How To Understand The Safety Of A Cell Phone (Cell Phone)

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1 Compliance Testing of Mobile Phones Masao Taki Tokyo Metropolitan University JAPAN

2 Outline Exposure Standards/Guidelines Product Standard of MTE and Standard Procedures of Compliance Testing Some remarks

3 Exposure Standards/Guidelines on Mobile Telecommunications Equipments (MTE)

4 Radiofrequency (RF) Exposure Guidelines International ICNIRP(1998) IEEE C National US: FCC ET Docket (1996) EU: EC Recommendation (1999) Japan: TT Council Report (1990,1997) Korea: KEES (2000) MIC (2002)

1-1999 National US: FCC ET Docket 93-62 (1996) EU: EC

5 Basic Concepts of Guidelines Dose metric to be limited for protection Induced current density (f < 10 MHz) Whole body SAR (100 khz < f < 10 GHz) Maximum local SAR (100 khz < f < 10 GHz) Power density (f > 10 GHz) SAR : Specific Absorption Rate Energy absorption rate per unit mass of tissue [W/kg]

Maximum local SAR (100 khz < f < 10 GHz) Power density (f > 10 GHz) SAR :

6 Threshold for Whole-body Exposures Biological Response WBA-SAR [W/kg] T [ C ] Remarks Developmental effects Jensh et al Transiently reduced male fertility Blood/cell immune response Hormone change Reduced performance of learned tasks De Lorge et al Thomas et al Reduced task acquisition 1-2 * Schrot et al Behavioral/physiological thermoregulation 1 * Stern et al From NRPB Report R240, tabulated by N. Kuster.

5 Blood/cell immune response 2 13 1 3 Hormone change 3-4 1 2 Reduced performance of learned tasks 2.5 5 1 De Lorge et al.

7 Derivation of WBA-SAR Limit Estimated Threshold 4 W/kg Safety/Reduction Factor of 10 Limit for Controlled Condition/Occupational Exposures 0.4 W/kg Additional Safety/Reduction Factor of 5 Limit for Uncontrolled Condition/General Public Exposures 0.08 W/kg

8 Threshold for Local Exposures Biological Response Local SAR [W/kg] T [ C ] Remarks Lens Cataract Guy et al MW Auditory Effect << 0.1 << 0.1 Chou, et al GHz, PW From NRPB Report R240, tabulated by N. Kuster.

5 Guy et al. 1975 MW Auditory Effect << 0.1 << 0.

9 Maximum Local SAR Limit IEEE (100 khz < f < 6 GHz) Spatial peak SAR values can exceed a wholebody average value by more than a factor of 20 Controlled environment 8 W/kg averaged over any 1g of tissue except extremities Extremities (hands, wrists, feet and ankles): 20 W/kg averaged over any 10 g of tissue Uncontrolled environment 8 W/kg average over any 1g of tissue except extremities Extremities (hands, wrists, feet and ankles): 20 W/kg averaged over any 10 g of tissue Pinna is going to be included in extremity

ankles): 20 W/kg averaged over any 10 g of tissue Uncontrolled environment 8 W/kg average over any 1g of tissue except

10 Maximum Local SAR Limit ICNIRP (100 khz < f < 10 GHz) Temperature rise should be limited to be less than 1 C Occupational exposures Head and trunk: 10 W/kg averaged over any 10 g of contiguous tissue Limbs: 20 W/kg (averaged over 10 g) General public exposures Head and trunk: 2 W/kg averaged over any 10 g of contiguous tissue Limbs: 4 W/kg (averaged over 10 g)

of contiguous tissue Limbs: 20 W/kg (averaged over 10 g) General public exposures Head and

11 Summary of Exposure Limits for MTE Maximum local SAR should be limited 1.6 W/kg for any 1 g of tissue 2 W/kg for any 10 g of tissue The limits have sufficient safety/reduction factors to the threshold of established hazardous effects The values of 1.6 or 2 are not significantly different in the viewpoint of biological rationale

sufficient safety/reduction factors to the threshold of established hazardous

12 Product Standard of MTE and Standard Procedures of Compliance Testing

13 Roles in NIR Protection Health risk assessment and recommendation of protection guidelines WHO, ICNIRP, etc. Social, economic, and political considerations National governments and their authorities Technical advice and development of practical measures to assess compliance with guidelines IEC, CENELEC, etc.

Social, economic, and political considerations National governments and their

14 Standard Setting Bodies and Standards for Compliance Testing CENELEC TC211 (EU) pren 50361, pren (2001) IEEE SCC 34 SC 2 (USA) IEEE Std X (2002?) IEC TC106??? ARIB (Japan) ARIB Std T56 (1997) under revision KEES (Korea)

SC 2 (USA) IEEE Std 1528-200X (2002?) IEC TC106?

15 Specific Absorption Rate (SAR) Energy absorption rate per unit mass of tissue [W/kg] Definition SAR = dp dm = dp dv ρ E-field Temperature rise σ E SAR = ρ T SAR = c t 2 t +0

16 Basic Concept Surrogate for actual SAR in the user s head is needed Specific Anthropomorphic Mannequin (SAM) is defined as the standard shape of head. Electric field strengths E in the homogeneous tissue simulating material is measured SAR is obtained by σe 2 /ρ, where σ is the conductivity of the material andρis the mass density of the head. The mass of the head is assumed to be 1000 kg/m 3 1 g or 10 g average value of SAR is calculated

Electric field strengths E in the homogeneous tissue simulating material is measured SAR is obtained by σe 2

17 Example of Measurement System Robot controlled E field probe measures SAR in a head phantom

18 E-Field Probes cm

19 Specific Anthropomorphic Mannequin (SAM)

20 Dielectric Properties of Head Phantom Tissue Frequency (MHz) Relative Dielectric Constant (ε r ) Conductivity (σ) (S/m)

835 900 1450 1800 1900 2000 2450 3000 45.3 43.5 41.5 41.5 40.5 40.0 40.

21 Liquid Simulant Materials An Recipe Sucrose Sodium Chloride De-ionized water (16 Mega-ohms minimum) Hydroxyethyl Cellulose (HEC) Bactericide Diethylene Glycol Butyl Ether (DGBE) Triton X-100

22 Phone Positions 1. Cheek or Touch position

23 Phone Positions 2. Tilted position

24 SAR Distribution

25 Tests to be Performed Determination of worst case position Left and right Cheek and tilted positions At center frequency Determination of maximum Low end and high end frequencies Operated at highest output power for each operational mode Antenna extended and retracted

26 Uncertainty (1) ERROR SOURCES Description (Section) Uncertainty Value (%) Standard Probability Distribution Divisor c Uncertainty i (%) Measurement Equipment Calibration Normal 1 or k 1 Isotropy Rectangular 3 1 Linearity Rectangular 3 1 Detection limits Rectangular 3 1 Boundary effect Rectangular 3 1 Measurement device Normal 1 or k 1 Response time Normal 1 1 Noise Normal 1 1 Integration time Normal 1 1 Mechanical constraints Scanning system Rectangular 3 1 Phantom shell Rectangular 3 1 Matching between probe and phantom Rectangular 3 1

27 Uncertainty (2) g p Physical Parameters Liquid conductivity (deviation from target) % Rectangular Liquid conductivity (measurement error) Rectangular Liquid permittivity (deviation from target) % Rectangular Liquid permittivity (measurement error) Rectangular Drifts in output power of the phone, probe, temperature and humidity % Rectangular 3 1 Perturbation by the environment % Normal 1 or k 1 Post-Processing SAR interpolation and extrapolation Rectangular 3 1 Maximum SAR evaluation Rectangular 3 1 Combined standard uncertainty Expanded uncertainty (confidence interval of 95 %) < 30 %

28 Summary of Compliance Testing SAR in the head is evaluated by a surrogate of the SAR in a liquid phantom in a shell with standard shape of a human head. Harmonization has reduced variations among different standards. Uncertainty is high but required to be less than 30 %.

29 Some Remarks

30 SAR Values and Actual Exposures The SAR value obtained by the standard procedure provides in principle worst-case value for the device A device with the lower SAR value by this procedure does not necessarily cause the lower SAR in actual use as the radiation power varies depending on the condition of signal strength. This fact should be noted when the SAR values of devices are opened to the public.

31 Product Standard Compliance testing standard is a product standard. Product standards should be based on the exposure standard but practical aspects are also important (cf. PS of MW oven). Conformity to the exposure standard is judged with a certain confidence interval.

32 Simple Measures Development of secondary measures to predict SAR in the developmental stage could be encouraged. Computation Fixed-probe measurement

33 Local SAR estimation system using solid phantom and fixed e-field probe SAR display High resistance feeder E-field sensor inside Dry phantom Mobile phone E-field meter E/O unit

34 Harmonization Further efforts should be done to harmonize the local SAR limits The difference between 1.6 W/kg in 1g and 2 W/kg in 10g is not significant in the viewpoint of biological data that have been established to date. Controversy on 1.6 and 2 W/kg will mislead the public as if the difference were biologically significant.

35 Future Needs Extend the frequency range Higher frequencies (extrapolation error, etc.) Lower frequencies (standing waves, etc.) Extend the applicable devices Variety of devices will appear with different configurations Improve efficiency May need simpler modeling of human body, e.g. of geometric shape instead of anatomical data. Simple model would reduce uncertainty of measurement at the cost of plausibility of modeling

36 Scientific Data We should note the absence of established hazardous effect of local exposure < 100 W/kg. SAR of 10 W/kg corresponds to about 100 V/m of internal electric field strength. We do not have sufficient data to prove the absence of athermal effects at this level, which might be or not be hazardous. It is necessary to find out more scientific rationale for local SAR limit that we could rely on.

37 Acknowledgment and Disclaimer I thank the following outstanding specialists for providing information and materials Dr. C-K Chou (Motorola, USA) Dr. Niels Kuster (IT IS, Switzerland) Dr. Joe Wiart (French Telecom, France) Dr. Soichi Watanabe (CRL, Japan) Dr. Toshio Nojima (NTT Docomo, Japan) Disclaimer This presentation does not represent the view of ICNIRP nor its SC III but the personal view of the author

38 Thank you END

ARIB TR-T12-34.925 V3.0.0. Specific Absorption Rate (SAR) requirements and regulations in different regions

ARIB TR-T12-34.925 V3.0.0. Specific Absorption Rate (SAR) requirements and regulations in different regions ARIB TR-T12-34.925 V3.0.0 Specific Absorption Rate (SAR) requirements and regulations in different regions Refer to "Notice" in the preface of ARIB TR-T12 for Copyrights. Technical Report 3rd Generation