evaluation and characterization of fetal exposures … · 2014. 4. 16. · basics of a dosimetric...

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


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


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


‘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


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


True RMS

(1) Measurement setup

Narda-ELT400

Agilent U2531A


Narda-ELT400

Analog outputs

(2) Developement of numerical ICNIRP filters

( )( ) HzbHzaAbsas

sAsH ffc 008282

21025.6

1)(

6

2

⋅=⋅=⋅⋅

=++

= − ππ

B98pop


( )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 %


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


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


BLPC

CLPC

(3) Characteristics of the measured B field (LPC)


DLPCE

LPC


(BTC)

ABTC


BBTC

CBTC


(BTC)


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


BTC


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


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



7.8 x

7.9 x

5.3 x

5.6 x

4.2 x


0.7- 30 µT BTC


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


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



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


0.7- 30 µT BTC


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


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.


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


)(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 ,,


)(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.


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)


WPJ WPE

WPE in skin (A,LPC)


WPE-PNS battery charger

TISSUE MAX 99%-ile

Skin 0.631 0.039

WP10=0.225

WPE in skin (MRI)


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.


1.75 0.225


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


1.75 0.225


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


• 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


Thank you for your attention

evaluation and characterization of fetal exposures … · 2014. 4. 16. · basics of a dosimetric...

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