?

ASSESSMENT OF SAR IN THE HUMAN HEAD,

CAUSED BY MOBILE PHONE WITH MEASUREMENT OF THE EMITTED ELECTRIC FIELD

Branko Stepanovski, Gjorgi Spasovski - Military Medical Center Skopje Macedonia.

Trajče Trajčev - ECO DETECT Accredited laboratory for testing of non-ionizing radiation according EN 17025 standard

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

CONTENT



introduction



equipment



model for SAR assessment



in which cases we use this model



some advises for reducing radiation



results and conclusion

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

INTRODUCTION

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

INTRODUCTION

The primary goal of this research is based on measurements of the emitted electric field (

E

) from mobile phone to assess the

Specific Absorption Rate SAR

, at some point in the brain of the user.

To achieve this, it is necessary to establish such conditions that the field strength (

E

) before reaching the sensor of the instrument is weakened (by passage through a water phantom), as much as it would undermine the field passing through the tissues of head (skin, ear shell, skull bone, brain liquid) and reach the point at a depth of 2,5 mm in the human brain.

The equation for transformation of the measured electric field

E

into the operational quantity SAR, in near field conditions, according the standard EN 50413, has the following shape: where

σ

- specific conductivity of brain tissue [S/m]

ρ

- mass density of the brain tissue [kg/m3] RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

E

QUIPMENT USED IN OUR STUDY

Willtek RF Shield

4921

Аntenna Coupler

4916 Freq. range 700MHz - 6GHz

Willtek Handheld Spectrum Analyzer

9102B Frequency range 100kHz – 4GHz RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

MEANING OF NEAR - AND FAR-FIELD

All measurements were performed in near-field region  (900 MHz) = 0,33 m;  (1800 MHz) = 0,17 m

Reactive near-field region Radiating near-field region Far-field region

Lateral edge of the region, measured from antenna

E



H Z

=

E

/

H

Component to be measured 0 to

E

 No Z 0  &

H

 to

E

 +2

D

2 /  Quite Yes 

Z

0 or

H

 +2

D E

Yes = 2 /

Z

 or 0

H

to  “Because all the tissues in human body are non-magnetic (the relative permeability μ

r

although in the region of the near-filed both, magnetic and electric components of the ≈ 1)”

[6]

, electromagnetic field should be considered, conclusion is drawn that main contribution to SAR at RF, is from the interaction with the electric field.

That is why, our assessment of SAR is made with analysis of the electric field. RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Incident radiation

I NTERACTION OF ELECTROMAGNETIC RADIATION WITH MATTER

absorption reflection attenuation transmission RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

ESTABLISHING EQUALITY BETWEEN

E B

AND

E D E b E d – –

E b

= E

d

electric field strength at 2.5 mm depth in the brain; electric field strength at the detector’s surface.

Attenuation

tissue

= Attenuation

phantom average relative dielectric constant RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

T

ISSUE DATA All data are valid for an average adult man

Type of tissue ρ = Brain 1040 kg/m 3 Dielectric constants of each tissue

ε

rb

σ

[S/m] Skull bone Skin Ear cartilage

ε

rsb

ε

rs

ε

rc 900 MHz 56,0 0,97 16,62 41,41 46,00 Brain liquid

ε

rbl 71,71 Dura

ε

rd 44,4 Air Equivalent

ε

ra 1 34,7 1800 MHz 43,5 1,15 15,56 38,10 38,87 (1,9 GHz) 67,2 42,9 1 30,6 Average thickness of each tissue [mm] 2,5 6,5 2 6 4 0,3 5 26,3

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

BASIC CALCULATIONS FOR THE TISSUE

Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution to the interaction with the radiation, the average dielectric constant of all these tissues can be calculated.

q

(

t

) – antenna’s electrical charge in dependence of time; average relative dielectric constant All contribution in tissue attenuation RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

PHANTOM MATERIAL DATA

Type of material Relative dielectric constants of each material 900 MHz 1800 MHz

ε

Air ra 1 1 Plexiglas

ε

rp 2,63 2,59 T hickness of each material [ mm ] 14

(900 MHz)

16

(1800 MHz)

6 (2 x 3 = 6) Distilled water Equivalent

ε

rw 78,2 77,4 15

(900 MHz)

13

(1800 MHz)

34,7 30,6 35

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

BASIC CALCULATIONS FOR THE PHANTOM

r

tf – distance between the mobile phone and the surface of the detector All contribution in phantom attenuation RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

SPECIFIC CHARACTERISTIC OF THE INTENSITY OF THE MOBILE PHONE RADIATION

Hold it at he bottom By covering large areas of the phone with your hand, you reduce its ability to send and receive signals. The phone then increases its power and transmits stronger radiation to compensate this. So hold the phone as far down as possible, so it can operate at low power.

Get in the best position You can see the signal reception strength in the display. When reception is good, the phone reduces power and radiation. If reception is poor , the phone uses maximum power and radiation. RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

DIFFERENT INTENSITY OF RECEIVED SIGNAL

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

B A S I C R E S T R I C T I O N S F O R T I M E VA RY I N G E L E C T R I C A N D M A G N E T I C F I E L D S F O R F R E Q U E N C I E S U P TO 1 0 G H Z .

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RADIATION PENETRATES DEPENDING ON AGE

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

TIME DEPENDENCE OF TEMPERATURE DURING TALK

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PHASES OF RADIATION DURING THE USE OF MOBILE PHONE

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RESULTS AND CONCLUSION

Results:

In the case of optimal received signal of the tested mobile phones, assessed SAR values are close to the values that are declared by the manufacturers, for those mobile phones (valid for an ideal case). In case of weakening of the received signal by mobile phones (real situation), SAR values can be increased multiple times.

E

is 3 to 4 times greater

Conclusion:

Possibilities of the measuring equipment and the applied mathematical model opens up the doors for the following research: • With change of the received signal for the tested phones, SAR assessment is made for many different situations in reality, for the same phone (in places where received signal of mobile phones is lower) . For such places SAR grows dramatically, due to its dependence on |E | i 2 .

• With change of the attenuation factor (changes of the thickness of water phantom), it can be determined SAR for different depths in the brain or in any other tissue, • With accurately calculated SAR we can assess temperature increase at the point of measurement, located in brain tissue.

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

R

EFERENCES

1. Guidelines for Limiting Exposure to Time-varying Electric, Magnetic and Electromagnetic

Fields (up to 300 GHz)

, ICNIRP 2. 50413 Basic Standard on Measurement and Calculation Procedures for Human Exposure

to Electric, Magnetic and electromagnetic Fields (0 Hz – 300 GHz)

, European Committee for Standardization 3. Elektromagnetizam I, II , Mirjana Jonoska 4. FDTD Computation of Temperature Rise in the Human Head for Portable Telephones , Wang, J. and O. Fujiwara 5. On Averaging Mass of SAR Correlating with Temperature Elevation due to a Dipole

Antenna

, A. Hirata, K. Shirai, and O. Fujiwara 6. Interaction between mobile terminal antenna and user, Juho Poutanen 7. SAR and Temperature Elevation in a Multilayered Human Head Model due to an

Obliquely Incident Plane Wave,

A. I. Sabbah and N. I. Dib 8. SAR Estimation for Cellular Phone , Association of Radio Industries and Businesses 9. Review of the scientific evidence for Limiting Exposure to EMFs (0–300 GHz) , NRPB Britain RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Thank yu for your attention

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

П

РАШАЊА

S

OME REMARKS

Unlike the brain itself, “temperature elevation 0.2 K– 0.3 K in hypothalamus leads to altered thermoregulatory behavior”

[5]

. Acute RF heating (more than about 41-43 o C for 2-3 hours) can induce lens opacities (cataracts) in experimental animals. However, threshold for cataract induction resulting from chronic exposure to RF EMFs has not been defined.

[9]

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

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П РОЦЕНА НА ДОЗА КАЈ НЕЈОНИЗИРАЧКОТО ЗРАЧЕЊЕ За процена на количеството на апсорбираната енергија во човековото тело (дозата) потребно е де се дефинираат неколку клучни поими: • •

Специфична енергетска апсорпција (ЅА):

Се дефинира како апсорбирана енергија по единица маса биолошко ткиво изразена со џул врз килограм

(J/kg).

Количина на специфична енергетска апсорпција (ЅАR):

Се дефинира како апсорбирана енергија по единица маса биолошко ткиво за одредено време,

(W/kg)

.

•

Густина на моќност (Ѕ)

: Кога моќност на зрачењето на рамен бран ќе помине низ единица површина нормална на правецот на движење на бранот. Се дефинира (

W/m2) SA(Jkg -1 ) = SAR (Wkg -1 ) * време на експозиција (секунди)

Основни единици J/kg *1/т

J/kg

Единици за јонизиречко зрачење

Sv

Доза

W/kg

RAD2012, 25-27 A PRIL

Sv/т

Количина на доза 2012 - N IŠ , S ERBIA Единици за не-јонизирачко зрачење

SA

Специфична апсорпција

SA/h SAR

Количина на специфична апсорпција

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

S

IMPLIFIED MODEL OF TISSUE LAYERS

Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution for each can calculate the average dielectric constant of all these tissues

E b

Depth in brain CSF – liquor (brain liquid) D u r a Skull bone 26,3 mm

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Ear c artilage Air S k i n

E

in

The Heart's Electromagnetic Field

IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Affected part of the head, taken in consideration

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Depth in brain CSF – liquor (brain liquid) D u r a Skull bone Cartilage Air S k i n

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

S

IMULATING THE ATTENUATION FROM THE HEAD TISSUES

E d

detector P l e x i g l a s Distilled water P l e x i g l a s 19 (21) mm 35 mm Air

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

E

in

mobile phone

T

ISSUE DATA

Type of tissue ρ = Brain 1040 kg/m 3 Skull bone Skin Ear cartilage Brain liquid CSF Relative dielectric constants of each tissue 900 MHz

ε

rb 56,0

σ

[S/m]

ε

rsb 0,97 1800 MHz Average thickness of each tissue [ mm ] 43,5 2,5 1,15 6,5

ε

2 rs

ε

6 rc

ε

rbl 16,62 15,56 41,41 46,00 38,87 38,10 (1,9 GHz) 71,71 67,2 4 Dura

ε

rd 44,4 42,9 0,3 Air Equival ent

ε

ra 1 1 5 34,7 30,6 26,3

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

M

EANING OF

SAR

SAR – specific absorption rate

[W/kg] Time derivative of the incremental electromagnetic energy (d

W

) absorbed by (dissipated in) an incremental mass (d

m

) contained in a volumen element (d

V

) of given mass density (

ρ

).

where

E

i

σ ρ c

i dT/dt r.ms. value of the electric field strength in the tissue in V/m;

conductivity of body tissue in S/m; density of body tissue in kg/m 3 ; heat capacity in body tissue in J/kg K; time derivative of temperature in body tissue in K/s.

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

Table below indicates the method at different distances from radio-stations:

Lateral edge of the region, measured from antenna

Reactive near-field region

0 to 

Radiating near-field region

 to  +2D 2 /  E  H Z = E / H Component to be measured  No Zo E & H Quite Yes  Zo E or H

Far-field region

 +2D 2 /  to  Yes = Zo E or H RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

S

IMPLIFIED MODEL OF TISSUE LAYERS

Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution for each can calculate the average dielectric constant of all these tissues

Depth in brain CSF – liquor (brain liquid) D u r a Skull bone Cartilage Air S k i n

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

E d

P l e x i g l a s Distilled water P l e x i g l a s Air

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

E

in

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA mobile phone air plexiglas distilled water detector

ASSESSMENT OF SAR IN THE HUMAN HEAD,

CAUSED BY MOBILE PHONE WITH MEASUREMENT OF THE EMITTED ELECTRIC FIELD

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA Branko Stepanovski, Gjorgi Spasovski - Military Medical Center Skopje Macedonia.

Trajče Trajčev - ECO DETECT Accredited laboratory for testing of non-ionizing radiation

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

RAD2012, 25-27 A PRIL 2012 - N IŠ , S ERBIA

В

ЗАЕМНОДЕЈСТВО НА ЕЛЕКТРОМАГНЕТНОТО ЗРАЧЕЊЕ СО МАТЕРИЈАТА

Количина на специфична енергетска апсорпција (ЅАR) (W/kg)

.

Апсорпција Упаден зрак Рефлексија

Aпсорбирана доза Густина на моќност

(Ѕ) (W/m2)

Трансмисија

RAD2012, 25-27 A PRIL N IŠ , S ERBIA 2012 -