This publication is intended as support for decision makers, when making decisions on health hazards and electromagnetic fields. It has been based on joint consultations between the National Board of Occupational Safety and Health, the National Board of Housing, Building and Planning, the National Electrical Safety Board, the National Board of Health and Welfare and the National Radiation Protection Institute, on the strength of scientific findings hitherto, at the same time as technical and economic aspects of possible measures are considered in the light of limited community resources. The national authorities recommend a precautionary principle based primarily on non-discountable cancer risks. Similar precautionary principles should also be applied to other suspected effects on health. This guide offers supportive documentation to decision-makers' tasks with assessing what is reasonable in each individual case, balancing possible hazards against technical and economic considerations.
The research findings presented hitherto afford no basis for and cannot be said to justify any limit values or other compulsory restrictions on low-frequency electrical and magnetic fields. The limit values which we have today for high-frequency electromagnetic fields afford protection against thermal effects. In the case of low-frequency fields, we do not know which properties may possibly entail hazards, nor do we know how doses are to be evaluated. If the fields are harmful to health, are the hazards mainly connected with brief, intense exposures or with prolonged, low-level ones? Or is it perhaps widely fluctuating fields that cause the problems? We do not know, but even so we have come to believe that a certain amount of caution may be justified where exposure to low-frequency magnetic fields is concerned.
The Criteria Group of the National Institute for Working Life (1995) has observed that the scientific foundations for limit values on magnetic fields are insufficient but that action based on some form of precautionary strategy ought to be possible. In the Group's opinion, however, action of this kind entailed socio-economic considerations which it considered to be beyond the bounds of its mandate. In the USA, researchers at Carnegie Mellon University, Pittsburg, have formulated an approach to magnetic fields problems which they have termed "prudent avoidance". They argue that, as long as our knowledge of the connection between health hazard and exposure remains incomplete, society cannot resort to expensive, peremptory measures. On the other hand, given reasonably strong suspicions of effects on health, one should still take steps which do not in themselves entail heavy expenditure or other inconvenience. A similar approach has been advocated, for example, in the preparatory work of both the Radiation Act and the Health Protection Act, to the effect that suspicion, on firm scientific grounds, of injury risks must in itself constitute sufficient grounds for implementing the enactments. Most of the authorities responsible for the present publication recommended, in 1994 in a brochure entitled "Magnetic fields and possible risks to health as known in May 1994", that a certain degree of caution should be observed in urban planning and construction if this could be done at reasonable expense.
The national authorities join in recommending the following precautionary principle: If measures generally reducing exposure can be taken at reasonable expense and with reasonable consequences in all other respects, an effort should be made to reduce fields radically deviating from what could be deemed normal in the environment concerned. Where new electrical installations and buildings are concerned, efforts should be made already at the planning stage to design and position them in such a way that exposure is limited. The overriding purpose of the precautionary principle is eventually to reduce exposure to magnetic fields in our surroundings, so as to reduce the risk of injury to human beings.
"The magnetic field level in the environment concerned" refers to the magnetic field level in areas where human beings can be expected to be repeatedly present for a considerable length of time, e.g. housing, schools, day nurseries and workplaces. "Normal magnetic field level" refers to the average obtained, after calculation or several measurements, for the magnetic field in the surroundings concerned and in conditions which can be taken to reflect the field level over a long period. Measurements close to specific sources with rapidly decaying fields shall not be deemed to reflect the magnetic field level unless individuals can be expected to be present close to the specific source for a large part of the day or working day. Measurement must take place at a sufficient number of points in the space in order to obtain a fair picture of the magnetic field level, and at a sufficient number of points in time in order for the result to be reproducible. Documentation of the measuring methods is important. Where power lines are concerned, field calculations may very often be preferable to measurements. As a general rule magnetic fields in homes and day nurseries far away from power lines are very low. The median value for homes and day nurseries in major towns or cities is approximately 0.1 µT (microtesla). The values in smaller towns and rural areas are approximately half this. In metropolitan regions, about 10 per cent of homes have at least one room with a magnetic field exceeding 0.2 µT. Close to power transmission lines and transformer stations, the magnetic fields are higher. Right underneath a power line, the figure can be about 10 µT. It is estimated that some 0.5 per cent of the housing stock has a magnetic field exceeding 0.2 µT, owing to the proximity of electric cables of different kinds. Measurements have been carried out for a large number of occupational categories at their places of work. The median value obtained was approximately 0.2 µT. Understandably, there are many industrial environments where values fluctuate considerably. The highest daily average, 1.1 µT, was obtained for welders. Levels of hundreds of µT can occur, briefly, where certain individuals or working situations are concerned.
Some benchmarks for expenditure per fatality/casualty avoided
| HAZARD | AUTHORITY | EXPENDITURE |
|---|---|---|
| Traffic death | Road Administration | MSEK 7 |
| Cancer from ionising radiation | The Nordic Radiation Protection Authorities | MSEK 12 |
| Lung cancer from radon | The National Board of Health and Welfare | MSEK 2 |
A human life cannot be valued in money, but even so it will be readily understood that there are many situations where the possibilities for society or individual persons to save lives or avert serious illness are limited by lack of resources. Resource constraints are an inescapable fact and do not reflect any desire to put a price tag on people's lives. The amount which society is ready to pay in order to save a "statistical life" varies a great deal from one sector of society to another and from one risk factor to another. One reasonable approach would seem to be for protective measures to be ranked according to their benefit in relation to their cost, but this is not always the practice. In certain cases there are great differences between declared ambitions and practical measures taken. The above table is based on known conditions a couple of years ago and reflects the data on which the national authorities were then able to base their priorities. Similar tables from the USA show values between MSEK 5 and 50, with the highest figures emanating from nuclear power and the environment protection and the lowest ones from the traffic sector. In several of the fields mentioned above, the causal relations have been made clear, the risks are well known and the effects of funding inputs are calculable or quantifiable. In the field of radiation protection, measures against ionising radiation costing less than MSEK 5 per statistical case avoided are looked on as urgently necessary.
Health hazards feared from exposure to low-frequency electrical and magnetic fields have been under discussion since at least the beginning of the 1980s. The main apprehensions have concerned the risk of cancer, pregnancy disturbances (foetal lesions) and so-called electrical hypersensitivity. The debate has at times been both intense and acrid. One reason for this is that still very little is known about the ways in which human beings and other living creatures are affected by electrical and magnetic fields. The results presented by different research groups have sometimes been contradictory. Contrary to what is the case, for example, with chemical substances and ionising radiation, it has been difficult so far to discover harmful effects experimentally even at very high levels of exposure to electrical or magnetic fields. The best-known effects are thermal effects from exposure to high-frequency electromagnetic fields and the effects of the currents induced by low-frequency magnetic fields. In these cases, however, the field strengths are greater than those for presumed, but unconfirmed, connections between cancer, foetal lesions and electrical hypersensitivity and the fields referred to. Very little indeed is known about the possible biological effects of low-strength fields. The dominant sources of exposure to low-frequency magnetic fields are power lines, installations and electrical equipment. At the same time as the fields may conceivably pose a threat to our health, without electricity modern society would come to a standstill, so it is absolutely essential that both risk assessment and protective measures be based on knowledge and sense and that they should be properly thought out. In January 1995 a group of experts appointed by the National Board of Health and Welfare presented a scientific evaluation of all published research reports in this field. An international group of experts, commissioned by the WHO, has evaluated the state of research concerning the risk of cancer and pregnancy disturbances. In October 1995 the Criteria Group of the National Institute for Working Life presented supportive data for possible limit values, following an evaluation of the cancer risks.
There are a large number of epidemiological studies in which statistical methods have been applied to connections between illness and an environmental factor, for example in order to see whether there may be a connection between exposure and magnetic fields and elevated risk of cancer. Where exposures in the working environment are concerned, the main focus of attention has been on the risks of certain forms of leukaemia and brain tumour. For exposure in the dwelling environment, the main concern has been with leukaemia risks to children. The results contain many points of uncertainty. For example, different scientific reports indicate excess risks of completely different kinds of cancer. Nor are there any convincingly accepted connections between dose and the magnitude of risk. Epidemiological studies imply the analysis of a statistical connection between exposure and disease. A statistical connection does not mean that the exposure causes the disease, and so often the results of the epidemiological studies have to be verified through experimental studies, which tell us about possible mechanisms of harmful influence, and through animal studies, in which exposure to the suspected carcinogenic factor is isolated. So far, studies of this kind have not yielded any results to corroborate suspicions of cancer risks or other health hazards from these fields. The above mentioned groups of experts all come to the conclusion that exposure to low-frequency magnetic fields cannot be convincingly shown to entail elevated risks of cancer. Certain epidemiological studies, however, provide some cause for suspecting that there may be a connection with particular forms of cancer. In this connection, it is also important to know that cancer is a disease attributed to a whole combination of factors, by far the most important risk factors among them being diet and smoking. The Swedish Cancer Committee, analysing the causes of cancer in Sweden, has arrived at the results presented in the table below. The results of the studies which have been undertaken show that if exposure to electrical and magnetic fields contributes to the occurrence of cancer, the possible risks of developing cancer are small compared with other risk factors. Every year in Sweden, about 40,000 people develop cancer. According to some estimates, not more than about 100 of these cases might be related to exposure to magnetic fields.
Some causes of cancer in Sweden according to the Cancer Committee (SOU 1984:67)
| CAUSAL FACTOR | PERCENTAGE OF TOTAL INCIDENCE* IN SWEDEN |
|---|---|
| Dietary factors | 30 % |
| Smoking | 15 % |
| UV and other ionising radiation (mainly solar irradiation and radon) | 8 % |
| Work environment factors | 2 % |
| General air pollution | 1 % |
*Incidence = morbidity rate, i.e. the percentage of individuals falling ill or the
percentage of new cases of a disease occurring in a population during a certain period of
time.
Child leukaemia is one of the forms of cancer about which there has been most discussion. The number of children developing leukaemia in Sweden has remained constant over the past 30 years, at the same time as total electricity consumption has multiplied several times over. Domestic electricity use has multiplied tenfold during the same period. Certain other forms of cancer show a numerical increase, skin cancer most of all. In 1992, some 3,500 Swedes developed skin cancer, and of these 1,300 contracted the serious form known as malignant melanoma. UV solar radiation is known to be a very important cause.
The debate on risks in connection with pregnancy also began in Sweden about 15 years ago, when it was triggered by office computerisation. Clusters of miscarriages were reported from certain workplaces, but these initial suspicions have not been confirmed by systematic epidemiological observation studies. One or two studies hint at a connection, while an overwhelming majority of studies argue against it. Often it has been impossible to distinguish exposure to electrical or magnetic fields from other important factors.
Persons with electrical hypersensitivity often suffer from skin disorders in the form of flushing, smarting, itching etc. and also, in more serious cases, other symptoms such as fatigue, headache, palpitations of the heart, perspiration and stomach trouble. Symptoms of this kind are common in the Swedish population and can have many causes. But the electrically hypersensitive individual sees a clear connection between the symptoms and proximity to various forms of electrical equipment or, sometimes, exposure to sunlight. On the other hand, it has not yet proved possible to induce the symptoms in experiments where the electrically hypersensitive individual has not been aware of experimentally induced electrical and magnetic fields being activated. Additional research and evaluation of treatment methods, among other things, are needed in order to improve our knowledge of the causes of symptoms presented by the electrically hypersensitive, and so for the time being we have refrained from issuing any joint, general recommendations on this subject. It is very important, however, that electrically hypersensitive persons should be unconditionally examined by health and medical services, on the basis of their symptoms.
On average in Sweden and most other industrialised countries, one child in 25,000 per annum develops leukaemia. Although the hypothesis of the connection between the occurrence of child leukaemia and exposure to magnetic fields cannot be deemed scientifically established, the observed risks are presumed valid in our examples. In one Swedish epidemiological survey, it was observed that children living close to power transmission lines ran a 2.7 higher risk of developing leukaemia than those living a long way away from such transmission lines. This figure has also been applied to transformer stations and stray currents in the following examples, for lack of other risk estimates. We also assume a lifetime of 40 years for the measure taken and an interest rate of 4 per cent. On these assumptions, it can be shown that the cost per statistical case avoided will be R=735 K/N [SEK/case], where K is the cost of the measure taken and N the number of individuals whose exposure the measure eliminates. Cost is only slightly affected by the lifetime chosen for the measure if it is long lasting. If the lifetime of the measure is put at 80 years instead of 40, the estimated costs in the examples below will be 17 per cent lower. It is not possible in these examples to make general allowance for the effect of different doses on the number of leukaemia cases. It has to be noted that our examples are only intended to illustrate a calculation model for arriving at a comparison between different costs. Depending on the circumstances of the individual case, there may be other solutions or bases of economic calculation which are more appropriate. The calculation model deals only with statistical cases, and many people will have to derive benefit from a measure in order for public health to be influenced. The examples show that exposure reduction measures can cost between a couple of million and several hundred million kronor (MSEK) per statistical case of child leukaemia avoided, subject to the risk estimates employed remaining valid. Note that the precautionary principle recommends that measures should be considered when the fields deviate strongly from what can be deemed normal in the environment concerned.
Power line near multi-family dwellings
An existing 220 kV power transmission line crosses a multi-family housing area with 300
children living within a distance of the line where the risk of child leukaemia is
presumed to be elevated by proximity to the power line. The cost of replacing the power
line with another solution Ð laying a cable along an existing road Ð is MSEK 60. If this
measure is taken, the cost per case avoided, assuming the estimated risk to be true, will
be about MSEK 150. Calculations by local authorities may involve other aspects on which a
value can be placed, e.g. the fact of land being released for alternative use.
Pre-school near a power line
A day nursery used every day by 40 children is so close to a power transmission line that
the risk of child leukaemia can be deemed elevated. The cost of building a new day nursery
elsewhere is MSEK 4. If this measure is taken and there are no other economic aspects to
be taken into consideration, the cost per case avoided will be MSEK 74. If instead it were
possible to use tuned, screened circuits, at an estimated cost of MSEK 0.5, the cost per
case would be about MSEK 9. Transformer station in a school building
A transformer station in a school building causes elevated magnetic fields in three
classrooms. One possible means of reducing the magnetic fields is to line the space with
sheet metal. A measure of this kind costs about SEK 1,000/m2, materials and labour
included, which can mean a total cost of about SEK 200,000. Assuming the measure to reduce
exposure for 75 children using the classrooms, the cost per case avoided will be less than
MSEK 2. Stray currents in single-family dwellings
A single-family dwelling has elevated magnetic fields which are presumed to augment the
risk of child leukaemia. These magnetic fields are caused by stray currents from
installations in the house, and these currents will cost SEK 5,000 to eliminate. Assuming
that there will be, on average, one child living in the home over a period of 40 years,
the cost per statistical case avoided would be about MSEK 4. Power line in rural area
A 400 kV power transmission line is planned in a rural area. An effort has been made at
the planning stage to locate the line as favourably as possible, e.g. from the viewpoint
of persons living close by. It is intended to use a power line structure, a T-pole, which
is more advantageous from a magnetic field viewpoint than the traditional transmission
line structure. These measures can be taken without any appreciable added expense or other
consequences. Even so, for 80 km of its length the line will pass within such a distance
of 71 scattered properties that the magnetic fields in the properties can be deemed
elevated. With a view to reducing the fields locally on each property, the possibility is
being investigated of using tuned screened circuits. Every such circuit costs an estimated
MSEK 0.5. Assuming that, on average, there is one child living on each property and there
are no other economic aspects to be taken into consideration, the cost per case avoided
will be about MSEK 370. The cost per case will be the same if it is preferred to purchase
the properties for an average of MSEK 0.5 each. Power line planned through suburban
area
A 220 kV power transmission line is planned through a suburban area. The line will pass a
multi-family dwelling within a distance at which it can be deemed to elevate the risk of
child leukaemia. There are 60 children living in the building. To avoid an elevated
magnetic field, it is planned to splice a split-phase line into the section which passes
the building. The additional cost entailed by this solution is estimated at MSEK 0.7. If
the measure is taken, the cost per case avoided will be about MSEK 9.
(The above titles are available in Swedish only)
Copies of this guide are available from the following participating authorities:
Arbetarskyddsstyrelsen
National Board of Occupational Safety and Health
171 84 Solna
Tel 08-730 90 00 Fax 08-730 19 67
Boverket
National Board of Housing, Building and Planning
Box 534, 371 23 Karlskrona
Tel 0455-530 00 Fax 0455-531 00
Elsäkerhetsverket
National Electrical Safety Board
Box 1371, 111 93 Stockholm
Tel 08-453 97 00 Fax 08-453 97 10
Socialstyrelsen
(National Board of Health and Welfare)
106 30 Stockholm
Tel 08-783 30 00 Fax 08-783 32 52
Statens strålskyddsinstitut
Radiation Protection Institute
171 16 Solna
Tel 08-729 71 00 Fax 08-729 71 08
Considerations for restricting phone
base-station mast emissions 20th February 2000
First chapter Prepared by Alasdair Philips, Technical
Director, Powerwatch
We suggest setting a precautionary signal level of 3 V/m from masts at houses and schools and other areas where the public have common access. This is equivalent for one full continuous channel producing 2.7 uW/cm2. We believe that this would be workable for the cellular industry, with higher levels being allowed on roof areas for maintenance purposes and near higher-powered rural masts which are not close to buildings containing people. Some contracts have already been signed accepting this limitation. The reason that we are promoting this as a Code of Good Practice is that it matches EU and UK EMC (Electromagnetic Compatibility) Regulations which have the force of law. We suggest the Heavy Industry EMC limit of 10 V/m as a limit in other outdoor areas for common public access, with possibly even the ICNIRP limits near remote rural masts. The power will rise for multiple transmitters at 3 V/m : 10 channels @ 3 V/m produce 5.2 uW/cm2.
The ElectroMagnetic Compatibility (EMC) legislation (Europe wide and UK specific) was brought in to prevent electronic equipment failing or operating incorrectly due to electromagnetic field emissions. Most equipment now has to be tested and found to emit virtually zero radiation (very low levels indeed ~ less than 0.0001 volts/metre). Transmitters, which are intended to radiate signals, are, of course, exempt.
Because it was rare to encounter signal levels above 0.3 volts/metre, a level of immunity of 3 volts per metre was generally adopted as providing a reasonable margin of safety. For this reason I suggest that it is unreasonable to allow cellular phone base stations to pollute the general public’s environment at levels greater than this.
A 3 V/m limit in general
public access areas will normally result in levels less than 1V/m inside nearby buildings.
Most microwave meters measure V/m and mathematically convert to power.
Over 95% of current base-stations will already comply
with these levels. I have measured the areas and buildings surrounding many
base-stations and virtually never found levels above these. The few that exceed these
levels could have their power decreased which would be in line with the cellular companies
plans to have smaller cell sizes to cope with the volume of telephone traffic which is
currently starting to overload large area, higher powered, cells. A maximum 3V/m
code of practice would:
(i) Provide the most
precautionary levels anywhere in the world. See a table of
below.
(ii) Be based on an
‘equipment based Standard’ so no-one would have to admit to low level
bio-effects.
(iii) Allow almost all base-stations to
remain where they are and only require a reduction in power output from less that 5% of
the highest output transmitter masts. Large rural masts not near buildings, or places
where people gather, could be exempt so that large open country areas could still be
covered economically by the cellular system operators. <![endif]>
The
EMC Standards are:
EN
50082-1:1992 Electronic
equipment must be immune to 27-500 MHz @ 3V/m
EN
50082-1:1997 (revised) Generic Standard 80-1000 MHz @ 3V/m
plus 900 MHz
@ 3V/m pulsed on/off at 200 Hz to simulate a mobile phone signal
EN
601-1-2/ EN 60601-1-2:1993 Collateral Standard for Medical Equipment 26-1000
MHz @ 3V/m
IEC 601-1-2: Draft 1998 Collateral Standard 3 V/m 80-2000 MHz (covers the high band mobile phones)
CISPR
14-2/ EN 55014-2:1997 Household
appliances 80-1000 MHz @ 3 V/m
EN
61000-4-3 80-1000
MHz @ 3V/m
ENV 50204:1995 900 MHz @ 3V/m pulsed on/off at 200 Hz
NOTES:
‘Near-field’ levels next to a working mobile phone handset vary enormously depending on the antenna design and other parameters but will almost always exceed the electric field and power density levels set in the general exposure standards. Instead of using these standards, attempts are to mathematically model, and also to measure using a ‘phantom’ model head, the likely Specific Absorption Rates (SAR) and these are compared with the basic restrictions in the various standards.
Average SARs from phones are always below the NRPB maximum head SAR 10 W/kg in any 10g sample of tissue; typically 0.3 to 1.5 W/kg, but ranging up to about 6 W/kg in the worst case. The US Standard of 1.6 W/kg in any 1g sample of tissue is almost certainly exceeded by some mobile phone handsets. It is not clear that the SAR is the only metric that needs to be specified. It is possible that the high localised electric field levels could be causing the reported headaches, earaches and skin problems. Some phones with low SAR levels have a high number of users reporting headaches, etc.
I gather that the EU Health Ministers have now formally adopted the ICNIRP standard listed above. The UK NRPB have always advised against the need to adopt these lower levels that are still based on thermal (tissue heating) considerations even when the Parliamentary Select Committee have told them to do so (September 1999).
Italy and Switzerland are the only European countries with non-thermal regulations: Italian Decree No 381 of 10 September 1998, 'Regulation laying down standards for the determination of radio frequency ceilings compatible with human health', entered into force on 2 January 1999, and provides for an exposure limit of 6 V/m for transmitters in respect of buildings in which people live or work for more than four hours per day. The Swiss ORNI Ordinance came into force on 1st February 2000 and is almost identical to the Italian Standard.
The maximum natural thermal background level at 900 to 1800 MHz is somewhere between 10 and 30 microvolts/metre (20 dBmV/m and 30 dBmV/m) based on 20 to 200 attowatts/cm2/MHz.
The “man-made electrosmog” level is usually below 100 mV/m, (40 dBmV/m), with even very strong broadcast TV (c.500 MHz) and FM radio (c.100 MHz) signals normally not exceeding 0.1 V/m (100 dBmV/m) and usually much lower than this unless you are close to a large broadcast transmission mast where they still rarely exceed 2 or 3 volts/m (130 dBmV/m).
Magnetic (far) field = (V/m)/(377) A/m; multiply by 1.26 to get flux in mT; 3V/m=> 0.008 A/m= 6 nT
** ‘Near-field’ levels next to a working mobile phone handset
vary enormously depending on the antenna design but
can often exceed the electric field and power density levels set in the general exposure
standards.
General Public Levels |
Frequency MHz |
E field V/m |
Power W/m2 |
Power m W/cm2 |
| NRPB, 1993 (Current UK Investigation Levels) |
900 1800 |
112 194 |
33 100 |
3300 10000 |
| FCC OET65:1997-01 (USA) based on ANSI/IEEE C95.1-1992 |
900 1800 |
47 61 |
6 10 |
600 1000 |
| Canadian Safety Code 6 (SC6) 1993 |
900 1800 |
47 61 |
6 10 |
600 1000 |
| ICNIRP, 1998 (recognised by WHO) CENELEC, 1995 (EU) |
900 1800 |
41 58 |
4.5 9 |
450 900 |
| Australia 1988 (under review) | 900 / 1800 | 27 | 2 | 200 |
| Two USA research bases (1995) | 30 - 100000 | 19 | 1 | 100 |
| Poland (non-stationary people) (stationary people) |
300 - 300000 | 19 6 |
1 0.1 |
100 10 |
| Russia 1988 (general public) | 300 - 300000 | 6 | 0.1 | 10 |
| Italy, Decree 381 (1999) | 30 - 30000 | 6 | 0.1 | 10 |
| Toronto Health Board 2000, proposal based on SC6/100 |
900 1800 |
5 6 |
0.06 0.1 |
6 10 |
| Swiss Ordinance ORNI ( for base stations ) From 1st.Feb.2000 |
900 1800 |
4 6 |
not specified |
not specified |
| EU & UK EMC Regulations equipment suscept test level (domestic & comm.) |
30 - 2000 | 3 any signal |
not specified |
not specified |
| Typical max in public areas near base station masts (can be much higher) | 900 & 1800 | 2 | 0.01 | 1 |
| Dr Cherry (NZ) proposal for now aiming for a level by 2010 |
300 - 300000 | 0.15 0.06 |
0.00005 0.00001 |
0.005 0.001 |
| Average US (EPA 1980)-----> City Dweller max (FCC 1999)-----> |
approx 30 - 300000 |
< 0.13 < 2 |
< 0.00005 < 0.01 |
< 0.005 < 1 |
| Broadband ‘natural’ background | 300 - 3000 |
< 0.00003 | < 0.00000001 | < 0.000001 |
| ** Typical, close to handset antenna | 900 & 1800 | 50 - 300 | 2 - 50 | 200 - 5000 |
A Canadian proposal : by Wolfgang W. Scherer ( 25. March 1994 )
An alternative to exposure levels used at this time : calculations are based on the electrophonic effect, which I have recommended as an adequate comparison. Calculations lead to an ambient level of about 100 pW/cm² = 0.1 nW/cm² as the equivalent value at which ambient noise is perceived as "quiet" (8 db). Subliminal noise levels are here not considered.
If we accept this level as maximum for permanent exposure most populated areas in Canada are heavily overexposed already! Unless convincing data are provided one can argue that the lowest value that can be derived from existing data should prevail. Safety Code 6 allows for much higher levels which could be rejected for being inadequate and based on insufficient procedures.
The above given level still allows for the operation of systems from a technical point of view. Considering that 0.6 W = 600mW are sufficient to reach this towers with a cellular phone the opposite direction should be able to communicate with the same power level. This is technically achievable !
here are some examples
According to my local office of Industry Canada the normal output is on average 70W but up to 10 channels are allowed so the maximum output at such towers can be 700W and the safe distance would then be 7.5 km (4.6 miles).If 400 m (1330 ft) is the distance from a 300 ft (100m ) tower the maximum power at this site should not exceed 2 W ! With 10 channels on one site operated with 3W each, the same as car phones and bag phones, the total output would be 30 W. The safe distance for such a site would be 1600m (~ 1 mile ). In many cases these distances are not maintained and the allowable power exceeds the above given values excessively. Using this value would translate to a safe distance from a tower with 100 W radiation power of about 2.8 km (1.75 miles).
The calculations assume a permanent radio output, as it is the case with most cellular communication towers .
They do not take in consideration other sources of radiation like TV, or Radio transmitters. If there are more transmitters in the vicinity the radiation has to be added up, consequently reducing the power at the new site, or moving it to a safe distance that the combined levels are below this value.
It is to be expected that this level will be dismissed as unrealisticly low, but even if higher levels would be proven guaranteed safe one should demand that only the lowest possible level is permitted that still allows the operation of the system (energy conservation). There may be some technical adjustments necessary, but that should be done! The operation of the system is generally not jeopardized with lower power.
This can not be set aside only for the reason that Safety Code 6 allows higher levels. One could even take the position that there is no specific reference in the code at all, so zero tolerance is valid until the code refers to accumulative permanent exposure. The code is still only refering to occupational exposure. Considering that the exposure of the public is involuntary and permanent, asking for power limits to such transmitters seems quite reasonable, and it is technically possible and justifiable.
However, the currently permitted levels of radiation are more than hundred thousand times higher ! With the powerful interest of the industruies in this field unfortunately no change is to be expected.
| Update September 1997 : The new review of Safety Code 6 in its preliminary form has again no accumulative limits, it will state and allow permanent public exposure levels (accumulative over 24 hours) nearly equivalent to those for worktime occupational exposure ( 8 hours). Professionals in this field are well payed and covered by disability insurance - the unaware public is not "protected". The radio/micro wave pollution continues to increase steadily. Update February 1998: The World Health Organisation WHO has called for a symposium on the health hazards of wireless communications citing such possible dangers as tumors and cancers caused by the use of modern telecommunication devices. Hopefully this will lead to new research and better standards and not only to a whitewash on behalf of the industry. |
Biological effects news 2000
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