Differences in voltage produce electric fields: the higher the voltage, the stronger the resultant field. Magnetic fields are formed when electric current flows: the greater the current, the stronger the magnetic field. Even when no current is flowing, an electric field will still exist. If current flows, the magnetic field strength will vary with power consumption, but the strength of the electric field remains constant.

Natural sources of EMF

Although the human eye cannot see EMFs, they exist everywhere in the environment. Electric fields are created by the local build-up of electric charges in the atmosphere related to thunderstorms. While the magnetic field of the earth causes a compass’s needle to orient in a North-South direction,  the birds and fish utilise the magnetic field for navigation.

Human-made sources of EMF

In addition to natural sources, the electromagnetic spectrum includes fields created by human-made sources, such as X-rays to diagnose broken limbs after sports accidents. There are low-frequency electromagnetic fields associated with the electricity that comes out of power sockets. Information is also transmitted using a variety of higher frequency radio waves. In today’s world, electromagnetic (EMF) Radiation is everywhere. Many types of equipment in the home or office environments, intentionally or unintentionally, generate EMF. Such equipment includes televisions, mobile phones, modems, personal computers and microwave ovens. 

All are powered by electricity, which itself creates EMF. High levels of EMF are found in our surroundings.

High-Frequency Electromagnetic Radiation (E-field)

Electric fields are mostly caused by the fast switching of electronic and electro-mechanical switching devices (drives, relays, motors…) and high-frequency signal transmission (Radio, Mobile Phone…). The symptoms of the electric interference, in any case, are identifiable in the computer rooms of the buildings.
This electric radiation can often provoke the computer network to frost. Even if the network does not have any breakdown, it can lose speed in the operation due to some transmission error, which created a lot of retransmission.

Low Frequency Magnetic Radiation (H-field)

Magnetic Fields are the natural consequence of the use and distribution of electricity. The strength and area of magnetic field emitted is proportional to the amount of current being used. Magnetic fields are associated to low frequencies.
Consequently, all commercial buildings have areas with elevated fields. These areas are caused by high current carrying devices (transformer, electric panels, cables…) which are commonly found in all buildings. Wiring errors, as well, can lead to elevated magnetic field levels. This can be really dangerous because the electromagnetic radiation coming from the electrical current can provoke malfunctions in the computers (monitor flickering) and can possibly be dangerous to human health

Electromagnetic field exposure is not a recent phenomenon. During the 20th century, environmental exposure to artificial electromagnetic fields has steadily increased due to the increasing number of artificial sources being produced because of the rising electricity demand, changes in social behaviour, and ever-advancing technologies. From the generation and transmission of electricity, industrial equipment and personal appliances to broadcasting and telecommunications, everybody is exposed to a complex mix of weak electric and magnetic fields, both at work and home.

Even in the absence of external electric fields, tiny electrical currents exist in the human body due to chemical reactions in regular bodily functions. Nerves, for example, relay signals by transmitting electric impulses. The rearrangement of charged particles is involved in almost all biochemical reactions, from brain activity to digestion. The heart is also electrically active, which your doctor can monitor with an electrocardiogram.

Low-frequency electric fields have the same effect on the human body as they do on any other material made up of charged particles. The distribution of electric charges at the surface of conductive materials is influenced by electric fields acting on them. They make current flow through the body and down to the ground.

Within the human body, low-frequency magnetic fields cause circulation currents. The external magnetic field’s intensity determines the strength of these currents. These currents, if large enough, might stimulate muscles, nerves or impact other biological processes.

Electric and magnetic fields cause currents and voltages in the body. Still, even directly beneath a high voltage transmission line, the generated currents are tiny compared to thresholds for causing shock and other electrical effects.

The main biological effect of the electromagnetic fields of radiofrequency fields is heating. This attribute is used to warm up food in microwave ovens. People are typically exposed to far lower levels of radiofrequency fields than are required to cause significant heating. The key reason for existing guidelines is the heating effect of radio waves. Also, the possibility that effects below the threshold level for body heating occur due to long-term exposure is being examined by scientists. As of now, there have been no confirmed harmful health effects from low level, long-term exposure to radiofrequency or power frequency fields. However, scientists are continuing to investigate this area.

Source: WHO – Radiation: Electromagnetic fields