laboratory room or field less than 1000 m2, the use of the number 3 condition can be permitted. But, in case of the situation where many rectennas or receivers are used all over the Earth, it is difficult to control all of the ecological systems being fluctuated by the existence of many rectenna sites, even under the condition number 2). We can not decide now. In a case where we can apply the condition 3), biota is not a concern. All we have to consider is the heat effect on local and/or global climate. In case of ii), we must, and may be able to, predict the resulted new ecological system according to the amount of the excess heat. For example; Desert —> More sterile desert Plain —> Desert Temperate zone —> Desert, Plain or Subtropical zone (depending on the humidity supply) Antarctic (inner land)-> Emergence and development of any kind of ecological system supported by the heat of the beam. Antarctic (shore line)-> Destruction and modification of the peculiar biota there. And in this case, we should consider the direct heating of living organisms by the laser beam or the microwaves, as much as possible, too. In case of condition 1) using microwave power transmission, all we have to consider is the direct nonthermal effects of microwave on living organisms. Consequently, the condition 2) is the most important issue in consideration of the excess heat effect on biota. A General Aspect on the Usage of the Microwave Beam Unlike laser beam, microwave effects are not restricted to the skin surface. The depth of the effects depends on its wavelength. The effects can concentrate in a wavelength-specific part of animal and plant bodies because of the resonance between the body and microwave. For example, microwaves of 2.45 GHz have a resonance with a body whose thickness is around 6,12 or 18 cm. The major effect of microwaves on animal bodies is thermal, but some reports say there are some non-thermal biological effects of microwave. Human Protection Standard Against Microwave The USA and former USSR have their own microwave safety standards and they are referred to by many other countries. We summarize them in Table 6.2. [Murakami, 1982] As you can see in Table 6.2, the safety standards against microwave radiation on the human body is 103 times different between the USA and former USSR. In the USA, only the thermal effect is considered and the temporary biological effect which will disappear after the irradiation period is not regarded as a problem which should be removed. However the non-thermal direct microwave effects on living organisms is considered in USSR. In the ANSI(1979) standards of USA, the limit 5[mW/cm2] for more than 0.1 hour, is determined as ten times (safety margin) the “2 x heat emission” from a common human body surface. The mechanism for normal heat transportation from internal organ to body surface is not considered. Also, it should be noted that microwave effects are not restricted to body surface.
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