The following summary of the Procedings of the International Symposium on the Biological Hazards of Microwave Radiation, held in Warsaw, Poland, October 15-18, 1973 represents the status of this field of research. The subjects of the reports given at this symposium fall generally into four categories: (1) the gross effects of acute exposure of experimental animals to microwaves; (2) the more subtle effects of less severe and of chronic, low-level exposures to both experimental animals and occupationally exposed humans; (3) the electrical properties of biological systems, and possible modes of interaction of microwaves with cells and biological molecules; and (4) the problems and proposed methods of quantifying exposure and absorbed dose. This summary sets forth significant points from each of these categories. A number of studies of the microwave lethal dose for small animals were referenced. A wide range of parameters were used in these studies: wavelengths in the range of millimeters to decimeters, power densities up to 300 mW/cmS and both pulsed and continuous waves. It was reported that the most rapid deaths were produced using continuous "10 cm waves" of high power density with most of the work apparently being done at 10.7 and 12.2 cm wavelengths. It was also noted that, in addition to the direct heating effect of the microwaves, "there is evidently also a direct effect of microwaves on thermoregulatory centers." With regard to less severe microwave exposures, there was much debate as to whether or not certain effects were cumulative, delayed, and/or non-thermal. Results indicate an apparent threshold power density for cataractogenesis in animals, but there are indications that other effects, (e.g., disturbances in brain metabolism and central-nervous-system functions) may be cumulative in nature. One report asserted that "thermal stimulation of peripheral nerves can produce the neurophysiological and behavioral changes that have been observed"; however, others reported observations which seem to contraindicate this stance. Epidemiological studies conducted on microwave workers in the Soviet Union and Czechosol- vakia found not only an increase in certain subjective and objective disorders, but defined "microwave sickness" as a nosological entity; similar studies in Czechoslovadia and Poland found no "statistically significant" increase in disorders. A variety of experiments were described with wide variation in parameters and dosimetry. It was stressed, however, that no serious cardiovascular disorders attributable to microwaves had ever been found, and that "microwave sickness" was generally not found to be a serious disorder. A number of methods and instruments have been used for measuring field strength and absorbed dose. All had shortcomings, usually serious. At the time of this conference, the lack of accurate, noninterfering dosimetry remained a serious problem. There are two miscellaneous points which seem deserving of mention. The first is that the recommended maximum power density (based mainly upon the risk of thermal cataractogenesis) for occupational exposure
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