What are EMFs?
EMFs stands for electromagnetic fields. An EMF wave can travel through space while carrying energy at the speed of light. All EMF waves consist of electric fields and magnetic fields. These fields are characterized by their frequency (or energy). Electrical power has an extremely low frequency (ELF) of 60 Hz (or 60 wave cycles per second). These fields can be thought of as ocean waves with the frequency referring to the number of waves passing in one second. The highest energy fields are X-rays and gamma rays with frequencies of 10 billion trillion Hz. EMFs from power lines, electrical appliances, computers and cell phones are non-ionizing radiation (contains enough energy to move atoms but not enough to alter them chemically as X-rays and Gamma rays do.)
It is relatively easy to shield people from exposure to electric fields at 60 Hz using commonly available materials. Houses do a reasonable job of reducing electric fields at 60 Hz. The 60 Hz magnetic fields, however can pass through anything. Surprisingly, shielding from microwave oven radiation and cell phone EMFs can be blocked rather easily by thin sheets of metal.
How do 60 Hz electrical appliance magnetic fields compare to the earth’s magnetic field?
The earth’s magnetic field, to which we are all constantly exposed, is stronger (sometimes over 100 times stronger) than the magnetic fields produced by many appliances, electric wiring and power lines. However, the earth’s magnetic field is primarily a static field, meaning it is not time varying and has no wave frequency or energy. Static magnetic fields do not induce currents in stationary objects. Our bodies seem to react differently to these different types of magnetic fields so comparing them can be misleading.
The strength of the field at the Earth's surface ranges from less 300mG (milligauss =0.001 Gauss) in an area including most of South America and South Africa to over 600 mG around the magnetic poles in northern Canada and south of Australia, and in part of Siberia.
What is involved in a EMF home survey?
Magnetic field (flux density) in mG is measured in each room in the home. The room is scanned for the highest level within the living space in the room and that is recorded. Any particularly high levels along walls are also noted in the notes portion of the data sheet. Particular attention is paid to the field levels around beds in the home. If the family is not typically at home during the day, then we recommend an evening appointment (no extra charge) to better establish the approximate long term EMF exposure.
The magnetic field levels from any appliances requested by the family can be accommodated at no extra charge.
The cell phone EMFs are also measured and recorded in each room. The room is first scanned for the highest level within the living space and that is recorded.
The survey takes approximately one hour. At the conclusion a completed data sheet is provided along with a summary of EMF information to aid in interpreting the results.
What type of equipment does Puget Sound EMF Testing use to evaluate EMF levels?
Our test engineers use a 3-axis digital gauss meter with an accuracy verified and certified by the manufacture to insure accurate measurements. These certifications are available for customer inspection. Measurements include magnetic fields up to 75,000 Hz with resolutions to 0.01 mG.
For cell tower and microwave oven EMF measurements, the power density is measured up to 3,000,000,000 Hz to a resolution of 0.001 ?W/cm2. The certifications of these instruments are also available for customer inspection.
Are electrical hybrid cars a concern for EMF levels?
Little is known about the EMF levels in hybrids. Informal communications from owners have been reported in the 100 to 200 mG range.. This is quite high but well within the current United States and international EMF guidelines. If future research required changes to the guidelines, shielding or wiring changes may be required on hybrid vehicles to better protect passengers who spend hours each day in their cars.
How does day and season affect EMF field strength?
Distance from the power transmission line, while important, is not the only important factor. The strength of the magnetic field varies directly as the current passing through the power line varies.
Typically, in the evening and during the night the load capacity on the electric grid is different than during the day. The variation can be dramatic and often taking magnetic field data in the evening is a better indicator of a family’s long term exposure to EMFs.
In the middle of summer in Los Angeles, when many people are running air conditioners and thus the load on the electrical grid is high, a lot of current is passing through the power transmission lines, and the magnetic field strength will be quite high - thus extending further from the power lines and being measurable at higher levels than it will during times of low electricity usage. Therefore no single instantaneous magnetic field measurement at a particular spot may be quite repeatable.
A power transmission company will tell you the kilovoltage that a given transmission line is designed to carry. This is not enough data to calculate exposure or risk. One would need to know the actual minute-to-minute load on the transmission line to be able to predict the probable EMF strength during those intervals. A magnetic field measurement due to power lines taken with a load capacity of 30% would be 50% higher with a power line load capacity of 60%.
The absence of this data has plagued attempts to correlate proximity to power transmission lines, EMF exposure, and health risks.
How does distance from EMF sources effect field strength?
The strength of an electromagnetic field diminishes as the square of the distance from the source. For example the power density 600 feet from a cell phone tower will be one fourth the power density 300 feet away.
A brief summary of a few research findings are listed below:
A comprehensive World Health Organization (WHO) EMF health risk assessment was published in June 2007. The main conclusion was:
Scientific evidence suggesting that everyday, chronic, low intensity ELF (60 Hz) magnetic field exposure poses a possible health risk based on epidemiological studies showing a consistent pattern of increased risk of childhood leukemia. Therefore, the conclusion is that ELF magnetic fields remain classified as possibly carcinogenic.
A California Department of Health Sciences Evaluation concludes EMFs "can cause some degree of increased risk of childhood leukemia, adult brain cancer, Lou Gehrig’s Disease, and miscarriage" [emphasis added]. The Evaluation—which is the culmination of a 9 year, $7 million research effort—further concludes that magnetic fields may cause suicide and adult leukemia.
A doubling of risk among children with average exposures above 4 mG is "unlikely to be due to chance," according to ICNIRP, a leading European quasi-governmental authority on the dangers of radiation. In a detailed review of the literature on ALS (Lou Gehrig's Disease), the ICNIRP believes that the data "point toward a possible risk increase."
A major study found that children whose birth address was within 200 meters of an overhead power line had a 70% increased risk of leukemia. Children living 200 to 600 meters away from power lines had a 20% increased risk. This indicates the danger from power lines is appreciably further from the lines than had been identified in previous studies. The study, which was partially funded by the power-line industry, mapped how far each child lived from a high voltage overhead power line. It compared the children who had cancer with a control group of 29,000 children without cancer, but who lived in comparable districts, Appearing in the June 2005 British Medical Journal, the study concludes there is a statistical link between EMF from power lines and leukemia. The study looked at cancer data or children aged up to 15 years old in England and Wales between 1962 and 1995, and was a collaboration between the Childhood Cancer Research Group at the University of Oxford and National Grid owners, Transco.