Fetus (all the other) 1.61 0.034 47
In CNS and in the foetus the new guidelines allow exposures almost 40 times (intended as average) higher than the old ones
(5) Results (A, BTC)
5.2 x65 x
Tissue WP03 WP10WPJ
max
WPE
PNS
99%
WPJ / WPE
Blood 1.935 0.011 172
Bone Cortical 1.716 0.049 35
Cartilage 1.17 0.017 69
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
1.75 0.225
Cerebellum 0.87 0.010 84
Fat 1.23 0.039 32
Small Intestine 1.46 0.018 81
Uterus 2.08 0.017 124
Bone Cancellous 1.60 0.040 40
Muscle 1.41 0.018 77
Skin 0.48 0.039 12
1. A possible approach to the evaluation of the complex waveform magnetic fields and the (complex waveform) induced quantities induced by them was presented.
2. Particular attention was focused on the calculation of the so called WPJ and WPE indexes that implement the WP approach for basic dosimetricquantities.
3. A possible problem was evidenced related with WPE index in skin and less refined body models (skin-skin contacts)
Conclusions and future developments
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
• An extension of the presented dosimetricmethod was developed that allows tocalculate the WPJ and WPE indexesstarting from B field measurements, movingthe same instrument in a set of fixed pointsdisposed in convenient way.
Thank you for your attention
International Conference on Non-Ionizing Radiation and Children's Health 18 - 20 May 2011, Ljubljana, Slovenia
Thank you for your attention