Path: bloom-beacon.mit.edu!gatech!howland.reston.ans.net!news.moneng.mei.com!uwm.edu!post.its.mcw.edu!admin-one.radbio.mcw.edu!user From: jmoulder@its.mcw.edu (John Moulder) Newsgroups: sci.med.physics,sci.answers,news.answers Subject: Powerlines and Cancer FAQs (3 of 4) Supersedes: Followup-To: sci.med.physics Date: 27 Mar 1994 19:57:21 GMT Organization: Medical College of Wisconsin Lines: 516 Approved: new-answers-request@MIT.edu Distribution: world Expires: 30 April 1994 00:00:00 GMT Message-ID: References: Reply-To: jmoulder@its.mcw.edu (John Moulder) NNTP-Posting-Host: admin-one.radbio.mcw.edu Summary: Q&As on the connection between powerlines, electrical occupations and cancer (continued) Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing radiation, FAQ Xref: bloom-beacon.mit.edu sci.med.physics:1308 sci.answers:1018 news.answers:16897 Archive-name: powerlines-cancer-FAQ/part3 Last-modified: 1994/3/27 Version: 2.4 FAQs on Power-Frequency Fields and Cancer (part 3 of 4) 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. 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 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). 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. 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. ------ 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.Ó 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.Ó 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]. LŠkartidningen 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. ÒBecause 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 noiseÓ. 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 EarthÕs 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. End: powerlines-cancer-FAQ/part3