I. Chatterjee

Human Body Impedance and Threshold Currents for Perception and Pain for Contact Hazard Analysis in the VLF-MF Band

The body impedance and threshold currents needed to produce sensations of perception and pain have been measured for 367 human subjects for the frequency range 10 kHz to 3 MHz. A sufficient number of subjects (197 male and 170 female subjects of ages between 18 and 70 years) were utilized in the study to make valid statistical predictions for the general adult population. Various types of contact with metallic electrodes were used to simulate the situation where a human being would be in contact with a large metallic object (car, van, school bus, etc.) in an electromagnetic field in the VLF to MF band. Based on these measurements, it is speculated that the body impedance of a human being is inversely proportional to the body dimensions and the threshold current for perception is directly proportional to the square of the body dimensions. Predictions are made, based on scaling, for the corresponding threshold values for ten-year-old children. The average measured impedance and threshold current values are used to calculate threshold electric fields required to produce sensations of perception and pain in humans in contact with these vehicles. It is concluded from these calculations that many situations can exist in which the present ANSI (American National Standards Institute) recommended standard of 632 V/m for the frequency band 0.3-3 MHz is too high.

Head Resonance: Numerical Solutions and Experimental Results

We have used numerical solutions and experiments with phantom models of man, and experiments with the Long Evans rat to show the existence of head resonance. Greatest absorption in the head region of man occurs at a frequecy of about 375 MHz. Absorption is stronger for wave propagation from head to toe than it is when the electric field is parallel to the long axis. The highest absorption cross section for the human head is projected to be approximately 3.5 times its physical cross section.

Electromagnetic-Energy Deposition in an Inhomogeneous Block Model of Man for Near-Field Irradiation Conditions

The plane wave spectrum approach is used to calculate the electromagnetic energy absorption and its distribution in a 180-cell, inhomogeneous model of man for a prescribed vector electric field generated by RF sealers and other electronic equipment. The whole-body-averaged absorption density increases approximately as (Delta/lambda)/sup 2/ to the asymptotic plane wave value where Delta/lamda is the width in wavelengths of the best-fit half-cycle cosine function to prescribed E-values.

Quantification of electromagnetic absorption in humans from body-mounted communication transceivers

The internal electric (E) field and energy deposition in a full-size adult male mannequin in the immediate vicinity of 1.5 W body-mounted communication transceivers have been measured. Transceivers operating at the four frequencies 50, 150, 450, and 800 MHz, and placed at various locations vis-à-vis the body were used. The mannequin was filled with two-thirds muscle-simulant biological phantom mixtures at each of the four frequencies. The complex permittivities (ε*) of these mixtures were confirmed by measurement. The internal E-field distribution was measured by three-dimensional implantable E-field probes. Relatively superficial energy depositions were obtained at points close to the location of the transceiver antenna for the two higher frequencies with energy depositions typically less than 1-2 W/kg. Considerably reduced energy depositions were measured at the two lower frequencies on account of in-depth and wider dissemination of the absorbed energy and the relatively high ε*of the tissues which results in an increased shielding of the body.

Human Body Impedance for Electromagnetic Hazard Analysis in the VLF to MF Band

A knowledge of the average electrical impedance of the human body is essential for the analysis of electromagnetic hazards in the VLF to MF band. The purpose of our measurements was to determine the average body impedance of several human subjects as a function of frequency. Measurements were carried out with the subjects standing barefoot on a ground plane and touching various metal electrodes with the hand or index finger. The measured impedance includes the electrode polarization and skin impedances, spread impedance near the electrode, body impedance, stray capacitance between the body surface and ground, and inductance due to the body and grounding strap. These components are separated and simplifed equivalent circuits are presented for body impedance of humans exposed to free-space electromagnetic waves as well as in contact with large ungrounded metaltic objects therein.

Electromagnetic Absorption in a Multilayered Model of Man

A multilayered planar model is used to examine the dependence of whole-body power absorption on the configuration of surface layers, e.g., skin, fat, and muscle which normally occur in biological bodies. It is found that the layering resonance for three-dimensional bodies (as opposed to the geometrical resonance) can be predicted quite accurately by a planar model. Calculations for a multilayered prolate spheroidal model of man predict a whole-body layering resonance at 1.8 GHz with a power absorption 34 percent greater than that predicted by a homogeneous model.

An Inhomogeneous Thermal Block Model of Man for the Electromagnetic Environment

An inhomogeneous thermal block model of man with 476 cubical cells has been developed. It incorporates inhomogeneous blood flow rates, metabolic heat production, specific heats, and thermal conductivities, obtained by volume-weighted averaging of the values for eleven different tissue types which constitute the human body. The transient heat conduction equation for the thermal model includes the effects of internal metabolic heat generation, electromagnetic energy deposition, heat conduction through the tissues, convective heat transfer by blood, evaporative heat dissipation by sweating and insensible perspiration, respiratory heat loss, and heat transfer to the environment by radiation and convection. The standard implicit finite difference technique has been utilized to solve the three-dimensional heat conduction equation.

Radio-frequency hazards in the VLF to MF band

The body currents induced in a human in conductive contact with various ungrounded metallic objects like cars, trucks, fences, etc., are calculated for the frequency band 10 kHz to 10 MHz. The calculated incident E-fields required to produce thershold perception and let-go currents indicate that the recently proposed ANSI guideline of 100 mW/cm2(∼615 V/m) in the frequency band 0.3 to 3.0 MHz may result in a potential for RF burns.

Numerical and Experimental Results for Near-Field Electromagnetic Absorption in Man

Experimental results are presented for the whole-body-average energy absorption and the internal E-fields in man exposed to leakage-type near fields. An empirical relationship, previously presented.

An Empirical Relationship for Electromagnetic Energy Absorption in Man for Near-Field Exposure Conditions

An empircal relationship is presented for the whole-body-average electromagnetic energy absorption in a 180-cell block model of man for near-field exposure conditions. Consideration is restricted to near fields with P polarization (no component of E directed arm-to-arm) in which the magnitude of the incident electric field is maximum immediately in front of the abdominal region. A highlight of this work is the considerably reduced whole-body average energy absorption for near-field partial-body exposures as compared to that obtained under plane-wave irradiation conditions.