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.
Statistical studies of cancer risks close to nuclear power stations and power lines
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.
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.
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.
Table 5 - Source : ICNIRP, "EMF guidelines", Health Physics 74, 494-522 (1998)
This threshold level for behaviour is not equal to the guideline limit. ICNIRP applies a safety factor of 10 to derive occupational (working areas) exposure limits, and a factor of 50 to obtain the guideline value for the general public (private or uncontrolled environments). Therefore, for example, in the RF and microwave frequency ranges, the maximum levels you might experience in the environment or in your home are at least 50 times lower than the threshold level at which first behavioural changes in animals become apparent. It is a good news ! Maybe less for your small rat of your mouse taken out of a laboratory.
Table 6 - Source : WHO Regional Office for Europe
Equations and computing 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)
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.
Information about RF Safety and EM measurements
- RF Field Strength Meter (in kit)
- Using a cell phones for one hour increases cancer risk by 500% study shows, Natural News, 2016
- 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)
- ARRL Book "RF Exposure and You" ($23).
- EMF guidelines, ICNIRP, Health Physics, 74, specially section pp.494-522 about EM fields up to 300 GHz (1998)
- In their TIS pages, ARRL also provide some interesting studies about Power-Line Noise Mitigation Handbook for Naval and Other Receiving Sites.
- The Institute of Electrical and Electronics Engineers published in 1992 IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 KHz to 300 GHz, Ref. IEEE Standard C95.1-1991. This publication was extended and replaced in 2002 with IEEE Standard C95.3-2002 ($77).
- A complete list of publications dealing with biological effects of RF and others tissue interactions with EM fields is available on Spread Spectrum Scene website.
- A document describing effects of CellPhone on the health has been published by FDA.
- The World Health Organization (WHO) wrotes also a long article titled "What are electromagnetic fields" with tables.
- The Environmental Protection Agency published a free consumer-level booklet entitled, "EMF in Your Environment," document 402-R-92-008, dated December 1992. Look for the nearest office of the EPA in your phone book.
- ICNIRP published a complete report, the "International Commission on Non-Ionizing Radiation Protection Guidelines for limiting exposure to time varying electric, magnetic and electromagnetic fields (up to 300 GHz)", in Health Physics 74(4), p494-522, (1998).
- The Medical College of Wisconsin published a *very complete* FAQ page about Cellular Phone Antennas and Human Health, including external links.
- Physicist John W. Farley has published in 2003 a report titled "Power Lines and Cancer: Nothing to Fear" in which he criticizes some hasty and wrong conclusions and provides many external links.
- RF Safe has published an article titled "Effects of RF radiation" in which it discusses biological effects of radiations emitted by GSM. This site has published several articles on the same theme.
- The Finnish Institute of Occupational Health (FIOH) published a very understandable report in PDF format (2.3 MB) titled "Overview of Effects and Protection of Non-Ionizing radiation", listing several interesting measurements on various devices.
- For a general coverage of EM measurements, ITS provides several online documents in PDF format too.
- I2Stech sells a software named REMS to simulate in 3D the electromagnetic field emitted by antennas working over 30 MHz.
- At last, UBA, the belgian IARU association, has published an Excel sheet associated to an Access database to calculate the EM field emitted by amateur HF antennas. Select the language "Français" then the section "Dossiers".
°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 and tables are from LX4SKY. This material may be reproduced for noncommercial use, provided that credit is given.