Electromagnetic fields - RTE

manyhuntingUrban and Civil

Nov 16, 2013 (3 years and 11 months ago)

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Electromagnetic fields
7 questions…
7 answers.
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E
3
ecently, we have seen considerable public debate sur-
rounding electromagnetic fields and their effects on
health.
For example:
!
Are they dangerous for people and animals?
!
Should people take any special precautions against them?
!
How reliable are the studies that have been carried
out on this subject ?
!
What is EDF and RTE's position on this issue?
These are legitimate questions that deserve clear and well-sup-
ported answers.
This document is intended to provide those answers, giving rea-
ders the information they need to draw their own informed
conclusions.
R
R
1
RTE is the exclusive Transmission System Operator in France. Originally conceived by the Law of 10th
February 2000 on modernisation and development of public service electricity, it was officially set up
on 1st July 2000.
This Law sets the conditions for the opening of the French electricity market, and stipulates that the
transmission system operator must be independent from EDF's other activities.
T
What is an
electromagnetic field ?
T
he concept of a field is
used mainly by
physicists.
It refers to the influence that
an object (for example a
magnet or a lamp) may exert
on the space around it. In the
same way, we talk about a
gravitational field to describe
the force of attraction that the
Earth exerts on living beings
and objects situated within its
orbit.
In the electricity sphere,
there are two distinct types
of field:
!
The electric field.
This is linked to voltage, in other
words electrical charges. It exists
as soon as an appliance is plug-
ged in, even if it is not yet swit-
ched on.
!
The magnetic field.
This is linked to the movement
of electrical charges, in other
words the flow of a current. In
order for it to exist, the
appliance must be both
plugged in and switched on.
The combinaton of these
two fields leads us to
speak of "electromagne-
tic field".
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1
)
The current is
flowing. The
magnetic
field is
present along
with the
electric field.
The lamp is
plugged in but
not switched
on: there is an
electric field,
but no
magnetic field
5
)
!
Electric fields are measured
in volts per metre (V/m) or for
higher values in kiloVolts per
metre (kV/m).
They become much weaker
with distance. All kinds of obs-
tacles (trees, fences, etc.) can
reduce them or even stop
them altogether.
!
Magnetic fields are measured
in Tesla (T) or microTesla (µT or
0.000 001 T). The old unit of
measurement, the Gauss (G), is
still sometimes used (1 G is
equivalent to 100 µT), especially
in English-speaking countries.
It, too, fades rapidly depen-
ding on the distance, but com-
mon materials practically do
not stop it.
!
All the fields are also characte-
rised by a frequency, in other
words, by a number of oscilla-
tions in a given time. This fre-
quency is measured in Hertz
(Hz).
E
Where can
electric and magnetic fields
be found ?
E
verywhere! They exist
in all parts of the world,
although they may be
produced by very different
sources: some are natural,
whilst others are the result of
human activity.
!
The Earth's magnetic field.
We are all fami-
liar with this one,
which is respon-
sible for pointing
compass needles
due north. It is
about 50 µT in
our part of the world.
6
2
)
Natural el ectri c and
magneti c fi el ds.
Two examples:
!
The atmosphere.
It contains electrical charges which
exist constantly and everywhere.
The magnitudes of the resulting
electric fields may
vary considerably,
from 100 V/m
when the wea-
ther is fine up to
20,000 V/m in the
midst of a cloudy
storm.
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2
)
!
Natural electric and magnetic
fields are constant or vary very
little over time. They are said
to be static as their frequency
is very low, or even zero.
!
Most man-made fields ocsilla-
te rapidly and regularly: they
are alternating fields. Their
frequency, expressed in
Hertz, is therefore positive.
Man-made electric and
magnetic fields.
!
These might be the 50 to 60
Hertz fields created by electric
currents.
They come from anything which
runs on electricity or which is used
to channel it.
This includes everything from RTE's
electric installations such as high-
voltage and very high-voltage
lines, right down to low-voltage
domestic appliances such as
hairdryers, electric razors, televi-
sions and computers.
P
Are electromagnetic fields
linked to ...
... magnetism?
... X-rays and microwaves?
P
ublic awareness has
been drawn to these
issues in a somewhat
alarmist fashion.
This has led to a certain
amount of confusion...
With magnetism...
!
The dictionary gives two very dif-
ferent definitions of the word
magnetism. On the one hand, it
is the area of science concerned
with the properties of magnets.
On the other hand, it is the force
of attraction exerted by a person
upon those around him or her. In
particular, this second definition
covers what we refer to as divi-
nation and paranormal pheno-
mena.
This explains why, for may
people, magnetism has myste-
rious connotations.
Electromagnetism is a scientific
discipline that forms part of the
study of physics. Its basic
principles were laid down over a
century ago. Its characteristics
are well known and shown
mathematically.
8
3
)
With X-rays and microwaves...
These two pieces of equipment
do indeed work on the principle
of electromagnetic fields.
However, the fields they use
have very different frequen-
cies.
!
The frequency of X-rays is bet-
ween 10
16
and 10
22
Hertz
(1 followed by 16 or 22
zeroes!). These are extremely
high values, and so X-rays have
enough energy to break the
bonds between molecules.
!
The frequency of microwaves is
between 10
9
and 10
12
Hertz
(between 9 and
12 zeroes). This
radiation is
what heats
food in micro-
wave ovens.
!
The frequency of electric
current is only around 50 or 60
Hertz. In other words, several
thousand (or billion…) times
less than the two previous ones.
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3
)
!
And neon tubes?
Why do they light up
underneath electricity
lines?Simply because the
electric field produced by the
line excites the electrons of
the gas in the tube, causing
it to glow.
C
C
ertainly. Since 1979, a
great many studies have
been carried out throu-
ghout the world, in the United
States, Sweden, Norway,
Canada, Great Britain, Japan,
Russia, France, etc.
10
These studies are concerned
with the electromagnetic
fields encountered in day-to-
day life
(extremely low frequency
fields of between 50 and 60 Hertz).
They are mainly based on two
methods :
!
Some are carried out under labora-
tory conditions: living cells in the
form of mice are exposed to intense
electromagnetic fields, and the
results are studied.
Have any studies examined
the risks attached to
electromagnetic fields?
4
)
!
Others are taken from everyday life.
First, the analysts take a test-group
of people with a serious illness (such
as cancer) and another test-group
of people without this illness. Then
they determine whether those in
the first group have had a greater
exposure to electromagnetic fields
than those in the second. This is
known as epidemiology.
No expert report has provided
evidence of a causal relationship bet-
ween exposure to EMF and the risk of
developing cancer.
!
In June 2001, the IARC
(International Agency for
Research on Cancer) carried out
a monograph study
1
to measu-
1
The IARC has assessed 860 chemical and physical
agents, or mixtures - see www.iarc.fr/ - and has publi-
shed monographs since 1972.
11
4
)
re the possible carcinogenic
effects of EMF. The results led
to magnetic fields being classed
as "possibly carcinogenic",
along with substances like cof-
fee and exhaust fumes. For this
category, "there is limited evi-
dence of carcinogenicity in
humans and inadequate evi-
dence in animals". Electric fields
were considered to be "not
classifiable as to their carcino-
genicity to humans" due to
insufficient data. According to
WHO
1
, this means that EMF nei-
ther trigger nor promote cancer
in animals.
Official positions
!
As early as 1998, the Minister
for Territorial Planning and the
Environment (D.Voynet) ratified
the opinion of the CSHPF
(Higher Council for Public
Health and Hygiene in France)
published in 1996, which
concluded that there was no
proof that electromagnetic
fields have any impact on the
health of animals or humans of
any age.
!
In 1999, the Secretary of State for
Health and Social Action
(B.Kouchner) pronounced that "a
consensus is now emerging among
members of the scientific communi-
ty. On the basis of current results,
we cannot completely rule out the
existence of a very low risk, which
would in any case have no bearing
on the other risks of daily life."
!
In 2001, the Secretary of State for
Industry (C. Pierret) confirmed
these stances.
European Recommendations
!
In 1999, the Council of European
Union Health Ministers adopted a
Recommendation on public expo-
sure to magnetic and electric fields.
This Recommendation uses the
values advocated by in 1998 by the
ICNIRP (International Commission
on Non-Ionizing Radiation
Protection).
!
The ICNIRP proposed exposure
levels based on the current induc-
tion in the organism of electric and
magnetic fields with an extremely
low frequency (50 and 60 Hertz)
1
C.f. WHO memorandum n°263 and www.who.int/.
N
N
umerous studies have
been carried out on this
subject in several diffe-
rent countries.Researchers
concentrated on several types of
livestock: cows, pigs, chickens,
horses, dogs bees, etc.
The studies found that, as in
humans, there was no evidence to
suggest that EMF have an impact
on the health of animals.
12
The expert opinion.
!
This is a summary of an article publ
i-
shed in 1993 by veterinary journal
"la Dépêche vétérinaire": "Studies o
f
animal health, which are sometime
s
carried out on a massive scale, have
not revealed any potentially harmfu
l
effects. This confirms data obtained
from tests on
laboratory ani-
mals exposed
to fields with
similar forms
and intensi-
ties".
!
Occasionally, farm animals may receive very small electric shocks,
often as a result of faulty insulation or poorly earthed farming equip-
ment.
!
This is in no way linked to the effects of electromagnetic fields.
However, such shocks are easily avoided, for example by ensuring that
electric farming equipment is in good condition or that drinking
troughs are properly earthed.
Are there any risks to
livestock grazing near high
voltage lines?
5
)
13
I
Even so, are there any precautions
that need to be taken?
I
t is important to remem-
ber that on Earth, everyo-
ne is constantly exposed
to "natural" electromagnetic
fields. Moreover, the entire
populations of developed
countries are exposed to fields
resulting from man-made
energy. It is therefore point-
less to try and avoid coming
into any contact with them at
all.
example if a person was expo-
sed to fields one thousand
times more intense than nor-
mal.
n In 1999, the Council of EU
Health Ministers adopted a
Recommendation attributing
measurable reference levels to
zones where members of the
public spend substantial
amounts of time, or where they
are exposed for long periods:
• 5000 V/m
for electric fields,
• 100 µT
for magnetic fields.
!
In day-to-day life, the fields we
encounter are much weaker
than the values indicated in the
recommendations issued by the
ICNIRP and the European
Union.
" " "
!
Under normal day-to-day condi-
tions, no precautions need to
be taken. Studies carried out up
to now show that electroma-
gnetic fields do not present any
risks to public health.
!
It is possible that in some extra-
ordinary situations, there could
be some harmful effects, for
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)
5000
100 µT
14
" " "
!
And mobile phones?
Although they emit waves at 0.9
x 10
9
or 1.8 x 10
9
Hertz, the
energy they produce is very low.
No study has scientifically establi-
shed its harmfulness.
Nevertheless, as its use is recent,
studies are going on, particularly
at European level.
Electric fields
(in V / m)
Razor negligible
Computer negligible
Toaster 40
Television 60
Hi-Fi 90
Refrigerator 90
90,000 Volt
power line 100
(at distance of 30m)
400,000 Volt
power line 200
(at distance of 100m)
Electric blanket 250
Magnetic fields
(in µT)
Refrigerator 0.30
Toaster 0.80
Hi-Fi 1.00
90,000 Volt power line 1.00
(at distance of 30m)
400,000 Volt power line 1.20
(at distance of 100m)
Computer 1.40
Television 2.00
Electric blanket 3.60
Razor 500
N.B.:these are maximum values measured at a distance of 30 centimetres, except for appliances which require close contact for utilisation purposes.
List of values recommended by
the Council of European Union Health Ministers
15
What is EDF and RTE's
common position
on the issue of electromagnetic fields ?
Over the past twenty years, numerous
studies have researched the effects of
EMF on health, some of which were carried out by official
bodies such as the World Health Organisation (WHO), the American
National Academy of Sciences, the British National Radiological
Protection Board (NRPB) and the International Agency for Research on
Cancer (IARC).
Based on the results of these studies, international organisations such
as the International Commission on Non-Ionizing Radiation Protection
(ICNIRP) or the European Commission have been able to draw up
recommendations on public exposure to EMF, in an effort to guarantee
"a high level of health protection". The NRPB has confirmed that
conclusions drawn from the latest research do not justify changing
these recommendations.
In the light of all this, EDF and RTE are committed to :
• supporting biomedical research in the field in co-ordination with inter-
national bodies, guaranteeing the independence of scientists and
publishing the results obtained ;
• respecting recommendations issued by the French or international
health authorities and in particular the recommendation made by the
European Commission ;
• providing up-to-date and transparent information to their staff, the
public, the health sector and the media ;
• guaranteeing consultation with various partners: the public authori-
ties, elected representatives, associations and local residents.
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GESTIONNAIRE DU RÉSEAU DE TRANSPORT DÉLECTRICITÉ
(ELECTRICITY TRANSMISSION SYSTEM OPERATOR)
NATIONAL GRID RESEARCH CENTRE
ADDRESS: IMMEUBLE AMPÈRE-LA-DÉFENSE 6 - 34-40, RUE HENRI RÉGNAULT - 92400 COURBEVOIE
POSTAL ADDRESS: CEDEX 48 - 92068 PARIS-LA-DÉFENSE
TEL : 01 41 02 10 00 - FAX : 01 41 02 26 69
INTERNET SITE: www.rte-france.com