THIS weekâ€™s column looks at Electromagnetic fields, what they are and how they affect human life on a day to day basis.
Electromagnetic fields (EMF) consist of magnetic and electrical fields interacting together. At low frequency, magnetic fields are predominant. EMF occurs naturally and may also be produced intentionally. EMF can broadly be divided into static and low-frequency electric and magnetic fields, where the common sources include power lines, household electrical appliances and computers, and high frequency or radiofrequency fields, for which the main sources are radar, radio and television transmitters, mobile base stations and handsets, induction heaters and anti-theft devices.
EMF on the human body
Most biochemical reactions, from those associated with digestion to those involved in brain activity, involve electrical processes. The effects of external exposure to EMF on the human body and its cells depend mainly on the EMF frequency and magnitude or strength. The frequency simply describes the number of oscillations or cycles per second.
At low frequencies, EMF passes through the body while at radio frequencies the fields are partially absorbed and penetrate only a short depth into the tissue. Low-frequency electric fields influence the distribution of electric charges at the surface of conducting tissues and cause electric current to flow in the body. Low-frequency magnetic fields induce circulating currents within the human body. The strength of these induced currents depends on the intensity of the outside magnetic field and the size of the loop through which the current flows. When sufficiently large, these currents can cause stimulation of nerves and muscles.
At radiofrequencies (RF), the fields only penetrate a short distance into the body. The energy of these fields is absorbed and transformed into the movement of molecules. Friction between rapidly moving molecules results in a temperature rise. This effect is used in domestic applications such as warming food in microwave ovens, and in many industrial applications such as plastic welding or metal heating.
The levels of RF fields to which people are normally exposed in our living environment are much lower than those needed to produce significant heating. Prolonged environmental exposure, even if minor, may constitute a health hazard if it results in stress. In humans, an adverse health effect results from a biological effect that causes detectable impairment in the health or wellbeing of exposed individuals.
An increasingly alarmed army of international scientists have reached a controversial conclusion: The â€œelectrosmogâ€ that first began developing with the rollout of the electrical grid a century ago and now envelops every inhabitant of Earth is responsible for many of the diseases that impair or kill them. During the past 100 years, we have methodically filled in the electromagnetic spectrum far beyond what occurs in nature. Recently, several developments have highlighted the growing hazards of EMF pollution and the crucial need to address them.
Dealing With EMF in Zambia
The 2009/2010 EMF survey conducted in Zambia by ZICTA on mobile base stations, radio and TV transmitters indicated that emission levels from these installations are below the recommended safe values.
ZICTA adopted the safe values recommended by the International Commission for Non Ionizing Radiation Protection (ICNIRP).Â Â Through necessary guidelines and measurement methodologies, ZICTA will ensure that operators comply with the National Human Exposure Limits.
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