When any of the major body dimensions are parallel to the RFR energy’s plane of polarization, the produced effects  are  likely  to  be  more  pronounced  than  when they are oriented in other positions. The  depth  of  penetration  and  coincident  heating effects  of  energy  on  the  human  body  depend  on  the energy’s frequency. The region of transition between major damage and minor or no damage is between 1 and 3 GHz. Below 1 GHz, the RFR energy penetrates to  the  deep  body  tissues.  Above  3  GHz,  the  heating effect   occurs   closer   to   the   surface.   At   the   higher frequencies, the body has an inherent warning system in   the   sensory   elements   located   in   the   skin.   At frequencies between 1 and 3 GHz, the thermal effects are subject to varying degrees of penetration, with the percentage of absorbed energy ranging from 20 to 100 percent. The two microwave cooking oven frequencies fall close to this range. The lower frequency, 915 MHz, produces a deeper heating effect on tissue (i.e., roasts) and is not as effective for surface cooking (browning) as the higher frequency, 2,450 MHz. R F R    H A Z A R D    T O    T H E    E Y E S . — T h e transparent lens of the eye may be damaged by radiated energy   (ultraviolet,   infrared,   or   radio   frequency), causing the development of cataracts or opacities. The lens is very susceptible to thermal damage, since it has an  inefficient  vascular  system  to  circulate  blood  and exchange heat to the surrounding tissues. Unlike other cells   of   the   body,   the   cells   of   the   lens   cannot   be replaced  by  regrowth.  When  cells  in  the  lens  die  or become damaged, a cataract may form. The damaged cells   may   lose   their   transparency   slowly   and, depending   upon   the   extent   of   damage,   cause   the individual  to  suffer  impaired  vision.  Apparently,  the presence of even a relatively few damaged cells may act  upon  other  lens  cells,  either  by  releasing  toxic substances   or   by   preventing   normal   chemical transformation to take place within other cells. RFR   HAZARD   TO   THE   TESTICLES.— Testicular   reaction   to   heat   injury   from   excessive exposure  to  RFR  radiation  can  be  the  same  as  the reaction to a high fever associated with many illnesses. Although a condition of temporary sterility may occur, the condition does not appear to be permanent and will ultimately   correct   itself.   However,   injury   to   the testicles  may  be  permanent  because  of  an  extremely high dosage or because of high exposures for extended periods of time (i.e., months to years). S H I P B OA R D R A D I AT I O N H A Z A R D ZONES.—Because of the danger of radiation hazards to  personnel,  the  fire  control  radar  is  equipped  with cutout switches that turn off the transmitter for certain director   bearings   and   elevations.   The   information c o n c e r n i n g    c u t o u t    z o n e s    f o r    y o u r    p a r t i c u l a r installation  is  located  in  the  radar  OPs(Operational Publications). You should know the cutout zones for your particular radar. The equipment OPs also give the radiation  pattern  and  the  minimum  safe  distance  for personnel exposed to the mainbeam of the radar. The safe   limit   of   radiation   exposure   to   personnel, established  by  the  Naval  Medical  Command,  is  10 mW/cm averaged over any one-tenth hour period (six minutes). No exposure in a field with a power density in excess of 100 mW/cm   is permitted. RFR Burns You can receive an RFR burn if your skin contacts a source of RFR voltage. This is because your skin’s resistance  to  the  current  flow  in  the  area  of  contact produces heat. The effect of this heat on your skin can range from noticeable warmth to a painful burn. Mild  RFR  burns  are  usually  indicated  by  small white   spots   on   the   skin   and   possibly   the   odor   of scorched   skin.   More   severe   burns   may   penetrate deeper into the flesh and produce painful and slower healing injuries. For our purposes, “hazardous” will be associated  with  the  RFR  voltage  level  sufficient  to cause   pain,   visible   skin   damage,   or   an   involuntary reaction. The term  hazard  does not include the lower voltage that causes annoyance, a stinging sensation, or m i l d    h e a t i n g    o f    t h e    s k i n . T h e   N ava l   S h i p s Engineering  Center  has  prescribed  that  an  open circuit   RFR   voltage   exceeding   140   volts   on   an object   in   an   RFR   radiation   field   be   considered hazardous. A common source of potential RFR burns is crane hooks.   Transmitting   antennas   can   induce   RFR voltages  in  nearby  crane  structures  and  wire  ropes. Figure 3-3 shows areas on a crane in which inductive and capacitive charges may be induced by RFR. Some crane/antenna   problems   can   be   eliminated   by relocating   the   associated   antennas,   but   each installation   requires   special   considerations.   The locations of ship’s antennas are based on the desired radiation  patterns,  taking  into  account  the  physical limitations imposed by the ship’s structure. Often, the r e l o c a t i o n    o f    a n t e n n a s ,    a l t h o u g h    p h y s i c a l l y permissible, is not feasible because of the location of the associated transmitters. RFR  voltages  measured  aboard  ships  show  that resonance effects may occur at frequencies between 2 3-7