AN INVESTIGATION INTO THE HAZARDS OF TRAVELLING (ELECTRO)MAGNETIC WAVES AND SOUND WAVES ON HUMAN HEALTH

AN INVESTIGATION INTO THE HAZARDS OF TRAVELLING (ELECTRO) MAGNETIC WAVES AND SOUND WAVES ON HUMAN HEALTH

                                         EDITOR: B. Somanathan Nair

Email: profbsnair@gmail.com

Abstract: A current topic of active discussion is on the hazards of microwave radiation from mobile towers and phones. Several experts have argued that microwave radiation is highly dangerous to man and animals. But so far, nobody has given any solid proof confirming this theory. In this paper, we intend to prove that microwave radiation from mobile towers and phones in current use is not dangerous. To prove the conditions under which travelling waves in general and microwaves in particular become dangerous, we make use of three basic laws.  The proof is consolidated through computer simulations using COSMOL MULTIPHYSICS software, whose human brain model is used for simulation. We also intend to prove that microwave radiation (and for that matter, radiation of any type) in concentrated form is highly dangerous.

1.     INTRODUCTION

      Currently there exists a widespread propaganda, belief, or myth that microwave radiation is dangerous to human and animal health. Some people argue that it is true; some others argue that it is false. But so far nobody has been able to give any solid proof on the fact that microwaves are really dangerous. In this paper, we make a detailed study about the conditions under which travelling waves, such as (electro)magnetic waves, sound waves, and water waves, which hit human bodies can become hazardous. It may be noted that the concern about the waves arises from the fact that all these waves, except water waves, hit all the living and non-living things continuously without any break throughout every day; water waves hit only those entities that are in touch with it.

2. Conditions UNDER WHICH WaveS BECOME Hazardous

      What are the conditions under which a travelling wave becomes hazardous to human and animal health? To answer this question, we first propose the following three laws:

1.      The wave-particle interaction law

2.      The high-power wave law

3.      The concentrated-power law

We shall now make use of these three laws to find out the conditions under which a travelling wave becomes hazardous to health.

1. The Wave-Particle Interaction Law

This law states that a travelling wave will interact and strike only those objects whose physical dimensions are comparable to or larger than its own size (expressed in terms of its wavelength); it will not interact with objects much smaller in size than its wavelength.

Proof: Law 1 can be proved easily by considering the interaction between sea waves and objects of different sizes existing on the sea shore. Assume that a typical sea wave is moving towards shore. Assume also that there exists a huge rock on that shore. We notice that, as soon as the wave approaches the shore, it strikes the rock with huge force provided that its wavelength λ is comparable to the width w of the rock (here we have chosen the width of the rock as its dimension under the assumption that the wave is striking across its width). This action is illustrated in Fig. 1. Since the rock is a naturally existing object on earth and firmly rooted to it, the sea wave will not harm it. However, in the place of the rock, if we have a rock wall constructed, then the high-power sea waves may destructively strike it. In this discussion, the important point to be noted is that the sea wave will strike or hit objects of size comparable to its wavelength.

      Next, consider Fig. 2, which shows a small sand particle lying in the path of the same sea wave. It can be seen that the wave will not hit or strike the particle, as its wavelength is much larger than the size of the particle. Instead of interacting destructively with the particle, the wave will rather ride over it. In this process, the particle will not get destroyed at all by the wave. However, the wave may push and pull the particle so that it moves slightly forward or reverse from its initial location. It can be seen that the arguments given here prove Law 1.

 

2. The High-Power Wave Law

This law states that high-power travelling waves are dangerous to human and animal health, which in turn suggests that low-power travelling waves are not that dangerous. 

Proof: Law 2 can be proved by using the example of sound produced by the loudspeakers (LS) of public-address (PA) systems. It is found that modern music bands employ PA systems that produce audio output power of 10,000 watts or more. To compute the amount of acoustic power spreading into the space surrounding the LS, we make use of the formula P_R = P_T/4πr², where P_R is the power received at r meters away from LS and P_T is the acoustic power generated and radiated by it.

      To quantify the process, let us assume that P_T = 10,000 watts. Then, using the formula given above, we find that P_R at 1 meter away from the LS is approximately 80 milliwatts/cm². However, in majority of the cases, LS used are highly directive so that most of the 10,000 watts of sound power hits the human body as such (see Law 3). This power can be seen to be much above the power that an average human body can bear!

     A second aspect to be considered here is regarding the danger of sound power hitting human ears. The minimum acoustic power that a normal human ear can sense¹ is approximately10 nW/cm². Experiments have proved that audio power that can produce severe pain in human ears is about 120 dB above this basic level. Conversion from dB to W shows that 120 dB above 10 nW/cm² is equivalent to 10,000 W/cm². If this huge amount of acoustic power hits a human ear, then there will be no doubt about the final result!

     The two examples cited above prove Law 2. It may be noted in this context that majority of the general public are unaware of the dangers hidden in high-power sound; in fact they are least bothered about them.

3.  The Concentrated-Power Law

This law states that any wave travelling in concentrated form is highly dangerous to the health of living bodies; this also suggests that waves that travel in wide-spread form is not that dangerous.

Proof: Law 3 can be proved by using a couple of very simple examples. First, consider the case of solar power (see Section 3 also) falling on earth. Everybody knows that if this solar power is focused on to a human body using a simple convex lens, it produces tremendous amount of heat, which can lead to the burning of the focused part of the body. However, if the sunlight falls on a human body in unfocussed form, normally it will not harm it; in fact, we really need direct exposure to sun for short durations to get some vitamins!

      To illustrate further, consider the situation in which the optical output from a low-power laser is applied directly onto a human eye. Let the power output of the laser be in microwatts. We find that when this low-power concentrated form of light falls on the human eye, the lens of the eye focuses it onto the retina, which produces further concentration of the laser power onto a very small spot on it. It can be seen that the power density at the focused point will be extremely high so that the retina gets destroyed if the focusing time is on the order of a few seconds. However, it may also be noted that laser power of less than a few milliwatts directed without focusing on to the human skin may not be dangerous.

      We now make use of the three laws stated above to investigate into the truths and myths associated with travelling waves in general and microwaves in particular.

3. Dangers of Radiation from Sun

      Sun is the most natural source that emits extremely large amount of electromagnetic waves lying in the range of 1 millimeter to 0.1 micrometer towards earth. Of these, waves from 1 millimeter to 0.7 micrometer are infrared (IR) waves, those from 0.7 micrometer to 0.4 micrometer are visible light waves, and those from 0.4 micrometer to 0.1 micrometer are ultraviolet (UV) waves².

Let us first consider the case of UV radiation from the sun. Assume that a human cell³ of size 2 micrometers is subjected to UV radiation of wavelength λ = 0.3 micrometer. Comparing their sizes, we notice that the size of the human cell is much larger than the wavelength of the UV radiation. Then according to Law 1, the UV radiation will definitely attack and destroy the human cell, which means that UV radiations are highly dangerous to human health, regardless of its power content.

      International regulatory bodies have laid down the condition that UV radiations of power equal to or greater than 1 mW/cm² are extremely dangerous^4,5,6. This restriction does not mean that UV radiations of power less than 1 mW/cm² are not dangerous. Longtime exposure to such low-power UV radiations can definitely cause health hazards such as cancer.

      We have thus seen that UV radiations of small wavelengths attack human cells. Extending this theory, we find that attacks on human cells become more and more severe as wavelength of the magnetic radiation become smaller and smaller. Thus, we find that X-ray, γ-ray, and cosmic-ray radiations are extremely dangerous to human and animal health since their wavelengths lie in the nanometer to picometer range, which are much smaller than human-cell dimensions. But in these cases also we have safe power limits defined by various international regulatory bodies above which only they become hazardous.

      In this context, it may be noted that through the paper⁷ published in October, 2014, it has been established that radio waves travel as magnetic waves only; the electric part in the waves appears only when they strike an antenna and generate current in it. Hence the term “electromagnetic” waves is a misnomer; it must be changed to magnetic waves only with the electro part omitted. Therefore in our discussions to follow, we will be using the term magnetic waves instead of electromagnetic waves.

Next, let us consider the IR waves in the solar spectrum. We know that IR waves are heat waves which heat the earth’s atmosphere. If the atmospheric temperature exceeds 45ºC, then it will cause severe skin burns on the human and animal bodies which may ultimately lead to death. This is known as sun stroke. This is a major health hazard in countries which receive sun light directly (Law 2 gets applied here).

      The visible light frequency part of solar radiation in between 0.7 micrometer (red) to 0.4 micrometer (blue) is highly essential for sustaining life on earth. Until recently, everybody believed that visible light is danger-free. However, as per Law 1, since these wavelengths are comparable to the size of human cells, they are potentially dangerous to human health. That this observation is true has been proved in recent studies^8,9 on the dangers of visible light on human skin and eyes. However, these references have given only the experimental facts about the hazards of light on skin; they have not given any reason as to why visible light acts dangerously on human skin. However, as stated above, we find that the actions obey Law 1, which confirms its validity.

       

4. Hazards of Man-Made light Sources

      Let us now consider the emission of magnetic waves from the man-made light sources such as incandescent lamps, fluorescent and compact fluorescent lamps, and LED lamps. It has been found that energy generated by incandescent lamps consists mainly of the infrared and visible light waves and a very small amount of UV rays. However, fluorescent and compact fluorescent lamps emit more amount of UV radiation than incandescent lamps. Similarly, LED lamps, the current sensation in the history of lighting, also can cause damage to human health by the effect of UV radiation emitted by them [Law 1].

        To get a quantitative idea about the power levels contained in these radiations, and the dangers lying in them, consider the light emitted by a 100-W incandescent lamp. This emission actually contains a large amount of infrared radiation also. Now, substituting for P_T = 100 W in P_R = P_T/4πr², for r = 1 m, 10 m, and 100 m, we find P_R = 800 μW/cm², 8 μW/cm², and 80 nW/cm², respectively. These values of incandescent lamps are low enough to create any health hazard. However, it may be noted that if the exposure time of a human body to these lamps is large, they can become hazardous.

5. Hazards of Ultrasonic Waves

After having discussed about optical and sound waves, we now discuss the dangers of ultrasonic (US) waves. It is generally believed that US scanning of human bodies is not at all dangerous. This assumption is not entirely correct; they can become dangerous under the conditions discussed below.

Conventional US scanners make use of sonic frequencies ranging from 1 MHz to 20 MHz for human-body scanning. Assuming that the velocity of sound is 340 m/s, wavelengths corresponding to 1 MHz and 20 MHz lie in the range of 340 micrometers to 17 micrometers. These wavelengths are much larger than wavelengths of visible-light spectrum and hence are not dangerous to human cells, provided that the power involved in the process¹⁰ is less than 720 mW/cm². This also implies that, if the power used for a scanning process exceeds this limit, it will be harmful to the body being scanned (Law 2).

     Let us now assume that the ultrasonic frequency to be used for a scanning is 1000 MHz. Corresponding wavelength is 0.34 micrometer. This value is comparable to the wavelength of ultraviolet radiations. Under such conditions, it becomes dangerous to human cells [Law 1], even if the power used for scanning is much less than the so-called safe limit of 720 mW/cm². Hence human-body ultrasonic scanning equipments must use ultrasonic frequencies much below 1000 MHz.

     In applications such as cutting drilling, and welding, focused ultrasonic waves are used. These waves are really dangerous and, unless carefully handled, they may indirectly harm the body of the person using them [Law 3].

      

6. MEDIUM-WAVE AND SHORT-WAVE Radio transmitters

      What are the conditions under which radio waves emitted by medium-wave (MW) and short-wave (SW) transmitters can become dangerous? This may be explained with the help of the equation¹¹

                                                            H =A/r + B/r²

where H is the magnetic field produced by a transmitting antenna, r is the distance from the antenna to a given receiver, and A and B are constants.

The first of the two terms on the right-hand side of the equation represents a magnetic field that is inversely proportional to r. It is called radiation field and is responsible for spreading transmission to places far away from the transmitter. Since the power of the magnetic field in the radiated waves is very low due to wide spreading, this field does not produce any danger to human health. For example, the power density received at 1 km away from a 100-kW MW transmitter will be only 8 μW/cm², which is a very safe value [Law 2].

In this context, it is interesting to note that FCC regulations¹² prescribe safe limits of medium-wave emission as 100 mW/cm² for occupational or controlled exposure. For the general population, the safe value is given by the expression 900/f² (where f is the frequency of emitted radiation with unit in MHz). In this case, if f = 1 MHz, then we get the safe limiting value as 900 mW/cm². Both these values (i.e., 100 mW/cm² and 900 mW/cm²) are much above 8 μW/cm² confirming our argument that radiation from medium-wave transmitters is not dangerous.

The second term on the right-hand side of the equation is inversely proportional to r² and is known as induction magnetic field, or simply, induction field. It is found that this magnetic field is very powerful in the vicinity of the transmitting antenna. But, as the distance from the transmitter increases, this field gets reduced drastically. In fact, the distance up to which this field remains effective is approximately equal to λ/6, where λ is the wavelength of the emitted radiation.

To illustrate the effective distance of induction field, consider a MW station transmitting 1200-meter radio waves at 10-kW power. The induction field of this transmitter is very powerful up to a distance of 1200/6 = 200 meters. It must be noted that induction field is much more dangerous than the radiating field. When a MW or SW high-power transmitter is in operation, nobody is permitted to go anywhere near the transmission tower. This is because the very strong induction magnetic field will attract and pull the objects in its vicinity onto the antenna tower with very high velocity (in this case the antenna acts as a very powerful magnet). The result of this pulling action on a living thing can really be imagined! 

      It may also be noted in this respect that the induction field of a microwave transmitter operating at 1 GHz (or λ = 30 cm) exists only up to a distance of 5 cm from the antenna tower. Further, its radiating power, as stated earlier, is usually in the range of a few watts only. Hence it is not dangerous to go near a microwave transmitter while it is radiating.

7. Radiation from high-voltage Transmission Lines

Another potentially dangerous candidate for the consideration of radiation effects is the very long high-voltage, high-power ac transmission lines. These power lines exist through out the length and breadth of countries all over the world.  Even though they appear as harmless to the common man, in reality, they are potentially hazardous to human health¹³. This is due the following reasons:

1.      They carry thousands of amperes of 50/60-Hz ac current at or above 110 kV. This huge current at very high potential produces very powerful induction magnetic field around the wires through which it flows. The high-power magnetic field so generated can adversely affect the mind and bodies of people residing near these lines.

2.      Since ac power lines are very long (extending over several hundreds of kilometers), they can also act as efficient antennas, since their lengths are comparable to λ/8 (where λ = 3×10⁸/50×8 = 750 km), which is the length required for a wire to act as an efficient radiator.  Hence, the long power lines can radiate 50/60-Hz electromagnetic waves efficiently around them; these powerful radiating magnetic fields can also become hazardous.

8. Hazards of Microwave Radiation

        Magnetic waves lying in the range of 1 GHz (wavelength = 30 cm) to 1 THz (wavelength = 0.3 mm) are generally called as microwaves. Of these, at present, mobile towers and phones all around the world operate only in the frequency ranges of 800 to 900 MHz (wavelength = 37.5  cm to 33 cm) and 1800 to 2100 MHz (wavelength = 17 cm to 14.3 cm).

Now, comparing the size of human cells ranging from 1 micrometer to 100 micrometer with wavelengths of 37.5 cm to 14.3 cm of microwaves, we find that microwaves are much bigger in size than human cells. Therefore, as per Law 1, it is very clear that microwaves can not harm human cells.

Next, consider the power radiated and received in mobile microwave transmissions. It is found that many of the transmitters installed in several countries all around the world radiate typically 100 W of microwave power into the space surrounding them. Then, using the formula P_R = P_T/4πr², we find that at r = 1 m and 10 m, P_R = 800 μW/cm² and 8 μW/cm², respectively.  Further, it is to be noted that mobile handsets of customers will be usually at least 100 m away from a radiating transmitter. At this point, P_R = 80 nW/cm² only, which is an extremely low power that can cause any significant damage to human cells (Law 2).

      The argument given above also suggests that there is a possibility of these waves affecting the working of human DNA chains whose dimensions range from a few centimeters to a few meters. However, since the radiations from mobile towers are very weak, there is very little probability of them affecting the DNA chains adversely.

      It has now been proved that low-power mobile tower radiations are harmless (see Section 10 below, which describes a computer simulation using COMSOL MULTIPHYSICS SOFTWARE that confirms this argument). However, there exists a negative propaganda against such transmissions preventing the installation of new mobile towers at various locations in a country. The crowding of several antennas on a single tower is really a sight that produces fear in the minds of even the strong-hearted men; it may be this psychologically generated fear that produces stress-generated diseases in people with weak mindset.

9. Hazards Of Mobile Phones

      Are mobile phones hazardous? This again is a question frequently raised by the general public. The answer to this question also is a vehement “no”. This answer is based on the same arguments given above in the case of radiation from mobile towers.

      An additional reason to be considered in the case of mobile handsets is regarding the heat generated in them. Mobile phones are powered by lithium-ion batteries. The capacity of these batteries ranges from 1000 mAh (milli-ampere hour) to several thousands of mAh. 1 mAh is defined as the capacity of a battery to supply or dissipate current at the rate of 1 milliampere for a period of 1 hour continuously. Since in most cases, the battery voltage is about 3.7 V, the power dissipated for 1 mA of current over a period of 1 h is only 3.7 mW. This means that the power dissipated per second is only a few μW. This low power level can not heat the brain if handsets are used for short durations of time.

      However, if a mobile phone is continuously used for several minutes, the heat developed in the handset can heat the brain cells because of the proximity of the phone to the human skull. As stated above, this heat is due to the power dissipated by the battery for energizing the electronic circuitry in the handset and not due to microwave radiation.

       The problem described above can be eliminated completely by using earphones (or headsets) for conversation between calling and called parties. It may be noted that all modern mobile manufacturers supply headsets as an auxiliary gadget along with each mobile phone they sell. Headsets very conveniently keep mobile phones far away from human ears so that the heat developed in them will in no way affect the human brain. Any discomfort felt by persons using these gadgets is purely psychological.

10. Computer Simulation using COMSOL SOFTWARE to Prove that Microwaves Do Not Harm Human Brain

For studying the effects of microwave radiation from mobile towers and phones on human brain, computer simulation programs using COMSOL MULTIPHYSICS SOFTWARE were carried out. This software has a built-in human- brain model, known as the COMSOL BRAIN MODEL (CBM). It also has a built-in microwave generator that can simulate the generation of microwave frequencies from 835 MHz to 10 GHz.

Simulations were performed to study specific absorption rate (SAR) of the brain tissues. SAR is defined as the power absorbed per unit mass of human tissue. SAR is measured in the units of watts per kilogram (W/kg), averaged over the whole body or over a small volume of tissue weighing 1 g (USA) or 10 g (Europe).

COMSOL simulations yielded data in the form of two different graphs. The first graph, called as the SAR graph, shows the relation between SAR and the location of the point in the brain where microwaves are absorbed. On this graph, SAR is indicated by different colour patches. These colour patches, in turn, represent the heat generated in the brain by the incident microwave radiation. To get an idea of the SAR value in terms of equivalent temperature, consider the experiments conducted on the eyes of rabbits. In this experiment, exposure of eyes to microwave radiation for a period of 2 to 3 hours has been found to produce a temperature of 41ºC for a SAR value¹⁴ of 100 to140 W/kg.

The second graph shows the relation between the total energy density generated within the brain by incident radiation, expressed in J/m³ (y-axis) and arc length representing the radius of the brain expressed in cm (x-axis).

Now, consider the first simulation using the frequency of 835 MHz (lowest microwave frequency available in the software). Let this be applied as input to the ‘ear portion’ of the CBM. The input power of the microwave frequency is set at 20 mW, which is much more than that reaching a human body from a radiating mobile tower. The results of the simulation are shown in Figs. 3, 4, and 5, respectively. Figures 3 and 4 represent two views of the human brain showing the temperature generated in by 835-MHz.

       In Figs. 3 and 4, the blue-colour patch indicates the region of the human brain where it is least affected by the input radiation. Similarly, the brown-colour patch indicates the maximum affected region. The red line shown in Fig. 3 represents the 20-mW, 835-MHz microwave power striking the human ear. It can be seen that the maximum temperature generated by the input power around the ear portion of the brain is only 0.19 K at 835 MHz and hence is too small to create any problem to the affected human body!

The graph shown in Fig. 5 is the energy density/arc length graph. In this graph, the peak represents the maximum energy absorbed by the human brain from the input power of 20 mW, 835 MHz. We find that the maximum power density absorbed in this case is only 1.6 μJ/m³ (=1.6 pJ/cm³). This is a negligibly small value and hence can not create any problem to human brain tissues.

Consider now the microwave radiation of 2.123 THz, which is the maximum frequency in the microwave range available in the software package, being applied as input to the ‘ear portion’ of the CBM. The results of the simulation outputs for this case are shown in Figs. 6 and 7, respectively. It can be seen that Fig. 6 is similar to Fig. 3. In this case also the maximum temperature generated is too small (9.86×10^‒20 K at 2.123 THz) to create any problem to human brain!

Figure 7 is the energy-density plot and is similar to Fig. 5. The peak in this graph shows that the maximum power density is only 1.6×10⁻²³ J/cm³, which, as in the first case, is negligibly small to create any sort of problems to human brain tissues.

Simulations were done with several frequencies in between 835 MHz and 2.123 GHz. It has been found that in these cases also, the simulation results indicate that the heat generated in the human brain by these microwave frequencies is negligibly small and hence can not create any danger to human brain tissues.

11. SUMMARY AND CONCLUSION

In this article, we have discussed the conditions under which various types of radiating (travelling) waves can become hazardous to human and animal health. For this, we have defined three laws based on logical reasoning. These laws are then used for the discussions.

Employing actual physical examples and using the three laws mentioned above, it has been proved that audio waves and microwaves at low-power levels and in spread form are not dangerous to human beings and animals. Using computer simulations employing actual practical values, we have corroborated our argument that microwave radiation from mobile towers and phones are not hazardous to human health. The propaganda that microwave radiation from mobile towers and phones is dangerous is false and not based on any logical reasoning. It is also concluded that waves (such as microwaves, optical waves, sonic waves, and ultrasonic waves) travelling in concentrated form and at high power levels are definitely dangerous.  

12. ACKNOWLEDGEMENTS

This article was published in KSEBA HYDEL, Technical Journal of Kerala State Electricity Board Engineers Association in volume 63, 2017. The Authors take this opportunity to acknowledge their gratitude to KSEBA for the same..

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