1 Samuel Terhemba Kungur
2 Terseer Terrumun Humbe
Department of Physics
College of Education Katsina-Ala
Man is exposed to high levels of electromagnetic radiation due to technological advancement. The effects of the electromagnetic radiation (EMR) on human health are among the most significant concerns in the world. These effects are classified into two main categories: ionizing and non-ionizing radiation. The ionizing radiation has the ability to knock off molecules from cells and lead to a change in their natural status and is therefore dangerous to humans, since exposure to it can lead to cancer and other diseases. On the other hand, non-ionizing radiation cannot change atomic structure. They just impact on tissues and can lead to irreparable hurts. This paper takes a review on the electromagnetic spectrum and the impact of the electromagnetic radiation it produces as it affects human health. It reviews the sources, effects and safety guidelines to the use of electromagnetic radiation.
In recent times, many people have shown concern and expressed interest in learning whether the use of cell phones is associated with the risk of cancer and other ailments. Many have heard or read about possible links between cell phones and cancer, but conclusions are rarely definitive. As a matter of fact, engineers in the areas of Radio Frequency are usually faced with the following questions:
- What are the effects of radio waves on the health of humans?
- What health risks are associated with the use of cell phones, mobile radios, microwave ovens, broadcast radio and television transmitters, power lines and X-rays/gamma rays?
With the aforementioned, this paper seeks to answer these questions, as well as developing a basic understanding of electromagnetic radiation (EMR).
What is electromagnetic radiation (EMR)
Electromagnetic radiation is a term used to describe different kinds of energies released into space by stars such as the sun. These kinds of energies include; Radio waves, TV waves, heat (infrared radiation), ultraviolet light, X-rays, short waves, microwaves, Gamma rays (Liebel, Kaur, Ruvolo, Kollias & Southall, 2012).
Electromagnetic frequency spectrum
The electromagnetic spectrum is the collective term used for all known frequencies and their linked wavelengths of the known photons (electromagnetic radiation). Through this spectrum, wireless communication links have been used worldwide for many years, as solution for connectivity in point – to – point and point – to – multipoint applications. The most common wireless solutions include AM and FM radio, television broadcast stations, mobile and cellular phones, radar and microwave systems
The electromagnetic (EM) spectrum contains an array of electromagnetic waves increasing in frequency from extremely low frequency and very low frequency (ELF/VLF), through Radio Frequency (RF) and microwaves, to infrared (IR) light, visible light, ultraviolet (UV) light, X-rays and Gamma rays.
Below is a pictorial representation of the spectrum of electromagnetic radiation in ascending frequency or decreasing wavelength.
Fig1: A spectrum of electromagnetic radiation in ascending frequency or decreasing wavelenght: Source; Grupen, Cowan, Eidelman and Stroh (2005).
This is radiation that carries enough energy to free electrons from atoms or molecules, thereby ionizing them, i.e, it contains enough/sufficient electromagnetic energy to strip atoms and molecules from the tissue and alter chemical reactions in the body converting molecules totally or partially into ions. Gamma rays, X-rays and the higher ultraviolet part of the electromagnetic spectrum are examples of ionizing radiation. They are known to cause damage to tissues (Grupen, Cowan, Eidelman and Stroh, 2005).
Human beings are constantly exposed to low levels of ionizing radiation from natural sources, which are usually referred to as background radiation.
Non – Ionizing Radiation
Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules – that is, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, the electromagnetic radiation has sufficient energy only for excitation.
Non-ionizing radiation can be found in the lower part of the spectrum.
Examples of non-ionizing radiations are:
- Static electromagnetic fields
- Low-frequency waves from electric power
- Extremely low frequency (ELF) and very low frequency (VLF) fields
- Radio frequencies (RF)
- Microwaves (MW)
- Ultraviolet (UV) light
All the aforementioned generate some heating effect, though not enough to cause severe damage to human tissue, although it is possible that higher power densities, such as those very near high-voltage power lines or high-power broadcast transmitters could have long term health effects.
Nowadays, some studies suggest that potential health hazards could be linked to exposure to high-power densities of non-ionizing radiation since more and more people now use mobile or cell phones. These health hazards include cancer, tumors, headaches, fatigue and Parkinson disease (Little, Rajaraman, Curtis and Devesa, 2012).
Extremely low frequency (ELF) and very low frequency (VLF) Radiation
Everyone is exposed to a complex mix of electromagnetic fields (EMF) of different frequencies that permeate our environment. Exposures to many EMF frequencies are increasing significantly as technology advances unabated and new applications are found. While the enormous benefits of using electricity in everyday life and health care are unquestioned, during the past 20 years the general public has become increasingly concerned about potential adverse health effects of exposure to electric and magnetic field at extremely low frequency (ELF) which arises mainly from the transmission and use of electrical energy (Coe, 2006).
Furthermore, very Low Frequency (VLF) is the designation for radio frequencies (RF) in the range of 3kHz to 30kHz and corresponding wavelength from 100 meters to 10 kilometers, respectively. Due to its limited bandwidth, audio transmission is highly impractical, and therefore, only low data rate coded signals are used. The VLF band is used for secure military communication, government time radio stations etc (Gosh, 2002).
EMR in the ELF and VLF range is both naturally occurring and man-made. Naturally occurring EMR includes a background electromagnetic field created by the earth as well as additional EMR created by thunderstorms, solar and cosmic activity in the atmosphere (Horton and Goldberg, 1995).
Exposure to man-made ELF/VLF occurs primarily due to the generation, transmission and use of electrical energy. Electromagnetic fields are created whenever electricity passes through a conductor. Here, two fields are created; an electric field and a magnetic field. The strength of the electric field depends on the voltage being used, while that of the magnetic field depends on the amount of current being carried. Hence, electromagnetic fields are being created by a variety of electrical household appliances like refrigerators, hair dryers, computers and pressing irons.
In the event of being close to these appliances, the level of electromagnetic fields created are often far greater than those produced by transmission lines. However, the appliances only create electromagnetic fields when in use, whereas transmission lines electromagnetic fields are continuous. While these man – made ELF/VLF fields may cause biological effects, the adverse effects on human health are being contested.
Power line effects from electricity
Electromagnetic fields emitted by power lines have long been a topic of discussion in the power industry and other associated areas. Conflicting studies and reports are published on a yearly basis. While it is easy to shield against electric field generated by nearby power lines, it is much more difficult to shield against the magnetic fields they generate. This can best be shielded by burying power transmission lines, but at a higher cost (Greenland, Kaune, Poole and Kelsh, 2000).
Several experiments, laboratory studies, simulations using phantoms and others have been conducted to determine the relationship between exposure to electromagnetic fields and a number of disorders. Numerous reports have been presented providing information of adverse health, while others fail to correlate. As of recent, the National Cancer Institute has released major studies finding no evidence of link between electromagnetic fields and cancer. These studies suggest that power lines are much less likely to cause cancer than was previously suspected (Hans, Ulrich and Pierre, 2009).
Radio frequency radiation
As seen on the frequency spectrum, radio frequency (RF) energy is often referred to as radio waves, RF radiation or RF emissions. RF energy constitutes all frequencies between 30 kHz and 300 GHz (Semat and Albright, 1979).
As regards to human health, the biological effects of RF energy are usually proportional to the rate of the absorbed energy which varies little with frequency. This shows that RF energy has the ability to heat up human tissue, and can be hazardous, if the exposure is prolonged and sustained. Injuries that can be possibly gotten from this long and sustained heating include skin burns, deep burns, heat exhaustion and heat stroke.
Radio broadcasting is a unidirectional wireless transmission of radio waves intended to reach a wide audience; stations can be linked in radio networks to broadcast a common radio format. Audio broadcasting also can be done via cable radio, local television networks, satellite radio and internet radio via streaming media on the internet (Guamieri, 2012).
Commercial AM/FM radio and TV broadcast stations transmit very high levels of RF energy radiating sometimes power levels of several megawatts from their antennas. Fortunately, these antennas are generally placed on high towers / buildings where human activity is not rampant. However, human beings absorb more RF energy from AM/FM radios and TV broadcast station antennas than from mobile telephone, hence research has shown that there is a risk of leukemia and other skin diseases for people that live near broadcast stations.
Cellular phones, cordless phones and hand-held radios
Cellular phones are also called mobile telephones. Most cellular and cordless telephones have a small antenna in-built into the body of the phone. Because the antenna of a cellular phone is close to the users head, it creates greater RF exposure than other similar devices.
Other cordless devices have similar effects. The effect of mobile phone radiation on human health is the subject of recent interest and study, as a result of the enormous increase in cellular/mobile phone usage throughout the world. A large body of research exists, both epidemiologically and experimentally. The majority of this research shows that there is no definite causative relationship between exposure to mobile phones and harmful biological effects in human (Bhattacharjee, 2012)
Concerns Regarding Radio Frequency (RF)
The quantity used to measure how much RF energy is actually absorbed in a body is called the Specific Absorption Rate (SAR). In case of whole – body exposure, a standing human adult can absorb RF energy at a maximum rate when the frequency of the RF radiation is in the range of about 80kHZ and 100 MHz, meaning that the whole body SAR is at a maximum under these conditions (Christensen, Schulz, kosteljanetz, Poulsen, Thomsen and Johansen, 2004).
In general, however, studies have shown that environmental levels of RF energy routinely encountered by the general public are typically far below levels necessary to produce significant heating and increased body temperature. However, there may be situations, particularly workplace environments near high – powered RF sources, where recommended limits for safe exposure of human beings to RF energy could be exceeded. In such cases, restrictive measures or actions may be necessary to ensure the safe use of RF energy. Some studies have also examined the possibility of a link between RF and microwave exposure and cancer. Results to date have been inconclusive. While some experimental data have suggested a possible link between exposure and common formation in animals exposed under certain specific conditions, the results have not been independently replicated. In fact, other studies have failed to find evidence for a casual link to cancer or any related condition.
In 1996, the World Health Organization (WHO) established a program called the International EMF Project designed to review the scientific literature concerning biological effects of electromagnetic fields, identify gaps in knowledge about such effects, recommend research needs and work towards international resolution of health concerns over the use of RF technology.
Various organizations and countries have developed exposure standards for RF energy. These standards recommend safe levels of exposure for both the general public and for workers. In the United States, the Federal Communications Commission (FCC) has adopted and used recognized safety guidelines for evaluating RF environmental exposure since 1985. In Nigeria, the Nigerian Communication Commission (NCC) has the mandate to monitor all significant matters relating to the performance of all licensed telecom service providers.
Magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used to form pictures of the anatomy and the physiological processes of the body in both health and disease. MRI scanners use strong magnetic fields, radio waves and field gradients to generate images of the inside of the body (Hollingsworth, Todd and Bell, 2000).
MRIs use a powerful magnet to produce magnetic fields that are stronger than those produced by the earth. A small percentage of hydrogen atoms within a human body will align with the static magnetic field. When focused, radio wave pulses are transmitted toward the aligned hydrogen atoms in tissues of interest where they result in a weak signal. These signals are created through the reception and analyzed/reconstructed into tissues and organs. Even though power is deposited into the patient, no side effects are usually experienced since MRI does not utilize ionizing radiation.
However, certain hazards of improperly applied MRI therapy usually exist and can cause severe injuries/or even death.
Ultraviolet, visible and infrared light
The sources that constitute optical radiation exposure include sunlight, heat lamps, lasers, other incandescent sources etc. When optical radiation is intense, it causes electron excitation which means electrons in tissues near the body surface can absorb energy from intense optical sources causing heating and even burns.
Radiation from optical sources is not very penetrating, therefore the eye and the skin are the organs of greatest concern. It could cause injury to the retina as well as skin redness and sunburns. Delayed effects include cataract formation, retinal degeneration, accelerated aging and skin cancer.
Effects of infrared (IF) and ultraviolet (UV) radiations
Infrared (IR) radiation is of longer wavelength than the visible high frequencies and is perceptible as heat. This is radiation that is typically emitted by heat lamps, molten metal or glass, embers from the fire place and other hot objects.
Some studies have shown that prolonged exposure causes a gradual but irreversible opacity of the lens. But if applied in moderation, has no damaging effect on human health (Chung and Eun, 2007).
On the other hand, ultraviolet radiation is photochemical, which to a lesser degree is with visible light. All humans are exposed to this kind of radiation which is contained in sunlight.
Some amount of UV radiation is very beneficial for people and essential in the production of vitamin D. UV radiation is also used to treat several diseases including rickets, psoriasis, eczema and jaundice (Chung and Eun, 2007). This takes place under medical supervision and the benefits of treatment versus the risk of UV radiation exposure are a matter of clinical judgment. It is also used in the process of photosynthesis in plants. However, prolonged human exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye and immune system. Sunburn is the best known acute effect of excessive UV radiation exposure. Over the longer term, UV radiation induces degenerative changes in cells of the skin, fibrous tissue and blood vessels leading to premature skin aging.
X-rays and Computed Tomography (CT) Scan
X-rays have sufficient energy to break down chemical bonds in living tissue due to their frequency of interaction. A CT scan is a sophisticated type of X-ray that makes use of computer-processed combinations of many X-ray images taken from different angles to produce cross-sectional images of specific areas of scanned object, allowing the user to see inside the object without cutting. Whole – body scans require higher doses of the X-radiation to make CT scan images. As with the case of other ionizing radiation, X- rays over long term usage have the ability to modify genetic cells and cause mutation leading to cancer (Herman, 2009).
It is important to note that the amount of X-ray radiation used in most medical diagnostic procedures is so small that the risk is extremely small. It is pertinent to note that, it is always safe to assume that the same kind of effect that occurs at high doses of X-radiation could occur at low doses and therefore, exposure to X-rays should be avoided as much as possible.
Gamma radiation (Gamma rays)
Gamma rays are found beyond X-rays in the electromagnetic spectrum (fig.1). They are penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. They are able to ionize other atoms and are thus biologically hazardous. Natural sources of gamma rays are observed in the gamma decay of radionuclide’s and from atmospheric interaction with cosmic ray particles.
Gamma rays even though hazardous are used sometimes to treat cancerous tumours in the body by damaging the DNA of the tumour cells. However, care must be taken because these rays can damage the DNA of surrounding healthy tissues. One way to maximize the dosage to cancer cells while minimizing the exposure to healthy tissues is to direct multiple gamma ray beams from a linac on to the target organ/region from many different directions. This is the operating principle of the cyber knife (Annunziata, 2007).
Guidelines to Safety
Many countries of the world including the USA and Nigeria require that all equipment emitting electromagnetic radiation comply with exposure guidelines. These guidelines are designed and streamlined to protect both occupational workers and the general public, to the highest sense of safety. These limits have been endorsed by agencies such as Federal Ministry of Health, NAFDAC, Environmental Protection Agency, NNRA etc.
Studies have shown that workers exposed to strong electric and magnetic fields from power lines provide no consistent evidence that they are damaging to DNA or capable of causing mutation and cancer. Also, the most apparent biological effect of RF energy to body cells is heating. However, there are concerns regarding radiation from antennas of mobile/cellular phones. The concerns exist because these cellular phones contain antennas which deliver most of the RF energy to small portions of the user’s brain/head. It is pertinent to note here that exposure to typical levels of RF and EMF radiation may not be completely safe at certain levels and frequencies and thus it is good to avoid unnecessary exposure to radiation whenever possible.
Finally, exposure to X-rays and gamma rays is a source of serious biological damage and should therefore be avoided, unless medically recommended.
This review has provided a basis for public health action and assists to reduce the morbidity and mortality from cancer and other ailments and to improve the quality of life of patients and their families, anywhere in the world.
Based on the foregoing, the following suggestions are made;
- The level of radiation in the environment should always be monitored/measured on a regular basis to sensitize and inform the general public on its probable risks.
- There should be regulatory enforcement by agencies of government.
- Put distance between you and radiation source thus limiting your lifetime dose.
- Human beings should shield themselves from radiation.
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