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3910.3A 10/ 19/83 <br /> (b) The lens of the eye cannot dissipate heat as readily <br /> as the rest of the body and can suffer damage from microwave radiation. <br /> This has been demonstrated experimentally with small animals. <br /> b. Nonthermal Effects. Nonthermal effect refers to an observable <br /> or measurable biological change produced by exposure to RF/microwave <br /> radiation without a detectable temperature rise in a test system. Recent <br /> research has suggested that nonthermal effects do occur. The phenomenon <br /> of RF "hearing" has been reported and verified. Alterations in animal <br /> behavior patterns following RF/microwave radiation exposure have been <br /> observed. Effects on the immune response system and upon the central <br /> nervous system are receiving considerable attention. Efforts continue to <br /> determine if these subtle and usually reversible changes have any public <br /> health significance. <br /> 32. SOURCES OF EXPOSURE. Many potential exposure sources lie within the <br /> RF range of the electromagnetic spectrum. Among them in ascending <br /> frequency order are AM and FM radio, television, VHF and UHF <br /> communications, radar, diathermy, microwave cooking, and materials <br /> drying. Natural sources of RF and microwave energy also exist, as in the <br /> case of measurable ground level electric fields produced by the movement <br /> of cold fronts. <br /> The most attention by far has been directed toward the microwave region. <br /> It is in this range that a great number of commercial applications have <br /> developed and it is in this range that biological effects have been <br /> studied the most. However, with this writing, attention is shifting to <br /> some of the lower frequencies; i.e. , < 1,000 MHz, and to the potential <br /> effects of exposure to sources that lie within this range. <br /> VHF and UHF radio and television broadcasts are the main source of <br /> ambient RF exposure in the United States. Of these the FM radio <br /> broadcast band is the greatest contributor. On January 1, 1980, there <br /> were 9,756 broadcasting stations in operation including 1,008 television <br /> stations, 4,554 AM radio stations, and 4,194 FM stations. <br /> Within the FAA, the sources of RF radiation include the ASR and ARSR • <br /> radars, ASDE and airborne radars, microwave landing sytems, VORTAC's and <br /> TACAN's, communication systems (VHF, UHF, RMLs, etc. ), diathermy <br /> machines, and microwave ovens. The sources of greatest concern are those <br /> that are capable of generating and emitting strong RF field intensities; <br /> i.e. , the radars. <br /> Chap 3 <br /> Page 24 Par 31 <br />