Electrical appliances in the household

Electrical appliances in the household

Appliance  Magnetic field (T)

Distance of  Distance of  Distance of 3 centimetres  30 centimetres  1 metre

Hairdryer  6 – 2000  0.01 – 7  0.01 – 0.3 Electric shaver  15 – 1500  0.08 – 9  0.01 – 0.3 Drill  400 – 800  2 – 3.5  0.08 – 0.2 Electric saw  250 – 1000  1 – 25  0.01 – 1 Vacuum cleaner  200 – 800  2 – 20  0.1 – 2 Washing machine  0.08 – 50  0.15 – 3  0.01 – 0.15 Clothes dryer  0.3 – 8  0.1 – 2  0.02 – 0.1 Clothes iron  8 – 30  0.1 – 0.3  0.01 – 0.03

Kitchen appliances

Appliance  Magnetic field (T)

Distance of  Distance of  Distance of 3 centimetres  30 centimetres  1 metre

Electric cooker top  1 – 50  0.15 – 8  0.01 – 0.04 Microwave oven  40 – 200  4 – 8  0.25 – 0.6 Refrigerator  0.5 – 2  0.01 – 0.3  0.01 – 0.04 Coffee machine  1 – 10  0.1 – 0.2  0.01 – 0.02 Hand-held mixer  60 – 700  0.6 – 10  0.02 – 0.25 Toaster  7 – 20  0.06 – 1  0.01 – 0.02

0.4 1.8 0.2

1.6 0

1.4 0.2

1.2 0.4

1.0 0.6

m 0.8 0.6

0.6 0.4 0.2 0 0.2 0.4 0.6 0.8

Magnetic field of a hairdryer. The most intensive fields occur close to  the casing. The significance of the solid lines is indicated in the colour  scale below.

0.4

0.2 0.1

m 0.2 0 0.2 0.4 0.6 0.8

Like all appliances that consume high levels of electricity to produce heat, electric cookers (hotplates) generate intensive magnetic fields. However, the exposure quickly diminishes with increasing distance.

0.1 1 10 100 1000 10 000

Scale of magnetic flux density in microtesla (T).

Electrical appliances in the home

Reducing electrosmog in bedrooms  – Mains powered clock radios should nev-

er be kept close to the head (minimum  We spend about a third of our life in bed.  distance, 1 metre).

In view of this, the situation in bedrooms  – Never sleep on electric cushions or elec- is of particular importance. If we place  tric blankets for lengthy periods if they  electrical appliances in the wrong loca- are switched on.

tions, we risk lengthy exposure to their  – No extension cables should be placed  electric and magnetic fields. For example,  beneath the bed.

the magnetic field of a clock radio placed  – Beds should not be placed near electric  near the head of the bed can extend well  risers or fuse boxes/panels.

into the bed, but at distance of 1 metre it  – Maintain an adequate distance: main- is practically no longer detectable.  Screens tain a distance of at least 50 centi - To reduce exposure to non-ionising radia- metres from computer monitors, and tion while we sleep, the following recom- Cathode ray monitors for computers and  a minimum distance of 2 metres from mendations should be observed: TV sets generate different types of fields  TV  screens (also  applies  in  adjacent

– Appliances such as computers and TV and radiation: electrostatic fields, low- rooms).

sets in the bedroom and in neighbour- frequency electric and magnetic fields,  – Flat screens produce less electrosmog: ing rooms should be placed at a min- high-frequency  non-ionising  radiation  since  they  consume  electricity,  flat imum distance of 2 metres from the  and weak X-rays. To reduce exposure from  screens also generate low-frequency bed. During the night, appliances should  screens and monitors, the following rec- electric and magnetic fields, but other- be switched off completely (not left in  ommendations should be observed: wise they are free of radiation.

standby mode). – TCO label: when buying a new screen, look

– Electrical  appliances  for  monitoring  for the TCO label (originally from Swe-

babies and small children should also  den). Labels like TCO 99 or TCO 03 indi-

be kept at least 2 metres away from  cate low-radiation computer screens.

their bed.

Appliance  Magnetic field (T)

Distance of  Distance of  Distance of

3 centimetres  30 centimetres  1 metre Clock radio  3 – 60  0.1 – 1  0.01 – 0.02 Electric blanket  Up to 30

0.3 m 0.3

TV set  2.5 – 50  0.04 – 2  0.01 – 0.15 Monitor with  0 TCO label  0.2 (50 cm)

Electric floor heating  0.1 – 8

Stove  10 – 180  0.15 – 5  0.01 – 0.25 0.1 0.2

0.5 0.4 0.3 0.2 0.1 0 0.1 0.2

Magnetic field of a clock radio. To avoid long-term exposure while asleep, permanently operated electrical appliances like clock radios should be kept at least one metre away from the bed. The significance of the solid lines is indicated in the colour scale below.

0.1 1 10 100 1000 10 000

Scale of magnetic flux density in microtesla (T).

Lighting – Energy-efficient lamps. These produce  – Low-voltage halogen systems. These pro-

slightly stronger fields than filament  duce the strongest magnetic fields of all Lighting systems such as low-voltage hal- lamps due to the choke in the base, but  forms of lighting. It is recommended to ogen lamps produce relatively intensive  the fields disappear already at a dis- install transformers and conductors at magnetic fields. These originate partly  tance of around 50 centimetres. Thanks  a distance of at least 2 metres from fre - from the transformers that reduce the  to their lower electricity consumption  quently occupied areas.

normal voltage in the household from 230  and longer service life, these lamps are

to 12 V, and partly from the current-bear- more ecological than filament bulbs.

ing wires. In order to yield the same light  – Fluorescent tubes. Since their fields are

output, the current in the cables of lamps  more intense than those from energy-

operated with low voltage has to be high- efficient lamps, a distance of at least

er than is the case in conventional light- 1 metre is recommended.

ing systems, and this means that the mag-

netic fields are also stronger. In addition, if

the current conductors are not close to - Appliance  Magnetic field (T)

gether, the field intensifies and can also be  Distance of  Distance of  Distance of

measured on the floor above. 3 centimetres  30 centimetres  1 metre

To reduce exposure, the following points  Filament bulb (60 W)  0.1 – 0.2

should be observed when buying lighting  15-watt energy-

equipment: efficient lamp (with

– Filament bulbs. These produce the lowest  electronic choke)  1  0.1

magnetic fields of all forms of lighting,  Halogen

but in view of their poor light efficien- table lamp  25 – 80  0.5 – 2  Up to 0.15

cy they require significantly more elec- Low-voltage

tricity than energy-efficient lamps.  halogen lighting  Up to 0.3

1.0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8

1.0 1.2 1.4 1.6 1.8 2.0 2.2

m 1.0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1.0

Low-voltage halogen lighting systems produce the strongest magnetic fields of all forms of electric lighting. If they are installed on the ceiling, they can also cause considerable levels of exposure in rooms located directly above.

Railway lines Contents

Electric fields from catenaries > P The magnetic fields from the catenary

system (railway contact and feeder  Lmaarggneeftluiccftiuealdti >o nPs of the

lines) fluctuate considerably. When

locomotives accelerate or brake, they  Srapielwciaayl  pchowarearc st ue prips lt yi c >s P o f the increase the flow of current and this  Focusing the reverse current > P

intensifies the magnetic field. The  Precautionary regulations of the ONIR > P busier the route, the higher the expo - Exposure inside trains > P 7

sure levels.  Motor cars are not an alternative > P 7

Direct current (DC) transport systems > P 7

Highly fluctuating magnetic fields along railway lines

Electric fields  Special characteristics of the  .7 Hz by means of frequency changers. from catenaries railway power supply Electricity generated in power plants is fed

to the railway sub-stations via separate

Most railway services in Switzerland are  Like the public electricity supply network,  high-voltage transmission lines at operated with alternating current with  most railway lines in Switzerland are oper- kilovolts (kV). The voltage is then reduced to a frequency of 16.7 Hz. This means that  ated with alternating current. Despite this   kV, the level required by locomotives. electric and magnetic fields occurring  common factor, however, there are certain

alongside railway lines also have this fre- significant differences that also affect mag- Fewer current conductors: The public quency.  netic fields in the vicinity of railway power  electricity supply is a three phase system – The strength of the electric field direct- supply systems: here the circuit comprises three phase con-

ly beneath the catenary (e.g. at a level  ductors. By contrast, the transmission net- crossing) is around 1,500 volts per metre  Lower frequency: The railway power sup- work for the railway electricity supply uses (V/m), and it decreases with increasing  ply has a frequency of .7 hertz (Hz), whereas  only a feed and a reverse conductor, both of distance. The applicable exposure limit  the frequency of the public electricity supply  which are live. Along the railway line itself, value in Switzerland for 16.7 Hz electric is 0 Hz. This difference can be attributed to  the power required by locomotives is fed fields – 10,000 V/m – is therefore easily  the fact that the earliest electric motors for  only via the contact line, while the reverse complied with. And since the voltage in  trains required the lowest possible frequency  current passes through the rails, the return

the catenary remains fairly constant, in- in order to function reliably. In view of this, at wire and the soil.

dependently of the level of operation, the  the beginning of the 0th century a number

electric field also does not vary – unlike  of European countries (including Switzerland) Mobile power consumers: As a rule, elec-

the magnetic field. agreed, after various trials, to adhere to the  trical appliances and machines are used at

frequency of .7 Hz, which is still used today. a fixed location, but locomotives fed by the Large fluctuations of the  This decision called for the construction and  railway supply network are constantly on the magnetic field operation of a separate electricity supply  move. They can even generate current them-

network for railways, and as a result, major  selves when applying electric brakes: here Since the catenaries do not always carry  railway operators like the SBB (Swiss Federal the engine becomes a generator that con-

the same current, the magnetic fields in  Railways) possess their own power plants and verts brake energy into electricity which it

the vicinity of railway lines can fluctuate  own transmission lines. But in addition, they  feeds back into the supply network. considerably. Whenever locomotives and  also use 0 Hz alternating current from the

railcars  accelerate  or  feed  electricity  public grid, which has to be converted to

back into the network when braking, the

current increases, and so does the mag- 2.5

netic field. And locomotives also require

more electricity when they are travelling

uphill or pulling heavy goods trains. 2.0

Typically, current is fed into the contact

line at points 25 to 30 kilometres apart.  1.5

If there is no train travelling along a sec-

tion between two feed points, no current

is flowing and therefore no magnetic field  1.0

is created. In the example depicted here,

this is the case between 1 a.m. and 4.30 a.m.

But if there are trains in operation, the  0.5

magnetic field exists along the entire sec-

tion in which the locomotives are being

supplied with electricity. The exposure  0

alongside the railway line varies according  Time 00 h 02 h

04 h 06 h 08 h 10 h 12 h 14 h 16 h 18 h 20 h 22 h 24 h

to the amount of traffic along each supply

section, the current location of each train  16.7 Hz magnetic field on the double track railway line between Luce rne and Basel near Nottwil, and the fluctuating electricity demand of  measured at a distance of 10 metres from the centre of the rails: the exposure level fluctuates the locomotives.  depending on traffic volume. If there are no trains on this stretch, there is no exposure. The Since the magnetic fields of the public  24-hour average level (green line) is 0.41 microtesla. This is of relevance for comparison with electricity network and the railway sup- the installation limit value, which (again averaged over a 24-hour period) is 1 microtesla, and ply network have different frequencies,  is therefore complied with in this example.

their intensities cannot be directly com-

pared. Depending on the frequency, the  ONIR and aimed at protecting against

threshold of the magnetic field strength  short-term effects are 100 microtesla (µT)

for eliciting health effects is different.  for 50 Hz magnetic fields, but 300 µT for

The exposure limit values specified in the  16.7 Hz fields.

Railway lines

40 30 20 10 0

–10 m

40 30 20 10 0 10 20 30 40

Magnetic field on a typical double track railway line. The magnetic flux density at the perimeter of the tunnel-like area (perspective view, left) is 1 microtesla (average over a 24-hour period). The cross-section of the magnetic field vertical to the railway line (right) shows how exposure diminishes with increasing distance from the contact line. The grey line represents a 24-hour average level of 10T, and the white line depicts

a reading of 1 T.

Focusing the reverse current

The fact that the feeds and reverse cur - rents are fairly far apart is another fac -

0.1 1 10 100 1000 10 000 tor that is of significance with respect to the intensity of magnetic fields from rail- Installation limit value way catenary systems. Electricity is fed via the contact line, whereas the reverse

Scale of magnetic flux density in microtesla (T). current flows via the rails and the return wire. Due to the contact between the rails

and the ground, however, some of the re- verse current flows through the soil or via underground metal pipes (e.g. those used for gas or water supply). Stray currents of

Power feed this sort can propagate over considerable distances and only return to the railway

line in the vicinity of the sub-station.

The further apart the feed and reverse Canodn nreecttuironn wbierteween rail  currents are, the greater the reach of the

magnetic field (at the same current). To re- Return wire Other reverse conductors duce this, the best solution is for the larg- est possible fraction of reverse current to

flow via the return wire, since this is clos-

est to the contact line.

Sub-station

Reverse current via rail

Precautionary regulations of the ONIR Stray current

The precautionary emission limitations for catenary systems specified in the ONIR vary according to whether the installation is new, to be modified or old.

– New installations: These include cate- nary systems for new railway lines and

Power is fed from the sub-station to the locomotive via the contact line (blue arrow). The  for lines that are to be re-routed. At current then flows back to the sub-station via the rails (green arrow), the return wire (yellow  places of sensitive use they are required arrow), the soil and other reverse conductors in the ground (red arrows). The spatial extension  to comply with the installation limit val- of the magnetic field of a railway catenary is relatively broad due to the distance between  ue of 1 microtesla (µT). This is measured the power feed and reverse currents. as a 24-hour average. On a double track

line, for example, the specified instal- lation limit value is normally complied  

with from a distance of between 10 and  25 metres from the contact line, de - pending on the traffic volume. In cer- tain exceptional circumstances, the rel- evant authorities may allow the instal- lation limit value to be exceeded.  

– Installations to be modified: In the ONIR  the term "modified" refers to the addi- tion of tracks to an existing railway line.  At places of sensitive use at which the  installation limit value was already ex- ceeded prior to the implemented chang- We are also exposed to magnetic fields when we are inside a train. The level of exposure varies es, the magnetic field intensity must not  according to the part of the train we are in.

be increased. At all other places of sen-

sitive use, the installation limit value  coach, whose importance diminishes with  Motor cars are not an alternative

must be complied with. As with new in- increasing distance from the locomotive.

stallations the specified requirements  On the upper level of the first coach be- The presence of magnetic fields inside may be eased in certain circumstances.  hind the locomotive, and on both levels at  trains is not a reason for changing the

– Old installations: This term refers to  the other end of the train, the magnet - means of transport, however: magnetic catenary systems that are not being  ic field intensity was approximately the  fields also occur in motor cars. These are modified or that are renewed on exist- same (average level for the full journey,  partly attributable to on-board electrical ing lines. If the installation limit value  around 0.7 µT, with short-term peaks of  systems, but can also be produced from is exceeded at places of sensitive use,  up to 3.5 µT). magnetised wheel rims and steel belts in these systems have to be equipped with  Since trains are not included in the defini- tyres. Measurements carried out inside a return conductor (earth wire) placed  tion of places of sensitive use, no precau- moving cars showed that the highest ex- as close to the contact line as possible.  tionary limitation applies inside railway  posure occurs in the area around the pas- This is already the case on most railway  coaches for the magnetic field. senger's feet and on the rear seat. Read- stretches today. The ONIR does not re- ings varied greatly from model to model, quire any further measures for old in- and covered the same range as fields in- stallations. side trains.

Exposure inside trains

We are also exposed to magnetic fields

when we are inside a train. These fields  

are produced partly by the currents in  

the catenary system and the rails, but also  

by the on-board power supply that is re-

quired for lighting, heating and air-con-

ditioning purposes. This internal power  

supply consists of a special cable that is  

fed by the locomotive and runs beneath  

each coach right along the entire length  

of the train.

Measurements carried out in a double-

decker train on the stretch between Bern  

and Zurich have shown that the magnet-

ic fields fluctuate considerably through-

out the journey, and can also vary great- Direct current (DC) transport systems

ly in different parts of the train. The mag-

netic field was found to be at its strongest  Trams, trolley buses and some narrow- large margin. Research has not yielded any on the lower level near the locomotive. At  gauge railways are operated with direct  indications of potential health risks asso- seat level, the mean reading for the jour- current, and these systems produce stat - ciated with DC fields encountered in ev- ney was 4 µT, and short-term peak levels  ic (DC) electric and magnetic fields. For DC eryday life, and for this reason the Ordi- of up to 10 µT were recorded. At this posi- magnetic fields, the ONIR specifies an ex- nance does not specify any installation tion the main source of the magnetic fields  posure limit value of 40,000 µT, and this  limit value for DC transport systems.

is the supply cable running beneath each  level is always complied with by a very

Mobile telephony

Thanks to the existence of thousands of base stations, we

can now communicate by mobile phone throughout the entire country. On the other hand, the numerous antennae give rise

to an increase in high-frequency radiation throughout the country. In the vicinity of mobile phone base stations, the level of exposure varies in the course of the day depending on the volume of transmitted calls. However, due to the fact that mobile phones are held close to the head, the exposure level for users

is much higher than that from any base station.

Constantly increasing high-frequency radiation from mobile telephony

Contents

Mobile communication boom > P  Structure of the network > P Units and dimensions > P

Radiation in the vicinity of  

a mobile phone base station > P

How mobile phones and base  stations function > P

Electric field strength near base  stations in the course of a day > P

Precautionary regulations  

of the ONIR > P The fact that we hold a mobile phone so close to our head when calling means that the level of

exposure is much higher than that from a base station antenna.

Licensing and supervision

of mobile phone base stations > P Mobile communication boom Structure of the network

Hints for users of mobile phones > P The majority of the population of Switz- A mobile communication network com-

erland now own a mobile phone, and more prises multiple cells. Each cell has an an- Comparison of exposure from  than 9,000 base stations ensure that we  tenna that establishes a wireless connec- base stations and mobile phones > P can make calls with them from almost  tion to the mobile phones in its vicinity.

anywhere in the country. After 1993, the  Normally a number of cells are supplied Specific absorption rate  GSM  mobile  communication  standard  from a given location, and all the antennae for mobile phones > P gradually replaced the existing Natel C  at this location form a base station.

network and thus contributed towards the  Base stations are linked to a network

boom in mobile telephony. In 2002 the im- switching centre via standard cable con-

plementation of UMTS – a third generation  nections or via point-to-point microwave

network – was initiated. But the constant- links. From here they receive calls that

ly expanding range of services and grow- they have to pass on to mobile phones in

ing demand in the area of mobile commu- their cells. And vice versa, they also trans-

nication are also resulting in increasing  mit calls to this switching centre that are

exposure to high-frequency electromag- being made with a mobile phone in their

netic waves. By contrast with electricity  supply area.

supply, in which radiation is an undesirable  Each base station can only transmit a lim- by-product, in the area of mobile commu- ited number of calls. The range of each nication it is used deliberately as a means  cell is thus determined by the intensity of transmitting data without wire. of utilisation. In rural areas with low mo-

bile phone density, cells can have a radi- us of several kilometres, whereas in ur- ban centres they only have a range of a few hundred metres. And the micro-cells frequently used in town centres are even

GSM: the GSM (Global System for Mobile  UMTS: UMTS (Universal Mobile Telecommuni- Communications) standard has been in use  cations System) is the standard for the third in Switzerland since . GSM networks generation of mobile communication. The

 operate in two frequency ranges: 00 MHz  UTMS network, for which implementation (GSM00) and ,00 MHz (GSM00). began in 00, operates in the gigahertz

frequency range (,00 to ,00 MHz). It is able to transmit much higher volumes of

data than GSM, and thus enables the trans- mission of moving images.

Mobile telephony

smaller. These are used in areas where call  

volumes are particularly high, or cover-

age is difficult due to building density. Fi-

nally there are also pico-cells, which have  

a radius of only a few dozen metres and  

are used for providing connections with-

in buildings.

The transmitting power of an antenna has  

to be so high that the signals to be trans -

mitted also reach the mobile phones at the  

perimeter of the cell. On the other hand,  

they must not be too intensive, otherwise  

they would interfere with signals in other  

cells. Since antennae in small cells operate  

with a lower transmitting power, they pro-

duce a lower level of radiation exposure.  

Although more antennae are required, the  

overall power radiated by all base stations  

is lower, not higher – at least in urban are-

as. A fine-meshed network can even trans-

mit more calls with an overall lower trans-

mitting power. Reproduced with the kind permission of swisstopo (BA056863)

Reproduced with the kind permission of swisstopo (BA056863)

The higher the demand for phone services, the greater the density of the mobile communi- cations network, as we can see from a comparison between the city of Geneva and the small country town of Bière (canton of Vaud). Each red dot represents a mobile phone base station. The two maps depict the situation as of 1 June 2004. The locations of all transmitters in Switzerland can be viewed at www.funksender.ch.

Mast with mobile communication antennae (top) and antennae for point-to-point trans- mission (round). The latter link base stations to the switching centres.

Units and dimensions

Mobile phone antennae transmit high- frequency electromagnetic waves or radia- tion – also referred to as high-frequency  non-ionising radiation.

Frequency: This refers to the number of  oscillations of an electromagnetic wave  

per second, and it is measured in hertz (Hz),  megahertz (MHz) or gigahertz (GHz).

• Hz = oscillation per second

• kHz = ,000 Hz

• MHz = ,000,000 Hz

• GHz = ,000,000,000 Hz

Mobile communication networks in Switzer- land operate at 00 MHz (GSM00), ,00 MHz  (GSM00) and between ,00 and ,00 MHz  (UMTS).

Transmitting power in watts (W): This  

indicates how much energy is supplied to an  

antenna per time unit. Typical levels per  

direction are between a few thousandths of  The antennae

a watt and 0 to 0 watts. Fluctuations  installed at base occur in the course of each day due to varia- stations establish

ble loads of mobile communication systems.  contact with mobile

phones within Equivalent radiated power (ERP) in watts:  their range.

ERP is another means of indicating transmit-

ting power, and is also expressed in watts.  Power flux density: This, too, indicates  field strength to double, four antennae of It is used for calculating exposure and in  radiation intensity. It measures the energy  the same power would have to transmit to Switzerland it is also of relevance for the  flux per unit time through a perpendicular   a given location, and 00 antennae would be licensing of mobile phone base stations. ERP  reference area, and is indicated in watts per  required for the field strength to increase levels are significantly higher than those of  square metre (W/m) or microwatts  tenfold.