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Coupling of GWEN Electromagnetic Fields to the Human Body
Pages 25-44

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From page 25...
... According to calculations by the MITRE Corporation, the maximum power density of exposure at the perimeter fence would be 0.001 mW/cm2, and this would decrease rapidly with increasing distance from the antenna and the perimeter fence. INDUCED FIELDS AND CURRENTS IN THE HUMAN BODY We have used an anatomically based model of the human bodyl 2 to estimate induced fields and currents for both EF and UHF electromagnetic fields.
From page 26...
... An induced current of 2.~8 mA is calculated to be flowing through the feet of a standing person. The calculated current is in excellent agreement with that estimated with the empirical equation given previously by Gandhi et al.4 In the empirical equation, the foot current Ah for a vertically polarized E field flowing through a standing, barefoot person is given by Ah = 0- i°8hm fMmE, where hm is the height of the human in meters (~.75 m for our model)
From page 27...
... 1 1 1 FIGURE 3-1. Calculated section currents for grounded anatomically based model of human body for exposure to electromagnetic fields at 174.625 kHz.
From page 28...
... Brain 165.7 3.5 170 Neck 155.2 8.1 380 Lung 140.8 7.2 475 Heart 133.0 8.4 250 Kidney 1 122.5 1 7.1 1 220 Liver 117.2 7.5 200 Bladder 89.7 10.4 405 Ankle 16.4 71.4 2,140 SARs FOR UHF ELECTROMAGNETIC FIELDS According to calculations by the MITRE Corporation, the maximum power density for the general public would be at the 4-ft perimeter fence, where the power density is estimated to be 0.001 mW/cm2. We have calculated the whole-body-averaged specific absorption rates (SARs)
From page 29...
... TABLE 3-2. Whole-Body-Averaged SARs Calculated for Anatomically Based Model of Human Body (Incident Power Density, 0.001 mW/cm2; Vertically Polarized E Field)
From page 30...
... Both isolated and grounded conditions of mode} are considered. Calculations assume incident power density of 0.001 mW/cm2 that is estimated for 4-ft perimeter fence around GWEN antennae.
From page 32...
... 350 MHz MICROSCOPIC FIELD INTERACTIONS AT THE MOLECULAR, CELLULAR AND TISSUE LEVELS As described in the preceding section of this report, the coupling of both LF and UHF signals from the GWEN system at locations beyond the site perimeter is too weak to produce measurable tissue heating. However, it has been reported that electromagnetic fields can produce biological effects through nonthermal interactions.6 7 As discussed in Chapters AS, effects of nonthermal fields have been reported to occur in the nervous, cardiovascular, endocrine, immune, and reproductive systems 32
From page 33...
... , whereas other effects may be attributable to electric fields induced across the cell membrane. The threshold induced current density for reproducible cellular responses to ELF fieldsi4 appears to be in the range of 0.~-~.0 ,uA/cm2, which is comparable with the intrinsic current densities flowing in the body as 33
From page 34...
... Those EF current densities are therefore about 10 times the threshold of ELF current densities for eliciting membrane and cellular responses. However, the effective E field induced within the cell membrane wall be substantially lower, by a factor of about I, 000, at low frequencies than at extremely low frequencies, because of the lower membrane impedance.~7 ~8 Consequently, the maximum currents induced in body tissues by the EF fields of a GWEN transmitter would be expected to establish electrical signals in cell membranes that are approximately one-hundredth the magnitude of the threshold values found to elicit reproducible cellular responses to ELF fields.
From page 35...
... ~ rat ,_, Gandhi et al.23 and Chatterjee et al.24 have estimated the threshold E fields that produce various sensations upon contact with various commonly metallic objects. Because somewhat larger currents would flow at 174.625 kHz than at 150.625 kHz and the threshold currents for various sensations are generally independent of frequency for frequencies higher than 100 kHz, somewhat smaller E fields can cause sensations at 174.625 kHz than at 150.625 kHz.
From page 36...
... TABLE 3-3. Incident Vertical Threshold E Fields Needed to Produce Various Sensations in Contact with Ungrounded Metallic Objects Finger contact, Grasping contact area = 144 mm2 contact, E ~ perception ~ E ~ pain ~ E I perception, Object Person V/m V/m V/m Compact car Man 280 340 1,490 Woman 300 400 1,200 10-year-old child 205 255 950 Van Man 155 I80 735 Woman 155 220 580 10-year-old child 120 140 430 Bus Man 160 200 480 Woman 165 230 425 10-year-old child 130 155 360 Fork-lift Man 95 120 395 truck Woman 90 125 330 10-year-old child 65 80 260 50-ft fence Man 420 450 2,700 Woman 390 450 2,250 10-year-old child 250 300 1,680 Source: O
From page 37...
... The data associated with a particular layer consisted of three numbers for each square cell: x and y positions relative to some anatomical reference point in the layer, usually the center of the spinal cord and an integer indicating which tissue the cell contained. Because the cross-sectional diagrams available in Eychleshymer and Schoemaker2s are for variable separations, typically 2.3-2.7 cm, a new set of equispaced layers was defined at 0.25-inch (0.635-cm)
From page 38...
... N ~4 N lo Lo b U]
From page 39...
... At low frequencies, use of the FDTD method is not as straightforward: a horrendous number of iterations would be needed to cover three to four periods of oscillation for converged results. A scaling procedure was recently developed that recognizes the quasistatic nature of coupling at lower frequencies, as previously pointed out by Kaune and Gillis38 and Guy et al.39 According to a logic similar to that of those authors, the fields outside the body depend not on the internal tissue properties, but only on the shape of the body, as long as the quasistatic approximation is valid; that is, the size of the body is smaller by a factor of 10 or more than the wavelength, and ~ a + jos ~ > > osO where a and ~ are the conductivity and the permittivity of the tissues, respectively, ~ = 27rf is the radian frequency, and SO is the permittivity of the free space outside the body.
From page 40...
... Quantities of interest for the EF band are the internal total electric fields and current densities for the various regions of the body. We have used the calculated internal fields to obtain the total electric field ET (i, i, k)
From page 41...
... Pp. 187-208 in Extremely Low Frequency Electromagnetic Fields: The Question of Cancer, B
From page 42...
... 1979. The direct influence of electromagnetic fields on nerve and muscle cells of man within the frequency range of 1 Hz to 30 MHz.
From page 43...
... 1984. A review of numerical models for predicting the energy deposition and resultant thermal response of humans exposed to electromagnetic fields.
From page 44...
... 1989. Numerical simulation of annular phased arrays for anatomically based models using the FDTD method.


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