About electric and magnetic fields
Electric and magnetic fields (EMFs) are part of our everyday lives and are created in varying degrees by electrical devices and power lines.
SRP strives to ensure our customers' safety by staying abreast of the latest research about EMFs. In addition, we support and fund EMF-related medical and scientific research, primarily through the Electric Power Research Institute (EPRI) .
Since the 1970s, there have been several thousand scientific papers published and over two dozen expert panels have reviewed the research.
EMFs have not been established as a cause of any disease or illness. With regard to cancer, the U.S. National Cancer Institute (one of the National Institutes of Health) has concluded that "no consistent evidence for an association between any source of non-ionizing EMF and cancer has been found." Additional information is available from the National Cancer Institute.
The World Health Organization (WHO) has reviewed the available scientific research and stated that, "based on a recent in-depth review of the scientific literature, the WHO concluded that current evidence does not confirm the existence of any health consequences from exposure to low level electromagnetic fields."
Sources of EMFs
Electric and magnetic fields are produced by various electrical devices, many of which we use daily. Electric fields are produced as electricity moves through wires, while magnetic fields are only produced when current is flowing, usually when a device is turned on. Together, these are referred to as EMFs. The strength of an EMF decreases significantly as distance from the source increases.
Home and workplace
Exposure to magnetic fields from electric power sources occurs during common activities at home and virtually everywhere we go, including places of work and school. Sources of exposure include any electrical device, appliance or other equipment during operation, in addition to building wiring.
Magnetic fields from common household appliances (mG)1
|Electrical device||Distance from source2|
1In the U.S., the unit of measure for a magnetic field is the gauss (abbreviated as G), with exposure expressed often in milligauss, or mG (1/1000th of a gauss). The international unit for a magnetic field is the tesla, with exposures usually expressed in units of microtesla (μT); one μT is equal to 10 mG. Most of the fields experienced in daily life are anywhere from 1 to 10 mG but can be up to 1,000 mG near electrical appliances and equipment.
2A dash (–) means that the magnetic field at this distance from the appliance in operation could not be distinguished from the background measurements taken before the appliance had been turned on.
3Microwave ovens produce 60 Hz fields of several hundred milligauss, but they also create microwave energy inside the appliance that is at a much higher frequency (about 2.45 billion hertz). We are shielded from the higher frequency fields but not from the 60 Hz fields.
Power transmission lines
Transmission lines, a key component of the electrical grid, deliver power to your home and can be located overhead or underground. Peak EMF levels resulting from power lines can vary considerably depending on the amount of current carried by the line, whether the line is located overhead or underground and the distance from the power line.
Typical EMF levels near SRP power lines (mG)*
|Directly under overhead transmission line||5 to 100|
|100 feet away from overhead transmission line||1 to 20|
|Directly over underground distribution line||6 to 30|
|20 feet away from underground distribution line||2 to 10|
There are no federal or State of Arizona requirements to limit public exposures to 60 Hz EMFs. Some guidelines established by international expert groups include:
- 2,000 mG for the general public and 10,000 mG for occupational settings, International Commission on Non-Ionizing Radiation Protection, updated 2010, see tables 3 and 4 .
- 9,040 mG for persons in unrestricted environments, or "general public exposure," and 27,100 mG for persons permitted in unrestricted environments, or "occupational exposure." See IEEE C95.1-2019, "IEEE Standard for Safety Levels with Respect to Human Exposure to Electric, Magnetic, and Electromagnetic Fields, 0 Hz to 300 GHz," Table 2.