Guide to Interpreting Electromagnetic Field Strength EMF Survey Results
Readers are urged to consult expert sources and to give any suggestions regarding these notes to the author. Some studies by some experts have suggested a possible link between exposure to electromagnetic fields and various
cancers or other health problems. Other studies suggest that no definite correlation could be demonstrated. It is
likely that the jury will be out on this matter for some time, for both economic and political reasons.
It is risky and may be misleading for untrained personnel to express opinions for which they have no scientific basis. There are
very few standards for allowable exposure to EMF.
The health studies are, according to some experts, inconclusive. Some
health studies showed an increase in childhood leukemia and other diseases at long exposure to field strengths as low as
1 or 2 mG. However, keep in mind that "doubling" the risk of a disease may in some cases be doubling a number that was
extremely small to start with. Doubling a very small number yields still a very small number. If your clients are
worried about EMF but smoke, or don't fasten seat belts, or have dangerous stair or railings, their attention has been
Pending acceptance of conclusive research by the scientific and engineering community at large, the most accurate
position which can be taken by a consultant is that this is a controversial subject.
There may be a health risk from EMF exposure, but regardless of the real level of health risk,
there are definitely economic risks because of fear felt by some property buyers.
Building owners and occupants should not let this topic distract them from attending to other
high risks that may be at a given property such as tripping hazards, fire hazards, shock hazards, and carbon monoxide hazards.
While the health risks remain under argument, with some recent studies suggesting that there may really be a risk, it
is possible to infer whether or not a given property is likely to be exposed to EMF:
Any property which uses electrical devices will have at least some measurable electromagnetic fields. If the fields are
continuous and close to people the people may be exposed. (EG. sleeping with head 8" from the electric meter-- you can
move away, or sleeping in a building 50 ft from a 500KV power transmission line--you cannot move away within the building
to escape the field).
If you do not find any EMF levels at a property that is served by electricity and has electrical power turned on and some devices in operation (even an electrical clock) then you should doubt your instruments.
If we measure any detectable electromagnetic field outside and all around a building attributable to a nearby power line, it is
very likely that at times the building and its interior are exposed to more powerful fields (when load on the line is
If we can measure no EMF at a given property (attributable to a power line which is nearby) but if the line is
within 1000 meters of the building (at 500KV) then it's still quite possible that under some conditions (of heavy load) the building will be in a field.
As EMF field strength falls off with the square of the distance, and as field strengths are less for smaller transmission and
distribution lines, this 1000 meters is not a sacred distance.
The effect on property value and resale-time for properties located close to power transmission lines should be confirmed by frank conversation with real estate sales people (unless the conversant has a conflict of interest), is real, and is in our opinion rather independent of any demonstrable health hazard.
Small absolute health risk from EMF:
Most researchers indicate that where a risk is present, the absolute risk level from EMF is likely to be small, and
less than other less obscure hazards. (Automobile accidents, trip and fall, fire, and shock hazards, smoking and other
health risks.) Consumers should not let focus on a specific emotionally-charged hazard distract them from these other
more mundane but more dangerous concerns.
The EMF Field strength at any given moment depends on the load on the power line:
A serious problem has limited research and conclusions regarding possible hazards of electromagnetic fields in the
U.S.: the lack of publicly available load data. EMF field strength varies depending on the load on the
system/conductors. Measurements made at different times and under different conditions will vary widely.
Additional explanation of the causes of variation and error in measurements of electromagnetic fields
can be found at my article on Enviro-Scare and EMF this website.
In our opinion if you can establish any field measurement at a property it is likely that under some conditions
the field strength will be greater than the time of your measurement. Further, even if you measure no field effects, if
the property is close to large power transmission or some power distribution lines, it is possible that at some times and
conditions it's in a measurable field.
This material represents research thinking. Anyone having any comment, content correction or suggestion is welcome to contact the author.
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"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).
US Environmental Protection Agency, Office of Pesticides
and Toxic Substances, TSCA Assistance Office (TS-799), 800-424-9065
"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
"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