Electromagnetic radiation can be classified into ionizing radiation and non-ionizing radiation, based on whether it is capable of ionizing atoms and breaking chemical bonds. Ultraviolet and higher frequencies, such as X-rays or gamma rays are ionizing. These pose their own special hazards: see radiation and radiation poisoning.
Non-ionizing radiation, discussed here, is associated with two major potential hazards: electrical and biological. Additionally, induced electric current caused by radiation can generate sparks and create a fire or explosive hazard.
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Electrical hazards
The oscillating electric and magnetic fields in electromagnetic radiation will induce an electric current in any conductor through which it passes. Strong radiation can induce current capable of delivering an electric shock to persons or animals. It can also overload and destroy electrical equipment. The induction of currents by oscillating magnetic fields is also the way in which solar storms disrupt the operation of electrical and electronic systems, causing damage to and even the explosion of power distribution transformers,[1] blackouts (as in 1989), and interference with electromagnetic signals (e.g. radio, TV, and telephone signals).[2] All of these effects can adversely impact human safety and health.
Fire hazards
Extremely high power electromagnetic radiation can cause electric currents strong enough to create sparks (electrical arcs) when an induced voltage exceeds the breakdown voltage of the surrounding medium (e.g. air). These sparks can then ignite flammable materials or gases, possibly leading to an explosion.
This can be a particular hazard in the vicinity of explosives or pyrotechnics, since an electrical overload might ignite them. This risk is commonly referred to as HERO (Hazards of Electromagnetic Radiation to Ordnance). MIL-STD-464A mandates assesment of HERO in a system, but Navy document OD 30393 provides design principles and practices for controlling electromagnetic hazards to ordnance.
On the other hand, the risk related to fueling is known as HERF (Hazards of Electromagnetic Radiation to Fuel). NAVSEA OP 3565 Vol. 1 could be used to evaluate HERF, which states a maximum power density of 0.09 W/m² for frequencies under 225 Mhz (i.e. 4.2 meters for a 40 W emitter).
Biological hazards
The best understood biological effect of electromagnetic fields is to cause dielectric heating. For example, touching or standing around an antenna while a high-power transmitter is in operation can cause severe burns. These are exactly the kind of burns that would be caused inside a microwave oven.
This heating effect varies with the power and the frequency of the electromagnetic energy. A measure of the heating effect is the specific absorption rate or SAR, which has units of watts per kilogram (W/kg). The IEEE[3] and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR, mainly based on ICNIRP Guidelines,[4] which guard against thermal damage.
There are publications which support the existence of complex biological effects of weaker non-thermal electromagnetic fields (see Bioelectromagnetics), including weak ELF magnetic fields.[5][6] and modulated RF and microwave fields[7][8] Fundamental mechanisms of the interaction between biological material and electromagnetic fields at non-thermal levels are not fully understood.[9]
Health effects of electric power transmission
The preponderance of evidence suggests that the low-power, low-frequency, electromagnetic radiation associated with household current does not constitute a short or long term health hazard, and whilst some biophysical mechanisms for the promotion of cancer have been proposed (such as the electric fields around powerlines attracting aerosol pollutants[10][11]), none have been substantiated.[12][13][14][15][16][17] Nevertheless, some research has implicated exposure in a number of adverse health effects. These include, but are not limited to, childhood leukemia,[12] adult leukemia,[18] neurodegenerative diseases (such as amyotrophic lateral sclerosis),[19][20][21] miscarriage,[22][23][24] and clinical depression.
Mitigation
One response to the potential dangers of overhead power lines is to place them underground. The earth and enclosures surrounding underground cables prevent the electric field from radiating significantly beyond the power lines, and greatly reduce the magnetic field strength radiating from the power lines, into the surrounding area.[25] However, the cost of burying and maintaining cables at transmission voltages is several times greater than overhead power lines.[26]
DNA fragmentation
One study in 2009 done by the University of Basel in Switzerland found that intermittent (but not continuous) exposure of human cells to a 50 Hz electromagnetic field at a flux density of 1 mT (or 10 G) induces a slight but significant increase of DNA fragmentation in the Comet assay.[27] However that level of exposure is already above current established safety exposure limits.
Leukemia and cancer
In 1996, the Stevens Report was released by the National Academy of Sciences. Based on the current research of EMF produced from power lines, the report concluded that there was no evidence that showed exposure to EMF from power lines presented a human health hazard. Another report was released on July 3, 1997 by the National Cancer Institute (NCI). The report published in the New England Journal of Medicine, "Residential Exposure to Magnetic Fields and Acute Lymphoblastic Leukemia in Children"[28] was a result of a seven year epidemiological investigation. The study investigated 638 children with acute lymphoblastic leukemia (ALL) and 620 controls and concluded that their study provided "little evidence that living in homes characterized by high measured time-weighted average magnetic-field levels or by the highest wire-code category increases the risk of ALL in children."[28] The NCI study was corroborated by a 1999 Canadian epidemiological study of leukemia in children.[citation needed] As a result of the NCI's findings, the US Department of Energy disbanded the EMF Research and Public Information Dissemination (RAPID) Program citing that its services were no longer needed.[citation needed]
In 2001, Ahlbom et al. conducted a review into EMFs and Health, and found that there was a doubling in childhood leukemia for magnetic fields of over 0.4 µT, though importantly summarised that "This is difficult to interpret in the absence of a known mechanism or reproducible experimental support".[29] In 2007, the UK Health Protection Agency produced a paper showing that 43% of homes with magnetic fields of over 0.4 µT are associated with overground or underground circuits of 132 kV and above.[30]
Ahlbom's findings were echoed by Draper et al. in 2005 when a 70% increase was found in childhood leukaemia for those living within 200 metres (656 ft) of an overhead transmission line, and a 23% increase for those living between 200 and 600 metres (656 and 1,969 ft). Both of these results were statistically significant.[31] The authors considered it unlikely that the increase from 200 m to 600 m is related to magnetic fields as they are well below 0.4 µT at this distance. Bristol University (UK) has published work on a theory that could account for this increase, and would also provide a potential mechanism, being that the electric fields around power lines attract aerosol pollutants.[32][33]
The World Health Organisation issued Factsheet No. 263 in October, 2001 on ELF (Extremely low frequency) EMFs and cancer. It said that they were "possibly carcinogenic", based primarily on IARC's similar evaluation with respect to childhood leukemia. It also said that there was "insufficient" data to draw any conclusions on other cancers.[34] The WHO issued a new fact sheet, No. 322, in June, 2007 based on the findings of a WHO work group (2007), the IARC (2002) and the ICNIRP (2003), which reviewed research conducted since the earlier publication. The fact sheet says "that there are no substantive health issues related to ELF electric fields at levels generally encountered by members of the public." For ELF magnetic fields, the factsheet says, "the evidence related to childhood leukaemia is not strong enough to be considered causal", and "[as regards] other childhood cancers, cancers in adults, ... The WHO Task Group concluded that scientific evidence supporting an association between ELF magnetic field exposure and all of these health effects is much weaker than for childhood leukaemia. In some instances (i.e., for ... breast cancer) the evidence suggests that these fields do not cause them."[12]
Although a doubled risk may sound dramatic, childhood leukemia is a rather rare disease, and even at a doubled risk it would still be rare. In the U.S., the chance that a person develops leukemia during childhood is about one in 1,300 (based on 3,000 cases per year).
According to Dr. Lakshmikumar at the National Physical Laboratory, India, a direct, causal, link between RF radiation and cancer (including Leukemia) would require one to be "willing to discard Planck's Law… and the entire body of quantum physics." [35]
UK SAGE report
The Stakeholder Advisory Group on ELF EMFs (SAGE) has been set up by the UK Department of Health to explore the implications and to make practical recommendations for a precautionary approach to power frequency electric and magnetic fields as a result of the HPA recommendations in March 2004.
The first interim assessment of this group was released in April 2007, and found that the link between proximity to power lines and Childhood Leukemia was sufficient to involve a precautionary recommendation, including an option to lay new power lines underground where possible and to prevent the building of new residential buildings within 60 m (197 ft) of existing power lines.
The latter of these options was not an official recommendation to government as the cost-benefit analysis based on the increased risk for childhood leukemia alone was considered insufficient to warrant it. The option was considered necessary for inclusion as, if found to be real, the weaker association with other health effects would make it worth implementing.[36]
Mobile telephones
Mobile phone radiation and health concerns have been raised, especially following the enormous increase in the use of wireless mobile telephony throughout the world (as of August 2005[update], there were more than 2 billion users worldwide). Mobile phones use electromagnetic radiation in the microwave range, and some[37] believe this may be harmful to human health. These concerns have induced a large body of research (both epidemiological and experimental, in non-human animals as well as in humans). Concerns about effects on health have also been raised regarding other digital wireless systems, such as data communication networks.
The World Health Organization, based upon the consensus view of the scientific and medical communities, states that health effects (e.g. headaches or promotion of cancer) are unlikely to be caused by cellular phones or their base stations,[38][39] and expects to make recommendations about mobile phones in October 2009.[40]
U.S. military definition
In Federal Standard 1037C, the United States government adopts the following definition:
- Electromagnetic radiation hazards (RADHAZ or EMR hazards): Hazards caused by a transmitter/antenna installation that generates electromagnetic radiation in the vicinity of ordnance, personnel, or fueling operations in excess of established safe levels or increases the existing levels to a hazardous level; or a personnel, fueling, or ordnance installation located in an area that is illuminated by electromagnetic radiation at a level that is hazardous to the planned operations or occupancy. These hazards will exist when an electromagnetic field of sufficient intensity is generated to: (a) induce or otherwise couple currents and/or voltages of magnitudes large enough to initiate electroexplosive devices or other sensitive explosive components of weapon systems, ordnance, or explosive devices; (b) cause harmful or injurious effects to humans and wildlife; (c) create sparks having sufficient magnitude to ignite flammable mixtures of materials that must be handled in the affected area.
—Department of Defense Dictionary of Military and Associated Terms
See also
- Electromagnetism
- Magnetobiology
- Mobile phone radiation and health
- Wireless electronic devices and health
- Specific absorption rate
- Electrical sensitivity
- EMF measurements
References
- ^ http://image.gsfc.nasa.gov/poetry/workbook/storms.html
- ^ Transcript of "Blackout: The Sun-Earth Connection", Part 4: When Solar Plasma Distorts Earth's Magnetic Field
- ^ "Standard for Safety Level with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3KHz to 300GHz". IEEE Std (IEEE) C95.1. Oct 2005.
- ^ International Commission on Non-Ionizing Radiation Protection (April 1998). "Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz)". Health Physics 74 (4): 494–522. PMID 9525427. http://www.icnirp.de/documents/emfgdl.pdf.
- ^ Delgado JM, Leal J, Monteagudo JL, Gracia MG (May 1982). "Embryological changes induced by weak, extremely low frequency electromagnetic fields". Journal of Anatomy 134 (3): 533–51. PMID 7107514.
- ^ Harland JD, Liburdy RP (1997). "Environmental magnetic fields inhibit the antiproliferative action of tamoxifen and melatonin in a human breast cancer cell line". Bioelectromagnetics 18 (8): 555–62. doi:. PMID 9383244.
- ^ Aalto S, Haarala C, Brück A, Sipilä H, Hämäläinen H, Rinne JO (July 2006). "Mobile phone affects cerebral blood flow in humans". Journal of Cerebral Blood Flow and Metabolism 26 (7): 885–90. doi:. PMID 16495939.
- ^ Aalto S, Haarala C, Brück A, Sipilä H, Hämäläinen H, Rinne JO (July 2006). "Mobile phone affects cerebral blood flow in humans". Journal of Cerebral Blood Flow and Metabolism 26 (7): 885–90. doi:. PMID 16495939.
- ^ Binhi, Vladimir N. (2002). Magnetobiology: underlying physical problems. Boston: Academic Press. ISBN 978-0-12-100071-4.[page needed]
- ^ Fews AP, Henshaw DL, Keitch PA, Close JJ, Wilding RJ (December 1999). "Increased exposure to pollutant aerosols under high voltage power lines". International Journal of Radiation Biology 75 (12): 1505–21. doi:. PMID 10622257.
- ^ Fews AP, Henshaw DL, Wilding RJ, Keitch PA (December 1999). "Corona ions from powerlines and increased exposure to pollutant aerosols". International Journal of Radiation Biology 75 (12): 1523–31. doi:. PMID 10622258.
- ^ a b c "Electromagnetic fields and public health". Fact sheet No. 322. World Health Organization. June 2007. http://www.who.int/mediacentre/factsheets/fs322/en/index.html. Retrieved 2008-01-23. "Thus, on balance, the evidence related to childhood leukaemia is not strong enough to be considered causal. ... A number of other adverse health effects have been studied for possible association with ELF magnetic field exposure. These include other childhood cancers, cancers in adults, depression, suicide, cardiovascular disorders, reproductive dysfunction, developmental disorders, immunological modifications, neurobehavioural effects and neurodegenerative disease. The WHO Task Group concluded that scientific evidence supporting an association between ELF magnetic field exposure and all of these health effects is much weaker than for childhood leukemia. In some instances (i.e., for cardiovascular disease or breast cancer) the evidence suggests that these fields do not cause them."
- ^ "Electromagnetic fields and public health". http://www.who.int/mediacentre/factsheets/fs296/en/index.html. Retrieved 2007-11-17. WHO factsheet on electromagnetic hypersensitivity
- ^ "Electric and Magnetic Fields and Public Health". National Policy. American Physical Society. 2005-04-15. http://www.aps.org/policy/statements/05_3.cfm. Retrieved 2008-01-29.
- ^ "Electric and Magnetic Fields Associated with the Use of Power" (PDF). National Institute of Environmental Health Sciences. 2002-06. http://www.niehs.nih.gov/health/docs/emf-02.pdf. Retrieved 2008-01-29.
- ^ International Commission on Non-Ionizing Radiation Protection (August 2004). "ICNIRP statement related to the use of security and similar devices utilizing electromagnetic fields". Health Physics 87 (2): 187–96. doi:. PMID 15257219. "Similarly, there is no convincing evidence for an association with neurologic disease, birth defects, heart disease, or suicide.".
- ^ "Report 7 of the Council on Scientific Affairs (I-94)". American Medical Association. December 1994. http://www.ama-assn.org/ama/no-index/about-ama/13682.shtml. Retrieved December 3, 2009. "no scientifically documented health risk has been associated with the usually occurring levels of electromagnetic fields"
- ^ Tynes T, Klaeboe L, Haldorsen T (May 2003). "Residential and occupational exposure to 50 Hz magnetic fields and malignant melanoma: a population based study". Occupational and Environmental Medicine 60 (5): 343–7. doi:. PMID 12709519.
- ^ Feychting M, Jonsson F, Pedersen NL, Ahlbom A (July 2003). "Occupational magnetic field exposure and neurodegenerative disease". Epidemiology 14 (4): 413–9; discussion 427–8. doi:. PMID 12843764.
- ^ Håkansson N, Gustavsson P, Johansen C, Floderus B (July 2003). "Neurodegenerative diseases in welders and other workers exposed to high levels of magnetic fields". Epidemiology 14 (4): 420–6; discussion 427–8. doi:. PMID 12843765.
- ^ Ahlbom A (2001). "Neurodegenerative diseases, suicide and depressive symptoms in relation to EMF". Bioelectromagnetics Suppl 5: S132–43. doi:. PMID 11170123.
- ^ Lee GM, Neutra RR, Hristova L, Yost M, Hiatt RA (January 2002). "A nested case-control study of residential and personal magnetic field measures and miscarriages". Epidemiology 13 (1): 21–31. doi:. PMID 11805582.
- ^ Li DK, Odouli R, Wi S, et al. (January 2002). "A population-based prospective cohort study of personal exposure to magnetic fields during pregnancy and the risk of miscarriage". Epidemiology 13 (1): 9–20. doi:. PMID 11805581.
- ^ Cao YN, Zhang Y, Liu Y (August 2006). "[Effects of exposure to extremely low frequency electromagnetic fields on reproduction of female mice and development of offsprings]" (in Chinese). Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi 24 (8): 468–70. PMID 16978513.
- ^ UK National Grid EMF information site
- ^ See Electric power transmission#Underground transmission for details and references.
- ^ Focke F, Schuermann D, Kuster N, Schär P (November 2009). "DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure". Mutation Research. doi:. PMID 19896957.
- ^ a b Linet MS, Hatch EE, Kleinerman RA, et al. (July 1997). "Residential exposure to magnetic fields and acute lymphoblastic leukemia in children". The New England Journal of Medicine 337 (1): 1–7. doi:. PMID 9203424.
- ^ Ahlbom IC, Cardis E, Green A, Linet M, Savitz D, Swerdlow A (December 2001). "Review of the epidemiologic literature on EMF and Health". Environmental Health Perspectives 109 (Suppl 6): 911–33. doi:. PMID 11744509.
- ^ Maslanyj MP, Mee TJ, Renew DC, et al. (March 2007). "Investigation of the sources of residential power frequency magnetic field exposure in the UK Childhood Cancer Study". Journal of Radiological Protection 27 (1): 41–58. doi:. PMID 17341803.
- ^ Draper G, Vincent T, Kroll ME, Swanson J (June 2005). "Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study". BMJ 330 (7503): 1290. doi:. PMID 15933351.
- ^ Fews AP, Henshaw DL, Keitch PA, Close JJ, Wilding RJ (December 1999). "Increased exposure to pollutant aerosols under high voltage power lines". International Journal of Radiation Biology 75 (12): 1505–21. doi:. PMID 10622257.
- ^ Fews AP, Henshaw DL, Wilding RJ, Keitch PA (December 1999). "Corona ions from powerlines and increased exposure to pollutant aerosols". International Journal of Radiation Biology 75 (12): 1523–31. doi:. PMID 10622258.
- ^ "Electromagnetic fields and public health: extremely low frequency fields and cancer". Fact sheet No. 263. World Health Organization. October 2001. http://www.who.int/mediacentre/factsheets/fs263/en. Retrieved 2008-01-23.
- ^ Lakshmikumar ST (2009). "Power Line Panic and Mobile Mania". Skeptical Inquirer 33 (5): 35. http://www.csicop.org/si/show/power_line_panic_and_mobile_mania.
- ^ "SAGE first interim assessment: Power Lines and Property, Wiring in Homes, and Electrical Equipment in Homes"
- ^ "Researcher sees cancer risk from mobiles (Dr. Ronald Herberman, director of the University of Pittsburgh Cancer Institute)". International Herald Tribune. 2008-07-24. http://www.iht.com/articles/2008/07/24/business/cellphone.php. Retrieved 2008-08-17.
- ^ "What are the health risks associated with mobile phones and their base stations?". Online Q&A. World Health Organization. 2005-12-05. http://www.who.int/features/qa/30/en. Retrieved 2008-01-19.
- ^ "Electromagnetic fields and public health: mobile telephones and their base stations". Fact sheet N°193. World Health Organization. June 2000. http://www.who.int/mediacentre/factsheets/fs193/en. Retrieved 2008-01-19.
- ^ Health and Environment - Science Milestones
External links
- Information page on electromagnetic fields at the World Health Organization web site
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