Assessment of the Possible Health Effects of Ground Wave Emergency Network (1993) / Chapter Skim
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In Vitro Cellular and Subcellular End Points
In Vitro Cellular and Subcellular End Points
Pages 85-108
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From page 85... ...
According to the data presented in Chapter 3 and some additional plane-wave approximations, relevant exposure and dose metrics predicted for GWEN site boundaries are listed in Table 7-1: TABLE 7-1 GWEN Exposure and Dose Metrics at Site Boundary Exposure or Dose Metric Maximum incident power density, W/m2 Maximum electric field in human, V/m Maximum magnetic induction in human, ,uT Maximum specific absorption rate (SAR) , W/kg Maximum induced current density, A/m2 Calculated from plane-wave approximation.
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From page 86... ...
With very limited data at low- or ultra-highfrequencies, results with low-level ELF fields might seem applicable to the GWEN situation, but there are several pitfalls, as follows: · At ELF, the intracellular electric fields and current densities are usually very small, because of poor coupling with external fields. Thus, an external field of hundreds of kilowatts per meter would be required to produce the internal fields listed in Table 7-~.
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From page 87... ...
At the other extreme of amplitude, Fitzsimmons et al.25 elicited bone tissue proliferation and mitogenic activity with an ELF electric field of approximately 1O-s V/m. Finally, three reports by Cossarizza et al.2628 describe increases in cell proliferation and interleukin-2 activity and decreases in DNA repair in human lymphocytes exposed to pulsed fields similar to those used clinically for lowleve} electric facilitation of bone repair.
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From page 88... ...
RNA transcription, polypeptide synthesis. Protein and DNA synthesis, Ca2+ and cyclic AMP concentrations, collagenproduction, alkaline phosphatase and mitogen activity, cell proliferation.
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From page 89... ...
BONE HEALING In connection with in viva experiments to stimulate bone healing in test animals, Brighton et al.~~3 measured in vitro responses of cultured bovine chondrocytes and rat bone cells to 60-kHz continuous sine-wave electric fields administered by capacitive coupling for various durations between 5 min and 48 h. In some conditions, modest but statistically significant field-associated changes in isotope uptake and in cyclic AMP (cAMP)
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From page 90... ...
CYTOGENETIC EFFECTS Studies of chromosomal changes in mammalian cells, although producing predominantly negative results, have sometimes produced conflicting results. Two studies have indicated chromosomal breaks after exposure to 2.45-GHz microwaves.39 40 In one study, incident power varied between 25 and 200 W;39 positive results were seen only when assays were performed without temperature control.
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From page 91... ...
, compared with controls.42 Vertical electric fields produced no difference from controls, and no effect was seen with a 4-15 wk exposure.43 Female CD-1 mice treated with 2.45-GHz microwaves at 200 W/m2 did not differ from controls in SCE frequency in bone marrow cells.44 Other studies in mice also failed to demonstrate significant differences in chromosomal aberrations in spermatocytes45 or bone marrow46 after treatment with 2.45-GHz microwaves; but positive results have been reported in rat bone marrow47 and Chinese hamster corneal epithelium.48 Studies on human cells exposed in vitro to low frequencies have also produced conflicting results. No increase in chromosomal breaks, SCE, or chromosomal aberrations were seen in several studies.~3 49-52 For example, one study used 60-Hz fields with variable electric current densities of 3 - 3,000,uA/cm2 and a fixed magnetic field of 0.22mT.~3 No changes in SCE, micronuclei, clonogenicity, or cell-cycle kinetics were observed.
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From page 92... ...
uridine; regions sensitive to DNase I, and therefore transcriptionally active, were examined with nick translation directly on the DNA of the cytological preparations; and RNAs of various size classes were isolated with sucrose density-gradient centrifugation. In the presence of a repetitive single pulse signal (single 380-,usec pulses used clinically to yield 0.15 V/m in bone, repeated at 72 Hz)
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From page 93... ...
There was no effect in cells exposed to a null electric field, so the magnetic field was claimed to play no role in the transcriptional changes. A transient increase in transcription rates with a maximum of 50 or 60~o enhancement was seen after 30-120 min of exposure to very small electric fields; the rate declined to basal values by 18 h.
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From page 94... ...
Strengths of induced electric fields were not reported. Those studies demonstrate biological effects, but not health consequences.
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From page 95... ...
The same laboratory reported an apparently contradictory study in which a decrease in Ca2+ efflux, rather than an increase, occurred when electric fields without an RF carrier were used; this study also contradicted the study of Blackman et al.,77 which showed that fields without an RF carrier net en increase in Ca2+ efflux. ~ ~ ~ ~ _~^ ~ ^_^ t—vets_ ~~$ ~ ~ ~ _ e .
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From page 96... ...
Although the function of polyamines has not been completely elucidated, it is known that they play a role in cell proliferation. Induction of proliferation in quiescent cell populations by hormones, growth factors, or tumor promoters is normally preceded by ODC induction and increases in cellular polyam~nes.84 rhe induction of ODC by most tumor promoters has been considered a necessary, although not sufficient, step in tumor promotion, so ODC has been used as an early indicator of tumor promotional effects.69 70 Some studies have suggested that EMFs can induce ODC in tissue-culture cells.
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From page 97... ...
The experiments suggested a synergistic effect of TPA and EMFs on ODC induction. Although those authors have shown that ELF electric fields and 16-Hz amplitudemodulated RF fields have some biological effect on ODC activity, they have not shown ODC induction by these fields.
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From page 98... ...
We are forced to state, in the absence of reports on cellular response to fields even remotely resembling GWEN fields, that firm conclusions cannot be drawn. In a search for a match of experimental exposures with maximum exposures expected at a GWEN station site boundary, we found some experiments that yielded positive results.
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From page 99... ...
Pp. 197-225 in CRC Handbook of Biological Effects of Electromagnetic Fields, C
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From page 100... ...
1991. Reproductive integrity of mammalian cells exposed to power frequency electromagnetic fields.
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1989. Extremely low frequency pulsed electromagnetic fields increase cell proliferation in lymphocytes from young and aged persons.
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From page 102... ...
1983. Pulsing electromagnetic fields induce cellular transcription.
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From page 103... ...
1986. The effect of low-level 60-Hz electromagnetic fields on human lymphoid cells: Il.
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1991. Spontaneous and niitomycin C-induced micronuclei in human lymphocytes exposed to extremely low frequency pulsed fields.
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1989. Exposure of human cells to low-frequency electromagnetic fields results in quantitative changes in transcripts.
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Pp. 21 I-249 in Extremely Low Frequency Electromagnetic Fields: The Question of Cancer, B
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From page 107... ...
1988. Increased ornithine decarboxylase activity in cultured cells exposed to low energy modulated microwave fields and phorbo} ester tumor promoters.
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