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WHAT ARE EMFs? - What are Electromagnetic Fields - EMFs? This document discusses common sources of exposure to electromagnetic fields and methods to reduce exposure, as well as mentioning some exposure standards.

While this NIOSH document is focused on the workplace it is of interest to home owners as well. Everyone in our modern society is exposed to the electric and magnetic fields (EMFs) that surround all electric devices. Readers should also see Electromagnetic Radiation Field EMF SURVEY Procedure and where property values may be affected by the presence of nearby power transmission lines, see Enviro-Scare, the Cycle of Public Fear.

Recently, scientific studies have raised questions about the possible health effects of EMFs. This fact sheet answers frequently asked questions about EMFs in the workplace.

You can use this information to help identify EMF sources at work and to take simple steps for reducing exposures. However, you cannot use this information to judge the safety of your exposures, since the scientific evidence does not yet show whether EMF exposures are hazardous. [This is a NIOSH document. Also see More Information about Electromagnetic Fields below.] Also see EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.

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EMFs are invisible lines of force created whenever electricity is generated or used. EMFs are produced by power lines, electric wiring, and electric equipment and appliances. The frequency of EMFs is measured in hertz (Hz, or cycles per second).

People are exposed to both electric and magnetic fields, but scientists are most concerned about magnetic fields. This fact sheet deals only with magnetic fields that have frequencies near 60 Hz the frequency of electric power in North America.

Static magnetic field
around a bar magnet.

EMF EXPOSURE - What do we know about workplace exposures to Electromagnetic Fields - EMFs?

Workers may be exposed to high magnetic fields if they work near electrical systems that use large amounts of electric power (for example, large electric motors, generators, or the power supply or electric cables of a building).

High magnetic fields are also found near power saws, drills, copy machines, electric pencil sharpeners, and other small electric appliances. The strength of the magnetic field depends on equipment design and current flow not on equipment size, complexity, or voltage. Though some electric equipment produces EMFs of other frequencies, most health research has considered only frequencies near 60 Hz.

These electric heaters for metal parts expose workers to magnetic fields that are 10,000 times greater than the average magnetic fields found outside the workplace.

TYPICAL EMF EXPOSURES - What are some typical Electromagnetic Fields - EMF exposures on the job?

The EMF exposures for many jobs have not been measured, but the following table shows average exposures to magnetic fields for typical workers who use electric equipment. Exposures during a work shift vary with the strength of the magnetic field, the worker s distance from the EMF source, and the time the worker spends in the field. For comparison, the table also lists worker exposures off the job.

Average magnetic field exposures for various types of workers (in milligauss*

                                    Average daily exposures
        Type of worker                 Median**     Range
Workers on the job:
    Clerical workers without
       computers                       0.5       0.2 - 2.0
    Clerical workers with
       computers                       1.2       0.5 - 4.5
    Machinists                         1.9       0.6 - 27.6
    Electric line workers              2.5       0.5 - 34.8
    Electricians                       5.4       0.8 - 34.0
    Welders                            8.2       1.7 - 96.0
 
 Workers off the job
    (home, travel, etc.)               0.9       0.3 - 3.7

EMF and CANCER? - Do Electromagnetic Fields - EMFs cause cancer or other health effects?

Studies have shown that some workers exposed to high magnetic fields have increased cancer rates. But such associations do not necessarily show that EMF exposures cause cancer (any more than the springtime association of robins and daffodils shows that one causes the other). Scientists have looked carefully at all the EMF evidence, but they disagree about the health effects of EMFs except to say that better information is needed.

EMF EFFECTS - What DO studies show about the health effects of Electromagnetic Fields - EMFs in workers?

Many studies report small increases in the rate of leukemia or brain cancer in groups of people living or working in high magnetic fields. Other studies have found no such increases. The most important data come from six recent studies of workers wearing EMF monitors to measure magnetic fields. All but one study found significantly higher cancer rates for men with average workday exposures above 4 milligauss.

However, the results of these studies disagree in important ways such as the type of cancer associated with EMF exposures. So scientists cannot be sure whether the increased risks are caused by EMFs or by other factors. A few preliminary studies have also associated workplace EMFs with breast cancer, and one study has reported a possible link between occupational EMF exposure and Alzheimer s disease.

The data from all of these studies are too limited for scientists to draw conclusions. However, a national research effort is under way, and more study results are expected in a few years.

No increased leukemia has been reported overall in studies of welders, yet they are among the occupations with the highest EMF exposures.

EMF EXPOSURE LIMITS - Have limits been set for worker exposures to Electromagnetic Fields - EMFs ?

Because of the scientific uncertainty, no Federal limits for worker exposures to EMFs have been recommended or established in the United States.

Two private organizations have developed guidelines to protect workers from the known effects of extremely high exposures (that is, those more than 1,000 times the exposures typically found in occupational environments). However, these guidelines do not address the possible health effects of the low EMF exposures usually found on the job.

Should workers and employers try to reduce exposures to Electromagnetic Fields - EMFs?

The National Institute for Occupational Safety and Health (NIOSH) and other government agencies do not consider EMFs a proven health hazard. Because some studies have associated high magnetic field exposures with increased cancer risks, the government will continue studying EMFs. While research continues, concerned workers and employers might consider the following simple, inexpensive measures for reducing EMF exposures:

• Inform workers and employers about possible hazards of magnetic fields.
• Increase the worker's distance from the EMF source. Since magnetic fields often drop off dramatically within about 3 feet of the source, workers can stand back from electrical equipment, and work stations can be moved out of the 3-ft range of stronger EMF sources.
• Use low-EMF designs wherever possible (for the layout of office power supplies, for example).
• Reduce EMF exposure times. No action should be taken to reduce EMF exposure if it increases the risk of a known safety or health hazard such as electrocution.

EMF exposures depend on the worker's distance from the source.

What is NIOSH doing about Electromagnetic Fields - EMF exposures?

NIOSH has been evaluating the possible health effects of EMFs since 1991. NIOSH scientists have measured the fields in workplaces where employees are concerned about their EMF exposures; they are also studying the biological effects of EMFs. In addition, NIOSH scientists work cooperatively with researchers in universities and other Federal agencies to share their study results. These cooperative efforts have increased recently under the National EMF Research and Public Information Dissemination (RAPID) program.

EMF RF FIELD & FREQUENCY DEFINITIONS
EMF ELECTROMAGNETIC FIELDS & HUMAN EXPOSURE
WHAT ARE EMFs?
EMF EXPOSURE
TYPICAL EMF EXPOSURES
EMF and CANCER?
EMF EXPOSURE LIMITS
REDUCING EMF EXPOSURE
NIOSH EMF ACTIONS
EMF Levels of Cancer Risk
EMF MEASUREMENT INSTRUMENTS
EMF MEASUREMENT PROCEDURES
EMF SURVEY PROCEDURE - Details

WORKPLACE EXPOSURE to Electromagnetic Fields

• Content primarily NIOSH public document. References and resources added by DF

References for Electromagnetic Fields and Cancer Risk/Carcinogenicity

• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear About Environmental Issues - online document by DF
• A Procedure for Measuring EMF electromagnetic fields online document by DF
• "Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields", Federal Communications Commission, Office of Engineering and Technology, US FCC, OET Bulleting 56, 4th Edition, August 1999
  " Many consumer and industrial products and applications make use of some form of electromagnetic energy. One type of electromagnetic energy that is of increasing importance worldwide is radiofrequency (or "RF") energy, including radio waves and microwaves, which is used for providing telecommunications, broadcast and other services. In the United States the Federal Communications Commission (FCC) authorizes or licenses most RF telecommunications services, facilities, and devices used by the public, industry and state and local governmental organizations. Because of its regulatory responsibilities in this area the FCC often receives inquiries concerning whether there are potential safety hazards due to human exposure to RF energy emitted by FCC-regulated transmitters. Heightened awareness of the expanding use of RF technology has led some people to speculate that "electromagnetic pollution" is causing significant risks to human health from environmental RF electromagnetic fields. This document is designed to provide factual information and to answer some of the most commonly asked questions related to this topic." - original source: U.S. Federal Communications Commission Office of Engineering and Technology, http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf
• "Magnetic Field Exposure and Cancer: Questions and Answers [ copy on file as /emf/EMF_Fact_Sheet_NCI_NIH.pdf ] - ," National Cancer Institute, U.S. National Institutes of Health, web search September 2010, original source: http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
  makes these five key points about EMF
  • Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1).
  • Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1).
  • Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2).
  • Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3).
  • Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4).
• "Magnetic Field Exposure and Cancer: Questions and Answers [ copy on file as /emf/EMF_Fact_Sheet_NCI_NIH.pdf ] - ," National Cancer Institute, U.S. National Institutes of Health, web search September 2010, original source: http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
  makes these five key points about EMF
  • Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1).
  • Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1).
  • Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2).
  • Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3).
  • Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4).
• EMF RF FIELD & FREQUENCY DEFINITIONS RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest. See EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
• Definitions of Gauss vs Milligauss for details about gauss and milligauss and definitions of these terms.
• Consumer Product Safety Commission, 800-638-CPSC.
• US Environmental Protection Agency, Office of Pesticides and Toxic Substances, TSCA Assistance Office (TS-799), 800-424-9065 or 202-554-1404.
• "Evaluation of Potential Carcinogenicity of Electromagnetic Fields," EPA Report #EPA/600/6-90/005B October 1990. EPA: 513/569-7562.
• "Biological Effects of Power Frequency Electric and Magnetic Fields" background paper, prepared as part of OTA's assessment of "Electric Power Wheeling and Dealing: Technological Considerations for Increasing Competition," prepared for OTA by Indira Nair, M. Granger Morgan, H. Keith Florig, Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213
• "Biological Effects of Power Line Fields," New York State Powerline Project. Scientific Advisory Board Final Report, July 1, 1987.
• "Extremely Low Frequency (ELF) Fields," Environmental Health Criteria 35. World Health Organization, Geneva, 1984.
• "Electric and Magnetic Fields at Extremely Low Frequencies: Interactions with Biological Systems. In: Non ionizing Radiation Protection, World Health Organization, Regional Office for Europe, Copenhagen, 1987.
• "Electric and Magnetic Fields from 60 Hertz Electric Power: What do we know about possible health risks?," Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213 1989.
• "Electromagnetic Fields Are Being Scrutinized for Linkage to Cancer," Sandra Blakeslee, New York Times, Medical Science section, April 2, 1991

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues
• Electromagnetic Fields in the Workplace sample very good NIOSH document online, links to other NIOSH docs.
• Electromagnetic Field Surveys & Hazards full list of our links to services and technical article
• Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear About Environmental Issues - online document by DF
• A Procedure for Measuring EMF electromagnetic fields online document by DF
• Environmental Concerns in buildings, hazards: allergens, asbestos, brownfields
• ...