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BLOG: February 2009
Electromagnetic spectrum: health connection
Radio-waves, microwaves, extremely low frequencies including 50/60Hz standard electricity waves, AM, FM, light, X-rays - they all belong to the form of energy that we generally call radiation. More specifically, electromagnetic radiation. It comes in the wide range of frequencies, called electromagnetic spectrum.
This form of energy is created at the atomic level, as electrons release energy while switching from higher- to lower-energy orbits, or while freeing themselves from atomic bonds. This movement of electrons results from the need to maintain energy balance within the atom under the input of some form of external energy.
Energy released by electrons propagates just like a wave sent along loose cord. A complete cycle, starting from the neutral point, through the top and bottom swing (i.e. amplitude) and back to the neutral level, makes a single wave oscillation. Number of oscillations per second is the frequency, and the length between these two points is the wavelength of electromagnetic wave.
Since this energy moves at a constant speed - the speed of light - the product of wavelength and frequency equals the distance traveled by light in a second.
The unit of energy released by electrons is called photon; it is proportional to the frequency, making higher-frequency fields as much more intense for given flux density (i.e. number of photons).
Thus, the radiated energy is defined by its frequency (of oscillation) or its wavelength. Since this energy comprises two distinctive forms, namely electric and magnetic force, the unit form of radiated energy is called electromagnetic wave, and its spatial expansion is electromagnetic field.
All forms of the man-made electromagnetic radiation - electrical fields, radio waves, TV, radars, cell phones, security (screening), medical/diagnostic - are created by manipulating atoms into releasing electromagnetic radiation. As such, it is a part of electromagnetic spectrum, which encompasses the entire range of electromagnetic radiation, from its lowest to its highest frequencies - or, correspondingly, from its longest to its shortest wavelengths. The EM spectrum is, somewhat arbitrarily, divided into a number of sub-ranges.
Following table shows the electromagnetic spectrum, with some of the main sources of electromagnetic pollution.
Hz=Hertz=1 cycle per second;
1,000Hz=1kHz (kilohertz, 103Hz),
Specific division of the electromagnetic spectrum vary from one source to another. For instance, the World Health Organization (WHO) limits "radio-frequency" to 10MHz-300GHz range, with 10MHz-300Hz frequencies being called "intermediate", and those below 300Hz "extremely low frequencies" (ELF). Microwave range, form 300MHz to 300GHz (1m to 1mm wavelength range) is often presented as an independent range. Some sources present the lower portion of infrared, from 300GHz to 10THz (terahertz, 1,000MHz) as a separate range - terahertz - and so on.
The most accurate division of electromagnetic spectrum, used by the industry, divides it into 20 sub-ranges within the 3Hz-300EHz span, starting at 3Hz frequency, with every next sub-range starting at ten times higher frequency that the previous.
ELF-extremely low frequencies, SLF-super low, VF-voice, LF-low, MF-medium, HF-high, VHF-very high, UHF- ultra high, SHF-super high, EHF-extremely high, FIR, NIR, MIR - far, mid and near infrared, NUV, MUV, EUV - near, mid and extreme ultraviolet, SX-soft X-ray, HX-hard X-ray, Y- gamma rays; THz=terahertz, PHz=petahertz, EHz=exahertz, Mm=megameter, μm=micrometer, nm=nanometer, pm=picometer
The most general division within the electromagnetic spectrum is based on the radiation energy level. High energy radiation - in excess of 10eV - can strip electrons from atoms, and break molecules and molecular bonds. Since this produces charged particles - ions - it is called ionizing radiation. Most of ultraviolet (UV), as well as X-rays and Gamma-rays are ionizing radiation.
There is no disagreement about ionizing radiation being capable of inflicting damage to life at exposure levels significantly below those causing even mildest direct sensory effects. Segment of the population exposed to this type of radiation is small - it mainly limits to occupational exposures and medical diagnostic field - but the harm it inflicts is far from negligible (see CAT scan cancer risk).
Non-ionizing radiation, ranging from the lowest outskirts of ultraviolet, through visual and infrared to radio frequencies, does not have the intensity needed to directly damage biological tissues but, if sufficiently strong at frequencies over 100kHz, can significantly raise body temperature (thermal effect, the primary acute effect at frequencies higher than 10MHz), or induce currents causing neurological effects at frequencies below 100kHz. Since the common exposure levels are much lower than those needed to cause these immediate effects, this ever present form of radiation created by man has been, for decades, assumed to be benign.
However, a number of studies implicate that non-ionizing radiation does have the capability of causing disturbances at the cellular level,
resulting in either near-instantaneous
It is uncertain how exactly and at what frequencies and intensities much lower levels of non-ionizing radiation than those needed to produce thermal or neurological effects can adversely affect health, but the evidence is both ample and very suggestive that it is taking place.
Visual electromagnetic frequencies are only a tiny window within electromagnetic spectrum, spanning 0.0003mm of the wavelength range, from 0.0004 to 0.0007mm (but with the range of frequencies greater than both, infrared and radio frequencies combined). Infrared wavelengths extend from 0.0007mm to 1mm; longer wavelengths belong to the radio frequency range, which has by far the widest span of wavelengths, ranging from 1mm to over 100,000km.
Due to the many uses of radio waves, this range has a number of frequency sub-divisions. The high-frequency radio range, between (approximately) 300MHz and 300GHz (corresponding to 1m to 1mm wavelength, respectively), is generally known as microwave radiation. Among others, it incorporates HF (high-frequency, such as ultrasound), VHF (very high frequency), UHF (ultra-high frequencies) and SHF (super-high frequencies). These waves are used for anything from radio (FM, or "frequency modulated") and TV broadcasting to cell phones, radars and microwave ovens.
Part of the narrow mid-frequency radio range is used for AM ("amplitude modulated") radio broadcast.
Low-frequency radio waves, below 300kHz include audible sound (approximately 20Hz to 20kHz). Super low (below 300Hz) and extremely low frequencies (below 30Hz) is where most of the standard electricity waves are emitted (regular electric power operates at the 50-60Hz frequency).
At the very bottom of electromagnetic frequencies is bioelectricity, ranging normally from about 1 to 100Hz. For instance, electromagnetic waves accompanying normal human brain activity range from below 1Hz (deep sleep) to 31Hz (highly alert).
Evidently, the variety of man-made electromagnetic fields share common nature with bioelectricity: both are a part of electromagnetic spectrum, merely different forms of what is generally called energy field. It is a scientific fact that energy fields do interfere; also, that human cells have the capability to detect extremely weak fields,
and react to them.
Hence, the question is not whether man-made electromagnetic fields, at any frequency or intensity level, affect functioning of the human body, but rather how.
The official medical and governmental stance is that there is no sufficient evidence proving that low-level EMF exposure causes adverse health effects. But growing segment of environmentally conscious population, as well as independent scientists and researchers think we have more than enough evidence to justify preventive protective action. Their call for action is increasingly difficult to ignore.
Who is right, and who is wrong?
We can only find out if we know the facts. Here they come. Before that, a few more words about the most widespread EMF pollutant - the standard electricity, and how it can affect health.