Electric & Magnetic Fields

What are electric and magnetic fields?

Electric and magnetic fields are invisible lines of force surrounding any wire or device that uses electricity. They are created whenever electricity flows through a wire, whether a power line, the cord to an electric kettle or the wires running through your home. Because these fields are found wherever there is electricity, we are continually exposed to them.

Electric fields are produced by voltage, which can best be compared to the pressure of water in a pipe. They are measured in kilovolts per metre (kV/m). There are electric fields whenever voltage is present. Even when an appliance is plugged in but turned off, for example, electric fields are present. The higher the voltage, the higher the electric fields.

Magnetic fields are produced by electrical current, which is comparable to the quantity of water flow in a pipe. They are measured in microtesla (mT) or milligauss (mG) (1 mT = 10 mG). They are only present when power is flowing through a wire, and will vary with the amount of power "drawn." The more current flowing through a wire, the higher the magnetic field.

Current research on magnetic fields
Researchers have conducted numerous studies over the past thirty years into possible effects from exposure to electric and magnetic fields. Some of the research has suggested that long-term exposure may affect human health. Other studies show no such connection.

Epidemiological and laboratory studies as well as data on residential and occupational exposures indicate that any potential risks are at a very low level.

How strong are electric fields?
The strength of an electric field increases with voltage. Electric fields are measured in kilovolts per meter (kV/m). Typical electric field levels in the home and at work are less than 0.1 kV/m (kilovolt per meter). Electric fields within one foot of small appliances are in the range of 0.02 to 0.2 kV/m, while the field immediately adjacent to the heating wires of an electric blanket can approach 10 kV/m.

There are no health-based standards for power system electric fields.

Electric fields from all sources are greatest in the area immediately surrounding the power line or electrical device. They drop off rapidly as you move away from the source.

Electric fields are easily shielded by physical objects such as trees, walls, and even skin. In other words, they do not easily pass through or penetrate most solid objects.

How strong are magnetic fields?
The strength of a magnetic field increases with the amount of current flow. Magnetic fields are measured in microtesla (mT) in Canada and most of the world, and in milligauss (mG) in the United States. One microtesla (mT) is equal to ten milligauss (mG). Typical magnetic fields levels in the home and at work can range from 0.1 mT to 5 mT (microtesla), but levels in most Ontario homes range from 0.1 to 0.4 mT (microtesla)—although it is not unusual to find homes above or below these levels. Magnetic fields within one foot of small appliances are typically between 1 and 100 mT, although some can exceed 1000 mT.

There are many possible indoor and outdoor electrical sources that can affect the magnetic field levels in homes. Indoor sources include house wiring, appliances, power tools, lighting, electronic equipment, and household electrical grounding systems. Outdoor sources include high voltage power lines (transmission lines), lower voltage power lines (distribution lines), electrical supply lines to building, and metal pipes supplying water to homes (due to electrical grounding practices). Because of the great number of possible indoor and outdoor sources of fields, the field levels in homes near power lines are often comparable to levels in homes away from lines. Power lines are only one possible source of fields.

Like electric fields, magnetic field strengths are greatest in the area immediately surrounding a power line or appliance or electrical device. Fields diminish quickly with distance from the source.

Magnetic fields, unlike electric fields, are not easily shielded. They penetrate through most materials, and are difficult and expensive to block.

Can I find out what fields are in my home?
For our customers, Horizon Utilities will measure fields in your home or on your property. Because there are no health based "standards" for power system electric and magnetic fields, having measurements taken cannot tell you whether existing levels are "safe" or "unsafe."

Assessing the research
Since 1977, scientific panels and government bodies have conducted 84 reviews of EMF science. While most of these studies identify areas for additional research and some uncertainties about the possibility of health effects, none of these reviews conclude that exposure to power-frequency EMF adversely affects human health.

No health agency in Canada or the United States has developed health based exposure standards for power line frequency electric or magnetic fields. In 1996, the Swedish government panel stated: "The research findings presented hitherto afford no basis for and cannot be said to justify any limit values or other compulsory restrictions on low-frequency electrical and magnetic fields."