Could it really be? Are all those upwardly mobile people who walk around with mobile phones stuck to their ears destined for an early grave due to cancer or brain damage? There have been many papers and journals written on this very topic, studying the biological effects of electromagnetic radiation, which is emitted by cellular hand-held transceivers. Specifically, these papers have investigated the effect of electromagnetic radiation on the areas of the human body which are exposed to the cellular phone when it is being used ie: the head, ear, eye and hand.
This article will describe the biological effects that Electromagnetic (EM) radiation (Electromagnetic spectrum shown below) may have. Ways of measuring radiation emission levels to the head will also be described including a way of modeling the human head for this purpose. This information can then be used to assess the real danger posed by the future usage of cellular communication for digital data and voice transmission.
General Biological Effects of Radiation
When ionizing radiation interacts with cells in the human body, the following events may occur:
The effects of radiation exposure can take effect either soon after the exposure or after a long delay (up 15-20 years in cases).
Biological effects of Electromagnetic Radiation
Exposure to electromagnetic fields results in the induction of electrical fields in biological tissues of the body. One of the most commonly visible effects of electric fields is the movement of body hair when a charged object is passed across it. A simple example being a charged comb which is passed over body hair.
The electric fields that are induced, may cause changes in psychological responses such as changes in complex reasoning and arousal of the human being. These effects may occur at levels of EM radiation present in the proximity of overhead power lines which are a very common site all over the UK. It has been shown experimentally that other physiological, psychological and behavioural effects do occur at certain conditions ie: certain magnitudes of electric and magnetic fields. These include the following:
Changes in this hormone level have been associated with causing cancer and so this is a very significant result. It isnt really clear if this gives conclusive evidence as to the danger of EM radiation when applied to cellular transceivers because usage of cellular transceivers would not give such a chronic level of exposure to a human being. Also very recent studies have not always observed these effects hence doubting the conclusion first made.
One of the more publicised effects of EM radiation has been the effect on reproduction in humans. This publicity first began when experiments on chick embryos showed that exposure to weak magnetic fields caused deformity in resulting new born chicks. Although the results of this experiment seem very ambiguous and the fact that the experiments were carried out on chicks and not mammals, which would have been more relevant to humans, the effects were publicised due to the controversial nature of the implications. It is concievable, though, that with intense exposure to fields, human reproduction may experience some behavioural deficiencies as well as some retardation in development. But this is at a very intense source of EM radiation, far in excess of any fields emitted from cellular transceivers or from any other everyday machinery ie: microwave ovens etc.
Another majorly publicised affect is that of the inducement of cancers. As explained above, depression of melatonin production has been related to causing cancer, but only at excessive levels of EM fields. There have been no conclusive results to prove any relationship between exposure to EM fields and cancer.
Measurement of Electromagnetic Radiation effects
If the future of data communications becomes more and more mobile orientated hence using cellular technology to a far greater extent than currently, then users of the system will not only utilise the data communciation facilities but also the voice communication facilities that are so common nowadays. This implies that exposure to EM radiation will be more intense in the vicinity of the head. So it is very useful to try to model the human head and measure the amount of radiation that would be absorbed by the head when a cellular transceiver is being used for voice communication (ie: as a mobile phone).
Modelling the human head
The human head can be modelled using the "phantom" model. This is a fibreglass shell filled with a liquid having the same dielectric as human brain tissue. The magnitude of EM fields can then be measured at specific points and depths in the modelled human skull when a cellular transceiever is placed in a close proximity ie: In these experiments a cellular phone was used in a regular position, by the ear.
There are problems with this model. The skin surrounding the skull, the facial muscles, eye chamber and the ears are not easily represented by the phantom model. In order to simulate this, extra simulated brain and muscle tissue needs to be used with the fibreglass model. Fatty tissue is approximated by using the same liquid as for brain tissue. This results in a higher measured value of radiation absorbed by the brain than the actual value. This is acceptable in these situations where safety levels of radiation emission are calculated and so the worst case level will be measured. The measurements are shown for a single unit cellular phone as an example. The measurements are given in Specific Absorption Rate explained below.
Quantification of Radiation absorption.
A widely adopted measurement of radiation absorption is the Specific Absorption Rate (SAR). This is defined as the derivative of energy divided by mass ie: dW/dm. It is measured in Watts per kilogram (W/kg).
Using the example of two types of cellular transcievers, a one unit phone and a flip phone, the diagrams below show the SAR distribution across the simulated tissue of a phantom model, when the phone is being used. This shows that the exposure of the face is well spread across the area of the phone and peaks of SAR occur at few points. This is advantageous as it implies that there are no major concentrations of field intensity on the head. As it has been explained above, intense concentration of EM fields may have dangerous implications.
The experiments have shown that the area of the head which is exposed to the largest SAR value of fields is the area shaded in the diagram below. This area contains the phone display and touch tone pad on the phone unit. The National Council for Radiation Protection and Measurements (NCRP) use SAR values to specify the maximum safe limits of radiation allowed to be emitted from cellular transceivers.
There have been many studies of the the biological effects of EM radiation, many of these have been inconclusive. Using the research available, the following observations can be made:
In conclusion, the effects of EM radiation are only a threat if the dosage of radiation is very high. In the case of cellular transceivers, the dose is not very high. Most of the latest studies that have been done on the subject, have returned inconclusive results and so it is impossible to give a definite answer to the question of whether cellular communications are bad for your health.
Further research is always being carried out, with phone companies eager to invest in research so as to ease their consumer's fears. Many companies are taking advantage of the public's fear by selling products such as shielding cases which enclose the cellular tranceiver and shield the user from the majority of EM radiation emitted by the phone. These tend to decrease the reception capability of the phone units.
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