EMF - for our purposes, it is an ElectroMagnetic Field. Wikipedia defines it as: a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field.
The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field.
Magnetic Field - this occurs, for our purposes, when electricity moves through a wire (technically an electromagnetic field). Permenent magnets can also genterate similar fields. In the diagram, the eletrcial current is flowing through the blue wire in the direction of the white arrow. The red lines are the magnetic field created by the flowing electricity. These magnetic fields can be tested with a gauss meter.
Source: https://en.wikipedia.org/wiki/Magnetic_field
The Environmental Protection Agency (EPA) has labeled magnetic fields a class 3 carcinogen. These fields can occur when there is an imbalance in the electrical wiring, and around electrical motors such as the motor in your refrigerator.
A MAJOR source of magnetic fields is next to the main power meter for your house. You definitely want to avoid sleeping up against a wall that has a power meter on the outside. Electric clock radios can also generate magnetic fields.
Fortunately, the effect drops off dramatically with distance, so simply putting some distance—typically about five or six feet—between yourself and the source is usually sufficient to drastically reduce or eliminate the danger.
Electric Fields - for our purposes, electric fields occur when electricity flows through a wire. Turning on a lamp, for example, will cause electricity to flow through the wire from the wall outlet and cause the filament of the lamp to glow. These electric fields can be strong if the (+) and (-) wires do not run close to each other (this can be caused by faulty wiring). This can be measured with an electric field meter.
Eletrical fields surrounding a positive (red) and negative (blue) charge.
Source: https://en.wikipedia.org/wiki/Electric_field
These are the fields that emanate from anything that has voltage; basically anything electric, such as lamps, electrical wiring, outlets, extension cords, electrical appliances, and power outlets.
Electric fields can affect the electrical communication in your body, such as your brainwaves, or the ability of your neurons to fire and communicate. It can also impede inter-cell communication anywhere in your body. Health problems that can manifest as a result to this type of exposure include neurological- and behavioral changes, altered cell growth, cell mutations, fibromyalgia, chronic fatigue, and even cancer.
Radio Spectrum - The radio spectrum is a subset of the electromagnetic spectrum. It extends from frequencies below 1 Hz up to around 3000 GHz or 3 THz, where it gives way to the infrared spectrum. Different frequencies have different uses because of different propagation, generation and general properties. The radio spectrum is divided into many different bands.
Source:http://www.spaceacademy.net.au/spacelink/radiospace.htm
Wireless Communications - This includes wireless power meters (so-called SmartMeters), cell phones, cell towers, wireless routers, and cordless phones. Most of these types of technologies expose you to both electric- and magnetic fields.
According to Dr. Mercola’s website, cordless phone bases are a MAJOR source of exposure, and should never be kept in your sleeping area. While the handset is a source of exposure while you’re talking on the phone, the base transmits constantly, whether the phone is in use or not. Still, it’s best to use the speaker phone or a headset when using a cordless phone because the thermal impact of the antenna can also cause problems, particularly if you’re frequently on the phone or talk for long periods of time.
The thermal impact is what the SAR rating on the phone refers to.
The radiation emitted by wireless communications decreases linearly, so you have to put a significant amount of distance between yourself and the source to sufficiently reduce your exposure. Having walls between yourself and the source will also help; preferably with reflective barriers such as metal foil and certain types of metallic paint.
Ideally, you’ll want the cordless base station located at least three full rooms away from where you’re sleeping. Keeping a cordless phone base on your desk is not recommended, as you’ll be continuously blasted with radiation throughout your work day.