Biological Effects - RF/Microwave Interaction with Biological Tissues - page 118

ophthalmic pretreatment (opioids), the sensitivity to microwave radiation was
observed to increase by about a factor 10, from 10 to 1 mW cm -2 for induction
of corneal endothelial lesions [92].

3.8 NONTHERMAL, MICROTHERMAL, AND ISOTHERMAL EFFECTS

Thermal effects have been investigated in Section 3.1. It was said that the pos-
sibility of either nonthermal or microthermal effects is not a recent question.
It was also mentioned that one needs to be very careful about the conditions
of an experimental study when investigating the possibility of nonthermal
effects, to be sure to take into account all the power components. It is obvi-
ously indispensable to be able to distinguish between thermal and nonthermal
effects.
There is quite a controversy about the possibility of nonthermal or
microthermal effects. This controversy is not only scientific; it is largely polit-
ical and commercial. Accepting the idea that RFs may cause nonthermal
effects or microwave exposure implies that such an exposure could be of a low
or very low level, and this is not well accepted. On the other hand, it is a rather
common mistake to consider that biological effects are almost necessarily
pathogenic for human beings. This is not true: Biological effects may or may
not result in an adverse health effect. In fact, this underlies the whole ques-
tion about how to establish guidelines for limiting electromagnetic field
(EMF) exposure: They must provide protection against known adverse health
effects. This subject will be investigated in detail in Section 3.11, devoted to
hazards and standards. The question of accepting or rejecting nonthermal
effects is not a minor question. In 1971, Michelson and Dodge, comparing
Soviet and Western views on the biological effects of microwaves, mentioned:
“The importance of the difference between the Soviet and Western views is
readily apparent when it is realized that practical consideration of Maximum
Permissible Exposure (MPE) is based on the acceptance or rejection of
non-thermal effects of microwaves as biologically significant” [96, p. 109].
This section offers a discussion on the scientific reasons for which non-
thermal or microthermal effects might be detected as well as the tools to be
used for the investigation. One main reference is a monograph by Chukova,
essentially based on the Soviet and Russian literature on nonthermal effects
[97]. In this literature there is a consensus that such effects do exist and that
they can be observed in weak fields, hence at a low level of absorbed energy.
Another main reference is the set of contributions by Fröhlich, for instance
[98]. Other significant references for this section are Morse [99] and
Sommerfeld [100].
In Section 1.4.1, the concepts of EM energy and power were developed. It
was said that Poynting's theorem expresses equality between the space varia-
tion of EM power and the time variation of EM energy. It is well known that
EM theory is connected with the structure of the problem, in particular with