August 5, 2009
HEALTH EFFECTS OF ELECTRIC AND MAGNETIC FIELDS
By: Kevin E. McCarthy, Principal Analyst
You asked that we update OLR report 2001-R-0666 regarding the potential health effects of electric and magnetic field (EMF) emissions from electric power lines. You were specifically interested in:
1. research conducted on this issue since the report was issued;
2. which level of government has jurisdiction over EMF issues from power lines, telecommunications facilities, and electronic devices;
3. information on EMF consumer safety training for electrical engineers and other professionals.
This report focuses on EMF exposures to people in their homes and workplaces, rather than on workplace exposure such as that experienced by electrical linemen.
The 2001 report discusses several studies that found that there was no conclusive and consistent evidence that exposure to residential EMFs produces cancer, adverse neurobehavioral effects, or reproductive and developmental effects. However, several epidemiological studies had found a relationship between EMF exposure from transmission lines (at EMF levels that substantially exceed those found in most homes) and increased risk of childhood leukemia. Based on these studies, in 2002 the International Agency for Research on Cancer stated that the extremely low frequency magnetic fields associated with transmission lines are “possibly carcinogenic to humans.” More recent studies have come to similar conclusions, finding limited evidence of a link between childhood leukemia and EMF exposure and little or no evidence of other adverse health effects.
Neither the federal or state governments have claimed regulatory jurisdiction over EMF produced from transmission lines, and there are currently no exposure limits in this area. However, the Connecticut Siting Council does require that electric companies use best management practices to minimize EMF exposure in developing new transmission lines. In addition, state law establishes a presumption in favor of placing new transmission lines underground in residential areas and near certain facilities.
The Federal Communications Commission has set EMF emission limits for certain cell phone transmission equipment. Under federal law, siting agencies cannot regulate cell phone towers and related facilities on the basis of their EMF emissions so long as they comply with these limits. Other federal agencies regulate other consumer products that produce ionizing and non-ionizing radiation. For example the Food and Drug Administration regulates the manufacture of microwave ovens, cell phones, and TV sets with regard to such radiation.
A wide range of entities are conducting research on EMF-related issues, but we have found no systematic programs for training electrical engineers and others on EMF consumer safety. The issue is periodically addressed at conferences held by the Institute of Electrical and Electronics Engineers and other professional organizations and at seminars conducted by consultants in the field. The Electric Power Research Institute sells software to help engineers and others model EMF exposure and has held seminars on managing EMF emissions. In addition, the National Institutes of Occupational Health and Safety is funding research to help develop recommendations for managing workplace EMF exposure, especially in the electric power and electricity and wireless communications industries. A summary of this project is available at http://www.cdc.gov/niosh/programs/manuf/noragoals/projects/927ZHNK.html.
Electric and magnetic fields exist wherever electricity is generated, transmitted, or distributed in power lines or cables, or used in electrical appliances. As a result, these fields occur throughout the built environment.
Electric fields arise from electric charges, are measured in volts per meter, and are shielded by materials such as wood and metal as well as human skin. Magnetic fields are created by the motion of electric charges (i.e., a current). In the United States, the unit of measurement is a gauss. These fields are not shielded by most common materials, and pass easily through them. The health concerns regarding EMF exposure have focused on magnetic rather than electric fields.
Neither type of field causes heating or ionization (the breakdown of molecular bonds). In contrast, forms of energy with very short wavelengths, such as microwaves and X-rays, cause these effects. Both electric and magnetic fields are strongest close to the source and diminish with distance. Magnetic field levels also vary depending on current load, height of the conductors, and separation of the conductors.
In the case of magnetic fields from a standard transmission line, the field strength falls geometrically with the distance from the line. While the strength of the field directly under such lines is about 17 milligaus (mG, one-thousandth of a gauss) at the line, it falls to about 8 mG at 10 meters (33 feet) from the line. At 20 meters (66 feet) the exposure is less than 4 mG. The level of the magnetic field becomes indistinguishable from levels found inside or outside homes, exclusive of fields emanating from sources in the home, at a distance of 100 to 300 feet, depending on the design and of the line and how much current it is carrying.
Most homes and businesses receive 0.1 to 3 mG from transmission lines and other sources whose magnetic fields vary over time. Much of this exposure comes from sources within the building itself rather than the transmission. For example, some household appliances can produce magnetic fields of up to 1 mG in their immediate vicinity. In contrast, the earth's magnetic field (which does not vary over time) is about 500 mG.
RESEARCH ON HEALTH EFFECTS
As noted in our 2001 report, in 1997 the National Research Council issued a report in which a scientific committee found that that there was no conclusive and consistent evidence that exposures to residential EMFs produces cancer, adverse neurobehavioral effects, or reproductive and developmental effects. The committee concluded that the evidence did not show that exposure to EMFs presents a human health hazard. In 1999, the National Institute of Environmental Health Sciences issued a report with similar findings. It found that the probability that EMF exposure is truly a health hazard is small. However, a scientific panel that participated in the study concluded that, since EMF cannot be ruled out as a possible source of cancer, it should be considered a potential carcinogen. In addition, several epidemiological studies had found a relationship between EMF exposure from transmission lines, at levels exceeding 3 mG, and increased risk of childhood leukemia. As noted above, most homes experience EMF exposure below this level and most of this exposure is from sources other than transmission lines.
More recent studies have come to similar conclusions. A 2005 National Cancer Institute (NCI) factsheet stated:
Among more recent studies, findings [regarding the relationship between EMF and cancer] have been mixed. Some have found an association; others have not . . . . Currently, researchers conclude that there is limited evidence that magnetic fields from power lines cause childhood leukemia, and that there is inadequate evidence that these magnetic fields cause other cancers in children….Animal studies have not found that magnetic field exposure is associated with increased risk of cancer. The absence of animal data supporting carcinogenicity makes it biologically less likely that magnetic field exposures in humans, at home or at work, are linked to increased cancer risk.
The factsheet is available at http://www.cancer.gov/cancertopics/factsheet/risk/magnetic-fields.
A 2007 update of an ongoing review by the Swedish Radiation Protection Authority focused on epidemiological studies of childhood leukemia and cardiovascular disease, and experimental data related to define “genotoxic” effects. It concluded that research published that year does not alter the conclusion that extremely low frequency magnetic fields should be classified as a “possible carcinogen” based upon epidemiological studies of childhood leukemia. On the other hand, the study concluded that the research does not support the hypothesis that EMF exposure causes any disease or illness.
Similar findings were reported by the European Commission's Scientific Committee on Emerging and Newly Identified Health Risks. It found that the previous conclusion that extremely low frequency (ELF) magnetic fields are possibly carcinogenic, chiefly based on occurrence of childhood leukemia, is still valid. For breast cancer and cardiovascular disease, recent research has indicated that an association is unlikely. For neurodegenerative diseases and brain tumors, the link to ELF fields remains uncertain. The committee's study is available at http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_007.pdf.
A 2008 report by the World Health Organization (WHO) concluded that:
Extremely low frequency fields generated by power transmission have been associated with an increased risk of childhood leukemia, but the findings are not conclusive. Even if this association is real, the number of excess cases is likely to be very small…With reference to ELF fields, available data allow us to exclude any excess risk of childhood leukemia and other cancers at the levels of exposure likely to be encountered by most (more than 99%) of the population…. To date there is no convincing biological or biophysical support for a possible association between exposure to ELF fields and the risk of leukemia or any other cancer.
Based on these findings, WHO recommended implementation of precautionary measures to reduce exposure that have no or low cost and do not compromise the benefits of electricity. This report is available online at http://www.who.int/peh-emf/publications/reports/WCR2008_212.pdf.
In 2008, the Brain Tumor Epidemiology Consortium, a group of 45 scientists sponsored by NCI, published a consensus review on the current state of the science related to brain tumors, and brain tumor research priorities. Based on epidemiological studies, it found that that residential power frequency EMF was probably not a risk factor for glioma, the most common type of adult brain cancer, and meningioma, a non-cancerous brain tumor. The study is available at http://www3.interscience.wiley.com/cgi-bin/fulltext/121411685/HTMLSTART.
In the U.S., there are no federal standards limiting residential or occupational exposure to transmission line EMF. The International Commission on Non-Ionizing Radiation Protection's recommended limit for public EMF exposure from transmission lines and related facilities in the United States is 0.83 Gauss, and the Institute of Electrical and Electronics Engineers' recommended limit for public and occupational exposure is 9.1 gauss. Several states set standards for the width of rights-of-way under high-voltage transmission lines because of potential for electric shock. The width of the right of way also affects EMF exposure.
Connecticut has addressed the issue of EMF exposure from power lines in several ways. Pursuant to PA 04-246, the Siting Council has adopted best management practices regarding EMF. The council requires transmission line applicants to initially develop a Field Management Design Plan that depicts the proposed project designed according to standard good utility practice and incorporating “no-cost” magnetic field mitigation design features. The applicant must then modify the base design by adding low-cost mitigation design features specifically where portions of the project are adjacent to residential areas, public or private schools, licensed child day-care facilities, licensed youth camps, or public playgrounds. The overall cost of low-cost design features are limited to 4% of the cost of the initial Field Management Design Plan, including related substations. The best management practices can be accessed at www.ct.gov/csc/cwp/view.asp?a=3&q=311180.
PA 04-246 also requires that an application for a Siting Council certificate to build an electric or gas transmission line or an electric substation address the impact of any EMF the proposed facility may produce. It also requires that maps submitted with the application show residential areas, schools, and certain other land uses. It requires the council to make findings on the impact of EMFs in deciding whether to grant a certificate for the energy (other than power plants) and telecommunications facilities it regulates. It requires that an electric transmission line be consistent with the council's best management practices. The act requires that the overhead portions of transmission lines be within a buffer zone that protects public health and safety, as determined by the council. In establishing the buffer zone, the council must, among other things, consider residential areas, private and public schools, licensed day centers and youth camps, and public playgrounds adjacent to the overhead portions of the line. It must also consider the voltage of the portions of the line covered by the application and existing overhead lines on the proposed route. At a minimum, the existing right of way must serve as the buffer zone.
The act establishes a presumption that transmission lines of 345 kilovolts or more (e.g., the lines from Bethel to Norwalk and Norwalk to Middletown) that are located adjacent to residential areas and certain land uses should be buried. (This provision was adopted, in part, due to concerns regarding EMF exposures from transmission lines.) The act allows an applicant to rebut this presumption by showing the council that burial is technologically infeasible, taking into account the reliability of the state's electric grid. It requires that overhead portions of transmission lines be located in a buffer zone. PA 07-4, June Special Session, modifies this last provision by requiring the council, in determining whether it is infeasible to bury the line, to consider whether the cost of any contemplated technology or design configuration could result in an unreasonable economic burden on the state's ratepayers.
Telecommunications Facilities and Equipment
The Federal Communications Commission (FCC) has set exposure limits for various telecommunications facilities equipment, e.g., cell phone towers and cell phones. With regard to facilities used to provide cell phone and related services, federal law limits the ability of states and municipalities to regulate the location of cell phone towers and antennas based on their EMF emissions. Specifically, section 704 of the Telecommunications Act of 1996 bars state and local governments from regulating the placement, construction, and modification of cell phone and other personal wireless service facilities on the basis of the environmental effects of their emissions to the extent that such facilities comply with the FCC regulations concerning such emissions. FCC has a webpage that addresses frequently asked questions regarding EMF from telecommunications equipment (http://www.fcc.gov/oet/rfsafety/rf-faqs.html).
Other federal agencies regulate other consumer products that produce ionizing and non-ionizing radiation. For example the Food and Drug Administration (FDA) regulates the manufacture of microwave ovens, cell phones, and TV sets with regard to such radiation. An FDA website, http://www.fda.gov/Radiation-EmittingProducts/ElectronicProductRadiationControlProgram/LawsandRegulations/default.htm describes the law in this area.