Subject: Powerlines and Cancer FAQs (1 of 4) Summary: Q+As on the connection between power

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Newsgroups: sci.med.physics,sci.answers,news.answers Subject: Powerlines and Cancer FAQs (1 of 4) Summary: Q&As on the connection between powerlines, electrical occupations and cancer. Discussion of the biophysics of interactions with EM sources, summaries of the laboratory and human studies, information on standards, and references. Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing radiation, FAQ Last-modified: 1994/3/25 Version: 2.4 Current version available by anonymous FTP from "rtfm.mit.edu" Directory: /pub/usenet-by-group/news.answers/powerlines-cancer-FAQ Files: part1, part2, part3, etc. . . . Revision notes: v2.4 (23-Mar-94): Expanded to four parts. Added table of contents. Expanded and annotated bibliography. Modified and expanded non-ionizing bioeffects sections. Expanded discussion of field reduction techniques. Added sections on measurement techniques. Expanded section on laboratory studies and broke into multiple parts. Added short section and references on reproductive toxicity studies. Table of Contents: Part 1 1) Why is there a concern about powerlines and cancer? 2) What is the difference between the electromagnetic (EM) energy associated with power lines and other forms of EM energy such as microwaves or x-rays? 3) Why do different types of EM sources produce different biological effects? 4) What is difference between EM radiation and EM fields? 5) Do power lines produce EM radiation? 6) How do ionizing EM sources cause biological effects? 7) How do RF, MW, visible light, and IR light sources cause biological effects? 8) How do the power-frequency EM fields cause biological effects? 9) Do non-ionizing EM sources cause non-thermal as well as thermal effects? 10) What sort of power-frequency magnetic fields are common in residences and workplaces? 11) Can power-frequency fields in homes and workplaces be reduced? 12) What is known about the relationship between powerline corridors and cancer rates? 13) How big is the "cancer risk" associated with living next to a powerline? 14) How close do you have to be to a power line to be considered exposed to power-frequency magnetic fields? 15) What is known about the relationship between "electrical occupations" and cancer rates? Part 2 16) What do laboratory studies tell us about power-frequency fields and cancer? 16A) Are power-frequency fields genotoxic? 16B) Are power-frequency magnetic fields cancer promoters? 16C) Do power-frequency magnetic fields enhance the effects of other genotoxic agents? 17) How do laboratory studies of the effects of power-frequency fields on cell growth, immune function, and melatonin relate to the question of cancer risk? 18) Do power-frequency fields show any effects at all in laboratory studies? 19) What about the new "Swedish" study showing a link between power lines and cancer? 20) What criteria do scientists use to evaluate all the confusing and contradictory laboratory and epidemiological studies of power-frequency magnetic fields and cancer? 20A) Criterion One: How strong is the association between exposure to power-frequency fields and the risk of cancer? 20B) Criterion Two: How consistent are the studies of associations between exposure to power-frequency fields and the risk of cancer? 20C) Criterion Three: Is there a dose-response relationship between exposure to power-frequency fields and the risk of cancer? 20D) Criterion Four: Is there laboratory evidence for an association between exposure to power-frequency fields and the risk of cancer? 20E) Criterion Five: Are there plausible biological mechanisms that suggest an association between exposure to power-frequency fields and the risk of cancer? 21) If exposure to power-frequency magnetic fields does not explain the residential and occupations studies which show increased cancer incidence, what other factors could? 21A) Could problems with dose assessment affect the validity of the epidemiological studies of power lines and cancer? 21B) Are there other cancer risk factors that could be causing a false association between exposure to power-frequency fields and cancer? 21C) Could the epidemiological studies of power lines and cancer be biased by the methods used to select control groups? 21D) Could analysis of the epidemiological studies of power lines and cancer be skewed by publication bias? 22) What is the strongest evidence for a connection between power-frequency fields and cancer? 23) What is the strongest evidence against a connection between power-frequency fields and cancer? 24) What studies are needed to resolve the cancer-EMF issue? 25) Is there any evidence that power-frequency fields could cause health effects other than cancer. Part 3 26) What are some good overview articles? 27) Are there exposure guidelines for power-frequency fields? 28) What effect do powerlines have on property values? 29) What equipment do you need to measure power-frequency magnetic fields? 30) How are power-frequency magnetic fields measured? Annotated Bibliography A) Recent Reviews of the Biological and Health Effects of Power-Frequency Fields B) Reviews of the Epidemiology of Exposure to Power-Frequency Fields C) Epidemiology of Residential Exposure to Power-Frequency Fields D) Epidemiology of Occupational Exposure to Power-Frequency Fields E) Human Studies Related to Power-Frequency Exposure and Cancer F) Biophysics and Dosimetry of Power-Frequency Fields Part 4 G) Laboratory Studies of Power-Frequency Fields and Cancer H) Laboratory Studies Indirectly Related to Power-Frequency Fields and Cancer J) Laboratory Studies of Power-Frequency Fields and Reproductive Toxicity K) Reviews of Laboratory Studies of Power-Frequency Fields L) Miscellaneous Studies M) Regulations and Standards for Ionizing and Non-ionizing EM Sources. ----- Subject: 1) Why is there a concern about powerlines and cancer? Most of the concern about power lines and cancer stems from epidemiological studies of people living near powerlines, and epidemiological studies of people working in "electrical occupations". Some of these epidemiological studies appear to show a relationship between exposure to power-frequency magnetic fields and the incidence of cancer. Laboratory studies have shown little evidence of a link between power-frequency fields and cancer. Subject: 2) What is the difference between the electromagnetic (EM) energy associated with power lines and other forms of EM energy such as microwaves or x-rays? X-rays, ultraviolet (UV) light, visible light, infrared light (IR), microwaves (MW), radiowaves (RF), and electromagnetic fields from electrical power systems are all parts of the EM spectrum. The parts of the EM spectrum are characterized by their frequency or wavelength. The frequency and wavelength are related, and as the frequency rises the wavelength gets shorter. The frequency is the rate at which the EM field changes direction and is usually given in Hertz (Hz), where one Hz is one cycle per second. Power-frequency fields in the US vary 60 times per second, so they are 60 Hz fields, and have a wavelength of 3000 miles (5000 km). Power in most of the rest of the world is at 50 Hz. The power-frequency fields are often referred to as extremely low frequencies or ELF. Broadcast AM radio has a frequency of around one million Hz and a wavelength of around 1000 ft (300 m). Microwave ovens have a frequency of about 2.5 billion Hz, and a wavelength of about 5 inches (12 cm). X-rays and UV light have frequencies of millions of billions of Hz, and wavelengths of less than a thousandth of an inch (10 nm or less). Subject: 3) Why do different types of EM sources produce different biological effects? The interaction of biological material with an EM source depends on the frequency of the source. We usually talk about the EM spectrum as though it produced waves of energy. This is not strictly correct, because sometimes EM energy acts like particles rather than waves; this is particularly true at high frequencies. This double nature of the EM spectrum is referred to as "wave-particle duality". The particle nature of EM energy is important because it is the energy per particle (or photons, as these particles are called) that determines what biological effects EM energy will have. At the very high frequencies characteristic of UV light and X-rays, EM particles (photons) have sufficient energy to break chemical bonds. This breaking of bonds is termed ionization, and this portion of the EM spectrum is termed ionizing radiation. The well-known biological effects of X-rays are associated with the ionization of molecules. At lower frequencies, such as those characteristic of visible light, RF, and MW, the photons do not carry enough energy to break chemical bonds. This portion of the EM spectrum is termed the non-ionizing portion. At RF and MW frequencies the energy of a photon is very much (by a factor of thousands or more) below those needed to disrupt chemical bonds. For this reason, there is no analogy between the biological effects of ionizing and nonionizing EM energy. Non-ionizing EM sources can still produce biological effects. One mechanism is by inducing electrical currents in tissues, which cause heating by moving ions and water molecules through the viscous medium in which they exist. The efficiency with which an EM source can induce electrical currents, and thus produce heating, depends on the frequency of the source, and the size and orientation of the object being heated. At frequencies below that used for broadcast AM radio, EM sources couple poorly with the bodies of humans and animals, and thus are very inefficient at inducing electrical currents and causing heating. Thus in terms of potential biological effects the EM spectrum can be divided into the three portions: 1) The ionizing portion, where direct chemical damage can occur (X-rays, hard UV). 2) The portion of the non-ionizing spectrum in which the wavelength is smaller than that of the body, where heating can occur (visible light, IR, MW and RF). 3) The portion of the non-ionizing spectrum in which the wavelength is much larger than that of the body, where heating seldom occurs (power frequencies). Subject: 4) What is difference between EM radiation and EM fields? When dealing with fields from an EM source it is customary to distinguish between fields (which do not transmit energy to infinity from the source) and radiation (which does). In general, EM sources produce both radiant energy (radiation) and non-radiant energy (fields). Radiated energy exists apart from its source, travels away from the source, and continues to exist even if the source is turned off. Non-radiant energy is not projected away into space, and it ceases to exist when the energy source is turned off. When a person or object is more than several wavelengths from an EM source, a condition called far-field, the radiation component of the EM source dominates. When a person or object is less than one wavelength from an EM source, a condition called near-field, the field effect dominates, and the electrical and magnetic components are unrelated. For ionizing frequencies where the wavelengths are less than a thousandth of an inch (less than 10 nm), human exposure is entirely in the far-field, and only the radiation from the EM source is relevant to health effects. For MW and RF, where the wavelengths are in inches to a few thousand feet (a few cm to a km), human exposure can be in both the near- and far-field, so that both field and radiation effects can be relevant. For power-frequency fields, where the wavelength is thousands of miles (thousands of km), human exposure is always in the near-field, and only the field component is relevant to possible health effects. Subject: 5) Do power lines produce EM radiation? The fields associated with transmission lines are purely near-field. While the lines theoretically might radiate some energy the efficiency of this is so low that this effect can for all practical purposes be ignored. To be an effective radiation source an antenna must have a length comparable to its wavelength. Power-frequency sources are clearly too short compared to their wavelength (3000 miles, 5000 km) to be effective radiation sources. This is not to say that there is no loss of power during transmission. There are many sources of loss in transmission lines that have nothing to do with "radiation" (in the sense as it is used in EM theory). Loss of energy is a result of resistive heating, not "radiation". This is in sharp contrast to RF antennas, which "lose" energy to space by radiation. Likewise, there are many ways of transmitting energy from point A to point B that do not involve radiation. Electrical circuits do it all the time. The only "practical" exception to the statement that power-frequency fields do not radiate is the use of ELF antennas to broadcast to submerged submarines. The US Navy runs a power-frequency antenna in Northern Wisconsin and the Upper Peninsula of Michigan. To overcome the inherent inefficiency of the frequency, the antenna is several hundred kilometers in length. Subject: 6) How do ionizing EM sources cause biological effects? Ionizing EM radiation carries sufficient energy per photon to break chemical bonds. In particular, ionizing radiation is capable of breaking bonds in the genetic material of the cell, the DNA. Severe damage to DNA can kill cells, resulting in tissue damage or death. Lesser damage to DNA can result in permanent changes in the cells which may lead to cancer. If these changes occur in reproductive cells, they can lead to inherited changes, a phenomena called mutation. All of the known hazards from exposure to the ionizing portion of the EM spectrum are the result of the breaking of chemical bonds in DNA. For frequencies below that of UV light, DNA damage does not occur because the photons do not have enough energy to break chemical bonds. Well-accepted safety standards exist to prevent significant damage to the genetic material of persons exposed to ionizing EM radiation [M3]. Subject: 7) How do RF, MW, visible light, and IR light sources cause biological effects? A principal mechanism by which RF, MW, visible light, and IR light sources cause biological effects is by heating (thermal effects). This heating can kill cells. If enough cells are killed, burns and other forms of long-term, and possibly permanent tissue damage can occur. Cells which are not killed by heating gradually return to normal after the heating ceases; permanent non-lethal cellular damage is not known to occur. At the whole-animal level, tissue injury and other thermally-induced effects can be expected when the amount of power absorbed by the animal is similar to or exceeds the amount of heat generated by normal body processes. Some of these thermal effects are very subtle, and do not represent biological hazards. It is possible to produce thermal effects even with very low levels of absorbed power. One example is the "microwave hearing" phenomenon; these are auditory sensations that a person experiences when his head is exposed to pulsed microwaves such as those produced by radar. The Rmicrowave hearingS effects is a thermal effect, but it can be observed at very low average power levels. Since thermal effects are produced by heat, not by the electric or magnetic fields directly, they can be produced by fields at many different frequencies. Well-accepted safety standards exist to prevent significant thermal damage to persons exposed to MW and RFs [M2] and also for persons exposed to lasers, IR and UV light [M4]. Subject: 8) How do the power-frequency EM fields cause biological effects? The electrical and magnetic fields associated with power-frequency fields cannot break bonds because the energy per photon is too low. The magnetic field intensities to which people are exposed in residential settings and in the vast majority of occupational settings cannot cause heating because the induced electrical currents are too low. Thus the known mechanisms through which ionizing radiation, MWs and RFs effect biological material have no relevance for power-frequency fields. The electrical fields associated with the power-frequency fields exist whenever voltage is present, and regardless of whether current is flowing. These electrical fields have very little ability to penetrate buildings or even skin. The magnetic fields associated with power-frequency fields exist only when current is flowing. These magnetic fields are difficult to shield, and easily penetrate buildings and people. Because power-frequency electrical fields do not penetrate, any biological effects from routine exposure to power-frequency fields must be due to the magnetic component of the field. Exposure of people to power-frequency magnetic fields results in the induction of electrical currents in the body. If these currents are sufficiently intense, they can cause heating, nerve excitation and other effects [F4,K1]. At power frequencies, the body is poorly coupled to external fields, and the induced currents are usually too small to produce obvious effects. Shocks, and other obvious effects usually require that the body actually touch a conductive objects, allowing current to pass directly into the body. It requires a power-frequency magnetic field in excess of 5 Gauss (500 microT, see Question 10 for typical exposures) to induce electrical currents of a magnitude similar to those that occur naturally in the body. Well-accepted safety standards exist to protect persons from exposure to power-frequency fields that would induce such currents (Question 27). Subject: 9) Do non-ionizing EM sources cause non-thermal as well as thermal effects? One distinction that is often made in discussions of the biological effects of non-ionizing EM sources is between "nonthermal" and "thermal" effects. This refers to the mechanism for the effect, non-thermal effects being a result of a direct interaction between the field and the organism, and thermal effects being a result of heating. Microwave burns are an obvious thermal effect, and electrical shocks are an obvious nonthermal effect. There are many reported biological effects (some of which have not been reproduced) whose mechanisms are totally unknown, and one should be very careful about drawing the distinction between "thermal" and "nonthermal" mechanisms for such effects. Subject: 10) What sort of power-frequency magnetic fields are common in residences and workplaces? In the US magnetic fields are commonly measured in Gauss (G) or milliGauss (mG), where 1,000 mG = 1G. In the rest of the world, they are measured in Tesla (T), were 10,000 G equals 1 T (1 G = 100 microT; 1 microT = 10 mG). Power-frequency fields are measured with a calibrated gauss meter (Questions 29 & 30). Within the right-of-way (ROW) of a high-voltage (115-765 kV, 115,000-765,000 volt) transmission line, fields can approach 100 mG (0.1 G, 10 microT). At the edge of a high-voltage transmission ROW, the field will be 1-10 mG (0.1-1.0 microT). Ten meters from a 12 kV (12,000 volt) distribution line fields will be 2-10 mG (0.2-1.0 microT). Actual fields depend on voltage, design and current. Fields within residences vary from over 1000 mG (100 microT) a few inches (cm) from certain appliances to less than 0.2 mG (0.02 microT) in the center of some rooms. Appliances that have the highest fields are those with high currents (e.g., toasters, electric blankets) or high-speed electric motors (e.g., vacuum cleaners, electric clocks, blenders, power tools). Appliance fields decrease very rapidly with distance. See Theriault [F3] for further details. Occupational exposures in excess of 1000 mG (100 microT) have been reported (e.g., in arc welders and electrical cable splicers). In "electrical" occupations typical mean exposures range from 5 to 40 mG (0.5 to 4 microT). See Theriault [F3] for further details. Subject: 11) Can power-frequency fields in homes and workplaces be reduced? There are engineering techniques that can be used to decrease the magnetic fields produced by power lines, substations, transformers and even household wiring and appliances. Once the fields are produced, however, shielding is very difficult. Small area can be shielded by the use of Mu metal, a nickel-iron-copper alloy with "high magnetic permeability and low hysteresis losses". Mu metal shields are very expensive, and limited to small volumes. Increasing the height of towers, and thus the height of the conductors above the ground, will reduce the field intensity at the edge of the ROW. The size, spacing and configuration of conductors can be modified to reduce magnetic fields, but this approach is limited by electrical safety considerations. Placing multiple circuits on the same set of towers can also lower the field intensity at the edge of the ROW, although it generally requires higher towers. Replacing lower voltage lines with higher voltage ones can also lower the magnetic fields. Burying transmission lines greatly reduces their magnetic fields. The reduction occurs because the underground lines use rubber, plastic or oil for insulation rather than air. This allows the conductors to be placed much closer together and allows greater phase cancellation. However, placing high voltage lines underground is very expensive, adding costs that are measured in hundreds of thousands of US dollars per mile. Subject: 12) What is known about the relationship between powerline corridors and cancer rates? Some studies have shown that children living near certain types of powerlines (high current distribution lines and transmission lines) have higher than average rates of leukemia [C1,C6,C10,C17], brain cancers [C1,C6] and/or overall cancer [C5,C15]. The correlations are not strong, and none of the studies have shown dose-response relationships. When power-frequency fields are actually measured, the correlation vanishes [C6,C10,C17]. Several other studies have shown no correlations between residence near power lines and risks of childhood leukemia [C3,C5,C7,C8,C9,C14,C15], childhood brain cancer [C5,C8,C14,C15,C17], or overall childhood cancer [C14,C17]. With one exception [C2] all studies of correlations between adult cancer and residence near power lines have been negative [C4,C8,C9,C11,C12,C16]. Subject: 13) How big is the "cancer risk" associated with living next to a powerline? The excess cancer found in epidemiological studies is usually quantified in a number called the relative risk (RR). This is the risk of an "exposed" person getting cancer divided by the risk of an "unexposed" person getting cancer. Since no one is unexposed to power-frequency fields, the comparison is actually "high exposure" versus "low exposure". A RR of 1.0 means no effect, a RR of less the 1.0 means a decreased risk in exposed groups, and a RR of greater than one means an increased risk in exposed groups. Relative risks are generally given with 95% confidence intervals. These 95% confidence intervals are almost never adjusted for multiple comparisons even when multiple types of cancer and multiple indices of exposure are studied (see Olsen et al, [C15], Fig. 2 for an example of a multiple-comparison adjustment). An overview of the epidemiology requires that studies be combined using a technique known as "meta-analysis". Meta-analysis is not easy to do, since the epidemiological studies of residential exposure use a wide variety of methods for assessing "exposure". Meta-analysis also gets out-of-date rapidly in this field. The following RRs (called summary RRs in meta-analysis) for the residential exposure studies are adapted from Hutchison [B4] and Doll et al [B5] by inclusion of the new European studies (Question 19). The confidence intervals should be viewed as measures of the diversity of the data, rather than as strict tests of the statistical significance of the data. childhood leukemia: 1.5 (0.8-3.0) 8 studies childhood brain cancer: 1.9 (0.9-3.0) 6 studies childhood lymphoma: 2.5 (0.3-40) 2 studies all childhood cancer: 1.5 (0.9-2.5) 5 studies adult leukemia: 1.1 (0.8-1.6) 3 studies adult brain cancer: 0.7 (0.4-1.3) 1 study all adult cancer: 1.1 (0.9-1.3) 3 studies As a base-line for comparison, the age-adjusted cancer incidence rate for adults in the United States is 3 per 1,000 per year for all cancer (that is, 0.3% of the population gets cancer in a given year),and 1 per 10,000 per year for leukemia [E6]. Subject: 14) How close do you have to be to a power line to be considered exposed to power-frequency magnetic fields? The epidemiological studies that show a relationship between cancer and powerlines do not provide any consistent guidance as to what distance or exposure level is associated with increased cancer incidence. The studies have used a wide variety of techniques to measure exposure, and they differ in the type of lines that are studied. The US studies have been based predominantly on neighborhood distribution lines, whereas the European studies have been based strictly on high-voltage transmission lines and/or transformers. Field measurements: Several studies have measured power-frequency fields in the residences [C6,C7,C10,C12,C17]. Both one-time (spot), peak, and 24-hour average measurement have been made; none of the studies using measured fields have shown a relationship between exposure and cancer. Proximity to lines: Several studies have used the distance from the power line corridor to the residence as a measure of power-frequency fields [C4,C5,C8,C9,C8,C9,C11,C12,C17]. When something we can measure (distance to the line), is used as an index of what we really want to measure (the magnetic field), it is called a surrogate (or proxy) measure. With two exception [C5,C17], studies that have used distance from power lines as a surrogate measure of exposure have shown no significant relationship between proximity to lines and the incidence of cancer. The major exception is a childhood leukemia study [C17] that showed a significant increase in leukemia incidence for residence within 50 m (150 ft) of high-voltage transmission lines. This same study [C12,C17] showed no elevation of child leukemia risks at 51-100 m (150-300 ft), and no increase in childhood brain cancer, overall childhood cancer, or any types of adult cancer at any distance. Wire Codes: The original US powerline studies used a combination of the type of wiring (distribution vs transmission, number and thickness of wires) and the distance from the wiring to the residence as a surrogate measure of exposure [C1,C2,C3,C6,C7,C10]. This technique is known as "wirecoding". Three studies using wirecodes [C1,C6,C10] have shown a relationship between childhood cancer and "high-current configuration" wirecodes. Two of these studies [C6,C10] failed to show a significant relationship between exposure and cancer when actual measurements were made. Wirecodes are stable over time [F5] and correlate with measured fields, although the correlation is not very good [F1]. The wirecode scheme was developed for the U.S., and does not appear to be readily applicable elsewhere. Calculated Historic Fields: The recent European studies have used utility records and maps to calculate what fields would have been produced by power lines in the past [C12,C14,C15,C17]. Typically, the calculated field at the time of diagnosis or the average field for a number of years prior to diagnosis are used as a measure of exposure (Question 19). These calculated exposures explicitly exclude contributions from other sources such as distribution lines, household wiring, or appliances. When the field calculations are done for contemporary measured fields they correlate reasonably well [C17]. Of course, there is no way to check the accuracy of the calculated historic fields. Subject: 15) What is known about the relationship between "electrical occupations" and cancer rates? Several studies have shown that people who work in electrical occupations have higher than average cancer rates. The original studies [D1,D2 were only of leukemia. Some later studies also implicated brain, lymphoma and/or breast cancer [B1,B2,B3,B4,B5]. Most of the cautions listed for the residential studies apply here also: many negative studies, weak correlations, no dose-response relationships. Additionally, these studies are mostly based on job titles, not on measured exposures. Meta-analysis of the occupational studies is even more difficult than the residential studies. First, a variety of epidemiological techniques are used, and studies using different techniques should not really be combined. Second, a wide range of definitions of "electrical occupations" are used, and very few studies actually measured exposure. The following RRs (Question 13) for the occupational exposure studies are adapted from Hutchison [B4] and Davis et al [A2]. Again, the confidence intervals should be viewed as measures of diversity rather than as tests of the statistical significance. leukemia: 1.15 (1.0-1.3) 28 studies brain: 1.15 (1.0-1.4) 19 studies lymphoma: 1.20 (0.9-1.5) 6 studies all cancer: 1.00 (0.9-1.1) 8 studies The above relative risks do not take into account more recent studies. Two recent European studies [D7,D9] have found excess leukemia in electrical occupations, but no excess of other types of cancer (Question 19 for details). Two other new occupational exposure studies [D4,D5] shows small but statistically significant increases in leukemia, but others [D3,D6,D8] do not. None of the new studies of electrical occupations show significant elevation of any types of cancer other than leukemia (specifically brain cancer or lymphoma)[D5,D7,D8,D9]. Adding these seven new studies raises the summary RR for leukemia slightly, and lowers the summary RRs for brain cancer and lymphomas to essentially one. Subject: 16) What do laboratory studies tell us about power-frequency fields and cancer? Carcinogens, agents that cause cancer, are generally of two types: genotoxins and promoters. Genotoxic agents (often called initiators) directly damage the genetic material of cells. Genotoxins usually effect all types of cells, and may cause many different types of cancer. Genotoxins generally do not have thresholds for their effect; in other words, as the dose of the genotoxin is lowered the risk gets smaller, but it never goes away. A promoter (often called an epigenetic agent) is something that increases the cancer risk in animals already exposed to a genotoxic carcinogen. Promoters usually effect only certain types of cells, and may cause only certain types of cancer. Promoters generally have thresholds for their effect; in other words, as the dose of the promoter is lowered a level is reached in which there is no risk. Subject: 16A) Are power-frequency fields genotoxic? There are many approaches to measuring genotoxicity. Whole-organism exposure studies can be used to see whether exposure causes cancer or causes mutations. Cellular studies can be done to detect DNA or chromosomal damage. Very few whole-organism exposure studies have been done. Bellossi et al [G13] exposed leukemia-prone mice for 5 generations and found no effect on leukemia rates; however, since the study used 12 and 460 Hz pulsed fields at 60 G (6 mT), the relevance of this to power-frequency fields is unclear. Otaka et al [G18] showed that power-frequency magnetic fields did not case mutations in fruit flies. Rannug et al [G19] found that power-frequency magnetic fields did not increase the incidence of skin tumors or leukemia in mice. RD Benz et conducted a multi-generation mouse exposure study in 1983-1985 as part of the NY State Powerlines Project; this study reported no increase in mutations rates or sister chromatid exchanges, but has never been published. A number of published laboratory studies have reported that power-frequency magnetic fields do not cause DNA strand breaks [G4,G16] chromosome aberrations [G1,G6,G15], sister chromatid exchanges [G2,G6,G11,G20], micronuclei formation [G9,G11] or mutations [G3,G15,G17]. Many of the above laboratory studies also examined power-frequency electrical fields and combination of power-frequency electrical and magnetic fields [G1,G2,G4,G8,G11,G16]. As with the studies of magnetic fields alone, the studies of electrical fields and combined fields showed no evidence of genotoxicity. There are two positive reports of genotoxicity. Khalil & Qassem [G12] reported that a 10.5 G (1.05 mT) pulsed field caused chromosome aberrations. Nordenson et al [E4] reported that switchyard workers exposed to spark discharges had an increased rate of chromosomal defects, but Bauchinger et al [E2] for no such increase in chromosomal defects in a similar study. Subject: 16B) Are power-frequency magnetic fields cancer promoters? There are agents (for example, promoters) that influence the development of cancer without directly damaging the genetic material. It has been suggested that power-frequency EMFs could promote cancer [L1]. In a promotion test, animals are exposed to a known genotoxin at a dose that will cause cancer in some, but not all animals. Another set of animals are exposed to the genotoxin, plus another agent. If the agent plus the genotoxin results in more cancers that seen for the genotoxin alone, then that agent is a promoter. Published studies have shown that power-frequency magnetic fields do not promote chemically-induced skin cancer [G10,G14,G19] or chemically-induced liver cancers [G21,G24]. For chemically-induced breast cancer, one study has shown promotion [G22] and one has not [G23]. Subject: 16C) Do power-frequency magnetic fields enhance the effects of other genotoxic agents? There are some other types of studies that are relevant to the carcinogenic potential of agents, but that are not strictly either genotoxicity or promotion tests. The most common of these are cellular studies that test whether an agent enhances the genotoxic activity of a known genotoxin; these studies are the cellular equivalent of a promotion study. Published studies have reported that power-frequency magnetic fields do not enhance the mutagenic effects of known genotoxins [G3,G9], and do not inhibit the repair of DNA damage induced by ionizing [G7,G8] or UV [G15] radiation. One study [G6] has reported that power-frequency fields can increase the frequency of sister chromatid exchanges induced by known genotoxins. Subject: 17) How do laboratory studies of the effects of power-frequency fields on cell growth, immune function, and melatonin relate to the question of cancer risk? There are other biological effects that might be related to cancer. There are substances (called mitogens) that cause non-growing normal cells to start growing. Some mitogens appear to be carcinogens. There have been numerous studies of the effects of power-frequency fields on cell growth (proliferation) and tumor growth (progression). Most recent studies of the effects of power-frequency magnetic fields on cancer progression have shown no effect [G5,G10,H3], but one has reported enhanced progression [G14]. Most recent studies of effects of power-frequency magnetic fields on cell growth have also shown no effect [G1,G11,G16,G20,H2,H7,H8], but some have shown increased [G6] or decreased [G12] cell growth. With one possible exception [H1] there have been no reported effects on proliferation or progression for fields below 2000 mG (200 microT). Suppression of the immune system in animals and humans is associated with increased rates of certain types of cancer, particularly lymphomas [E6,E7]. Immune suppression has not been associated with excess leukemia and brain cancer. Some studies have shown that power-frequency fields can have effects on cells of the immune system [K2], but no studies have shown the type or magnitude of immunosuppression that is associated with increased cancer risks. It has also been suggested that power-frequency EM fields might suppress the production of the hormone melatonin, and that melatonin has "cancer-preventive" activity [H6,H7,L2]. This is highly speculative. There have been some reports that EM fields effect melatonin production, but studies using power-frequency magnetic fields have not shown reproducible effects [H9,H10]. In addition, while there is some evidence that melatonin has "cancer-preventive" activity against transplanted breast tumors in rats, there is no evidence that melatonin effects other types of cancer, or that it has any effect on breast or other cancers in humans. Subject: 18) Do power-frequency fields show any effects at all in laboratory studies? While the laboratory evidence does not suggest a link between power-frequency magnetic fields and cancer, numerous studies have reported that these fields do have "bioeffects", particularly at high field strength [H4,H5,K1,K2]. Power-frequency fields intense enough to induce electrical currents in excess of those that occur naturally (above 5 G, 500 microT, see Question 8) have shown reproducible effects, including effects on humans [K1]. Below about 2 G (200 microT) there are few published (and replicated) reports of bioeffects, although there are unreplicated reports of effects for fields as low as about 200 mG (20 microT). Even among the scientists who believe that there may be a connection between power-frequency fields and cancer, there is no consensus as to mechanisms which would connect these "bioeffects" with cancer causation [K1,L1]. Subject: 19) What about the new "Swedish" study showing a link between power lines and cancer? There are new residential and occupational studies from Sweden [C12,C17,D7], Denmark [D9,C15], Finland [C14] and the Netherlands [C16]. The published studies are considerably more cautious in their interpretations of the data than were the unpublished preliminary reports and the earlier press reports. The authors of the Scandinavian childhood cancer studies [C14,C15,C17] have produced a collaborative meta-analysis of their data [B6]. The RRs (Question 13) from this meta-analysis are shown below in comparison to meta-analysis of the prior studies [B4,B5]. Childhood leukemia, Scandinavian: 2.1 (1.1-4.1) Childhood leukemia, prior studies: 1.3 (0.8-2.1) Childhood lymphoma, Scandinavian: 1.0 (0.3-3.7) Childhood lymphoma, prior studies: none Childhood CNS cancer, Scandinavian: 1.5 (0.7-3.2) Childhood CNS cancer, prior studies: 2.4 (1.7-3.5) All childhood cancer, Scandinavian: 1.3 (0.9-2.1) All childhood cancer, prior studies: 1.6 (1.3-1.9) - Fleychting & Ahlbom [C12,C17]. This is a case-control study of everyone who lived within 300 meters of high-voltage powerlines between '60 and '85. For children all types of tumors were analyzed; for adults only leukemia and brain tumors were studied. Exposure was assessed by spot measurements, calculated retrospective assessments, and distance from power lines. No increased overall cancer incidence was found in either children or adults, for any definition of exposure. An increased incidence of leukemia (but not other cancers) was found in children for calculated fields over 2 mG (0.2 microT) at the time of diagnosis, and for residence within 50 m (150 ft) of the power line. The increased incidence of leukemia is found only in one-family homes; there is no increased incidence in apartments. The retrospective fields calculations do not take into account sources other the transmission lines. No significant elevation in cancer incidence was found for measured fields. - Verkasalo et al [C14]. This is a cohort study of cancer in children in Finland living within 500 m of high-voltage lines. Only calculated retrospective fields were used to define exposure. The calculated fields are based only on lines of 110 kV and above and do not take into account fields from other sources such as distribution lines, household wiring or appliances. Both average fields and cumulative fields (microT - years) were used as exposure metrics. The total incidence of childhood cancer was not significantly elevated for average exposure above 0.20 microT (2 mG), or for cumulative exposure above 0.50 microT-years (5 mG-years). A significant excess incidence of brain cancer was found in boys; the excess was due entirely to one exposed boy who developed three independent brain tumors. No significant increase in incidence was found for brain tumors in girls or for leukemia, lymphomas or other cancers in either sex. - Olsen and Nielson [C15]. This is a case-control study based on all childhood leukemia, brain tumors and lymphomas diagnosed in Denmark between '68 and '86. Exposure was assessed on the basis of calculated fields over the period from conception to diagnosis. No overall increase in cancer was found when 0.25 microT (2.5 mG) was used as the cut-point to define exposure (as specified in the study design). After the data were analyzed, it was found that the overall incidence of childhood cancer was significantly elevated if 0.40 microT (4 mG) was used as the cut-point. No significant increase was found for leukemia or brain cancer incidence for any cut-point. A significant increase in lymphoma was found for the 0.10 microT cut-point but not for higher cut-points. - Guenel et al [D9]. This is a case-control study based on all cancer in actively employed Danes between '70 and '87 who were 20-64 years old in '70. Each occupation-industry combination was coded on the basis of supposed 50-Hz magnetic field exposure. No significant increases were seen for breast cancer, malignant lymphomas or brain tumors. Leukemia incidence was significantly elevated among men in the highest exposure category; women in similar exposure categories showed no increase in leukemia. -Floderus et al [D9]. This is a case-control study of leukemia and brain tumors in occupationally-exposed men who were 20-64 years of age in '80. Exposure calculations were based on the job held longest during the 10-year period prior to diagnosis. Many measurements were taken using a person whose job was most similar to that of the person in the study. About two-thirds of the subjects in the study could be assessed in this manner. A significant elevation in incidence was found for leukemia, but not for brain cancer. -Schreiber et al [C16]. This is a retrospective cohort study of people in an urban area in the Netherlands. People were considered exposed in they lived within 100 m of transmission equipment (150 kV lines plus a substation). Fields in the "exposed" group were 1-11 mG (0.1-1.1 microT), fields in the "unexposed" group were 0.2-1.5 mG (0.02-0.15 microT). The total cancer incidence in the RexposedS group was insignificantly less than that in the general Dutch population. No cases of leukemia or brain cancer were seen in the "exposed" group. Subject: 20) What criteria do scientists use to evaluate all the confusing and contradictory laboratory and epidemiological studies of power-frequency magnetic fields and cancer? There are certain widely accepted criteria that are weighed when assessing such groups of epidemiological and laboratory studies. These are often called the "Hill criteria" [E1]. Under the Hill criteria one examines the strength (Question 20A) and consistency (Question 20B) of the association between exposure and risk, the evidence for a dose-response relationship (Question 20C), the laboratory evidence (Question 20D), and the biological plausibility (Question 20E). These criteria are viewed as a whole; no individual criterion is either necessary or sufficient for concluding that there is a causal relationship between an exposure and a disease. Overall, application of the Hill criteria shows that the current evidence for a connection between power-frequency fields and cancer is quite weak, because of the weakness and inconsistencies in the epidemiological studies, combined with the lack of a dose-response relationship in the human studies, and the negative laboratory studies. Subject: 20A) Criterion One: How strong is the association between exposure to power-frequency fields and the risk of cancer? The first Hill criterion is the *strength of the association* between exposure and risk. That is, is there a clear risk associated with exposure? A strong association is one with a RR (Question 13) of 5 or more. Tobacco smoking, for example, shows a RR for lung cancer 10-30 times that of non-smokers. Most of the positive power-frequency studies have RRs of less than two. The leukemia studies as a group have RRs of 1.1-1.3, while the brain cancer studies as a group have RRs of about 1.3-1.5. This is only a weak association. Subject: 20B) Criterion Two: How consistent are the studies of associations between exposure to power-frequency fields and the risk of cancer? The second Hill criterion is the *consistency* of the studies. That is, do most studies show about the same risk for the same disease? Using the same smoking example, essentially all studies of smoking and cancer showed an increased risk for lung and head-and-neck cancers. Many power-frequency studies show statistically significant risks for some types of cancers and some types of exposures, but many do not. Even the positive studies are inconsistent with each other. For example, while a new Swedish study [C17] shows an increased incidence of childhood leukemia for one measure of exposure, it contradicts prior studies that showed an increase in brain cancer [B4,B5], and a parallel Danish study [D9] shows an increase in childhood lymphomas, but not in leukemia. Many of the studies are internally inconsistent. For example, where a new Swedish study [C17] shows an increase for childhood leukemia, it shows no overall increase in childhood cancer, implying that the rates of other types of cancer were decreased. In summary, few studies show the same positive result, so that the consistency is weak. Subject: 20C) Criterion Three: Is there a dose-response relationship between exposure to power-frequency fields and the risk of cancer? The third Hill criterion is the evidence for a *dose-response relationship*. That is, does risk increase when the exposure increases? Again, the more a person smokes, the higher the risk of lung cancer. No published power-frequency exposure study has shown a dose-response relationship between measured fields and cancer rates, or between distances from transmission lines and cancer rates. The lack of a relationship between exposure and increased cancer incidence is a major reason why most scientists are skeptical about the significance of the epidemiology. Not all relationships between dose and risk can be described by simple linear no-threshold dose-response curves where risk is strictly proportional to risk. There are known examples of dose-response relationships that have thresholds, that are non-linear, or that have plateaus. For example, the incidence of cancer induced by ionizing radiation in rodents rises with dose, but only up to a certain point; beyond that point the incidence plateaus or even drops. Without an understanding of the mechanisms connecting dose and effect it is impossible to predict the shape, let alone the magnitude of the dose-response relationship. Subject: 20D) Criterion Four: Is there laboratory evidence for an association between exposure to power-frequency fields and the risk of cancer? The fourth Hill criterion is whether there is *laboratory evidence* suggesting that there is a risk associated with such exposure? Epidemiological associations are greatly strengthened when there is laboratory evidence for a risk. When the US Surgeon General first stated that smoking caused lung cancer, the laboratory evidence was ambiguous. It was known that cigarette smoke and tobacco contained carcinogens, but no one had been able to make lab animals get cancer by smoking (mostly because it is hard to convince animals to smoke). Currently the laboratory evidence linking cancer and smoking is much stronger. Power-frequency fields show little evidence of the type effects on cells, tissues or animals that point towards their being a cause of cancer, or to their contributing to cancer (Question 16). Subject: 20E) Criterion Five: Are there plausible biological mechanisms that suggest an association between exposure to power-frequency fields and the risk of cancer? The fifth Hill criterion is whether there are *plausible biological mechanisms* that suggest that there should be a risk? When it is understood how something causes disease, it is much easier to interpret ambiguous epidemiology. For smoking, while the direct laboratory evidence connecting smoking and cancer was weak at the time of the Surgeon Generals report, the association was highly plausible because there were known cancer-causing agents in tobacco smoke. From what is known of power-frequency fields and their effects on biological systems there is no reason to even suspect that they pose a risk to people at the exposure levels associated with the generation and distribution of electricity. Subject: 21) If exposure to power-frequency magnetic fields does not explain the residential and occupations studies which show increased cancer incidence, what other factors could? There are basically four factors that can result in false associations in epidemiological studies: inadequate dose assessment (Question 21A), confounders (Question 21B), inappropriate controls (Question 21C), and publication bias (Question 21D). Subject: 21A) Could problems with dose assessment affect the validity of the epidemiological studies of power lines and cancer? If power-frequency fields are associated with cancer, we do not know what aspect of the field is involved. At a minimum, risk could be related to the peak field, the average field, or the rate of change of the field. If we do not know who is really exposed, and who is not, we will usually (but not always) underestimate the true risk [C13]. Subject: 21B) Are there other cancer risk factors that could be causing a false association between exposure to power-frequency fields and cancer? Associations between things are not always evidence for causality. Power lines (or electrical occupations) might be associated with a cancer risk other than magnetic fields. If such an associated cancer risk were identified it would be called a "confounder" of the epidemiological studies of power lines and cancer. An essential part of epidemiological studies is to identify and eliminate possible confounders. Many possible confounders of the powerline studies have been suggested, including PCBs, herbicides, traffic density, and socioeconomic class. - PCBs: Many transformers contain polychlorinated biphenyls (PCBs) and it has been suggested that PCB contamination of the power-line corridors might be the cause of the excess cancer. This is unlikely. First, PCB leakage is rare. Second, PCB exposure has been linked to lymphomas, not leukemia or brain cancer. - Herbicides: It has been suggested that herbicides sprayed on the powerline corridors might be a cause of cancer. This is an unlikely explanation, since herbicide spraying would not effect distribution systems in urban areas (where 3 of 5 positive childhood cancer studies have been done). - Traffic density: Transmission lines frequently run along major roads, and the "high current configurations" associated with excess childhood leukemia in the US studies [C1,C6,C10] are associated with major roads. It has been suggested that power lines might be a surrogate for exposure to cancer-causing substances in traffic exhaust. This may be a real confounder, since traffic density has been shown to correlate with childhood leukemia incidence [E5]. Note that this would explain only the residential connection, not the occupational connection. - Socioeconomic class: Socioeconomic class may be an issue in both the residential and occupational studies, as socioeconomic class is clearly associated with cancer risk, and "exposed" and "unexposed" groups in many studies are of different socioeconomic classes [C13]. This is of particular concern in the US residential exposure studies that are based on "wirecoding", since the type of wirecodes that are correlated with childhood cancer are found predominantly in older, poorer neighborhoods, and/or in neighborhoods with a high proportion of rental housing [C18]. Subject: 21C) Could the epidemiological studies of power lines and cancer be biased by the methods used to select control groups? An inherent problem with many epidemiological studies is the difficulty of obtaining a "control" group that is identical to the "exposed" group for all characteristics related to the disease except the exposure. This is very difficult to do for diseases such as leukemia and brain cancer where the risk factors are poorly known. An additional complication is that often people must consent to be included in the control arm of a study, and participation in studies is known to depend on factors (such as socioeconomic class, race and occupation) that are linked to differences in cancer rates. See Jones et al [C18] for an example of how selection bias could effect a powerline study. Subject: 21D) Could analysis of the epidemiological studies of power lines and cancer be skewed by publication bias? It is a known that positive studies in many fields are more likely to be published than negative studies (see Dickersin et al [E3] for examples from cancer clinical trials). This can severely bias meta-analysis studies such as those discussed in Questions 13 and 15. Such publication bias will increase apparent risks. This is a bigger potential problem for the occupational studies than the residential ones. It is also a clear problem for laboratory studies -- it is much easier to publish studies that report effects than studies that report no effects (such is human nature!). Several specific examples of publication bias are known in the studies of electrical occupations and cancer (see Doll et al [B5], page 94). In their review Coleman and Beral [B2] report the results of a Canadian study that found a RR of 2.4 for leukemia in electrical workers. The British NRPB review [B5] found that further followup of the Canadian workers showed a deficiency of leukemia (a RR of 0.6), but that this followup study has never been published. This is an anecdotal report, but publication bias, by its very nature, is usually anecdotal. Subject: 22) What is the strongest evidence for a connection between power-frequency fields and cancer? The best evidence for a connection between cancer and power-frequency fields is probably: a) The four epidemiological studies that show a correlation between childhood cancer and proximity to high-current wiring [C1,C6,C10,M2], plus the meta-analysis of the Scandinavian studies [B6]. b) The epidemiological studies that show a significant correlation between work in electrical occupations and cancer, particularly leukemia and brain cancer [B1,B2,D7,D9]. c) The lab studies that show that power-frequency fields do produce bioeffects. The most interesting of the lab studies are probably the ones showing increased transcription of oncogenes at fields of 1-5 G (100-500 microT) [H4,H5,L1]. d) The one laboratory study that provides evidence that power-frequency magnetic fields can promote chemically-induced breast cancer [G22]. Subject: 23) What is the strongest evidence against a connection between power-frequency fields and cancer? The best evidence that there is not a connection between cancer and power-frequency fields is probably: a) Application of the Hill criteria (Question 20) to the entire body of epidemiological and laboratory studies. b) The fact that all studies of genotoxicity, and all but one study of promotion have been negative (Question 16). c) AdairUs [F4] biophysical analysis that indicates that "any biological effects of weak (less than 40 mG, 4 microT) ELF fields on the cellular level must be found outside of the scope of conventional physics" d) JacksonUs [E8] and OlsenUs [C15] epidemiological analysis that shows that childhood and adult leukemia rates have been stable over a period of time when per capita power consumption has risen dramatically. Subject: 24) What studies are needed to resolve the cancer-EMF issue? In the epidemiological area, more of the same types of studies are unlikely to resolve anything. Studies showing a dose-response relationship between measured fields and cancer incidence rates would clearly affect thinking, as would studies identifying confounders in the residential and occupational studies. In the laboratory area, more genotoxicity and promotion studies may not be very useful. Exceptions might be in the area of cell transformation, and promotion of chemically-induced breast cancer. Long-term rodent exposure studies (the standard test for carcinogenicity) would have a major impact if they were positive, but if they were negative it would not change very many minds. Further studies of some of the known bioeffects would be useful, but only if they identified mechanisms or if they established the conditions under which the effects occur (e.g., thresholds, dose-response relationships, frequency-dependence, optimal wave-forms). Subject: 25) Is there any evidence that power-frequency fields could cause health effects other than cancer. While this FAQ sheet, and most public concern, has centered around cancer, there has also been suggestions that there might be a connection between non-ionizing EM exposure and birth defects. This concern has focused as much on video display terminals (VDTs) as on power lines. Little epidemiological or laboratory support for a connection between non-ionizing EM exposure and birth defects has been found. [J1,J2,J4,J5,J6]. Cox et al [J3] and Chernoff et al [K5] have recently reviewed this field. Subject: 26) What are some good overview articles? There really no up-to-date reviews of power-frequency fields and human health. The reviews by Davis et al [A2], Theriault [F3] and Doll et al [B5] are good, but were published before many of the important epidemiological and laboratory studies were available. Subject: 27) Are there exposure guidelines for power-frequency fields? Yes, a number of governmental and professional organizations have developed exposure guidelines. These guidelines are based on keeping the body currents induced by power-frequency EM fields to a level below the naturally-occurring fields (Question 8). The most generally relevant are: - National Radiation Protection Board (UK) [M5]: 50 Hz electrical field: 12 kV/m 60 Hz electrical field: 10 kV/m 50 Hz magnetic field: 1.6 mT (16 G) 60 Hz magnetic field: 1.33 mT (13.3 G) - American Conference of Governmental Industrial Hygienists [M6]: At 60 Hz: 1 mT (10 G); 0.1 mT (1 G) for pacemaker wearers - International Commission on Non-Ionizing Radiation Protection [M7] Magnetic field 24 hr general public: 0.1 mT = 1 G Short-term general public: 1 mT = 10 G Occupational continuous: 0.5 mT = 5 G Occupational short-term: 5 mT = 50 G EElectrical field 24 hr general public: 5 kV/m Short-term general public: 10 kV/m Occupational continuous: 10 kV/m Occupational short-term: 30 kV/m Subject: 28) What effect do powerlines have on property values? There is very little hard data on this issue. There is anecdotal evidence and on-going litigation (Wall Street Journal, Dec 9, 1993). There have been "comparable property" studies, but any studies done prior to about 1991 (when London et al [C10] was published) would be irrelevant. One comparable value study has been published recently [L3], and another has been presented at a meeting [L4]. Neither study shows hard evidence for an impact of power lines on property values. However, both studies indicate that many owners think that there will be an impact, particularly if concerns about health effects become widespread. It appears possible that the presence of obvious transmission lines or substations will adversely affect property values if there has been recent local publicity about health concerns of property value concerns. It would appear less unlikely that the presence of "high current configuration" distribution lines of the type correlated with childhood cancer in the US studies [C1,C6,C10] would affect property values, since few people would recognize their existence. If buyers start requesting magnetic field measurements, no telling what will happen, particularly since measurements are difficult to do (Questions 29 & 30), and even more difficult to interpret (Question 14). Subject: 29) What equipment do you need to measure power-frequency magnetic fields? Power-frequency fields are measured with a calibrated gauss meter. The meters used by environmental health professionals are too expensive for "home" use. A unit suitable for home use should meet the following criteria: - A reasonable degree of accuracy and precision, plus/minus 20% seems reasonable for home use. - True RMS detection, otherwise readings might be exaggerated if the waveform is non-sinusoidal. - Tailored frequency response, because if the unit is too broadband, higher frequency fields from VDTs, TVs, etc. may confound the measurements. - Correct response to overload; if the unit is subjected to a very strong field, it should peg, not just give random readings. - The presence of a strong electrical field should not affect the magnetic field measurement. Meters meeting these requirements are quite expensive, $600 would probably be the bare minimum. These meters are not suitable for the non-technically trained. There is an understandable reluctance to recommend any unit with unknown characteristics to a person whose technical abilities are also unknown, and no peer-reviewed articles on inexpensive instruments appear to be available. The suggestions that one wind a coil and use headphones or a high impedance multimeter are misguided. A clever physicist or engineer can anticipate and correct for nonlinearities and interferences, but for the average person, even one technically trained, this is unreasonable. Subject: 30) How are power-frequency magnetic fields measured? Measurements must be done with a calibrated gauss meter (Question 29) in multiple locations over a substantial period of time, because there are large variations in fields over space and time. Fortunately, the magnetic field is far easier to measure than the electrical field. This is because the presence of conductive objects (including the measurer's body) distorts the electrical field and makes meaningful measurements difficult. Not so for the magnetic field. It is important for the person who is making the evaluation to understand the difference between an emission and exposure. This may seem obvious, but many people, including some very smart physical scientists, stick an instrument right up to the source and compare that number with an exposure standard. If the instrument is not isotropic, measurement technique must compensate for this. In the case of power distribution line and transformer fields, the magnetic fields will probably vary considerably over time, as they are proportional to the current in the system. A reasonable characterization needs to be done over time, with anticipated and actual electricity usage factored in. It may seem to be as simple as walking in and reading the meter, but it's not. ------ Subject: Annotated Bibliography A) Recent Reviews of the Biological and Health Effects of Power-Frequency Fields A1) Electromagnetic field health effects, Connecticut Academy of Science and Engineering, Hartford, CT, 1992. "Absolute proof of the occurrence of adverse effects of ELF fields at prevailing magnitudes cannot be found in the available evidence, and the same evidence does not permit a judgment that adverse effects could not occur . . .If adverse health effects from residential magnetic field exposure exist, they are not likely to make a large contribution.S A2) JG Davis et al: Health Effects of Low-Frequency Electric and Magnetic Fields. Oak Ridge Associated Universities, 1992. "This review indicates that there is no convincing evidence in the published literature to support the contention that exposure to extremely low-frequency electric and magnetic fields generated by sources such as household appliances, video display terminals, and local power lines are demonstrable health hazards.S A3) JI Aunon et al: Investigations in power-frequency EMF and its risk to health: A review of the scientific literature, Universities Consortium on Electromagnetic Fields, 1992. "the conclusions from this review highlights the absence of health effects directly related to 60 Hz alternating current EMF on humans." A4) PA Buffler et al: Health effects of exposure to powerline-frequency electric and magnetic fields, Public Utility Commission of Texas, Austin, 1992. "no conclusive evidence to suggest that EMF due to electric power transmission lines poses a human health hazard." A5) JA Dennis et al: Human Health and Exposure to Electromagnetic Radiation (NRPB-R241), National Radiological Protection Board, Chilton, 1993. "the bulk of the evidence points to there being no effects at levels to which people are normally exposed". A6) P Guenel & J Lellouch: [Synthesis of the literature on health effects from very low frequency electric and magnetic fields], National Institute of Health and Medical Research (INSERM), Paris, 1993. "laboratory studies have never shown any carcinogenic effect [but] the epidemiological results presently available do not permit exclusion of a role for magnetic fields in the incidence of leukemia, particularly in children... The effect of magnetic fields on human health remains a research problem. It will only become a public health problem if definite effects are confirmed." A7) J. Roucayrol: [Report on extremely low-frequency electromagnetic fields and health]. Bull Acad Nat Med 177:1031-1040, 1993. "There is no conclusive evidence linking EMF to reproductive and teratogenic effects, and/or that EMF has a role in the initiation, promotion or progression of certain cancers, even though some data cannot exclude this possibility. . . reported associations between EMF and certain pathologies like leukemia and other childhood and adult cancers cannot be supported by current epidemiological data." B) Reviews of the Epidemiology of Exposure to Power-Frequency Fields B1) DA Savitz & EE Calle: Leukemia and occupational exposure to EM fields: Review of epidemiological studies. J Occup Med 29:47-51, 1987. Review of occupational exposures and leukemia, showing a small but significant excess of leukemia in electrical occupations. B2) M Coleman & V Beral: A review of epidemiological studies of the health effects of living near or working with electrical generation and transmission equipment. Int J Epidem 17:1-13, 1988. Review of both occupational and residential studies, including meta-analysis showing a small but significant excess of leukemia in electrical occupations. B3) D Trichopoulos, Epidemiological studies of cancer and extremely low-frequency electric and magnetic field exposures, In: Health effects of low-frequency electric and magnetic fields, JG Davis et al, editors, Oak Ridge Assoc Univer, Oak Ridge, pp. V1-V58, 1992. Meta-analysis of occupational exposure studies indicating small but statistically significant relative risks for leukemia and brain cancer. B4) G.B. Hutchison: Cancer and exposure to electric power. Health Environ Digest 6:1-4, 1992. Meta-analysis of residential exposure studies shows a significant excess for childhood brain cancer, but not for childhood leukemia or lymphoma. Analysis also shows an excess of leukemia and brain cancer in electrical occupations, but no significant excess of lymphoma or overall cancer. B5) R Doll et al, Electromagnetic Fields and the Risk of Cancer, NRPB, Chilton, 1992. Includes a meta-analysis of the childhood cancer data. For leukemia, the analysis shows a significant elevation when wirecodes are used to assess exposure, but not when distances or measured fields are used. For brain cancer, the analysis shows a significant elevation when wirecodes or distance are used to assess exposure, but not when measured fields are used. For all childhood cancer the analysis shows a significant elevation when wirecodes or measurements are used to assess exposure, but not when distance is used. B6) A Ahlbom et al: Electromagnetic fields and childhood cancer. Lancet 343:1295-1296, 1993. Pooled analysis of the Scandinavian childhood cancer studies indicates that if calculated historic power-line fields are used as a measure of exposure, a small but statistically significant increase is seen in the incidence of leukemia, but no statistically significant increase is seen in the incidence of CNS cancer, lymphoma, or overall cancer. C) Epidemiology of Residential Exposure to Power-Frequency Fields C1) N Wertheimer & E Leeper: Electrical wiring configurations and childhood cancer. Am J Epidem 109:273-284, 1979. Case-control study of childhood leukemia and brain cancer using type of powerlines (wirecodes) as an index of exposure. A significant excess of leukemia and brain cancer were reported. C2) N Wertheimer & E Leeper: Adult cancer related to electrical wires near the home. Int J Epidem 11:345-355, 1982. Case-control study of adult cancer. Significant excess reported for total cancer and brain cancer, but not for leukemia. C3) JP Fulton et al: Electrical wiring configurations and childhood leukemia in Rhode Island. Am J Epidem 111:292-296, 1980. Case-control study using wire-dose as an index of exposure. No excess of child leukemia found. C4) ME McDowall: Mortality of persons resident in the vicinity of electrical transmission facilities. Br J Cancer 53:271-279, 1986. Standard mortality ratio study using proximity to lines as a measure of exposure. No excess seen for total cancer or for leukemia in adults. C5) L Tomenius: 50-Hz electromagnetic environment and the incidence of childhood tumors in Stockholm County. BEM 7:191-207, 1986. Case-control study of childhood cancer using proximity to electrical equipment as indices of exposure. Proximity to 200 kV lines was associated with significant excess of total cancer, but proximity to other types of electrical equipment carried no significant excess risk. No significant excess of leukemia or brain cancer for any index of exposure. C6) DA Savitz et al: Case-control study of childhood cancer and exposure to 60-Hz magnetic fields. Am J Epidem 128:21-38, 1988. Case-control study of childhood leukemia and brain cancer in Denver, using measurements and wirecodes as indices of exposure. Possibly significant excess of leukemia for high-current-configuration wirecodes, but no excess incidence for measured fields. Significant excess of brain cancer for high-current-configuration wirecodes, but no excess incidence for measured fields. C7) RK Severson et al: Acute nonlymphocytic leukemia and residential exposure to power-frequency magnetic fields. Am J Epidem 128:10-20, 1988. Case-control study of childhood leukemia in Washington state, using measurements and wirecodes as indices of exposure. No excess leukemia for wirecode or measured fields. C8) MP Coleman et al: Leukemia and residence near electricity transmission equipment: a case-control study. Br J Cancer 60:793-798, 1989. Case-control study of childhood and adult leukemia, using proximity to powerlines and transformers as an exposure index. No significant excess of leukemia was found. C9) A Myers et al: Childhood cancer and overhead powerlines: a case-control study. Br J Cancer 62:1008-1014, 1990. Case-control study of childhood and adult leukemia, using proximity to powerlines as an exposure index. No significant excess of leukemia, solid tumors or all cancer was found. C10) SJ London et al: Exposure to residential electric and magnetic fields and risk of childhood leukemia. Am J Epidem 134:923-937, 1991. Case-control study of childhood leukemia in Los Angeles, using measurements and wirecodes as indices of exposure. Significant excess of leukemia for high current configuration wirecodes, but no excess risk for measured fields. C11) JHAM Youngson et al: A case/control study of adult haematological malignancies in relation to overhead powerlines. Br J Cancer 63:977-985, 1991. Case-control study of adult leukemia and lymphoma using proximity to powerlines and estimated fields as measures of exposure. No significant excess of cancer found. C12) M Feychting & A Ahlbom: [Cancer and magnetic fields in persons living close to high voltage power lines in Sweden]. L kartidningen 89:4371-4374, 1992. Case-control study of everyone who lived within 1000 feet of high-voltage powerlines; contains material on adult exposure not in the 1993 publication. No increased leukemia or brain cancer was found for adults when exposure was based on measured fields, distance from power lines or retrospective field calculations. C13) JM Peters et al: Exposure to residential electric and magnetic fields and risk of childhood leukemia. Rad Res 133:131-132, 1993. Discussion of the implications of finding a correlation of cancer with wire-codes, but not with measured fields. Possibilities: - There is a true etiological association, but there is a methodological bias in the measurement technique - There is a true etiological association, but average and/or spot fields are not the correct exposure metric - Selection bias in the control group - A confounder C14) PJ Verkasalo et al: Risk of cancer in Finnish children living close to power lines. BMJ 307:895-899, 1993. Cohort study of cancer in children in Finland living within 500 m of high-voltage lines. Calculated retrospective fields used to define exposure. No statistically significant increase in overall cancer incidence was found. A significant increase in brain cancer in boys was due entirely to one exposed boy who developed three brain tumors. No significantly increases were found for brain tumors in girls or for leukemia, lymphomas or "other" tumors in either sex. C15) JH Olsen et al: Residence near high voltage facilities and risk of cancer in children. BMJ 307:891-895, 1993. Case-control study of childhood cancer in Denmark. Exposure was assessed on the basis of calculated fields. No overall increase in cancer was found when 2.5 mG (0.25 microT) was used define exposure. After the data were analyzed, it was found that if 4 mG (0.40 microT) was used as the cut-off point, there was a statistically significant increase in overall cancer. No statistically significant increases in leukemia, lymphoma or brain cancer were found. C16) GH Schreiber et al: Cancer mortality and residence near electricity transmission equipment: A retrospective cohort study. Int J Epidem 22:9-15, 1993. Study of people living in an urban area in the Netherlands. People were considered exposed in they lived within 100 m of transmission equipment. Fields in the exposed group were 1-11 mG (0.1-1.1 microT). An insignificant decrease in total cancer was found in the exposed group compared to the general Dutch population. No leukemia or brain cancer was seen in the exposed group. C17) M Feychting & A Ahlbom: Magnetic fields and cancer in children residing near Swedish high-voltage Power Lines. Am J Epidem 7:467-481, 1993. Case-control study of children who lived within 300 m of high-voltage powerlines. Exposure assessed by measurements, calculated retrospective assessments, and distance from lines. No overall increase in cancer was found for any measure of exposure. An increase in leukemia (but not brain or other cancers) was found in children in one-family homes for fields calculated to have been 2 mG or above at the time of cancer diagnosis, and for residence within 50 m of the power line. No increase in cancer was found when measured fields were used to estimate exposure. C18) TL Jones et al: Selection bias from differential residential mobility as an explanation for associations of wire codes with childhood cancer. J Clin Epidem 46:545-548; 1993. The type of "high current configuration" distribution lines associated with cancer in the Wertheimer [C1], Savitz [C6] and London [C10] studies were more common in residential areas that were older, poorer, and which contained more rental properties. This could lead to a false association high current configurations with disease. D) Epidemiology of Occupational Exposure to Power-Frequency Fields D1) S Milham: Mortality from leukemia in workers exposed to electrical and magnetic fields. NEJM 307:249, 1982. Proportional mortality study of electrical occupations showing a significant excess incidence of leukemia. D2) WE Wright et al: Leukaemia in workers exposed to electrical and magnetic fields. Lancet 8308 (Vol II):1160-1161, 1982. Proportional incidence study of electrical occupations showing a significant excess of acute, but not chronic leukemia. D3) S Richardson et al: Occupational risk factors for acute leukaemia: A case-control study. Int J Epidem 21:1063-1073, 1992. Case-control study of acute leukemia across occupations. An increase in leukemia was found for all electrical occupations, but the increase was not statistically significant. Significant excesses of leukemia were associated with benzene, exhaust gasses and pesticides. D4) JD Bowman et al: Electric and Magnetic Field Exposure, Chemical Exposure, and Leukemia Risk in "Electrical" Occupations, EPRI, Palo Alto, 1992. Proportional incidence study of leukemia in electrical versus other occupations. For all electrical occupations there was a small, but statistically significant association of leukemia with electrical occupations. There was no relationship between the level of exposure and leukemia. D5) T Tynes et al: Incidence of cancer in Norwegian workers potentially exposed to electromagnetic fields. Am J Epidem 136:81-88, 1992. Cohort study of electrical occupations that showed a statistically significant excess of leukemia but not of brain cancer. D6) GM Matanoski et al: Leukemia in telephone linemen. Am J Epidem 137:609-619, 1993. Case-control of telephone company workers, which showed no statistically significant increase in leukemia in workers exposed to power-frequency fields. D7) B Floderus et al: Occupational exposure to electromagnetic fields in relation to leukemia and brain tumors: A case-control study in Sweden. Cancer Causes Control 4:463-476, 1993. Case-control study of leukemia and brain tumors of men in all occupations. Exposure calculations were based on the job held longest during the 10-year period prior to diagnosis. A statistically significant increase was found for leukemia, but not for brain cancer. D8) JD Sahl et al: Cohort and nested case-control studies of hematopoietic cancers and brain cancer among electric utility workers. Epidemiology 4:104-114, 1993. Both a cohort and a case-control study of utility workers. No significant increase was found for total cancer, leukemia, brain cancer, or lymphomas. D9) P Guenel et al: Incidence of cancer in persons with occupational exposure to electromagnetic fields in Denmark. Br J Indust Med 50:758-764, 1993. Case-control study based on all cancer in actively employed Danes. No significant increases were seen for breast cancer, malignant lymphomas or brain tumors. Leukemia was elevated among men in the highest exposure category; women in similar exposure categories showed no increase in any type of cancer. E) Human Studies Related to Power-Frequency Exposure and Cancer E1) AB Hill: The environment and disease: Association or causation? Proc Royal Soc Med 58:295-300, 1965. Concise statement of the methods use to assess causation in epidemiological studies. E2) M Bauchinger et al: Analysis of structural chromosome changes and SCE after occupational long-term exposure to electric and magnetic fields from 380 kV-systems. Rad Env Biophys 19:235-238, 1981. Lymphocytes from occupationally exposed 50 Hz switchyard workers showed no increase in the frequencies of chromosome aberrations. E3) K Dickersin et al: Publication bias and randomized controlled trials. Cont Clin Trials 8:343-353; 1987. A general discussion, with examples, of publication bias E4) I Nordenson et al: Chromosomal effects in lymphocytes of 400 kV-substation workers. Rad Env Biophys 27:39-47, 1988. Lymphocytes from occupationally exposed 50 Hz switchyard workers showed an increase in the frequency of chromosome aberrations. E5) DA Savitz & L Feingold: Association of childhood leukemia with residential traffic density. Scan J Work Environ Health 15:360-363, 1989. Analysis of the authors powerline study [C6] using traffic density as the exposure. Significant excess risk of leukemia and total cancer associated with high traffic density. E6) I Penn: Why do immunosuppressed patients develop cancer? Crit Rev Oncogen 1:27-52, 1989. Review of the relationship between cancer development and immune suppression E7) GR Krueger: Abnormal variation of the immune system as related to cancer. Cancer Growth Prog 4:139-161, 1989. Review of the relationship between cancer development and immune suppression E8) J.D. Jackson: Are the stray 60-Hz electromagnetic fields associated with the distribution and use of electric power a significant cause of cancer? Proc Nat Acad Sci USA 89:3508-3510, 1992. Argument that lack of correlation between electric power use and leukemia rates over time argues against a causal relationship. F) Biophysics and Dosimetry of Power-Frequency Fields F1) WT Kaune et al: Residential magnetic and electric fields. BEM 8:315-335, 1987. 24-hour average measurements correlate poorly with wirecodes. The correlation of 0.41, implies that codes account for only 20% of the variability in average fields. F2) J Sandweiss: On the cyclotron resonance model of ion transport. BEM 11:203-205, 1990. Cyclotron resonance theory inconsistent with basic physical principles because radius of ion rotation would be about 50 m, and because collisions would occur much too often for resonance to be achieved. F3) G Theriault: Cancer risks due to exposure to electromagnetic fields. Rec. Results Cancer Res. 120:166-180; 1990. Good, but dated review. Has good residential and occupational dosimetry data. F4) RK Adair: Constraints on biological effects of weak extremely-low-frequency electromagnetic fields, Phys Rev A 43:1039-1048, 1991. RBecause of the high electrical conductivity of tissues, the coupling of external electric fields in air to tissues of the body is such that the effects of the internal fields on cells is smaller than thermal noiseS. To get an effect you need a resonance mechanism, and "such resonances are shown to be incompatible with cell characteristics. . . hence, any biological effects of weak ELF fields [less than 500 mG, 50 microT] on the cellular level must be found outside of the scope of conventional physics". Also notes that the current induced by walking in the EarthUs static field are greater than those induced by a 4 microT (40 mG) 60-Hz field, and that any resonance found at 60 Hz would not work at 50 Hz. F5) T Dovan et al: Repeatability of measurements of residential magnetic fields and wire codes. BEM 14:145-159, 1993. Remeasure of homes that had been included in Savitz study [C6] found that neither measured fields nor wire codes had not changed significantly over a five-year period. G) Laboratory Studies of Power-Frequency Fields and Cancer G1) MM Cohen et al: Effect of low-level, 60-Hz electromagnetic fields on human lymphoid cells: I. Mitotic rate and chromosome breakage in human peripheral lymphocytes. BEM 7:415-423, 1986. 1 and 2 G (0.1 and 0.2 mT) fields had no effect on chromosome abnormalities or mitotic index of human lymphocytes. Also no effect for E-field or combined E- and H-fields. G2) MM Cohen et al: The effect of low-level 60-Hz electromagnetic fields on human lymphoid cells. II: Sister-chromatid exchanges in peripheral lymphocytes and lymphoblastoid cell lines. Mut Res 172:177-184, 1986. 1 and 2 G (0.1 and 0.2 mT) fields had no effect on rates of SCEs in human lymphocytes. Also no effect for E-field or combined E- and H-fields. G3) J Juutilainen & A Liimatainen: Mutation frequency in Salmonella exposed to weak 100-Hz magnetic fields. Hereditas 104:145-147, 1986. 0.125 microT (1.25 mG) to 0.125 mT (1.25 G) 100 Hz fields were not mutagenic in the Ames test, and did not increase the mutagenicity of known mutagens in the Ames test. G4) JA Reese et al: Exposure of mammalian cells to 60-Hz magnetic or electric fields: Analysis for DNA single-strand breaks. BEM 9:237-247, 1988. 0.1 and 0.2 mT (1 and 2 G) 60 Hz field had no effect on single-strand breaks. Also no effect with E-field or combined E- and H-fields. G5) RAE Thomson et al: Influence of 60-Hertz magnetic fields on leukemia. BEM 9:149-158, 1988. 1.4, 200, 500 microT (14 mG, 3G, 5G) 60 Hz fields had no effect on leukemia progression in mice. G6) M Rosenthal & G Obe: Effects of 50-Hertz EM fields on proliferation and on chromosomal aberrations in human peripheral lymphocytes untreated and pretreated with chemical mutagens. Mutat Res 210:329-335, 1989. 5 mT (50 G) 50 Hz field had no effects on chromosome or chromatid breaks or exchanges, and no effects on SCE rate. Some increase in SCE rates were seen for cells pretreated with other mutagens. Enhanced progression though the cell cycle was seen. G7) A Cossarizza et al: DNA repair after gamma-irradiation in lymphocytes exposed to low-frequency pulsed electromagnetic fields. Radiat Res 118:161-168, 1989. 2.5 mT (25 G) pulsed field (50 Hz) had no effect on repair of radiation-induced DNA damage in human lymphocytes. G8) ME Frazier et al: Exposure of mammalian cells to 60-Hz magnetic or electric fields: analysis of DNA repair of induced, single-strand breaks. BEM 11:229-234, 1990. 1 mT (10 G) 60 Hz fields had no effect on repair of radiation-induced DNA damage in human lymphocytes. Also no effect for E-field or combined E- and H-fields. G9) MR Scarfi et al: Spontaneous and mitomycin-C-induced micronuclei in human lymphocytes exposed to extremely low frequency pulsed magnetic fields. Biochem Biophys Res Commun 176:194-200, 1991. 2.5 mT (25 G) pulsed 50-Hz field showed no genotoxicity alone, and did not enhance drug-induced genotoxicity in human lymphocytes. G10) JRN McLean et al: Cancer promotion in a mouse-skin model by a 60-Hz magnetic field: II. Tumor development and immune response. BEM 12:273-287, 1991. 20 mT (200 G) 60-Hz fields did not promote or co-promote (with TPA) cancers in DMBA-induced skin tumor model. Also no effect on progression of skin tumors, and no effect on NK cells or spleen size. G11) GK Livingston et al: Reproductive integrity of mammalian cells exposed to power-frequency EM fields. Environ Molec Mutat 17:49-58, 1991. 0.22 mT (2.2 G) 60 Hz fields had no effect on SCEs, growth rates, cell cycle kinetics, or micronucleus formation rates in human lymphocytes or CHO cells. No effects were seen for E-fields. G12) AM Khalil & W Qassem: Cytogenetic effects of pulsing electromagnetic field on human lymphocytes in vitro: chromosome aberrations, sister-chromatid exchanges and cell kinetics. Mut Res 247:141-146, 1991. 1.05 mT (10.5 Gauss) fields pulsed at 50 Hz caused chromosome abnormalities, and a decrease in the mitotic index in human lymphocytes. G13) A Bellossi: Effect of pulsed magnetic fields on leukemia-prone AKR mice. No effect on mortality through five generations. Leuk Res 15:899-902, 1991. 6 mT (60 G) exposure of leukemia-prone mice to 12 and 460 Hz pulsed fields over five generations of exposure resulted in no effect on leukemia rates. G14) MA Stuchly et al: Modification of tumor promotion in the mouse skin by exposure to an alternating magnetic field. Cancer Letters 65:1-7, 1992. A 20 G (2 mT) 60-Hz field did not increase the number of chemically-induced skin tumors in mice, although the tumor appeared earlier. G15) DD Ager & J A Radul: Effect of 60-Hz magnetic fields on ultraviolet light-induced mutation and mitotic recombination in Saccharomyces cerevisiae. Mut Res 283:279-286, 1992. 10 G (1 mT) 60-Hz fields do not cause mutations or chromosome damage in yeast, and do not affect UV-induced DNA damage. G16) M Fiorani et al: Electric and/or magnetic field effects on DNA structure and function in cultured human cells. Mut Res 282:25-29, 1992. 2-2,000 mG (0.2-200 microT ) 50-Hz fields did not cause DNA damage in human cells, and did not affect the growth of human cells in culture. Also showed no effect for E-fields. G17) J. Nafziger et al: DNA mutations and 50 Hz EM fields. Bioelec Bioenerg 30:133-141, 1993. 10 and 100 mG (1 and 10 microT) 50-Hz fields did not cause mutations in bacteria or mammalian cells, and did not increase the amount of DNA damage in virus-transformed cells. G18) Y Otaka et al: Sex-linked recessive lethal test of Drosophila melanogaster after exposure to 50-Hz magnetic fields. BEM 13:67-74, 1992. 5 and 50 G 50-Hz fields do not cause mutations in fruit flies. G19) A. Rannug et al: A study on skin tumor formation in mice with 50 Hz magnetic field exposure. Carcinogenesis 14:573-578, 1993. 0.5 and 5 G 50-Hz fields do not increase the incidence of skin tumors or leukemia in mice, and did not increase the frequency of DMBA-induced skin tumors. G20) R. Zwingelberg et al: Exposure of rats of a 50-Hz, 30-mT magnetic field influences neither the frequencies of sister-chromatid exchanges nor proliferation characteristics of cultured peripheral lymphocytes. Mutat Res 302:39-44, 1993. 300 G 50-Hz field did not cause chromosome damage in human cells, and did not affect the growth of human lymphocytes in culture. G21) A Rannug et al: Rat liver foci study on coexposure with 50 Hz magnetic fields and known carcinogens. BEM 14:17-27, 1993. 5 mG (0.5 microT) and 5 G (500 microT) 50-Hz fields did not increase the frequency of chemically-induced liver tumors. G22) W Loscher et al: Tumor promotion in a breast cancer model by exposure to a weak alternating magnetic field. Cancer Letters 71:75-81, 1993. 1 G 50-Hz field increased the frequency of chemically-induced mammary tumors. G23) M Mevissen et al: Effects of magnetic fields on mammary tumor development induced by 7,12-dimethylbenz(a)anthracene in rats. BEM 14:131-143, 1993. 300 G (30 mT) 50-Hz fields did not increase the frequency of DMBA-induced mammary tumors. G24) A Rannug et al: A rat liver foci promotion study with 50-Hz magnetic fields. Environ Res 62:223-229, 1993. 5, 50, 500 and 5,000 mG (0.5, 5, 50 and 500 microT) 50-Hz fields did not increase the frequency of chemically-induced liver tumors. H) Laboratory Studies Indirectly Related to Power-Frequency Fields and Cancer H1) AR Liboff et al: Time-varying magnetic fields: Effects on DNA synthesis. Science 223:818-820, 1984. 15-4000 Hz, 0.0016-0.4 mT (16 mG-4 G) fields increased tritiated thymidine uptake in human embryonic fibroblasts. Effect appears to be independent of frequency and field strength. H2) WC Parkinson & CT Hanks: Experiments on the interaction of electromagnetic fields with mammalian systems. Biol Bull 176(S):170-178, 1989. 3 mT (30 G) 60-Hz field had no effects of mammalian cell growth. No effects on Ca transport under cyclotron resonance conditions, or under any conditions tested. H3) S Baumann et al: Lack of effects from 2000-Hz magnetic fields on mammary adenocarcinoma and reproductive hormones in rats. BEM 10:329-333, 1989. 0.1, 1, 2 mT (1,10, 20 G) 2000 Hz field had no effect on the growth of transplanted mammary tumors. H4) R Goodman & A Shirley-Henderson: Transcription and translation in cells exposed to extremely low frequency EM fields. Bioelec Bioenerg 25:335-355, 1991. Pulsed and sinusoidal fields of different types and intensities caused alterations in transcription of genes in human leukemia and dipteran salivary gland cells. Effect showed frequency, intensity and duration windows. H5) JL Phillips et al: Magnetic field-induced changes in specific gene transcriptions. Biochim Biophys Acta 1132:140-144, 1992. 60-Hz field of 1 G (100 microT) and above produced changes in gene transcription. H6) RJ Reiter & BA Richardson: Magnetic field effects on pineal indoleamine metabolism and possible biological consequences. FASEB J 6:2283-2287, 1992. Review of the hypothesis linking emf effects with effects on melatonin production. Notes that pulsed fields are the most effective. No mention of power-frequency fields. H7) RP Liburdy et al: ELF magnetic fields, breast cancer, and melatonin: 60-Hz fields block melatonin's oncostatic action on ER+ breast cancer cell proliferation. J Pineal Res 14:89-97, 1993. 2 and 10 mG (0.2 and 1 microT) 60-Hz fields did not affect the growth of human breast cancer cells in culture. Melatonin caused inhibition of growth that was blocked by a 12 mG field. H8) S Paradisi et al: A 50-Hz magnetic field induces structural and biophysical changes in membranes. BEM 14:247-255, 1993. A 35 G (3.5 mT) 50-Hz field did not affect the growth of mammalian cells in culture. H9) M Kato et al: Effects of exposure to a circularly polarized 50-Hz magnetic field on plasma and pineal melatonin levels in rats. BEM 14:97-106, 1993. 50-Hz fields at 10, 50, 500, 2500 mG (1, 5, 50, 250 microT) caused a small decrease in melatonin that is unrelated to field strength. H10) JM Lee et al: Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields. Biol Reproduc 49:857-864, 1993. Exposure to a 500 kV transmission line field (40 mG, 4 microT, 6 kV/m) had no effect on melatonin levels. J) Laboratory Studies of Power-Frequency Fields and Reproductive Toxicity J1) LJ Dlugosz et al: Congenital defects and electric bed heating in New York State: A register-based case-control study. Am J Epidem 135:1000-1011, 1992. A case-control study that found no statistically significant relationship between the use of electric bed heating and any type of congenital defects. J2) M Lindbohm et al: Magnetic fields of video display terminals and spontaneous abortion. Am J Epidem 136:1041-1051, 1992. Case-control study of spontaneous abortions in clerical workers who use VDTs. The use of VDTs alone had no effect, but when high-field VDTs were compared to low-field VDTs there was a statistically significant increase in spontaneous abortions. J3) CF Cox et al: A test for teratological effects of power-frequency magnetic fields on chick embryos. IEEE Tran Micro Theory Tech 40:605-610, 1993. 50-Hz 100-mG fields had no effects on the incidence of developmental abnormalities in chick embryos. The paper also analyzes the other published studies and concludes that there was, at best, a very weak statistical basis to hypothesize that magnetic fields cause malformations in chick embryos. J4) H Huuskonen et al: Effects of low-frequency magnetic fields on fetal development in rats. BEM 14:205-213, 1993. 360 mG (36 microT) 50-Hz field has no significant effect on fetal development in rats. J5) J Juutilainen et al: Early pregnancy loss and exposure to 50-Hz magnetic fields. BEM 14:229-236, 1993. Case-control study of early pregnancy loss and residential exposure to 50 Hz fields (fields measured at the front door) found an increase in the rate of early pregnancy loss in exposed cases. J6) E Robert: Birth defects and high voltage power lines - An exploratory study based on registry data. Repro Tox 7:283-287, 1993. Case-control study of the association between maternal residential proximity to powerline magnetic fields and congenital anomalies found no excess malformations, and a lower rate of skeletal and cardiac malformations in the exposed group. K) Reviews of Laboratory Studies of Power-Frequency Fields K1) TS Tenforde: Biological interactions and potential health effects of extremely-low-frequency magnetic fields from power lines and other common sources. Ann Rev Publ Health 13:173-196, 1992. Review of ELF magnetic field effects from a biologist's perspective K2) J Walleczek: Electromagnetic field effects on cells of the immune system: the role of calcium signaling. FASEB J 6:3177-3185, 1992. Review of ELF effects on immune system and the possible role of calcium. Suggests that threshold for proliferation effects for 50/60 Hz fields is between 0.2 mT (2 G) and 5 mT (5 G). K3) J McCann et al: A critical review of the genotoxic potential of electric and magnetic fields. Mut Res 297:61-95, 1993. "The preponderance of evidence suggests that neither ELF nor static electric and magnetic fields have a clearly demonstrated potential to cause genotoxic effects. However, there may be genotoxic activity from exposure under conditions where phenomena auxiliary to an electric field, such as spark discharges, electrical shocks or corona can occur." K4) JC Murphy et al: Power-frequency electric and magnetic fields: A review of genetic toxicology. Mut Res 296:221-240, 1993. "Considering the total body of available information, there is little evidence that exposure to [power-frequency electric or magnetic fields] directly causes genetic changes in biological systems." K5) N Chernoff et al: A review of the literature on potential reproductive and developmental toxicity of electric and magnetic fields. Toxicol 74:91-126, 1992. "From our review we conclude that laboratory experimental and epidemiological results to date have not yielded conclusive data to support the contention that such fields induce adverse reproductive effects under the test or environmental conditions studied." L) Miscellaneous Studies L1) RB Goldberg & WA Creasey: A review of cancer induction by extremely low frequency EM fields. Is there a plausible mechanism? Medical Hypoth 35:265-274, 1991. Review of evidence for and EMF-cancer connection, including the suggestion that the fields might be promoters. L2) RG Stevens et al: Electric power, pineal function, and the risk of breast cancer. FASEB J 6:853-860, 1992. Presentation of the EMF-melatonin-breast cancer hypothesis. L3) H Kung & CF Seagle: Impact of power transmission lines on property values: A case study. Appraisal J 60:413-418, 1992. Survey of homeowners who lived along transmission lines. None "had any knowledge of possible evidence connecting power transmission lines to health risks"; but 87% said that if they had known of potential health risks, it would have adversely affected then price they were willing to pay. The values of comparable houses adjacent to, and not adjacent to, the powerlines were found to be similar. L4) DE Martin: A highlight summary of the impact of electrical transmission lines on improved real estate values. EEI EMF Taskforce Meeting, Seattle, April, 1993. A utility study in Kansas City found no sale price or rental fee evidence for impacts of transmission lines on commercial property, apartment complexes, or single-family developments. However, a substantial fraction of the residential owners thought that future prices would be impacted. M) Regulations and Standards for Ionizing and Non-ionizing EM Sources. M1) [Safety of electromagnetic fields: Limits of field strengths for the protection of persons in the frequency range from 0 to 30 kHz], Technical Help to Exporters, British Standards Institution, Milton Keynes, 1989. Standard of Verband Deutscher Elektrotechniker (not a national standard). For 50/60 Hz electrical field: 2 V/m. For 50/60 Hz magnetic field: 5 mT (50 G). Based on prevention of acute health effects. States that "long term and delayed effects are considered unlikely to occur because many people have been exposed . . . over a long period of time without negative effects having come to light" M2) RC Petersen: Radiofrequency/microwave protection guides. Health Phys 61:59-67, 1991. A summary of RF/MW protection guidelines. M3) International Commission on Radiation Protection: Recommendations. Report 60, New York, Pergamon Press, 1991. Current recommendations for occupational and public protection standards for ionizing radiation M4) AS Duchene et al: IRPA guidelines on protection against non-ionizing radiation. Pergamon Press, New York, 1991. Current recommendations for occupational and public protection standards for non-ionizing electromagnetic sources. M5) Restriction on human exposures to static and time varying EM fields and radiation. Documents of the NRPB 4(5): 1-69, 1993. Exposure limits for power-frequency fields, as well as static fields and MW/RF frequencies; the standards apply to both residential and occupational exposure. For 60-Hz the limits recommended are 10 kV/m for the E-field and 13.3 G for the H-field. M6) Sub-radiofrequency (30 kHz and below) magnetic fields, In: Documentation of the threshold limit values, ACGIH, pp. 55-64, 1992. For 60-Hz fields the standard is 1 G (100 microT) for pacemaker users and 10 G (1 mT) for everyone else, this standard is applied only to occupational settings. Similar documentation is available for other frequencies. M7) HP Jammet et al: Interim guidelines on limits of exposure to 50/60 Hz electric and magnetic fields. Health Physics 58:113-122, 1990 [this is the 1990 ICNIRP interim guidelines that were approved in 1993]. For the general public the 50/60 Hz exposure standard is 1 G (100 microT) for continuous exposure and 10 G (1 mT) for short-term exposure. For occupational exposure the standard in 5 G (500 microT) for continuous exposure and 50 G (5 mT) for short-term exposure. In 1993, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) confirmed these guidelines (ICNIPR Press Release dated 12 May 1993). ------ Acknowledgments: This FAQ sheet owes much to the many readers of sci.med.physics who have sent me comments and suggestions, including: kfoster@eniac.seas.upenn.edu (mechanisms of non-ionizing EM bioeffects and "do powerlines radiate"); gary%ke4zv.uucp@mathcs.emory.edu (adding a quantum approach); aa2h@virginia.edu (suggestions on thermal effects and confounders); p.farrell@trl.oz.au (SI units, suggesting the pro/con arguments section); drchambe@tekig5.pen.tek.com (a start on the property value question); gemyers@anl.gov (how to measure fields) Notice: This FAQ is Copyright (C) by John Moulder, and is made available as a service to the Internet community. Permission is granted to copy and redistribute this document electronically as long as it is unmodified. Notification of such redistribution would be appreciated. This FAQ may not be sold in any medium, including electronic, CD-ROM, or database, or published in print, without the explicit, written permission of John Moulder. John Moulder (jmoulder@its.mcw.edu) Voice: 414-266-4670 Radiation Biology Group FAX: 414-257-2466 Medical College of Wisconsin, Milwaukee End: powerlines-cancer-FAQ/part4

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