February 7, 1990
The purpose of this bulletin is to present a review of health effects data associated with extremely low frequency (ELF) electromagnetic (em) radiation exposure as found in current publications. Findings addressed in this bulletin do not reflect any Occupational Safety and Health Administration (OSHA) position on em hazards.
Recently, public and employee concerns have been expressed about ELF exposure as a result of media coverage over the last few years. An example of such coverage is the detailed evaluation of em publications published by Savitz in 1987. Savitz's analysis deals with potential adverse effects of ELF fields, but it is probably equally applicable to the entire em field-cancer case study literature1. The issue of ELF bioeffects is very controversial with few safety and health organizations having adopted exposure limits. ELF radiation, a part of the em spectrum, discussed in this bulletin is confined to the nonionizing frequency range up to 300 gigahertz (GHz). Of particular interest is the 50 to 60 Hz range which is associated with electrical power distribution, and equipment utilizing alternating current.
ELF radiation is comprised of both electric and magnetic fields and occur naturally in the environment2. The generation of em radiation is often unintentional as in the case of motors and fluorescent light or deliberate for a specific application such as television equipment. Irradiation of biological systems with em energy under certain conditions leads to temperature elevations when the rate of energy absorption exceeds the rate of energy dissipation3. Biological changes that occur during ELF exposure (which is not readily absorbed, and therefore does not normally cause significant temperature elevation) have not been well documented.
The human body contains free electric charges (largely in ion-rich fluids such as blood and lymph) that move in response to forces exerted by charges on and current flowing in nearby conductors, such as power lines and the wiring of appliances (see figures 1 and 2). The processes that produce these body currents are called electric and magnetic induction. In electric induction, charges on a power line or appliances attract or repel free charges within the body. Since body fluids are good conductors of electricity, charges in the body move to its surface under the influence of this electric force. The nature of magnetic fields are greater near the periphery of the body and smaller at the center of the body. Because magnetic fields have only recently become a human health concern, data on the detailed distribution of magnetically induced currents in human and animals are quite sparse compared to the information available on electric induction.
Human exposure to em radiation from natural sources is often considered small by comparison to that of industrial sources. Recently some research has shown a potential risk of cancer due to exposure to em radiation. For example in one of many conflicting research efforts, higher incidents of cancer were observed among children who lived in the vicinity of high voltage electric power lines. These lines surrounded by fields of extremely low frequency electromagnetic energy were statistically linked to clusters of cancer among children. Research also indicates that em radiation can have varying effects on the human body dependent upon wavelength, intensity, and length of exposure.
As a result of our review of existing publications on em radiation, we have concluded that most research on occupational exposure to em radiation has been conducted using small laboratory animals. Controlled research studies on human exposure was also conducted. Most of the studies on human exposure to em radiation suffer from limitations: (1) Exposure for therapeutic purposes, namely partial body irradiation at high-intensities for relatively short periods of time is not representative of occupational exposure conditions. (2) Differences in methodologies used in different states make a comparison difficult if not impossible. (3) Errors in estimating field strength to which personnel were exposed due to the lack of adequate instrumentation. Nevertheless these studies show that the chief organs formerly thought to be at risk from exposure to em radiation, the skin, eyes, and ears, may not be the only ones effected. The roll em radiation plays in causing cancer is not yet defined.
For your information, an article by Slesin indicated that a 1988, epidemiological study by Dr. Marjorie Speers and others, showed the potential risk of brain tumors among workers exposed to electromagnetic fields5. This work seems to support earlier studies conducted by Dr. Samuel Milham, Jr. (Washington State Department of Social and Health Services in Olympia) and Dr. Ruey Lin (National Taiwan University in Taipei)6 Another example is a June, 1988, Seattle, Washington, court case in which an electronic technician diagnosed with leukemia filed a suit against his employer claiming that his condition was a result of exposure to electromagnetic radiation7. A third example is presented in a research conducted by Doctors Harry Brown and Swaraj Chattopadhyay (Rutgers University) concluding that exposure to nonionizing radiation can play a role in cancer.
On the other hand, in 1987, the Hazard Evaluation and Technical Assistance Branch of the National Institute for Occupation Safety and Health (NIOSH) conducted a field investigation into possible health hazards at an acceleration laboratory9. NIOSH's report addressed both radio frequency (rf) and static magnetic fields. The report at its conclusion indicates that evidence that rf radiation alone can produce cancer was weak but it might act as a cancer promoter in animals.
As you can see, there is no consensus on the potential hazard of exposure to em radiation. Additional human exposure research should help in understanding the transmission, and interaction mechanism of em radiation with the exposed worker as well as, how to detect and quantify this field, and how to protect workers from em radiation effects. Most experts agree that more research on human exposures to this type of radiation is needed.
In conclusion, it is clear that further epidemiological studies and research into biological effects of em radiation and magnetic field (including chemical reaction in the body) is needed to fully understand and determine all health effects resulting from exposure cases. Cases involving exposure to em radiation should be considered on a case by case basis taking into consideration the circumstances surrounding it. It is premature to enforce specific guidelines for exposure to ELF radiation. However, a program which addresses ELF hazards identification and training is encouraged.
For your information, we are attaching a bibliography of the health effect publications on em radiation published since 1980. Please distribute this bulletin to area offices, state plan states and consultation projects.
Figure 1: A schematic representation of the pattern of currents induced in the body of a person standing under a transmission line by the alternating magnetic field set up by the current flowing in that line. A 60 Hz magnetic field with a flux density of one gauss will induce currents in the periphery of the body with a current density of about 100 nanoAmps per square centimeter. The current density at the center of the body is zero. (From: Biological Effects of Power Frequency Electric and Magnetic Fields. U.S. Congress Report No. OTA-BP-E-53)
Figure 2: A schematic representation of the surface charges and internal currents that are electrically induced by the charges on an overhead powerline in a person under the line whose feet are well-grounded. The total current induced to flow from each foot to ground is about 8 microamps per kV/m of applied field (1 microamp is 1 millionth of an ampere). The density of electrically-induced current is the amount of current that passes through a body cross-section perpendicular to the direction of current flow. The current density induced by a 1 kV/m vertical electric field is about 30 nanoamps per square centimeter averaged over the entire volume of the body. One nanoamp is 1 billionth of an ampere. (From: Biological Effects of Power Frequency Electric and Magnetic Fields. U.S. Congress Report No. OTA-BP-E-53)
AU - Author TI - Title SI - Source NIOSH Computerized Index Number SO - Source
AU - Servanties B TI - Damase criteria for determining microwave exposure. SI - TOXBIB/89/213413 SO - Health Phys; vol 56, iss 5, 1989, p781-786 (ref: 15)
AU - Kolmodin-Hedman B AU - Hansson Mild K AU - Hasbers M AU - Jonsson E AU - Andersson M-C AU - Eriksson A TI - Health Problems Among Operators of Plastic Welding Machines and Exposure to Radio frequency Electromagnetic Fields SI - NIOSH/00181953 SO - International Archives of Occupational and Environmental Health, Vol. 60,No.4, pages 243-247, 16 references, 1988
AU - Knave B AU - Floderus B TI - Exposure to Low-Frequency Electromagnetic Fields A Health Hazard SI - NIOSH/00181593 SO - Scandinavian Journal of Work, Environment and Health, Vol. 14, Supplement 1, pages 46-48, 11 references, 1988
AU - Aldrich TE AU - Easterly CE TI - Electromagnetic Fields and Public Health SI - NIOSH/00179613 - SO - Environmental Health Perspectives, Vol. 75, pages 159-171, 13 references, 1987
AU - Anonymous TI - Guidelines on Limits of Exposure to Radiofrequency Electromagnetic Fields in the Frequency Range from 100 KHz to 300 GHz SI - NIOSH /00179608 SO - Health Physics, Vol. 54, No. 1, Pages 115-123, 34 references, 1988
AU - Bowman JD AU - Garabrant DH AU - Sobel E AU - Peters JM TI - Exposures to Extremely Low Frequency (ELF) Electromagnetic Fields in Occupations with Elevated Leukemia Rates SI - NIOSH/00180633 SO - Applied Industrial HYgiene, Vol. 3, No. 6, pages 189-194, 38 references, 1988
AU - Castillo M AU - Quencer PM TI - Sublethal Exposure to Microwave Radar SI - NIOSH/00177338 SO - Journal of the American Medical Association, Vol. 259, No. 3, pages 355, 3 references, 1988
AU - Smith JM AU - Conover CL AU - Cox C AU - Murray WE AU - Grajewski B TI - Limitations of Field Strength Parameters For Measurement of Radiofrequency Radiation exposure SI - BIOSIS/88/36757 SO - Thirty-third Annual Meeting Of the Health Physics Society, Boston, Massachusetts, USA, July 4-8, 1988. Health Phys; 54 (Suppl. 1). 1988
AU - International Labour Organization Radiation Protection Association TI - Occupational Hazards From Non-ionizing Electromagnetic Radiation SI - The Occupational Safety and Health Administration's Technical Data Center SO - Occupational Safety and Health Series No. 53.,1985
AU - Kolmodin-Hedman B AU - Mild KH AU - Hagberg M AU - Jonsson E AU - Andersson M-c AU - Eriksson A TI - Health Problems Among Operators of Plastic Welding Machines and Exposure to Radio frequency Electromagnetic Fields.
SI - BIOSIS/88/19834 SO - INT ARCH OCCUP ENVIRON HEALTH; 60 (4). 1988. 243-248.
AU - Jammet HP AU - Bernhardt J AU - Bosnjakovic B FM AU - Czerski P AU - Grandolfo M AU - Harder D AU - Knave B AU - Marshall J AU - Rapacholi MH AU - ET AL TI - GUIDELINES ON LIMITS OF EXPOSURE TO RADIOFREQUENCY Electromagnetic FIELDS IN THE FREQUENCY RANGE FROM 100 KHZ TO 300 GHZ SI - BIOSIS/87/29258 SO - HEALTH PHYS; 54 (1), 1988. 115-124.
AU - Indira Nair AU - Granger M M AU - Florig H K TI - Biological Effects of Power Frequency Electric and Magnetic Fields.
Background Paper SI - U.S. Congress Report no. OTA-BP-E-53 SO - Office of Technology Assessment Washington, D.C 20510-8025 May, 1989
AU - PAZ JD AU - Milliken R AU - Ingram WT AU - Frank A AU - Atkin A TI - Potential Ocular Damage From Microwave Exposure During Electrosurgery: Dosimetric Survey.
SI - BIOSIS/87/29258 SO - J OCCUP med; 29 (7). 1987. 77-80
AU - Miller TM TI - Results Of Microwave Oven Radiation leakage Surveys At Fermilab SI - BIOSIS/87/O8739 SO - AM IND HYG ASSOC J;48 (1). 1987. 77-80.
AU - Wertheimer N AU - Leeper E TI - Electrical Wiring Configurations and Childhood Cancer SI - SO - AMER.J.EPIDEMIOL.1O9:273-284. 1979
AU - Wertheimer N AU - Leeper E TI - Adult Cancer Related To Electrical Wires Near The Home SI - SO - INT.J.EPIDEMI0L.11:345-355 1982
AU - Savitz D.A AU - Wachtel H AU - Barnes F A AU - John E A AU - Tvrdik J G TI - Case-control study of Childhood Cancer and Exposure to 60-Hz Magnetic Fields.
SI - SO - AMER.J.EPIDEMIOL.128:21-38. 1982
AU - MILHAM S TI - Mortality From Leukemia In Workers Exposed To Electrical and Magnetic Fields SI - SO - New England J.Med.307:249. 1982
AU - Savitz D A AU - Calle E E TI - Leukemia And Occupational Exposure To Electromagnetic Fields:
Review Of Epidemiologic Surveys. SI - SO - J. Occup. Med. 29:47-51. 1987
1Savitz, D.A. and Calle, E.E., Journal of Occupational Medicine 29 "Leukemia and Occupational Exposure to Electromagnetic Fields: Review of Epidemiologic Surveys," pages 47-51, 1987.
2National Council on Radiation Protection and Measurements, Radio frequency Electromagnetic Fields, Properties, Qualities and Units, Biophysical Interaction and Measurement, page 19, March, 1989.
3Suess, M.J., Copenhagen: World Health Organization Regional Office for Europe: Non-ionizing Radiation Protection, page 104, 1982.
4Brown, H. D and Chattopadhyay, S.K., Cancer Biochemistry Biophysics, "Electromagnetic - Field Exposure and Cancer," page 297, May, 1988.
5Slesin, Louis. Microwave News: "A Report on Nonionizing Radiation," Page 1, July / August, 1988.
6 & 7Siesin, Louis. Microwave News: "Support for Radio Operator Cancer Risk," page 2, January / February, 1989.
8Brown, H.D and Chattopadhyay, S.K., Cancer Biochemistry Biophysics, "Electromagnetic - Field Exposure and Cancer," page 297, May, 1988.
9National Institute For Occupational Safety and Health (NIOSH), Cincinnati Ohio, Health Hazard Evaluation Report number HETA 87-329, page 5, 1989.
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