RF Radiation Hazards: An Engineering Status Review

Abstract

The su b jec t of microwave radiation hazards d ea ls with th e b io lo g ic a l e f f e c t s on man o f h igh l e v e l radio frequency rad ia t io n . This i s a form of n o n io n iz in g rad ia t ion , a s op p osed to io n iz in g radiation produced by X -r a y s , gamma r a y s , the re su l t s of nuclear f i s s i o n , e t c . M icrowave radiation com es from high power transmitters and radar s y s t e m s , and numerous in du str ia l , m edica l and d om estic d e v i c e s . Immediate e f f e c t s h av e a lready b een observed on man in the near v ic in ity o f high power radiating a n te n n a s , and on laboratory anim als in s im u lated microwave radiation environm ents . There is in c r e a s in g concern about the cum ulative e f fec t of l i te r a l ly th o u sa n d s .o f su ch radiating e le m e n ts , t o ­ gether with the m ill ions o f other lo w l e v e l transmitting d e v ic e s now operating in th is country. The q u est io n b e in g a sk e d with in creas in g em phasis is : what is th e e f f e c t upon the human b e in g , e s p e c i a l l y in urban a r e a s , of the accu m u la t ive l o w l e v e l radiation day after d ay , a l l the years o f o n e 's l i f e , from th e s e numerous emitting so u r c e s ? The answ er to th is q u e s ­ t io n , a s w e l l a s the entire su b jec t of th e immediate, and lon g-ran ge b io lo g ic a l e f f e c t s o f microwave rad i ­ a t ion upon th e human b e in g (and to a l e s s e r degree o f con cern , an im als and v e g e ta t io n ) , is a som ewhat gray area t o d a y . The importance o f r e sea rch in v e s t ig a t io n now stem s from the fact that the top ic d o es h a v e enormous p o ­ te n t ia l s i g n i f i c a n c e in that long-term e f f e c t s on the ind iv idual and his. offspring are yet to be determ ined, and from th e very p ractica l fact that modern man is in crea s in g the number of radiating s o u r c e s , and their power, in an unremitting e s c a l a t i o n . Thus th e pro­ b lem , w hi le at a le v e l of undetermined s e r io u s n e s s at p resen t , is c lea r ly one o f concern for the future, and major em p h asis i s being p la ce d upon the y ears of the next d e c a d e . INTRODUCTION AND HISTORICAL NOTES M icrowave radiation hazards has b een a su b jec t o f in crea s in g con cern in the r ecen t p a s t , la rg e ly over the la s t 25 years . U nlike som e other so u rces o f environm ental p o l ­ lu t io n , which ha ve a lw ay s been present but la y dormant until r eco gn it ion in modern t im e s , microwave radiation hazards were o f no concern until r e c e n t ly s im ply b e ­ c a u s e there w as l i t t le su ch radiation to be concerned w ith . It has on ly b een the proliferation of number and power o f RF radiat ion so u rc es that has g iv e n r i s e to in cr ea s in g concern about a s i tu a t io n that i s , a t b e s t , marginal tod ay , and c lea r ly hazardous for future y e a r s . At th e o u t s e t , le t us d e f in e microwave radiation as n o n io n iz in g radiat ion over th e entire RF spectrum , from DC to mill imeter w a v e s , s topp in g for c o n v e n ie n c e at the upper limit o f p resen t -d a y radars , 100 GHz. Probably no on e w as concerned with th e p o s s i b le future c o l la tera l e f f e c t s o f RF radiation at th e time of M a x w ell , Hertz and M arconi. From a laboratory cu r i­ o s i t y RF radiation d ev e lop ed into s c i e n t i f i c a l ly c o n ­ tro l led e x p er im e n ts , m athem atica lly d efin ed r e la t io n ­ sh ip s (M axwell) and com m ercia l ly and industr ia l ly u sab le means of com m u nication s . Over the p a st 3 0 40 y ears it has a l s o b ecom e the e s s e n t i a l e lem ent in dis tant ech o -ran g in g d e te c t io n (radar), coherent e m is s io n s (the sh o r t l iv e d maser and its far more durable and a p p l ic a b le o ffspr ing , th e la s e r ) , b e n e f ic ia l h eat in g e f f e c t s in industr ia l a p p l ica t ion s (RF induction or d ie le c tr ic heat s e a l in g equipments) and th e m edica l f ie ld (diathermy). And that growing d o m es t ic and com ­ mercial cook in g marvel, the microwave o v e n . In te rest in g ly , in a l l o f t h e s e a p p l ic a t io n s there is th e e lem en t o f hazard: to ordnance d e v i c e s , to instru ­ mentation and v o la t i l e s u b s t a n c e s , and of utmost importance to man. As w as the c a s e with io n iz in g radiation (X-ray and gamma, in particu lar) , the thought of a p o ten t ia l hazard a r is in g from a n ew ly d is co v ere d s c i e n t i f i c cu r io s ity did not a r ise until very much la ter , after man had s u c c e e d e d in d ev e lop in g the new tech n iq u e and in cr e a s in g its power for greater a p p l ic a b i l i ty to h is p r o c e s s e s . Thus neither Roentgen nor the C u r ie s , in a l l their laboratory experim entation and w r it in g s , e n v is io n e d th e d estru ct iv e power of ion iz in g rad ia t ion , and it was not until the modern era w hen distrubing c a s e s o f radiation l e s io n s d ev e lo p e d , that man becam e aware of th is u n p leasant s id e e f f e c t and took s t e p s to control i t . With in c r e a s ­ ing s c i e n t i f i c , comm ercial and military ap p lica t io n s o f nuclear e n er g y , great concern i s being m a n ife s ted , more and more, about th e s e s id e e f f e c t s o f ion iz in g radiation which accom pany the r e l e a s e o f n u clear energy and X -r a y s . The e f f e c t s can be ca ta s tro p h ic , a s in the c a s e of the immense radiation from a bomb (a s id e from the immediate d es tru ct ive b la s t e f f e c t ) , or far more su b tle and lin g er in g , a s in the c a s e o f l o w l e v e l rad i­ a t ion from m edica l X r a y s , byproducts o f nuclear power g en era t ion , e t c . So with microwave (or RF) ra d ia t ion . It w as not un­ t i l the proliferation of RF radiation so u r c e s and the in ­ c r e a se in their em itted power that con cern w a s mani­ f e s te d in th is new and growing area o f environm ental conta mination. DEFINITIONS AND AREAS OF INTEREST "Microwave radiat ion hazards" h as come into a c ­ c e p ta n c e by both th e public and s c i e n t i f i c comm unities as a gen era l term for hazards due to n o n io n iz in g e lec tro m a gn et ic ra d ia t ion , a lthough th e term "RF rad i­