All of us depend on electricity to meet basic needs such as heating, cooling and lighting our homes. We also depend on electricity to meet the transportation, communication, commercial, recreational, industrial and health care requirements of our society. Wherever we make use of electricity, power frequency electric and/or magnetic fields (EMF) are present.
EMF is measured in milligauss (mG). Most research on the potential health effects of EMF has focused on magnetic fields.
Electric fields
Electric fields are created around appliances and wires wherever a voltage exists. You can think of electric voltage as the pressure of water in a garden hose – the more voltage, the higher the electric field strength. Electric fields are present when an electrical appliance is plugged in even when turned off. Electric fields diminish rapidly with distance from the source and can be shielded by objects such as trees or the walls of a building.
Magnetic fields
Magnetic fields are created whenever there is a flow of electric current. This can be thought of as the flow of water in a garden hose. As the amount of current flowing increases, so does the magnetic field. Magentic fields are only present when there is a flow of electricity, such as when an electrical appliance is operating. Magenetic fields diminish rapidly with distance from the source, but are not shielded by objects such as trees or buildings. The level of magnetic fields from electrical appliances in homes can be as high as or higher than the magnetic fields people may experience under power lines. Magnetic field strength from power lines depend on many factors, including the design of the line, the amount of current the line carries, and the distance from the line.
Research on EMF – How it affects you
You may have questions about whether there are adverse health effects from exposure to power frequency EMF. For over 40 years, there have been many scientific studies conducted on power frequency EMF. Extensive reviews and research conducted by leading public health agencies – such as the World Health Organization (WHO) and the U.S. National Institute of Environmental Health Sciences (one of the U.S. National Institutes of Health) – have not established that exposure to power frequency EMF causes adverse health effects in humans or animals. In the view of WHO, “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.”
Two principal types of studiest have been conducted on power frequency EMF: laboratory studies and epidemiology studies.
Laboratory studies
Laboratory studies involve exposing cells, tissues and animals to EMF under controlled conditions in the laboratory. Many laboratory studies have examined whether cells exposed to EMF show significant permanent damage to the structure of DNA or chromosomes that could lead to the development of cancer. Other studies have examined whether adverse health effects are found in animals exposed to power frequency EMF for their entire lives. The reviews conducted by leading public health agencies, such as WHO and NIEHS have found that the laboratory studies do not show that exposure to power frequency EMF causes adverse effects in cells or animals.
Epidemiology studies
Epidemiology studies look for statistical associations between the incidence of disease and specific conditions or exposures. Some epidemiology studies have reported a weak statistical association between estimates of EMF exposures and some cancers, while other epidemiology studies have not found such an association. Leading public health agencies, such as WHO and NIEHS have found that, at most, these epidemiology studies can be interpreted as showing a “possible” but inconclusive relationship between EMF and childhood leukemia, and that the relationship is weak and lacks support from the laboratory research. As noted by WHO, “Despite extensive research, to date there is no evidence to conclude that exposure to low level electromagnetic fields is harmful to human health.”
Exposure limits
Neither the U.S. government nor the state of Washington has established exposure standards for public exposure to power frequency EMF. Two international organizations, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronic Engineers (IEEE), have developed exposure guidelines that have been endorsed by the World Health Organization (WHO).
| Established EMF exposure limits | |
| International Commission on Non-Ionizing Radiation Protection | 2,000 mG1 |
| Institute of Electrical and Electronic Engineers | 9,040 mG |
| 1In November 2010, ICNIRP updated its guidelines. These guidelines replace the prior exposure guidelines ICNIRP issued in 1998. Exposure limits under the new guidelines more than doubled: from 833 mG to 2,000 mG. See “ICNIRP Statement – Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1 Hz to 100 kHz)” and “Fact Sheet on the Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1 Hz to 100 kHz)” at www.icnirp.org. |
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Source PSE | Puget Sound Energy | Electric Current in Electromagnetic Fields