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High Design From July 2005 Copyright © 2005 Summit Technical Media EMR & HUMAN

Electromagnetic and Human Health: A Review of Sources and Effects

By Ali Zamanian and Cy Hardiman Fluor Corporation, Industrial and Infrastructure Group

adio Frequency Electromagnetic Frequency Spectrum This article provides an (RF) engineers are communication links have been extensive summary of the Rfaced many used worldwide for many years as solutions types of electromagnetic with the following two for connectivity in point-to-point and point-to- radiation and their thermal questions: “What are the multipoint applications. The most common and molecular effects effects of on wireless solutions include AM and FM radio, on the human body human health?” and, broadcast stations, mobile and cel- more specifically, “What lular phones, and systems. health risks are associated with the use of The electromagnetic (EM) spectrum con- phones, mobile , microwave radios, tains an array of electromagnetic waves microwave ovens, broadcast radio and televi- increasing in frequency from Extremely Low sion transmitters, power lines and X-rays?” Frequency and Very In recent times, many people have (ELF/VLF), through (RF) expressed an interest in learning if the use of and , to (IR) , Visible cell phones is associated with . Many Light, (UV) light, X-rays, and have heard or read about possible links Gamma rays. between cell phones and cancer, but conclu- Figure 1 is a graphical representation of sions are rarely definitive. This will the spectrum of electromagnetic or attempt to answer these questions, but first, radiation in ascending frequency (decreasing we must develop a basic understanding of ). The general of the effects electromagnetic radiation (EMR). is noted for different ranges.

Figure 1 · .

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Ionizing Radiation Microwave (MW) and Millimeter- made. Natural EMR includes a back- contains suffi- (30 kHz to 300 GHz) electromagnetic created cient electromagnetic energy to strip • Infrared (IR) light, Visible light and by the as well as additional and molecules from the tissue Ultraviolet (UV) light (above 300 EMR created by thunderstorms, as and alter chemical reactions in the GHz) well as and cosmic activity. The body (converting molecules totally or • [Editor’s note: the strength of an partly into ). X-Rays and Gamma between the highest microwave depends both on the power at the rays are two forms of ionizing radia- bands and infrared light are rarely source and the distance from the tion. These rays are known to cause used, but are being studied for future source. damage, which is why a lead vest applications] Exposure to man-made ELF/VLF must be worn when X-rays are taken occurs primarily due to the generation, of our bodies, and heavy shielding sur- Some heating effect is generated transmission and use of electrical rounds . by all of these waves. Insufficient energy. Electromagnetic fields are cre- Human beings are constantly energy is available from most common ated whenever passes exposed to low levels of ionizing radia- sources to produce any type of damage through a conductor. Actually, two tion from natural sources. This type of to human tissue, although it is proba- interdependant fields are created: an radiation is referred to as natural ble that higher power densities, such electric field and a magnetic field. The , and its main as those densities very near high-volt- strength of the electric field depends sources are: age power lines or high-power on the voltage being carried, while the (megawatt) broadcast transmitters, magnetic field strength depends on the • Visible light, ultraviolet light and could have long-term health effects. amount of current being carried infrared light () The power density of any source of (amperage). Thus, electromagnetic • Radioactive materials on the earth’s EMR is not only related to the power fields are created by a variety of elec- surface (contained in coal, granite, level at the source, but increases trical household appliances such as etc.) rapidly as the distance from the motors in refrigerators, vacuum clean- • Radioactive gases leaking from the source decreases. A common concern ers, dryers, , electric blan- earth () today, since more and more people are kets, microwaves, , stereo • Cosmic rays from outer enter- using cell phones than ever before, is receivers, and computers. In fact, ing the earth’s through that cell phone antennas radiate near because of the individual’s proximity to the a person’s head. Cell phones, however, household appliances, the level of elec- • Natural radioactivity in the human radiate very little power. So, even tromagnetic fields is often far greater body while close to the head, they are not than those levels produced by trans- considered a danger. mission lines strung on high towers. Non-Ionizing Radiation Some studies suggest that poten- However, the appliances only create The lower part of the frequency tial health hazards could be linked to electromagnetic fields while in use, spectrum is considered non-ionizing excessive exposure to high-power den- whereas the electro- Electromagnetic Radiation (EMR), sities of non-ionizing radiation. These magnetic fields are continuous. While with energy levels below that required health hazards include: these man-made ELF/VLF electro- for effects at the atomic level. magnetic fields may cause biological Examples of non-ionizing • Cancer effects, the adverse effects on human are: • Tumors health are highly controversial. • Headaches • Static electromagnetic fields from • Fatigue Electrical Power Line Effects direct current (0 Hz) • Alzheimer’s Disease The concern over electromagnetic • Low-frequency waves from electric • Parkinson’s Disease fields emitted by power lines (Figure power (50-60 Hz) 2) has long been a topic of conversa- • (ELF) Researchers, however, are unsure tion in the real estate and power and (VLF) of specific long-term effects resulting industries. New studies and conflict- fields (up to 30 kHz) from prolonged exposure to non-ioniz- ing reports are published every year. • Radio Frequencies (RF), including ing radiation. While it is easy to shield a house Low Frequency (LF), Medium against the electric field generated by Frequency (MF) High Frequency ELF and VLF EM Radiation nearby power lines, it is much more (HF), (VHF), EMR in the ELF and VLF range is difficult to shield against the magnet- (UHF) and both naturally occurring and man- ic fields they generate. The magnetic

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Type of Frequency (MHz) Average radiated power

Cellular/PCS 824-849 MHz A few hundred milliwatts 1850-1990 MHz Two-way, hand-held 30, 50, 150, 450 and Between 2 and 5 watts (walkie-talkie) 800 MHz bands 49, 915, 2450 MHz Tens of milliwatts

Table 1 · Typical portable/mobile radio equipment.

sions. For the purpose of this discus- the effects are basically the same. sion, the term “RF energy” is used for An Australian group claimed to all frequencies between 30 kHz and have evidence that living near televi- 300 GHz. Some known facts about RF sion broadcast station towers causes energy are: an increase in childhood leukemia. Figure 2 · Electric power line. However, follow-up studies conducted • The biological effects of RF energy in Australia and in the UK contradict- are proportional to the rate of ener- ed this claim. The follow-up studies field can best be shielded by burying gy absorption, and the level of found no significant correlation power transmission lines, but at a absorption varies little with fre- between RF exposure and the rate of much higher cost compared to over- quency. childhood leukemia in these cases. head lines. • RF energy has the ability to experiments, laboratory human tissue, much like the way Cellular Telephones, Cordless studies of cells, clinical studies, com- that microwave ovens heat food, and Phones and Hand-Held Radios puter simulations, and human popula- can be hazardous if the exposure is Most cellular/PCS and cordless tion (epidemiological) studies have sufficiently intense or prolonged. telephones have either a small anten- been conducted to determine the rela- • Damage to tissue may be caused by na attached or the is integrat- tionship between exposure to electro- exposure to high levels of RF energy ed into the body of the telephone. magnetic fields and a number of disor- because the body is not equipped to Because the antenna of a cellular ders, including depression, childhood dissipate the excessive amounts of phone is close to the user’s head, such leukemia, central nervous system dis- heat generated. Possible injuries telephones create greater RF exposure orders, cancer, , breast can- include skin , deep burns, heat than other types of RF systems. Home cer, etc. In the past, numerous reports exhaustion and heat stroke. cordless telephones and other two-way have presented conflicting informa- hand-held radios have a similar effect. tion. Some of these reports have pro- are particularly vulnerable to However, cordless telephones have vided evidence of adverse health extended exposure to RF energy; the very low RF power output and two- effects, and some other reports have lack of blood flow to cool the way hand-held radios are generally failed to find any such correlation. can result in . used in the push-to-talk mode, there- Recently, the National Academy of fore, transmission is not continuous. Sciences and the National Cancer Broadcast Stations Table 1 illustrates the frequency bands Institute have released major studies Commercial AM/FM radio and TV and average radiated power for cellu- finding no evidence of a link between broadcast stations transmit very high lar, PCS, hand-held radios and cordless electromagnetic fields and cancer. levels of RF energy. Some of their telephones in the United States. These studies suggest that power antennas radiate power levels of sev- transmission lines are much less like- eral megawatts but, fortunately, these Vehicular Mobile Telephones ly to cause cancer than was previously antennas are generally placed on high and Radios suspected. towers or buildings where no humans Vehicular mobile telephones (not are nearby. Even so, humans absorb cellular) and radios have an antenna Radio Frequency Radiation more RF energy from AM/FM radios mounted outside a vehicle, usually on RF energy in the frequency range and TV broadcast station antennas the roof, window, trunk or fender. The of LF, MF, HF VHF, UHF or than from mobile telephone and base metal surface of a vehicle provides a Microwaves is often referred to as station antennas. However, once the shield between the mobile telephone radio waves, RF radiation, or RF emis- energy is absorbed from either source, or radio user and the RF energy radi-

20 High Frequency Electronics Figure 3 · Exposure of humans to RF energy from radio sites. Figure 4 · Microwave communica- tion site. ated by the antenna. The distance between the user and the antenna also serves as protection against RF ing the use of these types of wireless energy. Because of these two factors, devices. Many of these experts believe users of mobile equipment have little that a cancer risk is associated with exposure to RF energy, even though EMR in the higher wattage ranges. the average radiated power is signifi- For base stations located at radio cant, between 10 and 100 watts. sites, the consensus of the scientific community is that the power pro- Base Stations and Radio Sites duced is far too low to cause health Cellular/PCS and other two-way hazards so long as people are prevent- radio system base stations (radio ed from being in close proximity to the sites) produce RF energy. Therefore, antennas. people near the base stations are No study, to date, has provided exposed to this type of energy. conclusive evidence that cell phones However, the exposure is generally can cause any illnesses. However, minimal due to the low level of power ongoing studies are examining the (less than 100 watts) produced and issue more closely. Recent reports the distance between the tower- from Europe raised concern over pos- mounted antennas and any humans sible links between cell phone use and in the area (Figure 3). tumors in the ear, with the risk being greater for children than adults. RF Exposure Concerns It is important to note that cellu- EMR from cellular/cordless and lar/PCS and cordless telephones are hand-held radios have billions of times relatively new technologies, and it is less energy needed to cause impossible to prove that any product or damage to DNA contained in or exposure is absolutely safe in the human tissue. The rapid and absence of long-term research. widespread use of this technology, Therefore, a good “precautionary” however, has raised concern over pos- approach would be for adults to keep sible adverse health effects, in particu- cell phone conversations short and to lar brain cancer. Several studies which discourage the frequent, extended use addressed this concern have been con- of cell phones by children. ducted in the United States and other A notable danger involving the use countries. These studies seem to rule of cellular phones is not radiation out, with a reasonable level of confi- related, but is rather the increased dence, any association between EMR risk of driving accidents while using from these devices and cancer. them. The results of several studies A growing number of scientific indicate that talking on a cellular tele- experts have shifted positions regard- phone while driving significantly High Frequency Design EMR & HUMAN HEALTH

Figure 6 · Visible Light Region of the Electromagnetic Spectrum

Figure 5 · Example of an MRI machine. Microwave Communication Links signal. Images are creates through the Microwave communication links reception and analysis of the reflected operate in frequency bands between 1 weak radio signals. These slight differ- increases the risk of having an acci- GHz and 60 GHz. As mentioned previ- ences in the signal received from vari- dent, with some suggesting that it is ously, heat will be generated in living ous body tissues enable the MRI to almost as dangerous as driving while tissue exposed to RF frequencies, produce images of extraordinary reso- drunk. including microwave radiation. The lution that differentiate organs, and human is particularly susceptible potentially contrast benign and malig- Effect of Microwave Ovens on to damage from microwave energy. In nant tissue (Figure 5). Human Health and Food extensive, but controversial, research Although power deposition in the Concerns are often expressed on the ocular effects of microwaves on patient can be substantial, no side regarding the effects of EMR from , cataracts have been pro- effects or after effects are experienced, microwave ovens on people nearby duced after exposure to very high fre- since MRI does not utilize ionizing and on the food prepared in them. quencies. radiation. However, hazards of Many people believe that microwave Microwave links used for commu- improperly applied MRI do ovens may cause cancer and that food nications employ highly focused exist that can cause severe injuries or prepared by them becomes toxic. beams of energy sent through space even death. These hazards are pri- This belief is simply not true. directly between antennas usually marily the result of: While forms of ionizing radiation such placed high on special towers (Figure as X-rays usually have sufficient local- 4). This practice makes it unlikely that • Strong magnetic fields from MRIs ized energy to cause chemical damage anyone can inadvertently come direct- causing interference with implanted to the molecules in their path, non- ly in the path of this type of energy. electronic devices such as pacemak- ionizing radiation, such as ers. microwaves, does not damage Magnetic Imaging • RF burns resulting from induced molecules. Microwaves generate pure- MRI is based on the magnetic currents in conductors accidentally ly , creating heat in properties of atoms. Magnetic reso- placed on the patient's skin surface moist food or tissue placed in the oven. nance technology is based on the (e.g., leads from electro-cardio- Microwave ovens are designed and absorption and emission of energy in graphs and other monitoring tested so that negligible micro-wave the radio frequency from various body devices). radiation escapes when the door is tissues. MRIs use a powerful magnet closed, making the level of the RF to produce a magnetic field approxi- Optical Effects (Ultraviolet, Visible radiation outside the oven quite safe. mately 10,000 times stronger than the and Infrared Light) However, leakage from a worn or dam- natural background magnetic field Sources of expo- aged gasket around the oven’s door produced by the earth, and generate a sure include: can allow radiation leakage which can variable RF radiation in the 1 MHz to create an unsafe condition. 100 MHz range. A very small percent- • Sunlight Foods cooked in a microwave oven age of atoms within a human • Heat suffer no lasting effects. No conclusive body will align with the static magnet- • evidence exists of any chemical ic field. When focused, • Other incandescent sources changes in microwave-prepared food pulses are transmitted toward the beyond those effects caused by heat- aligned hydrogen atoms in tissues of Intense optical radiation will cause ing, as in a normal oven. interest, where they will reflect a weak excitation. This means that

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in tissue near the body’s sur- the human body. However, overexpo- face can absorb energy from intense sure to UV radiation has adverse optical sources, thereby causing heat- health effects. In addition to the imme- ing and even burning. Visible light diate effect of , overexposure spectrum is illustrated in Figure 6. to UV radiation can cause , Optical radiations are not very eye damage, suppres- penetrating; therefore, the eye and the sion, and premature aging. Children skin are the organs of greatest con- are highly susceptible to harmful UV cern. The immediate effects can be radiation. Because of its greater bio- retinal injury to the eye as well as logical effects, some references consid- abnormal redness and burning of the er UV to be ionizing radiation. skin due to solar radiation (sunburn). Delayed effects include for- X-Rays, Gamma Rays and Other mation, retinal degeneration, acceler- Nuclear/Cosmic Rays ated aging, and skin cancer. The adverse effects of large doses of ionizing radiation were seen shortly Effects of Infrared (IR) after the discovery of radioactivity Infrared (IR) is an energy field and X-rays in the 1890s. In 1902, skin similar to visible light but with a were reported in scientists longer wavelength. This radiation, who were studying radioactivity. The typically emitted by heat lamps, role of radiation in causing leukemia molten metal or , fireplace in humans (primarily in physicians embers and other “hot” objects, is and radiologists) was first reported in invisible to the human eye. The ther- 1944. mal effects, characteristic of the IR region, extend into the spectrum of X-Ray and CT Scan visible light. However, while visible Due to the extremely high frequen- light energy is emitted by objects only cies and of these forms of at a high , infrared ener- EMR, they have sufficient energy to gy is emitted by all objects at ordinary break chemical bonds in living tissue. . Some studies have The well-known biological effects of X- shown that infrared energy can have rays are associated with the ionization positive effects on human cells in that of molecules. The many types of X-ray it can help to rebuild connective tis- devices include: sue. Infrared radiation has no correla- tion with ultraviolet radiation and, • Radiographic systems (dental, podia- applied in moderation, has no damag- try, veterinary, medical, chiropractic) ing effect on human health. • Fluoroscopic imaging systems; (hos- pitals, radiologists) Effects of Ultraviolet (UV) • Cancer therapy The main effect of Ultraviolet (UV) • CT Scan (Computed Tomography) radiation is photochemical; this effect • Mammography is also the case, but to a lesser degree, • Cabinet X-ray systems for security with visible light. Everyone is exposed (baggage inspection at airports) on a daily basis to the UV radiation • Industrial (pipe welds, contained in sunlight. The harmful circuit board analysis) effects of UV exposure depend on the • Bone Density Scans for detection of level of exposure, the duration of expo- osteoporosis sure and differences in the susceptibil- • Other medical and research applica- ity of individuals to UV light. UV radi- tions ation has both positive and negative effects. The positive effects of UV radi- A CT scan is essentially a sophisti- ation include warmth, cated type of X-ray that can take cross in plants, and synthesis in section images of the body.These scans

24 High Frequency Electronics High Frequency Design EMR & HUMAN HEALTH provide excellent bone detail by shoot- Safety Guidelines such as leukemia or bone, breast, and ing multiple X-ray beams through the In the United States, federal, state lung cancer. body to create a computer-generated and local authorities require that all image. Whole-body scans require high- equipment and facilities emitting elec- Acknowledgements er doses of the X-ray radiation to make tromagnetic radiation comply with Many thanks to Robert these images. As is the case with other their exposure guidelines. These Edmondson and Ernest Roiz for forms of ionizing radiation, X-rays, guidelines are designed to protect review comments and their valuable over the long term can the modify both occupational workers and the suggestions regarding ways to genetic material in cells and cause general public with a very large mar- improve this paper. leading to cancer. gin of safety. These limits have been It is important to realize that the endorsed by federal health and safety References amount of X-ray radiation used in agencies such as the Environmental 1. “Opinion on Possible Effects of most diagnostic procedures is so small Protection Agency, the Food and Drug Electromagnetic Fields (EMF), Radio that the risk is extremely low. Multiple Administration, etc. These standards Frequency Fields (RF) and Microwave X-Ray examinations do not appear to limit exposure to levels many times Radiation on Human Health,” increase risk, and no limits have been below those levels generally accepted Scientific Committee on Toxicity, placed on the number of medically nec- as having the potential to cause Ecotoxicity and the Environment essary X-ray examinations a person adverse health effects. (CSTEE). may undergo. However, it is always 2. Guidance for Industry and safe to assume that the same kind of Conclusions FDA—Regulation of Medical Devices, effects that occur at high doses of radi- Electricity—Studies of workers U.S. Department of Health and ation could occur at low doses; there- exposed to strong electric and magnet- Human Services, Food and Drug fore, it is better to try to reduce expo- ic fields (60 Hz ) from power lines pro- Administration, Center for Devices sure as much as possible. Patients vide no consistent evidence that these and Radiological Health. should, if possible, minimize their fields are damaging to DNA or that 3. Electromagnetic Fields and exposure to X-rays, especially to CT they are capable of causing mutations Human Health, by John E. Moulder, scans which should not be performed or cancer. Ph.D., Professor of Radiation on women who may be pregnant. RF—The most apparent biological . effects of RF energy to living cells are Gamma Rays due to heating. While it is not certain Author Information Everybody is basically aware of the that RF radiation generally poses any Ali Zamanian received a B.Sc. high degree of danger associated with risks to human health, some reasons degree in Iran in 1964 and a M.Sc. atomic radiation. Gamma rays, as well exist for being concerned about degree in Electrical Engineering from as Alpha and emitted human health effects from the cellular the University of Essex, England in from radioactive material and nuclear phones themselves. These concerns 1977. He joined Fluor Corporation’s reactions, are forms of ionizing radia- exist because the antennas of these Division in 1984 tion; these rays and particles can cause phones deliver much of their RF ener- and has been involved in RF system chemical or physical damage when gy to small portions of the user’s head. design, mainly on the Public they deposit energy in living tissue. No evidence exists regarding any Safety/911, two-way radio and cellu- Health effects resulting from expo- harmful effects resulting from expo- lar/PCS communication networks. He sure to radiation vary from no effect at sure to typical levels of RF and EMF is currently all to death, and can cause disorders radiation. However, everyone should Engineer Con-sultant with Fluor such as leukemia or bone, breast, and be aware that exposure to such radia- Industrial & Infrastructure Group. lung cancer. In addition, the children tion may not be completely safe at cer- Cy Hardiman is a Project Manager of pregnant women who were exposed tain power levels and frequencies. It is at Fluor Corporation. He received his to high doses of radiation have shown always a good idea to avoid unneces- B.S. degree in Construction Manage- an increased risk of birth defects. sary whenever ment from Purdue University in 1974. These effects have been observed possible. He joined Fluor in 1975 and worked in in various studies of medical radiolo- EMR exposure at the highest fre- the refinery, petrochemical and nucle- gists, miners, - quencies (X-Rays, Gamma rays) is a ar industries. His telecommunications ers, radiotherapy patients, and the source of serious biological damage. career began as a Project Manager in people exposed to radiation from Health effects from exposure to this 1987 managing various wireline, wire- Chernobyl and the atomic form of radiation vary from no effect less, Public Safety, and operations and dropped on Hiroshima and Nagasaki. at all to death, and can cause diseases maintenance projects.

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