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When it was reported in an Associated Press release that there was an increased rate of death due to certain types of cancer in Amateur Radio operators, this information was rapidly picked up by the radio community. As a physician who specializes in cancer surgery, I received many calls from amateur and non-amateur friends to find out more about what was going on and what I thought about it. As in many reports on medical topics in the lay literature and on television, there frewently is a difference between what is reported and what actually was said in medical articles, and this and other recent reports are no different.
After much time and consideration, several important concepts became apparent to me, and I hope that by making this report in QST, it will help us all to better understand what eally was said, and what is known about the reported association of leukemias and other blood cancers with Amateur Radio. This article does not purport to completely cover all the important articles and research studies which have ever been written on the effects of electromagnetic radiation on human biology, but is instead, an effort to review that literature which might be useful to Amateur Radio operators interested in responding to the questions that have been asked.
Radio-frequency waves are a form of electromagnetic waves, and in the frequencies of concern to Amateur Radio operators, these represent a form of nonionizing radiation. The terms ionizing and nonionizing radiation are frequently confused, and it is helpful to clarify what I mean by these terms early in our discussion.
Ionization occurs when there is enough energy in the radiation to displace an electron from an atom. Radiation that produces this effect has a very short wavelength, a high frequency and high energy level, and is typically that described as X-rays and gamma rays. Nonionizing radiation is otherwise known as infrared and radio-frequency waves, which are at a lower energy level, and have lower frequencies and longer wavelengths than ionizing radiation. Ionizing radiation is dangerous to living organisms in that it affects cellular elements such as DNA in the cell nucleus,leading to genetic damage in the individual cell, and mutations in future generations of cells. Although the energy level of nonionizing radiation is lower and thus may not affect large molecules or generate measurable amounts of heat in the same manner as ionizing radiation, there is substantial evidence that nonionizing radiation has subtle effects at a more basic cellular level, including effects on hormones, enzymes and the cooperative mechanisms involved in maintaining the integrity of intracellular systems.(1)
Experiments regarding the effects on human tissue of nonionizing electromagnetic fields have been conducted for many years.(2) The findings of these studies indicate that a modulated electromagnetic field, that is, one in which the energy is cycled on and off or is varied by intensity or frequency, has a greater inhibitory effect on the ability of cells in the body to communicate with each other than does a field in which the current remains at a steady and unmodulated strength.
Studies indicate that even in a weak electromagnetic field there is a modification of calcium binding at the cell membrane, as well as an alteration of a variety of calcium dependent enzyme systems which work between cells.(3) Experiments have noted that the effect on calcium flow in and out of cells is frequency dependent, and that curves can be drawn demonstrating these "frequency windows." Specifically, the combination of a very high or ultra high frequency carrier (147 or 450 MHz) modulated at specific extremely low frequencies (16, 40 or 60 Hz) has been studied and appears to be of biologic significance.(4).
Other studies have looked at the effects of electromagnetic energy on cells that have specific immune functions. An important type of white blood cell called a T-lymphocyte is involved in the recognition and destruction of foreign and malignant cells. There is evidence that the normal functioning of these cells is significantly reduced by electric fields that simulate 60-Hz high voltage power line fields and by weak microwave fields that are amplitude modulated at 60 Hz.(5)(6) The mechanism of this process is not clear, but may also be related to interactions at the level of the cell membrane.
More rapidly dividing cells, such as those in the bone marrow or small intestine, are usually more sensitive to the effects of bothionizing and nonionizing radiation than are those which divide more slowly. Thus, it is rapidly dividing cells that are more likely to demonstrate changes in response to exposure to these types of energy. However, cells which divide more slowly have less of an ability to repair any damage done to them by exposure over a long period of time. It is important to recognize that these effects are not necessarily dependent on damage to DNA or other cellular markers.
Evidence at this time seems to suggest that an appropriate interpretation of this data is not that nonionizing energy necessarily causes cancer, but that it may act instead to promote the efficacy of other agents in doing so.
In 1979, initial questions were raised regarding a positive relationship between high current electrical configurations in homes and the incidence of cancer deaths in children living in the Denver area.(7) Later, similar findings were noted for adults living near high current 60-Hz wiring as well.(8) Because of criticisms relating to the methodologies and assumptions used in these studies, other investigators looked at these same issues again, and came to similar conclusions.(9)(10)
It had been reported as early as 1982 that there appeared to be an increased death rate due to leukemia in people who were exposed to magnetic and electric fields in the course of their work.(11)(12) Additional articles appeared in 1983(13)(14) and 1985(15-18) which also suggested that electrical workers in general were at an increased risk of leukemia and that electromagnetic fields might be a cause of this form of cancer. A time/effect relationship has also been suggested for certain forms of brain tumors and occupational exposure to microwave and radio-frequency electromagnetic radiation,(19)(20) where the risk was 10 times as great in those workers who had industrial exposure to soldering fumes, solvents and a variety of other chemicals. Other reports have reviewed the possible relationship between spontaneous abortion rates and the use of electric blankets,(21) video display terminals,(22) and ceiling cable electric heat.(23) Cataract formation and damage to the retina has also been reported in humans exposed to high intensity electromagnetic fields and microwaves.(24)
The recent report which stirred up the most concern because it made particular reference to Amateur Radio operators, appeared in the January 1988 issue of the American Journal of Epidemiology, a respected and prestigious medical publication.(25)
In 1982, Samuel Milham, Jr, MD, MPH, who works in the Epidemiology section of the Washington State Department of Social and Health Services, reported that a study of workers whose stated occupation on death certificate records suggested an exposure to electrical or magnetic fields had a higher rate due to leukemia.(26) In 1985, at the suggestion of an Amateur Radio operator (W2EVE), he looked at all the "Silent Keys" listings that appeared in QST and studied the cause of death of amateurs who died between the years 1971 and 1983 and who lived in Washington State and California at the time of their death.(27)
To simplify things slightly, only males were studied as there were very few women among these deaths. A total of 1691 death certificates were identified with these Silent Keys.
Using a standard statistical analytic technique called proportionate mortality radio (PMR), and an analysis of all US deaths as a comparison group, 12.6 of the 1691 amateurs should have died from leukemia. Instead, 24 deaths were observed with a statistical significance of p < 0.01, meaning that there was less than a 1 in 100 chance that this was a random occurrence.
In the largest study reported,(28) Milham has expanded on his original work. He first identified all licensed amateurs with addresses in California and Washington State. This was followed by a computerized and manual review of all deaths of persons whose complete names and date of births corresponded to the list of known amateurs for the period January 1, 1979 to June 16, 1984.
A total of 67,829 amateurs were identified and 2485 deaths were studied. Eighty-four percent (2083 of 2485) deaths occurred in California, so this study was weighted heavily towards the California experience. After making certain statistical adjustments, the overall death rate for amateurs was no different than it was for the population of both states at large. Likewise, the overall death rate for all forms of cancer among amateurs was not significantly different from the larger population.
However, within this cancer death rate, there was a definite disproportion of deaths due to cancers of "other" lymphatic tissues, such as multiple myeloma and non-Hodgkin's lymphomas. The death rate for all leukemias was only slightly, but not statistically significantly, increased. Among those leukemias, however, one form particularly (acute myelogenous leukemia) was significantly increased. It was concluded that the increased number of only these highly specific forms of blood disorders, and not others, suggests that a biologic cause and effect is present.
It was not possible to make a direct analysis of any occupational link with these excess deaths due to the fact that this information was readily available only for Washington State deaths. It should be noted that of these 402 deaths, 31 percent of the amateurs apparently worked in or about electromagnetic fields as technicians, radio operators or television repairmen. Of all deaths in Washington State during this time, only 3 percent of the population worked at these occupations.
In addition, among Washington State amateurs, 5 of the 11 deaths due to leukemias, lymphomas or multiple myeloma, were in people who had such occupational electromagnetic exposures. It was pointed out that workers in these occupations also were exposed to other possible hazards, such as fumes from solder and toxic chemicals such as the polychlorinated biphenyls (PCBs), and asbestos, any of which in themselves might conceivably cause cancer as well.
No other cause of death was noted to be higher than normal in the amateur population, and in fact, several important and common causes of death were less than what would be expected from the population as a whole. Deaths due to cancer of the pancreas and the lung, as well as all deaths due to respiratory diseases (pneumonia, asthma, emphysema), circulatory diseases (those of the heart and blood vessels) and accidents were less in amateurs as a group than in the overall population. It was even suggested that there are fewer cigarette smokers among members of the American Radio Relay League than in the general US population as a whole.
Milham concluded that Amateur Radio licensees in California and Washington State do have a higher death rate due to acute myelogenous leukemia, multiple myeloma and possibly other specific types of lymphoma. He felt that exposure to magnetic or electrical fields either as a consequence of work or hobby should be considered among the cause of these rates.
It is important to recognize that studies based upon death certificate data alone are always subject to certain limitations. Data inaccuracies, from input as well as in coding, are not uncommon, and when one is measuring the incidence of small or rare occurrences, this may cause an inadvertent diminution or magnification of the determination of these occurrences. None of the studies discussed here look at an actual measurement of the electromagnetic or toxic chemical exposure that any of the deceased individuals may have had. The issue of what is called "confounding factors" such as the interaction of the effect of toxic chemicals and electromagnetic fields of different levels of energy is certainly unknown. As a result, statisticians may frequently differ on the interpretation of identical data.
On the basis of these research papers, however, it is now apparent that the data derived so far must be considered significant enough to support further research into both the epidemiology of and the biologic mechanisms involved in these effects. Some of that research is presently being done both in the United States and abroad and new articles are being published in the scientific literature frequently.
The question of exposure standards also deserves comment. In 1982, the American National Standards Institute (ANSI), a private, commercially sponsored organization, published a list of standards based upon the thermal effects of electromagnetic fields upon tissue.(29) There is much controversy regarding the validity of measuring this type of effect on biologic tissues as there is clear evidence that adverse tissue effects can occur without a detectable rise in temperature.(30) It should be noted that Australia, Sweden and the Eastern bloc countries as well as localities in the states of Oregon and Massachusetts have issued standards which recommend significantly lower exposure levels. Another voluntary standard has been proposed by the National Council for Radiation Protection and Measurement (NCRP), which is notably more stringent than the current ANSI standards.(31) ANSI is presently in the process of revising their standards.
It is interesting to note that the US Environmental Protection Agency has recently decided to defer the issuance of standards for exposure to electromagnetic fields under its RF Radiation Guidance Program for budgetary restrictions and other priorities. Despite the requests of the Federal Communication Commission, the National Association of Broadcasters, the Electromagnetic Energy Policy Alliance (of which the ARRL is a senior associate member) and other national organizations to complete this important work, the EPA has decided to put aside many years of effort on these guidelines and to focus its attention on other matters which it considers to be of greater public concern.
An article published recently studied the specific absorption rates in models of the human head exposed to hand-held radios operating in the 800-MHz band, which is where most cellular telephones are used.(32) The authors studied the RF energy absorbed by simulated tissues in the head (eye, brain, muscle, fat and bone) while holding the transmitter in vertical and tilted positions about the head. Also, a 1/2-wavelength antenna operated at 1.0 W power output was compared to a 5/8-wavelength antenna operated at 1.0 and 1.8 W. This study indicated the presence of a "hot spot" in the eye while using a 1/2-wavelength antenna, and one in the frontal portion of the brain while using a 5/8-wavelength antenna.
The authors concluded that if the transmitter is operated in a vertical position and is held at a distance of about 2 inches (5 cm) from the face during normal use, the specific absorption rates would not be significant enough to warrant concern, at least with reference to the present ANSI standards. These current ANSI standards essentially consider any device generating less than 7 watts output to be safe, an assumption with which almost all experts currently would not agree. Other studies using hand-helds operating at lower frequencies and different power outputs are being conducted and evaluated with reference to more stringent standards.
What does all this really mean for us as amateurs? We all know that there are intrinsic risks in all activities that we do every day. How many of us still smoke, or are overweight or do not bother to fasten our seat belts in our cars? Knowing about risks only sometimes causes us to change our ways. As Amateur Radio operators we certainly do not have any hesitations about discussing and protecting ourselves from the dangers of high voltage circuitry. Nor do we shy away from trying to prevent the risk of accidental falls from roofs or antenna towers.
Likewise, we should recognize a relatively newly identified environmental hazard which may be significant to those of us even without occupational exposure to electromagnetic fields or toxic substances. No one is absolutely certain about what may be causing this increased proportion of special cancers. Therefore, prudence dictates that Amateur Radio operators should take those simple measures which decrease the possibility of our personal exposure to electromagnetic fields or toxics that we may contact as a consequence of our interest in Amateur Radio. Articles have been published in QST and other Amateur Radio publications regarding some precautions in the past.(33-37) This current list includes some recommendations which are new, particularly in view of recent information.
To my knowledge, no other established guidelines are available to prevent potentially harmful exposure. Therefore until such time as a clearer picture emerges, we should follow these simple common sense precautions.
There is no question that additional information is needed and will ultimately be forthcoming on this important issue. This data will certainly be difficult to interpret, and confusing to many of us, both in the amateur and nonamateur community. We must therefore be prepared to work together to arrive at reasonable conclusions and appropriate actions.(41)
In preparing this paper, I personally communicated with several of these experts in the field whose works are referenced below. All of these experts, including Dr Milham, agreed that none of them would have any hesitation regarding their own personal use of currently available Amateur Radio equipment, provided that it was properly installed and operated, and that the recommended precautions were followed.(42) Unanimously, they all feel that no one should stop operating because of concern for the possible risk of illness, as these risks appear to be so relatively low.
Am I worried? Absolutely not. With common sense and safe operating practices, I look forward to many more years of enjoymentand satisfaction as an Amateur Radio operator.
The author wishes to thank those many individuals who provided encouragement, information, suggestions and were willing to offer multiple critiques of the numerous drafts of this article: W. Ross Adey, MD, (K6UI), Jim Cox (K7JAJ), Fried Heyn (WA6WZO), Thomas Mack, MD, MPH, Samuel Milham, MD, MPH, John Peters, MD, Tod Olson (KOTO), Wayne Overbeck, PhD (N6NB), David Rodman, MD (KN2M), Joseph Salvatore, MD (NIDJH), William Talton (W61PM).
An Amateur Radio operator continuously since 1963, Ivan Shulman says he was raised on Amateur Radio, and credits his late father W2SBX with getting him started. As a Fellow of the American College of Surgeons, Dr Shulman works as a general surgeon with a special interest in cancer of the thyroid, breast and gastrointestinal tract. In addition to his medical and radio activities, he has served as the physician for the Los Angeles Philharmonic on tours to Mexico, Japan, Korea and Europe. He also occasionally plays extra oboe with the orchestra as the need arises. When he manages to get on the air, he enjoys DX chasing and a good rag chew either DX on 20 meters or on UHF. in whatever spare time is left, he is busy introducing his wife and two young children to the ways of Amateur Radio.
WC2S, A. Shulman.