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Electromagnetic radiations and your health

Effects of EM fields on Health (III)

One or another day, we all have experimented tiny electrical discharge touching a metal or even embracing a person. The human body is "under tension" due to the chemical reactions that occur through our metabolical activity. These currents are even present in the absence of external electric fields : in the brain of course or during the process of digestion. Even the heart is  electrically active (remember the electrocardiogram).

Low-frequency electric fields affect the human body just as they influence any other electrically charged material. When tissues become conductive, they influence the distribution of electric charges at their surface; in other words they cause current to flow through the body to the ground.

Low-frequency magnetic fields induce circulating currents within the human body. The strength of these currents depends on the intensity of the outside magnetic field. If sufficiently large, these currents could cause stimulation of nerves and muscles or affect other biological processes.

Both electric and magnetic fields induce voltages and currents in the body but even directly beneath a high voltage transmission line, the induced currents are very small compared to thresholds for producing shock and other electrical effects.

Heating is the main biological effect of the EM fields at radiofrequencies (RF). In microwave ovens this fact is employed to warm up food. The levels of radiofrequency fields to which people are normally exposed are very much lower than those needed to produce significant heating. 

The first signs of electromagnetic radiation effects on the health arose after the Second world war to US Navy workers. American scientists were alerted by a syndrome resembling to a mild radiation poisoning. They find in surveying radar-exposed workers a high incidence of internal bleeding, 2 leukemia cases in 600 radar operators, 2 brain tumor cases in a 5-man microwave research team, and many complaints of headache. The report was sent to the Pentagone in 1953. Electrical engineers from the Navy then tried to identify a safe level of microwave exposure for servicemen. Biophysicist Herman Schwan played a major role in establishing at 10 mW/cm2 the thermally safe microwave exposure limit. Today, we have seen that FCC admits an upper limit of 5 mW/cm2 in controlled environments while european recommendations are 8 times higher !

The heating effect of radiowaves forms the underlying basis for current guidelines. Scientists are also investigating the possibility that effects below the threshold level for body heating occur as a result of long-term exposure. To date, no adverse health effects from low level, long-term exposure to radiofrequency or power frequency fields have been confirmed, but scientists are actively continuing to research this area.

Biological effects are measurable responses to a stimulus or to a change in the environment. These changes are not necessarily harmful to your health. For example, listening to music, reading a book, eating an apple or playing tennis will produce a range of biological effects. Nevertheless, none of these activities is expected to cause negative health effects.

The body has sophisticated mechanisms to adjust to the many and varied influences we encounter in our environment. An organism that doesn't react face to its environment is a death organism. It cannot survive because it is unable to adapt. Ongoing change forms a normal part of our lives and of our  evolution. But, of course, the body does not possess adequate compensation mechanisms for all biological effects. Changes that are irreversible and stress the system for long periods of time may constitute a health hazard. The best example is the effect of radioactivity or of a too high temperature.

To read : Centrale nucléaire et cancer: un lien de cause à effet ?

Statistical studies of cancer risks close to nuclear power stations and power lines

Effects of GSM-like radiation on rats and mice DNA. Document RF Safe/Dr. Lai and Singh.

An adverse health effect causes detectable impairment of the health of the exposed individual or related. Such an effect can be for example the leukamia or cancer of cells. A biological effect, on the other hand, may or may not result in an adverse health effect.

It is not disputed that electromagnetic fields above certain levels can trigger biological effects. Experiments with healthy volunteers indicate that short-term exposure at the levels present in the environment or in the home do not cause any apparent detrimental effects. Exposures to higher levels that might be harmful are restricted by national and international guidelines. The current debate is centred on whether long-term low level exposure can evoke biological responses and influence people's well being. The subject of all debates is of course the famous HV power lines.

Power lines and ELF

Due to their extremely high energy, HV power lines are of course a special case. Directly beneath power lines the fields are much stronger and epidemiological studies confirmed that they are source of cancers if the exposure is very long. Electric field levels underneath power lines and up to 25 m away can be as high as 10 kV/m, and are thus potentially at risk after a long exposure. But how long ? Probably a life... Thus the risk is not greater than the life itself (you can easier die in a car accident, a gas explosion, etc) ! However, the fields, both electric and magnetic, drop off  from the lines 4 times in intensity each time the distance double (law in 1/r2). At 50 m to 100 m distance the fields are usually at levels that are found in areas away from high voltage power lines. However, IRPA has noticed the development of leukamia when people are exposed to electromagnetic fields equivalent to a distance up to 75 m from a 400 kV power line.

The main sources of natural and man-made (in shade of red) radiations.

According to WHO, pooled analyses of epidemiological studies conducted in 2002-2003 provide insight into the epidemiological evidence that played a pivotal role in the IARC evaluation. These studies suggest that, in a population exposed to average magnetic fields in excess of 0.3 to 0.4 μT, twice as many children might develop leukamia compared to a population with lower exposures. In spite of the large number data base, some uncertainty remains as to whether magnetic field exposure or some other factor(s) might have accounted for the increased leukamia incidence. We must know that IARC has listed approximatively 900 carcinogenic agents !... Nobody can handle all possible permutations and side effects induced by so many possible reactions, hence the incertainty often haging over this kind of study. The uncertainty is still larger when speaking of potential risk for the foetus to pregnant women staying at home near HV power lines or deseases like cataract that some workers would have contracted after worked on HV pylons.

The case the most studied is the childhood leukamia. It is a rare disease with 4 out of 100,000 children between the age of 0 to 14 diagnosed every year. Also average magnetic field exposures above 0.3 or 0.4 μT in residences are rare. It can be estimated from the epidemiological study results that less than 1% of populations using 220-240 volt power supplies are exposed to these levels, although this may be higher in countries using 110-120 volt supplies.

In another hand, electrical companies have noticed strange behaviours in some electrical devices used in farms located just beneath HV pylons : flickening of neon lamps, temporary interruption of motors, etc. These effects are concrete and quantifiable and add to the epidemiological risk to confirm that these HV power lines induce unattended effected, and more than probably biological effects at short distance (< 75 m).

As for knowing if we can eat or not apples or strawberries that ripped under such EM fields or eat meat of animals having lived under these radiations, no one can answer because effects are little studied as it and hard to quantify. But if a health risk should occur, it seems in all cases by far lower that the one of transgenic foods as we haven't noticed yet biological effects in the nature of fruits or the metabolism of concerned animals. In all cases, nature has always created new species or varities of fruits or animals without that their consumption is harmful to human being.

A guideline

Intensity of the electromagnetic field emitted by an UHF antenna simulated with the software REMS. Document I2Stech.

Now that we gathered all elements and know the potential risks, what can we conclude from all those data ? As we told previously, all data gathered up to date give not black or white results in this matter. 

In this context, an important remark to make is that any guideline will never give a precise delineation between safety and hazard. There is no one level above which exposures become hazardous to health; instead, the potential risk to human health gradually increases with higher exposure levels. Guidelines indicate that, below a given threshold, electromagnetic field exposure is safe according to scientific knowledge. However, it does not automatically follow that, above the given limit, exposure is harmful, hence the "laisser-aller" in the matter by the authorities.

Nevertheless, the public does not react like authorities ! On one hand, we know from sad experiences, that some governments and many industrials, private or public, have sometime hidden accidents in which population was contaminated (Bophal, Mururoa, NTS, Tchernobyl, etc).

We have thus correctly to interprete these studies and check the behaviour of our leaders as the one of industrials sometimes criminals. On the other hand, the public has a tendency to fear what he doesn't know. Concerning EM fields, being invisible, odourless and silent, the non informed public has a tendancy to credit them with all harms of the earth despite transparency and results mostly negative emerging from scientific studies.

To be able to set limits on exposure, scientific studies need to identify the threshold level at which first health effects become apparent. As humans cannot be used for experiments excepted by accident (all cases of leukamia enter in this category), guidelines critically rely on animal studies. Subtle behavioural changes in animals at low levels often precede more drastic changes in health at higher levels. Abnormal behaviour is a very sensitive indicator of a biological response and has been selected as the lowest observable adverse health effect. Guidelines recommend the prevention of electromagnetic field exposure levels, at which behavioural changes become noticeable.

Summary of Exposure Guideline

 

European power frequency

Mobile phone (GSM)

frequency

Microwave oven frequency

Frequency

50 Hz

50 Hz

900 MHz

1.8 GHz

2.45 GHz

EM Field

Electric field

(V/m)

Magnetic field

(μT)

Power density

(W/m2)

Power density

(W/m2)

Power density

(W/m2)

Public exposure limits

5000

100

4.5

9

10

Occupational exposure limits

10000

500

22.5

45

 -

Table 5 - Source : ICNIRP, "EMF guidelines", Health Physics 74, 494-522 (1998)

This sanitary safety threshold is not equivalent to the limit recommended by the institutions or legally nor to the Specific Absorption Rate (SAR index). For security reasons, the ICNIRP applies a reduction factor of 10 in exposed work areas and a factor of 50 in public places (private or uncontrolled).

In general, it is agreed that maximum exposure to magnetic fields (power density) should not exceed 2 W/m2. In practice, the threshold of domestic appliances is often 10 to 20 times lower and therefore in theory without any effect on health. But people hypersensitive to electromagnetic fields will tell you that this level is still too high and these people have no choice but to isolate themselves in places without antennas or any device emitting a magnetic field.

In the RF spectrum (10 MHz - 300 GHz) the maximum energy levels to which we may be exposed in the environment or at home are at least 50 times lower than the threshold at which the first behavioural changes in animals become apparent. It's good news ! May be less for your little rat or mouse taken out of a laboratory.

That said, knowing that the risk 0 does not exist, there is a residual risk of exposure to electromagnetic fields and especially that of household devices (GSM, Wi-Fi, etc.) but their long-term effects are not yet known.

Maximum exposure levels (Power density)

Device

Typical maximum public exposure (W/m2)

TV and radio transmitters

0.1

Mobile phone base stations

0.1

Radars

0.2

Microwave ovens

0.5

Table 6 - Source : WHO Regional Office for Europe

One thing is sure. Animal experiments have shown that intense electromagnetic fields are harmful to health. In humans, as some hypersensitive people may testify, the magnetic fields can trigger an almost allergic reaction from one day to the next without the threshold of intolerance being defined since most people are apparently insensitive to it. Regarding mobile phones and other connected tablets, as a precaution, it is advisable not to have his mobile phone by ear several hours a day and every day of the week for years. It is best to use a hands-free kit and leave your mobile phone at a distance from yourself to avoid being in the field of the most powerful emissions (specially when it rings or search for a network). Same problem for tablets, Wi-Fi-routers and other devices emitting electromagnetic waves.

Avoid calling when the reception is bad. If this is the case, move to a better covered area or call back from your computer (Skype) or from a landline.

Finally, it is probably in the car and public transports that the electromagnetic fields are the most harmful because they must be strong enough to get through the metal body, therefore the reception is often bad in cars.

Equations and simulations

Most of the situations in which the power density would be high enough to be of concern are in the near field—an area roughly bounded by several wavelengths of the antenna. In the near field, ground interactions and other variables produce power densities that cannot be determined by simple arithmetic.

To check : Amateur Radio RF Safety Calculator

RF Field Strength Meter (in kit)

Power to Electric or Magnetic Field conversion

EIRP (Equivalent Isotropic Radiated Power) is the power P multiplied by the antenna gain G (compared to a isotropic antenna, from which you substracted losses) :

EIRP(W) = G(dBi) x P(W)

The fundamental relation given the electric field according the power and distance is :

E(V/m) = √(30 x EIRP(W)) / d(m)

Consequently, the relation giving the safe distance is :

d(m) = √(30 x EIRP(W)) / E(V/m)

As the electric field (E) and magnetic fields (H) are linked by the relation E/H = Zo = 377, we can also calculate the strength of the magnetic field :

H(A/m) = √(2.11x10-4 x EIRP(W)) / d(m)

For a distance d, we can consider a sphere which surface s = πd² where d = 2r. All the power is radiated through this sphere and the power density is thus equals to S = P/s or S = E x H, hence :

S(W/m²) = 0.0795 x EIRP / d²(m)

At last, to convert dBm in V/m, you need to know the "Antenna Factor" or AF. It gives the loaded (50 ohm) terminal voltage of a dipole immersed in an E-field. Although the calculation mixes units and cannot be accurate, a rule-of-thumb is to say that a 30-MHz dipole displays an AF of 0 dB. A 60-MHz dipole shows an AF of 6 dB, and a 15-MHz dipole shows an AF of -6 dB. The relation is next :

Dipole AF = 20 log (F/30), with F = frequency

A 30-MHz dipole in an E-field of 1 V/m gives an output of 1 volt. A 60-MHz dipole gives 0.5 volt and a 15-MHz dipole gives 2 volts. Then convert for example a value of 20 dBm to signal level dbuV : in a 50 ohms system add 107 dB to get 127 dBuV. Add the AF. If AF = -19 dB (for an 80-meter dipole cut for 3.5 MHz), the E-field is 127 - 19 = 108 dBuV. Converting 108 dBuV to volts, we get 0.25 volts.

Computer antenna-modeling programs such as MININEC or other codes derived from NEC (See simulations software on this site) And yet, these too have limitations. Ground interactions must be considered in estimating near-field power densities. Also, computer modeling is not sophisticated enough to predict "hot spots" in the near field— places where the field intensity may be far higher than would be expected. Intensely elevated but localized fields often can be detected by professional measuring instruments. These "hot spots" are often found near wiring in the shack and metal objects such as antenna masts or equipment cabinets. But even with the best instrumentation, these measurements may also be misleading in the near field.

One need not make precise measurements or model the exact antenna system, however, to develop some idea of the relative fields around an antenna. Computer modeling using close approximations of the geometry and power input of the antenna will generally suffice. Those who are familiar with MININEC can estimate their power densities by computer modeling, and those who have access to professional power-density meters can make useful measurements.

While our primary concern is ordinarily the intensity of the signal radiated by an antenna, we should also remember that there are other potential energy sources to be considered. 

You can also be exposed to RF radiation directly from a power amplifier if it is operated without proper shielding. Transmission lines may also radiate a significant amount of energy under some conditions.

By way of conclusion

The World Health Organization (WHO) has defined seven main health effects of EM field :

- A wide range of environmental influences causes biological effects. "Biological effect" does not mean "health hazard". Special research is needed to identify and measure health hazards.

- At low frequencies, external electric and magnetic fields induce small circulating currents within the body. In virtually all ordinary environments, the levels of induced currents inside the body are too small to produce obvious effects.

- The main effect of radiofrequency electromagnetic fields is heating of body tissues.

- There is no doubt that short-term exposure to very high levels of electromagnetic fields can be harmful to health. Current public concern focuses on possible long-term health effects caused by exposure to electromagnetic fields at levels below those required to trigger acute biological responses.

- Many institutions are today working on projects providing scientifically sound and objective answers to public concerns about possible hazards of low level electromagnetic fields.

- Despite extensive research, to date there is no evidence to conclude that exposure to low level electromagnetic fields is harmful to human health.

- The focus of international research is the investigation of possible links between cancer and electromagnetic fields, at power line and radiofrequencies. Without more indication, for your own health stay over 100 meters from HV power lines.

Further RF exposure suggestions

Potential exposure situations should be taken seriously. Based on the FCC/EPA measurements and other data, the "RF awareness" guidelines of Table 3 were developed by the ARRL RF Safety Committee. A longer version of these guidelines, along with a complete list of references, appeared in a QST article by Ivan Shulman, MD, WC2S (see Bibliography below). In addition, QST carries information regarding the latest developments for RF safety precautions and regulations at the local and federal levels.

If you are looking for an electromagnetic signal meter, two models are recommended, CellSensor or EM eye. Their price is about $100. Many other brands, world-wide, provide similar tools.

Regarding scientific publications on the impact of magnetic fields on health and especially GSM antennas, globally the opinions are divided, what explains that the subject has been debated for several decades with on the one hand researchers who have interests with industry of that sector and do not see any negative impact on the use of magnetic fields and on the other the few objective researchers and and hypersensitive persons who, on the contrary, have demonstrated the risks for health induced by electromagnetic fields that are too close or too intense.

For more information

Instruments

- RF Field Strength Meter (kit)

- PCE Instruments (including EM field detector PCE EMF 823)

- Radiofrequency Meters

Publications and standards

- Lennart Hardell's publications

- Alexander Lerchl's publications

- Olle Johansson's publications

- Cell Phone, FDA

- RF Exposure and You, ARRL ($23)

- Using a cell phone for one hour increases cancer risk by 500% study shows, Natural News, 2016

- Power-Line Noise Mitigation Handbook for Naval and Other Receiving Sites, ARRL/TIS

- Power Lines and Cancer: Nothing to Fear, John W. Farley, 2003

- Effects of RF radiation, RF Safe

- Overview of Effects and Protection of Non-Ionizing Radiation, Maila Hietanen/FIOH, 2000

- ITS Publications, ITS

- Spread Spectrum Scene (liste de publications sur les champs EM)

- International Commission on Non-Ionizing Radiation Protection Guidelines for limiting exposure to time varying electric, magnetic and electromagnetic fields (up to 300 GHz)", Health Physics, 74(4), p494-522, (1998).

- IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz", ref. IEEE Standard C95.3-2002, 2002 (data 1991).

°This document is reprinted from the "1997 ARRL Handbook for Radio Amateurs", Copyright ©1996 American Radio Relay League, Inc. Additional text about risks for health, temperature of semiconductors, concerns about GSM, Wi-Fi, ELF, references, tables and updates are from the author, LX4SKY. This material may be reproduced for noncommercial use, provided that credit is given.

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